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HomeMy Public PortalAbout2023 VKB K-8 BasinV illa g e o f K e y B is ca y n e K-BBasin Basis of Design Report (B O O R ) AECOM Project Number: 60690913 June 12, 2023 88 West McIntyre Street Key Biscayne, FL 33149 K-8 Basin Basis of Design Report (BOOR) Village of Key Biscayne AECOM Project No.: 60690913 Quality Information Prepared by Checked by Verified by Approved by Thomas McGowan, PE Senior Civil Engineer Karen Brandon, PE Senior Water Resource Engineer Peter May, PE Senior H&H Modeler Erik Alcantara, PE, PMP, ENV SP Senior Project Manager Revision History Revision Revision date Details Authorized Name Position Distribution List # Hard Copies PDF Required Association I Company Name K-8 Basin Basis of Design Report (BODR) Village of Key Bisca yne AECOM Project No.: 60690913 Prepared for: Village of Key Biscayne Public Works Department 88 West McIntyre Street Key Biscayne, FL 33149 Prepared by: AECOM 2 Alhambra Plaza Suite 900 Coral Gables, FL, 33134, United States aecom.com Respectfully submitted, AECOM \\\\\\II I /f ///11 .,s.''9J ~:!':1.:?o '~~ June 12, 2023 ~~--~,cEN.ti••~ ~ .;::;o:.. -.~~ ---~, ,-,,,,,, -- ;; L.:: : N0.44742 \ ~:: ._r-1 I - - . * . - =•i :•== S '•-\ ITA15 OF ,•~ ~ ,. 4·., . ~.:::: % 7<,;;;,.~~!':~'-!!°-~'.f..~ /111 Ss!ONAL ~,,,~ N - I/I/JI Iii l \\\\\ ~ + ~ Date:.Jv~\"2, "2.:,"2.3 Thomas F McGowan~ ' Senior Project Engineer Florida License #44 7 42 AECOM Technical Services, Inc. FBPE & BPR #8115 NOT FOR CONSTRUCTION Copyright© 2023 by AECOM All rights reserved. No part of this copyrighted work may be reproduced, distributed, or transmitted in any form or by any means without the prior written permission of AECOM. K-8 Basin Basis of Design Report (BO OR) Village of Key Biscayne AECOM Project No.: 60690913 K-8 Basin Basis of Design Report (BOOR) Table of Contents Executive Summary····-··································································································· 7 1 Introduction 13 2 Drainage Design Report 13 2.1 Existing Conditions 14 2.1. 1 Land Use 14 2.1.2 2.1.3 2.1.4 2.1.5 2.1.6 2.1.7 2.1.8 2.2 2.3 2.3.1 2.3.2 2.3.3 2.3.4 2.3.5 2.3.6 2.3.7 2.3.8 2.4 2.4 .1 2.4 .2 2.4 .3 2.4 .4 2.5 2.5.1 2.5.1.1 2.5.1.2 2.5.1.3 2.5.2 2.5.2.1 2.5.2.2 2.5.2.3 2.5.3 2.5.3.1 2.5.3.2 To pography 15 Flood Hazard M apping 16 Repetitive Loss 17 Frequently Flooded Areas 17 Existing Storm water Collection System 18 Stormwater O utfalls 19 Project Study Area 20 Stormwater Planning Criteria 21 Development of Altern ative Scenarios 22 Scenario 1 26 Scenario 2 26 Scenario 3 26 Scenario 4 27 Scenario 5 27 Scenario 6 28 Additional Possible Scenarios 28 Scenarios Summary 28 Pro posed Drainage System 30 K-8 School Project Stormwater Collection and Conveyance Improvements 31 Stormwater Pump Station 32 Water Quality and Storm water Treatment Units 33 Rehabilitation of Existing Outfalls 34 Stormwater Design Methodology 35 Hydro logy 35 Rainfall and Runoff 35 M odel Calibration Rainfall Events 35 Basin Areas 36 Hydraulics 37 Collection System 37 Nodal Stage vs. Storage 38 Tidal Boundary Condition 38 M odel Limitations and Assumptions 40 Existing Conditions M odel 40 Altern ative Scenario Baseline Model 40 2.6 Altern ative Scenario M odeling Summary and Analysis 40 2.6.1 Altern ative Scenario 1 41 2.6.2 Altern ative Scenario 2 41 2.6.3 Altern ative Scenario 3 42 2.6.4 Altern ative Scenario 4 42 2.6.5 Altern ative Scenario 5 43 2.6.6 Altern ative Scenario 6 43 Prepared for: Village of Key Biscayne AECOM 1 K-8 Basin Basis of Design Report (BO OR) Village of Key Biscayne AECOM Project No.: 60690913 2.7 Evaluation of Flooding Depth & Duration - K-8 School Vicinity 44 2.8 Drainage Design Report Conclusion 49 2.8.1 Follow-Up Issues 49 2.9 Drainage Design Report References 49 3 Streetscape Toolkit and Harbor Park Conceptual Design Ideas 50 4 Utilities 58 4.1 Hotw ire Communications 58 4.2 Florida Power & Light... 58 4.3 Comcast Cable 60 4.4 AT&T 60 4.5 M iami-Dade Water and Sewer Department 62 5 Maintenance of Traffic and Construction Phasing 62 6 Permitting Evaluation 62 6.1 United States Army Corps of Engineers 63 6.1.1 Section 404 Authorization or Section 10 Authorization 63 6.2 6.2.1 6.3 6.3.1 6.4 6.4 .1 6.4 .2 6.4.3 6.4.4 6.4.5 6.5 6.5.1 6.5.2 6.6 6.6.1 6.6.2 7 7.2 7.2.1 7.2.2 7.2.3 7.3 7.4 South Florida Water Management District 63 Environmental Resource Permit - Individual 63 Florida Department of Enviro nmental Protection 63 National Pollutant Discharge Elimination System - Conceptual Generic Dewatering Permit 63 M iami-Dade County DRER - Department of Environmental Resources Management 64 Class I Permit 64 Class II Permit 64 Class V Permit 64 Pollution Remediation Section 64 Tree Program 64 M iami-Dade County Water and Sewer Department... 64 Revision to the Existing Water and Sewer Permits 64 Right-of-Way Permit 65 Village of Key Biscayne - Intern al Departments 65 Public W orks Department 65 Building, Planning, and Zoning Department 65 Preliminary Marine Benthic Review 65 8 7 .1 Introduction 65 Results 66 O utfall 1 - South (VKB Outfall #12) 66 O utfall 2 - East (VKB Outfall #15) 66 O utfall 3 - North (VKB Outfall #14) 66 Summary 66 Photo Log 67 Essential Fish Habitat Assessment. 71 8.1 Action Area 71 8.1.1 EFH Consultation History 72 8.2 Pro posed Action 72 8.3 EFH, M anaged Fisheries, and Fishery Management Plans 72 8.3.1 Background 72 8.3.2 Essential Fish Habitat 74 8.4 EFH Habitat Types within the Proposed Action Area 80 8.4 .1 Estuarine Intertidal Scrub-Shrub W etland 80 8.4 .2 M arine and Estuarine Water Column Habitat 80 Prepared for: Village of Key Biscayne AECOM 2 K-8 Ba sin Ba sis of D e sign R e po rt (B O O R ) Village of Key Biscayne AE C O M Project No.: 60690913 8.4.3 8.4.4 8.4.5 8.5 8.5.1 8.5.2 8.5.3 Soft Bottom (Mud, Sand, Clay) 81 Seagrasses 82 Coral Reefs and Live/Hard bottom 82 Federally Managed Species 83 Spiny Lobster 83 Reef Fish 83 Sharks 84 8.5.4 Coastal Migratory Pelagics 84 8.5.5 Shrimp 84 8.6 Habitat Areas of Particular Concern 85 8.7 Assessment of Potential Impacts 85 8. 7.1 Construction Methods 85 8.7.2 8.7.3 8.7.4 8.7.5 8.7.6 8.8 8.9 9 9.1 9.2 9.2.1 9.2.2 9.3 9.3.1 9.3.1.1 9.3.2 9.4 9.4.1 9.4.2 9.4.3 9.4.4 9.5 9.6 10 Water Quality, Sediment Resuspension and Turbidity 86 Benthic Habitat 87 Corals 87 Underw ater Noise 87 Displacement 88 Proposed Mitigation Measures 89 The Effects of the Action: Summary and Conclusions 90 Marine Species Biological Assessment 90 Introduction 90 Protected Species and Habitats 90 Introduction 90 Assessment Methodology 90 Species Occurrence and Effect Determinations 91 State and Federally Listed/Protected Wi ldlife Species 92 Federally Listed Species 92 Critical Habitats 97 Assessment of Potential Impacts 98 Mammals 98 Reptiles 98 Birds 100 Construction Methods 101 Proposed Mitigation Measures 101 The Effects of the Action: Summary and Conclusions 102 Manatee Protection Plan (MPP) 102 10.1 Introduction 102 10.2 Manatee Protection Measures 103 11 Preliminary Design Plans 105 12 Preliminary Project Construction Cost Estimate 105 Appendix A Document Summary 106 A.1 ICPR 4 - Existing Conditions Model Input Report with Simulation and Basin Summaries 106 A.2 ICPR 4 -Alternative Scenarios Baseline Model Input Report with Simulation Summaries 106 A.3 ICPR 4 - Nodal Diagrams 106 A.4 ICPR 4 - Nodal Min/Max Stage Reports 106 A.5 ICPR 4 - Link Maximum Flow Reports 106 A.6 Standard Manatee Conditions for In-Water Work 106 A.7 Preliminary Plans 106 A.8 AA CEI Class 5 Preliminary Project Cost Estimate 106 Prep ared fo r: V illa ge of K ey Biscayne AEC O M 3 K -8 Ba sin B a sis of D e sig n R ep ort (B O O R ) Village of Key Biscayne AEC O M Pro ject No.: 60690913 DISCLAIMER FOR TRANSFER OF DIGITAL MODEL FILES - 107 Figures Figure 1, Key Biscayne Municipality and Location of K-8 School. 13 Figure 2, FLUCCS Level 1 Land Uses 14 Figure 3, Topography (ft, NAVO 88) 15 Figure 4, Village of Key Biscayne FEMA Flood Insurance Rate Map (FIRM) 16 Figure 5, Repetitive Losses 17 Figure 6, Frequently Flooded Areas 18 Figure 7, Existing Stormwater Management System 18 Figure 8, Village of Key Biscayne Outfalls 19 Figure 9, Existing Conditions Model Basins 20 Figure 10, K-8 School Project Study Area 20 Figure 11, K-8 School Project Existing Storm Sewer Network 21 Figure 12, Proposed K-8 Project Stormwater Collection System 32 Figure 13, Harbor Drive Pump Station System Performance Model 33 Figure 14, K-8 Project Drainage Sub-Basin Locations 36 Figure 15, K-8 Project Alternative Scenario Model Nodal Diagram 37 Figure 16, Selected Probability Exceedance Curves Illustrating Sea Level Rise 38 Figure 17, Southeast Florida Regional Compact for Climate Change 39 Figure 18, Alternative Scenarios Cross Section Location 44 Figure 19, School Basin (VKB-06) Time-Stage Hydrograph 45 Figure 20, Existing Conditions - Peak Stage and Flood Duration 46 Figure 21, Scenarios 2, 3 & 5 Peak Flooding and Duration - Crown Section 47 Figure 22, Scenarios 2, 3 & 5 Peak Flooding and Duration - Inverted Crown Section 48 Figure 23, Community Meeting Flyer 50 Figure 24, Existing Street... 51 Figure 25, Proposed Street (Option 1A): 51 Figure 26, Proposed Street (Option 1 B): 51 Figure 27, Proposed Street (Option 1C): 52 Figure 28, Proposed Street (Option 2A): 52 Figure 29, Proposed Street (Option 2B): 52 Figure 30, Proposed Street (Option 2C) 53 Figure 31, Harbor Park - Existing Site 53 Figure 32, Harbor Park Site - Reference Images 54 Figure 33, Conceptual Design -Architectural Elements 55 Figure 34, Conceptual Design - Hardscape Materials 55 Figure 35, Conceptual Design - Paving Materials 56 Figure 36, Conceptual Design - Lighting Typologies 56 Figure 37, Conceptual Design - Site Amenities 57 Figure 38, Conceptual Design - Landscaping 57 Figure 39, Sunshine Design Ticket 58 Figure 40, Existing Utilities: FPL (1 /2) 59 Figure 41, Existing Utilities: FPL (2/2) 59 Figure 42, Existing Utilities: Comcast Cable 60 Figure 43, Existing Utilities: AT&T 61 Figure 44, Search Pattern Used to Observe Resources at the Existing Outfall Locations 65 Figure 45, Existing Outfall Locations 72 P rep a re d fo r: V illa ge of Key Biscayne AEC O M 4 K -8 Ba sin B asis of Design R eport (B O O R ) Village of Key Biscayne AECOM Project No.: 60690913 Tables Table 1, K-8 School Basin Discharge Rates by Scenario 30 Table 2, Basin 6 Gravity Outfalls Discharge Capacities .' 34 Table 3, Existing Conditions Model June 2022 Calibration Storm Rainfall Data 35 Table 4, Existing Conditions Model, September 2022 Calibration Storm Rainfall Data 36 Table 5, K-8 School Project Sub-Basin Areas 37 Table 6 Probability Exceedance Values of Observed Data at Virginia Key in ft NAVO 88 39 Table 7, K-8 School Project Alternative Scenarios Design Storm Model Summary 41 Table 8, School Basin (VKB-06) Flood Depth and Duration Summary 45 Table 9, FMP Species with EFH and HAPC that may be within the Vicinity of the Proposed Action 74 Table 10, Potential Effects of the Proposed Activities on FMP Species 88 Table 11, Listed/Protected Wildlife Species, Designation, and Potential for Occurrence 91 Acronyms and Abbreviations AA CEI AECOM BA BMP BBAP CFR cfs CWA dB DRER DERM DO EEZ EFH EOP ER ERP ESA FDEP FOOT FFE FMC FMP FR FFWC FPL fps American Association Cost Engineers International AECOM Technical Services, Inc. Biological Assessment Best Management Practice Biscayne Bay Aquatic Preserve Code of Federal Regulations cubic feet per second Clean Water Act decibel Miami-Dade County Department of Regulatory and Economic Resources DRER Division of Environmental Resource Management dissolved oxygen Exclusive Economic Zone Essential Fish Habitat Edge of Pavement ecoregion Environmental Resource Permit Endangered Species Act Florida Department of Environmental Protection Florida Department of Transportation Finished Floor Elevation Fishery Management Council Fishery Management Plan Federal Register Florida Fish and Wi ldlife Conservation Commission Florida Power and Light feet per second P re pared for: V illa ge of K ey Biscayne AECOM 5 K-8 Basin Basis of D esign R eport (B O O R ) Village of Key Biscayne AECOM Project No.: 60690913 ft2 GOM HAPC JAXBO JPA mg/L MHW mm MOT MSA msl NAVO NEPA NGVD NMFS NOAA NPDES NTU ppt PRO PTS PWD SAV SEL SFWMD SLR TSS TTS U.S. USAGE USC U.S.C. USCG USEPA USFWS Village ZOI square feet Gulf of Mexico Habitat Area of Particular Concern U.S. Army Corps of Engineers Jacksonville District Programmatic Biological Opinion Joint Powers Agreement milligrams per liter mean high water millimeters Maintenance of Traffic Magnuson-Stevens Act mean seal level North American Vertical Datum National Environmental Policy Act National Geodetic Vertical Datum National Marine Fisheries Service National Oceanic and Atmospheric Administration National Pollutant Discharge Elimination System Nephelometric Turbidity Unit parts per thousand Protected Resources Division Permanent Threshold Shift Public Works Department Submerged Aquatic Vegetation Sound Exposure Level South Florida Water Management District Sea Level Rise total suspended solids Temporary Threshold Shift United States United States Army Corps of Engineers United States Code U.S. Congress United States Coast Guard United States Environmental Protection Agency United States Fish & Wildlife Service Village of Key Biscayne Zone of Influence Prepared for: V illage of K ey Biscayne AECOM 6 K-8 Ba sin Ba sis of D esig n R ep ort (B O D R ) Village of Key Biscayne AEC O M Project No.: 60690913 Executive Summary The Village of Key Biscayne (the "Village") is a highly urbanized community located on the southeast coast of Florida and is a m ajor economic resource to the region. The Vi llage has experienced tidal flooding for m any years. Tidal flooding can be significant during the higher astronomical tides experienced in the spring and the fall of each year ~ especially if occurring during periods of onshore winds. The fall high tides are the highest tides of the year and are also known as the King Tides. Tidal flooding occurs when the Biscayne Bay water surface elevation rises sufficiently to backflow into the Village's storm water management system, up through the storm w ater inlet grates and overflow s into the ro ad rights-of-way. During some high tide events and in localized areas, the tidal flooding can be over the ro adway curb and gutter and over the sidew alks filling the streets with salt water. Tidal flooding inconveniences the travelling public and is a public safety issue, has the potential to cause m ajor property damage, and has killed lawns and landscaping. Tidal flooding also saturates the base structure of roadways causing failure of ro adways prior to their expected useful design life. In addition to addressing tidal flooding, the Village is planning for future sea-level rise that will further dim inish the capacity of the current storm w ater m anagement system. As a member of the Southeast Florida R egional Clim ate Change Compact, the Village has been planning future stormwater management infrastructure to accom m odate the 2060 projection for sea level rise. The Vi llage is proposing a com prehensive storm w ater infrastructure impro vement project (Project)which is intended to improve the Vi llage's storm water m anagement system performance for the next 40 years. The existing storm water facilities are inadequate in m any areas of the Village. In most areas, the existing facilities w ere installed based on development pattern s and groundwater and coastal conditions of the 1960's and consist of im provements to address the drainage needs of discrete locations. Due to age, in­ fill development, and updated regulatory requirements, the overall system requires upgrades to impro ve both storm w ater quality and conveyance. The Pro ject is intended to improve public safety by reducing areas of tidal and localized rainfall induced flooding. During storm events, flooding occurs due to excess rainfall runoff as well as the inundation of the storm water netw ork by tidal backflow and elevated groundwater conditions. Predicted sea-level rise will exacerbate these conditions that contribute to flooding within the Vi llage. The Project will reduce tidal flooding, increase conveyance, and discharge capacity of the storm w ater network and provide water quality treatment, thus reducing localized flooding and untreated storm w ater discharges. The Village has a relatively low-lying topography that is bisected by intracoastal waterw ays, a subtro pical clim ate with high intensity rainfall, significant tidal influence, limited soil storage for infiltration, high amounts of im perv ious area, and lim ited available surface storage. These factors have all contributed to the historic flooding and have the potential to contribute to significant rainfall and tidal induced flooding during the planning horizon. These unique conditions m ake it impossible to apply conventional gravity discharge and detention m ethods to impro ve drainage infrastructure as sea-level rises. In developing design altern atives, stormwater m anagement facility components were evaluated based on their potential life span in combating future sea level rise, the amount of space needed to implement the facilities, and cost. The follow ing facilities were evaluated: Gravity Drainage and Shallow Injection Wells - The Village is currently utilizing these types of facilities as part of their storm w ater m anagement program. Unfo rtunately, these facilities are failing. As sea and groundwater levels rise, the available driving head and thus the capacity for discharge fro m these facilities decreases. Based on the SLR projections for the planning horizon and the corresponding increase in the gro undw ater table, these systems will not be a viable option as a long-term solution fo r the discharge and treatment of storm water runoff. Exfi ltration Trench - An exf iltration trench is a gravity-based system that utilizes perforated pipe such that storm w ater can be discharged into the groundwater. Similar to the drainage well systems discussed above, this type of facility will not be a viable long-term option for stormwater discharge and treatment based on predicted gro undw ater elevations. P repa red fo r: V illa ge of K ey Biscayne AE CO M 7 K-8 Basin Basis of Design Report (BO OR) Village of Key Biscayne AECOM Project No.: 60690913 Wet and Dry Detention and Water Gardens - These facilities are common practice in stormwater m anagement. These types of systems require land to construct catchment areas that could be used to collect the stormwater and attenuate the discharge of stormwater runoff. The green space within the Village consists of active open spaces and parks, neither of which are viable as areas within which wet or dry detention can be provided without impacting recreational uses. To provide enough wet and/or dry detention to aid the Village in reaching the needed storage for achieving their approved level of service, the Village would need to buy private lands and convert them into storm water facilities. Most of the private land within the Village is developed. Prices for undeveloped land range fro m approximately $500,000 for 0.1 acres to $17 million per acre. The cost for converting developed land is much more than this amount. Wh en utilizing wet or dry detention system(s), the Village would still require pump stations to discharge the water into the Bay. In addition, with rising groundwater, the loss of storage provided by these elements of the surface water management system over time must be taken into consideration. As such the amount of land to be purchased to meet the future projected level of service increases. Therefore, the cost, the amount of space, and the useful lifespan required for this type of facility would not be a viable option as a long-term solution. At elevated Bay and gro undwater elevations, these types of gravity drainage systems and conventional best m anagement practices will not function or provide the desired level of service. In addition, due to the lim ited amount of land available, these systems are not cost feasible. To address the storm w ater design challenges, the Village has been divided into twenty (20) study areas which are further combined into eight (8) "zones". Infrastructure upgrades are being developed for each zone to increase runoff capture capacity, stormwater conveyance and outfall discharge capacity. As necessary and within each zone, the pro posed stormwater network improvements include: 1) increasing the num ber of inlets, 2) a new collection and conveyance system consisting of larger diameter pipes, 3) trash racks and water quality structures, 4) a stormwater pumping station(s), and 5) the initial and incremental raising of the elevation of roadways. To avoid the "one size fits all scenario" and resulting issues with harmonization with adjacent private pro perties, and to provide the Village maximum flexibility in the development of an adaptation and resiliency strategy to m itigate for the projected SLR, a strategy was developed to allow for incremental and scalable pro ject solutions. W hile the m ajor underground infrastructure would be installed with the initial project, this concept allows for an initial ro ad raising within each zone project to a target elevation and subsequent incremental raising of the roadway infrastructure over time. The initial road raising is expected to be a minimum of 6-inches, or that which is necessary to achieve a minimum road crown elevation of 2.33 feet, NAVO . An example incremental road raising would be a 2-inch lift of asphalt and corresponding adjustments to m anhole rims and inlet grates every 10-years, or as SLR dictates. The expectation that the incremental changes to landscaping and greenspace areas will allow for mature tree canopies to adapt and adjust to the changing surface and groundwater elevations which will occur over time. In addition to increased overall system performance and redundancy, and to the extent practicable, each zone will be interconnected to the adjacent zones. Due to the significant cost of the improvements, the vary ing levels of flood impact thro ughout the Village and a limited arterial transportation network, construction will need to be accomplished in phases. Zones will be evaluated by a prioritization protocol. Ultim ately, an implementation and phasing plan will be developed based on project priority, neighborhood im pacts, and availability of funding. Located in Zone 1, the K-8 School Project is slated to be the first project constructed as a part of the Village's flood mitigation and resiliency efforts. The Village contracted AECO M Technical Services, Inc. (AECOM) to provide a Basis of Design Report (BO OR) for storm w ater drainage improvements surrounding the K-8 School ("the School"). On February 8, 2022, the Village Council appro ved AECO M's recommendations to keep roads passable for traffic to provide an enhanced level of service, design drainage facilities to accommodate a 10-year, 24-hour storm event and pro vide sea level rise resiliency for the NOAA Intermediate High projection. The adopted roadway Level of Service (LOS) includes a requirement to "keep roads passable" and allows for ponding to depths of 0-0.5 feet within swales for a m aximum duration of 6-12 hours. Prepared for: Village of Key Biscayne AECOM 8 K-8 Ba sin Ba sis of D e sig n R e p ort (B O O R ) Village of Key Biscayne A EC O M Project No.: 60690913 The design storm as adopted by the Village consists of a 10-year recurrence, 24-hour duration storm event w ith a total rainfall of eight (8) inches in the vicinity of the Village. As defined, such a storm has a ten percent (10%) pro bability of occurring at a given location in any given year. It is a statistical average which is not synchronized to any point of beginning. A storm of a m agnitude approximating the "design storm" can occur in any given year, m ore than once each year, and in the event of a close encounter with a major tropical w eather system , any spin-off storm could easily generate rainfall amounts equal to or exceeding design storm values. Additionally, the predicted peak hour rainfall runoff is approximately 3.2 inches. This is a significant volum e of water (40% of the total design storm rainfall) occurring over a very short period of time. D eveloping a storm w ater m anagement system for the Project as a stand-alone project, which is to be designed in concert with however, constructed in advance of, the stormwater infrastructure impro vements which w ill be put fo rth in the Village-w ide SWM P presented a significant challenge. Due to a lack of drainage easem ents, the Pro ject m ay ultimately require a connection to altern ate "extra-neighborhood" discharge locations and capabilities which are not presently available in the Project basin. This complicates the evaluation of the various design altern atives. Another contributing design constraint is that the Project incl udes the capture of an additional 17.6 acres of contributing runoff area from the K-8 School to the Project basin's existing outfalls. AECO M developed six (6) design concepts to evaluate the options and effectiveness of a stormwater m anagement system to serv e the Pro ject basin. All scenarios include the following components: an initial road raising, reconstruction and enhancement of the storm w ater collection and conveyance system, and the construction of water quality treatment devices and a storm water pump station within Harbor Drive Park. The differences between the scenarios essentially comes down to the amount of discharge capacity available within the K-8 School basin, or that which can ultimately be m ade available to the K-8 School basin either by obtaining additional drainage easements within the basin, or interconnection to a yet to be determined "extra-neighborhood" outfall to be developed with the Village-wide SWM P. The current and m axim um potential discharge capacity of the existing outfall locations within the K-8 School basin were evaluated and it w as determined that to m inimize disruption to the benthic environment the existing "local" outfall locations and easements are only capable of pro viding approximately 20% of the discharge capacity necessary to fully m eet the adopted ro adw ay level of service. However, it is important to note that depth and duration of ro adw ay inundation becomes a function of pumping capacity. The altern ative storm w ater m odeling scenarios described in detail in the body of the report are essentially as follows: • Scenario 1: Utilize Existing O utfalls M aintains existing outfalls and sizes and includes a pump station of a capacity equal to the sum of the existing peak discharge rate at each outfall location while m atching existing discharge velocity. Results: Scenario 1 is not a viable solution and would be the least preferred option. Due to the addition of the 17.6-acre School pro perty to the study area drainage basin, the model results show m inim al, to no, benefits as compared to the results of the existing conditions model. However, the recovery tim e for inundation over the crow n of ro ad (36-hours) is one-half that of the existing conditions. • Scenario 2: Rehabilitate and Impro ve Existing Outfall Locations Install the largest diameter pipes possible within the available easements and includes a pump station of a capacity equal to the sum of maximum discharge rate achievable at each outfall location such that proposed flows do not exceed existing outfall velocity. This Scenario provides a "partial solution" to the overall needs of the Project drainage basin. However, in the absence of som e other resolution to the discharge limitations imposed by the capacity of the Basin 6 Outfalls, this scenario most likely represents the predicted "near­ term" performance of the K-8 School stormwater management system. Near-term being defined as, until such time as the Village-wide SWM P improvements are constructed and operational. Pre pa red for: V illa ge of K ey Biscayne AEC O M 9 K-8 Ba sin Basis of De sign R eport (B O O R ) Village of Key Biscayne AECOM Project No.: 60690913 Results: As a stand-alone solution, Scenario 2 fails to meet Levels of Service for both finished floor elevation (FFE) and ro ad crown. Model results indicate that flooding over the crown of road would occur up to approximately 1.75 feet which approximates the existing conditions. However, an evaluation of the recession time for flooding performed for the area in the vicinity of the School indicates that the ro ad is submerged for approximately 7.75 hours as compared to over 3 days for the existing conditions. (See Report Section 2. 7 Evaluation of Flooding Depth & Duration - K-8 School Vicinity). G iven the current state of available options, Scenario 2 becomes an essential component of the K­ B School Project and represents a foundation for the adaptation and implementation of future impro vem ents and enhancements to the overall drainage system to supplement the K-8 School Project. The impro vements to be implemented with Scenario 2 are envisioned to be combined with additional work which would be implemented and supplemented by one of Scenarios 3-6, as part of an adaptable and incremental solution. Scenario 3: Rehabilitate and Improve Existing Outfall Locations and Provide Reserve Pump Station Capacity to Transfer Flows to a Central Facility to be Repumped to a Master Outfall. M aximizes the capacity of the existing outfalls as described in Scenario 2 however, includes a pump station of a capacity capable of pumping the design storm peak hour runoff (3.2 inches per hour) with the runoff in excess of the capacity of the local outfalls being pumped to a central re-pump facility (w hen available) and ultimately to a future Village-wide master outfall. Results: Scenario 3 shows significant benefit to the Project drainage basin. It achieves the paramount goal of pro ducing peak flood stages lower than any known FFE. However, model results predict that the m aximum depth of flooding over the crown of road would be up to 0.30-feet for approximately 15 minutes to one-half hour. • Scenario 4: Rehabilitate and Improve Existing Outfall Locations and Provides Significant Reserve Pum p Station Capacity to Transfer Flows to a Central Facility to be Repumped to a Master Outfall. Like Scenario 3, Scenario 4 m aximizes the capacity of the local outfalls as described in Scenario 2. Scenario 4 includes a pump station of a capacity such that the roadway level of service is met, and no flooding of the roadway occurs. Pumping capacity required in excess of the capacity of the local outfalls is to be pumped to a central re-pump facility (when available) and ultimately to a Village-wide m aster outfall. Results: Scenario 4 protects FF Es and fully meets the currently adopted roadway LOS with no flooding of the roadway occurring. The pump capacity in Scenario 4 is approximately 115% greater than that of Scenario 3. Scenarios 5 and 6 were developed to determine what would be necessary to maximize discharge capacity w ithin the K-8 School Pro ject basin, to reduce, if not eliminate reliance on future "extra-neighborhood" improvem ents to be constructed as part of the Village-wide SW MP. These scenarios envision the Village obtaining additional or enhanced drainage easements along the side lot lines and along the waterfront allowing fo r the installation of larger discharge pipes and the reconstruction of a seawall(s) incorporating both energy dissipation and increased capacity for the pump discharge. • Scenario 5: Rehabilitates and Improves two of the Existing Outfall Locations and Reconstructs the Remaining Existing Outfall and Adjoining Seawall to Include both Energy Dissipation and Increased Discharge Capacity Provides for a pump station capacity equivalent to Scenario 3 capable of pumping the design storm peak hour runoff (3.22 inches per hour). As desired, stormwater runoff exceeding the capacity of the improved local outfalls would be pumped to a central re-pump facility (when available) and ultimately to a Village-w ide m aster outfall. Results: Scenario 5 shows significant benefit to the Project drainage basin. Depending upon the ultim ate size of the reconstructed outfall structure, the model results indicate that some re-pumping m ay be necessary to pro duce peak flood stages lower than any known FFE. Prepared fo r: V illage of K ey Biscayne AECOM 10 K-8 Basin Basis of Design Report (BO OR) Village of Key Biscayne AECOM Project No.: 60690913 A dditionally, Scenario 5 does not fully achieve the desired roadway level of service with the maximum flooding over the cro w n of ro ad ranging fro m 0.4 to 0.94-feet. However, the evaluation of recession tim es for flooding indicates that the roadw ay w ould be inundated above the crown fo r appro ximately 45 m inutes. • Scenario 6: R ehabilitates and Im pro ves one Existing Outfall and Reconstructs Two of the Existing O utfalls and A djoining Seaw alls to Incl ude both Energy Dissipation and Increased Discharge Capacity. Pro vides fo r a pum p station capacity equivalent to the design discharge capacity of the reconstructed outfalls and capable of pum ping in excess of the design storm peak hour runoff of the Pro ject basin. Scenario 6 would not require re-pump to a central re-pump facility. Results: Scenario 6 show s significant benefit to the Project drainage basin. The m odel results indicate that this Scenario protects FFEs and fully m eets the currently adopted roadway LOS with no flooding of the roadw ay occurring. Scenario 6 demonstrates that it is possible to develop a storm water m anagem ent system fo r the K-8 School Project which does not rely upon a yet to be determined altern ative outfall location being developed. Pum p capacity in Scenario 6 is approximately 106% greater than that of Scenario 3. Further, the results of Scenario 6 dem onstrate that it is possible to generate "excess capacity" within the Project Basin which with the development of the Village-wide SWMP could be "shared" with adjacent basins via storm water piping interconnections. Should this scenario be successfully im plem ented in other basins within the Village, the reliance on the developm ent of an "extra-neighborhood" altern ate discharge location could be greatly reduced. Recommendation: T he proposed A ltern ative Scenarios fo r the K-8 Basin Project drainage im provements are all effective at reducing both the depth and duration of flooding w ithin the project drainage basin. As such, it can be unequivocally stated that the proposed K-8 Basin drainage im provements will be just that - pro viding im provem ents to both depths of inundation and recovery tim es fo r the design storm event and introducing an elem ent of w ater quality treatm ent lacking fro m a basin which discharges into Biscayne Bay, which is both an O utstanding Florida Water Body and an im paired w ater body. As pro posed, the capacity of the proposed storm w ater treatm ent units (SWT Us) exceed the one-hour water quality treatment volume. R egardless of the Scenario ultim ately chosen, the pum p station infrastructure should planned and constructed to have an ultim ate capacity of not less than the design storm peak hourly runoff rate of 247.2 cfs (~111,000 gpm ). Based on the results from the storm water m odeling, Scenario 3 is recommended as the Preferred Altern ative Scenario. Scenario 3 represents the m ost likely scenario to be implemented long term. Scenario 3 protects FFE of structures w ithin the project basin; how ever, it fails drainage Level of Service - defined as no allow able flooding above the road crow n - but achieves a peak flood elevation of 2.63 feet, NAV O w hich, based on 2060 SLR projections, by default becom es the required future m inimum road edge of pavem ent. It is anticipated that there w ould be an initial raising of the roadways during the neighborhood im p ro vem ents, and subsequent increm ental raising to be im plem ented over tim e. Subject to the gainful negotiations w ith affected stakeholders in securing additional easements necessary to im plem ent Scenarios 5 and 6, and the tim e lag to construct the Village-wide SWM P improvements to sup port Scenario 3, in the interim , Scenario 2 becomes the default scenario to be implemented, Both Scenario 2 and 3 represent significant im provem ents w ithin the basin. Scenario 2 pro duces slightly better flood stages than the existing conditions, how ever, demonstrates a ten-fo ld decrease in inundation times. Scenario 3 produces dram atic reductions in both flood stage and inundation time. However, should Scenario 5 or 6 becom e a possibility, given the decreased reliance of "extra-neighborhood" discharge fa ci lities and associated construction costs, then either would become the recommended preferred altern ative. A pproval of Scenario 2 as the interim preferred altern ative and ultim ately Scenario 3 (or Scenario 5 or 6) as the Preferred A ltern ative Scenario w ould require Village C ouncil to reconsider the definition of ro adway level of serv ice, to allow fo r ponding on the roadways and over the roadway crow n to a reasonable depth and duration. Prepared for: Village of Key Biscayne AECOM 11 K-B Basin Basis of Design Report (BO DR) Village of Key Biscayne AECOM Project No.: 60690913 Estimated Project Construction Cost: As part of the development of the Basis of Design Report for the Project, AECOM was tasked with preparing an expected construction budget. The planning level construction cost for this project has been estimated and organized at a unit price level by major work items. The estimate is an American Association of Cost Engineers, Intern ational (AA CEI) Class 5 estimate and was developed using concept level design documents. Based on the level of design, the Class 5 estimate is the "least" accurate - with an expected accuracy range of (-)50% to (+)10 0% at an 80% confidence level. The estimate carries a 35% design development contingency to account for further design development. Escalation has been applied based on the project starting the m iddle of 2024and taking 2 years to complete. The contract cost presented is the construction cost without the contingency and escalation. The project cost presented is the construction cost plus the 35% contingency and escalation. The estimated contract cost for the K-8 School Basin project is $25,865,000, and the project cost with escalation and contingency is estimated to be $36,235,000. {rem ainder of this page intentionally blank} Prepared for: Village of Key Biscayne AECOM 12 K-8 Basin Basis of Design Report (BO OR) Village of Key Biscayne AECOM Project No.: 60690913 1 Introduction The Village of Key Biscayne ("t he Village") contracted AECOM Technical Services, Inc. (AECOM) to provide a Basis of Design Report (BO OR) for stormwater drainage improvements surrounding the K-8 School ("the School"). O n February 8, 2022, the Village Council approved AECOM's recommendations to keep roads passable for traffic to provide an enhanced level of service, design drainage facilities to accommodate a 10 -year, 24-hour storm event (or 8 inches of rainfall within 24 hours) and provide sea level rise resiliency fo r the NO AA Intermediate High projection. These recommendations will be implemented to design the stormwater drainage improvements surrounding the K-8 School. The engineering design will include street improvements within the vicinity of the school and along West M cIntyre Drive to the proposed pump station located at Harbor Drive (betw een West M cIntyre Drive and West Enid Drive), which will serve the immediate area as well as areas adjacent to the site for future needs. The street improvements will be designed to the Village's level of service requirements. 2 Drainage Design Report AECOM has prepared this Drainage Design Report to summarize the stormwater drainage improvements included in the 30% Conceptual Basis of Design Report ("BOOR") for the neighborhood improvements surrounding the K-8 School ("t he School") in the Village. The Village is situated on a barrier island located east of the City of M iami and lying betw een the Biscayne Bay to the west and the Atlantic Ocean to the east. The Village m unicipality encompasses approximately 1,090 acres and includes various waterw ays and islands and open waters. The location of the School in relation to the overall Village limits is shown on Figure 1. I I I I I I I I I I I I I I I I , - ' I I ' .,.. - .,. ' I 1'" ..., ' I ~ ,.•, ' I I --- ---- I I ' I ' ' , ____ \ N A 0 500 1,000 2,000 Fee l I ' ' ' I I I ' Figure 1, Key Biscayne Municipality and Location of K-8 School The Village has adopted the National Oceanographic Atmospheric Administration ("NOAA ") intermediate­ high sea level rise projection as the basis for determining the sea-level boundary conditions for use in design and planning of storm water infrastructure improvements for the Village through the 2060 planning horizon. Prepared for: Village of Key Biscayne AECOM 13 K-8 Ba sin Ba sis of D esign R eport (B O O R ) Village of Key Biscayne AECOM Project No.: 60690913 T he A E C O M team is fo cused on short-term im provem ent projects where possible and the development of a Storm w ater M aster Plan ("S WM P ") w hich pro vides adaptable solutions and strategies as the infrastructure im pro vem ents are im plem ented incrementally over time. T he existing w ater m anagem ent system serv ing the School and surrounding area is deficient, and the frequency of flooding at the school location and vicinity caused the Village to place a high priority on the resolution of the drainage issues in the vicinity of the School - to the point that the K-8 School pro ject ("the Project") is proceeding concurrently w ith the development of a Village-w ide SW MP. The Project goals are to develop a Preferred Project A ltern ative for the School site and adjacent neighborhoods com prising the K-8 drainage basin, w hich w ill m itigate the recurring flooding and be consistent and com patible with, and adaptable to, the V illage-w ide SW M P project. Together both pro jects, when sufficiently im ple m ented, w ill enable the S chool and surrounding neighborhoods to meet the stormwater level of se rv ice ado pted by the V illage. 2.1 Existing Conditions T his analysis is based on previous m aster plan efforts listed in Section 2.9, Drainage Design Report R eferences (R ef. #'s 1, 2 and 3), and prior work performed for the Village by AECO M. Additional analysis w as conducted to im pro ve the G IS data, develop a robust hydraulic/hydrologic m odel ("existing conditions m odel") w hich w as used to determ ine the capacity of the system , define the deficiencies, and develop solution altern atives. 2.1.1 Land Use T he land uses w ithin the V illage according to Level 1 of the Future Land Use Code Classification System ("F LU C C S ") code is Urban and Built-U p and Water w ith R angeland, Wetland, Upland Forests outside of the urbanized areas show n on Figure 2. The study area is predominantly single-family homes, with an ele m entary school centrally located w ithin the neighborhood and com mercial development along Crandon Boulevard. W<DUSE R.UC CS Leve l 1 .. ,,....,,. - Transportatlon, CorMlunleatlon, and Uti HJe.s ,• 0 50 0 1 .000 2,000 Fee l Figure 2, FLUCCS Level 1 Land Uses Prepared fo r: V illage of Key Biscayne AECOM 14 K-8 Ba sin Ba sis of D esign R eport (B O O R ) Village of Key Biscayne AECOM Project No.: 60690913 2.1.2 Topography T he topography of the V illage w as evaluated based on the m ost current Light Detection and Ranging ("Li D A R ") surv ey data from 2022 and is show n on Figure 3. The elevation datum referenced is the North A m erican Vert ical Datum of 1988, ("N AV O "). It is im port ant to note that there are additional vertical surv ey datum s that were m ore common and historically used in the South Florida Region, incl uding the "Bay Datum" which is referenced to water levels in the B iscayne Bay, and the National Geodetic Vertical Datum of 1929 (aka the M ean Sea Level (MSL) datum ). There is a preponderance of surv ey data com piled using NG VD that is widely available. H ow ever, the U .S . G eological S erv ice thro ugh the National Geodetic Surv ey ("NG S") no longer supports and m aintains the netw ork of NG V D prim ary benchm arks, so there is a forced m igration, to the newer, and presum ably less vulnerable to SLR , N AV O elevations. This progression is slowly evolving and as discussed in Section 2.1.3, Flood Hazard Mapping, FEM A base flood elevations are currently published in NGVD elevations, so both datum s rem ain prevalent and in practical use and care m ust be taken by the user to ensure the user fully understands the difference. Based on the NG S Coordinate Conversion and T ransfo rm ation Tool ("N C AT"), available on the NO AA w ebsite and using the coordinates of the K-8 School site, conversion from NG V D to N AV O is (-1.56 feet). NAVO elevations in this area of North America are lower than the comparable NG VD elevation. T he topography w ithin the V illage is generally flat, with ground elevations ranging from 1.5 to 8.0 feet, N AV O . Based on Li D A R data, the centerline and edge of pavement ("EO P") elevations of the Village roadw ays vary from elevations of 1.50 to over 4 feet, NAVO. As a point of reference, the highest astro nom ical tide recorded in recent years reached an elevation of 2.3 feet, NAVO. The low -lying elevations of the existing roadw ay netw ork are significant because of the limited gradient betw een hydraulically distant inlets and the outfall locations, which m akes the existing gravity-based storm w ater collection system ineffective and incapable of m eeting the desired level of service in m any areas. This issue is exacerbated and m ade m anifest during periods of intense rainfall, seasonal high tides (king tides), storm surge, or the anticipated sea level rise. Legend rapl,v (ft NAVO 88) al ue less than 1 1.0()1 ~ 2 2.00] • 3 3.001 • 4 4,00] · 5 5,00] • 6 6.00] • 7 Figure 3, Topography (ft, NAVO 88) Prepa red for: V illage of Key Biscayne AECOM 15 K -8 B a s in V illage of Key Biscayne B a s is o f D e sig n R e p o rt (B O O R ) A E C O M Pro ject No.: 60690913 2.1.3 Flood Hazard Mapping Flood hazard m apping is an important part of the National Flood Insurance Program ("NFIP"), as it forms the basis of the NFI P regulations and flood insurance requirements. To identify a community's flood risk, the Federal Emergency M anagement Agency ("FEMA") conducts a Flood Insurance Study. The study incl udes inform ation on canal and stream flows, storm tides, hydrologic and hydraulic analyses, and rainfall and topographic surveys. FEMA uses this data to create a series of Flood Insurance Rate Maps ("FIRM") for a community that outlines each community's different flood risk areas. The FIRM is the official map which shows roads and m ap landmarks, a community's base flood elevations, delineated flood zones and floodplain boundaries, special hazard areas and risk premium zones. The most recent FEMA Flood Insurance Study and FIRM panels fo r the area including the Vi llage was conducted in 2009. The results of this study were prepared using the National G eodetic Vertical Datum of 1929 ("NGVD"). Therefore, it is necessary to convert the Base Flood Elevations depicted on the FIRM panels to the NAVO to provide consistency with the NAVO Li DAR and field survey data obtained for the Project. As discussed in Section 2. 1. 2, Topography, the conversion factor between NGVD and NAVO is (-)1.56 feet. As such, a Base Flood Elevation of 10 (NG VD) on the FEMA FIRM panel equates to an elevation of 8.44 feet, NAVO. FEMA has assigned the Village of Key Biscayne Community Identification Number ("CID") 120648. The FEMA flood information with respect to the NFIP for the Village was obtained and evaluated as part of this analysis and is depicted as Figure 4. National Flood Hazard Layer FIRMette ~FEM A Legend SPECtAL FlOOO I HAZARD AREAS 0 2" Al\!'11.1.11 Ch-. flood H111111d. Ai••• oll"•ntH1oltMr>0tlloodwllh-1t&• dtplhlM.tlhlln0Nloot0<wlthdf....,.., OIHI oflNl !Nin~ tqli<)fl ml1- , __ I l'uturttondltion11"Nlrlua1 Char>NfloodHUltfdr.,,,.• r AtH wit.II Rtdvud fJood Ril.k d,.._ lo OfHERARWOF ltYM S..Notff.,.-, FLOOD HA.ZARO,,,~ AiHwtthfloodRiuldu.ll)L"'"t.-0 NI) l,(ll(UI Af N of Min im.al Flood H.li tartf to,,, ' c:=:J [11.«NtlOMRI OTHER A.REAS AINoll/ftd.Urm1..-dfloodHa,,.,d_n GENERAL w-•• ~Cufve,t,OfSlormS.­ SlRUC TURES 11 1 1 1 t I la\-, Olb , Of rlood'w !M i c.-"'-·""'~"'~••"'-• ---1.ld. W ate,Su 1f:tca0 1W tlon , Coa1lal Trtn-.c:l -r,- BoMfloodEi..11tkMILl•,.(8ff) =um1101s111d)' -JU!'hdletlan8ouncl11y ··- ··- CNIUtl Tta!\Mel B.9 ... ine Ollt[R • - Prolil• S.M~nt FEATURES __ ttyclro&,aph~fHhlrl MAP PAN<l.S I 9 Withou t~ Flood Bewtion (BFE) l-Al(A,, W1th8f[o,01p\lllf:IMM..W.A11.\.1.4" RepiMltofyfloodwa,' Ol&J(IV &te At1ilatH Ho Dl&iUI Otta AVJ ib W. !JnrmPPN ' + Tl'MI pin d1$9 111)11d on 111, map Is an appro..imat. polntUIKt.Obylht UHi' and OOH not tlpl'Menl M1t11lho<tt1ln<lp,optr\1kK"I~ Thk map oomplln -.Ith F£M A'I uand 1ul1 for lht- of <fiCjt.ifl~m"Pt,lfititnotYOicl'"4ffcrilM'd"'°"'. ~ N ~o.p W-.n com pll N -.-ith F£MA'1 NUtl'\ap KC U•K)'.all!4 11!:t. Tl'Mlfloodt11111rdltlfotmatlonlt.df<1vt11dl1tctt,,llom01t .w.cwtt.111-tt NFHL -..0 Hrvkff p,<Mdfll by rou. Thi, map ..... , -.po11ff °" 2/2/2023 ,1 9 ~ I\M tnd does not ,.n.c1chan1Mora~ndmtl'l1twt!Mqutnftolh•dattond tlm t, Tht NrHL tnd tllklh't lnFom,11lon m ty cll.1n11 01 ~,u.,.f.-0.clbyntwCIIUtO'flfllmt. lhlsmtp lmo11 II \'old ,1 tM-0tmor1 oftNfollowl11,:mop .itmenudonottppt11:b1um1ptm111ry,flood1on.l1bel1, lt(llld, .ult H1. map c1-!lion data. wmmvnity ld1nlifier&. flRMpon.i nu~.ond FIRM 111.cllvtdn\1 Mllplfful&N fo, Uflm lpl)ff tnd utl '"°"llllted tlfllC61l not"llud lo, lfglll<UO,YJNllpoMil,. Figure 4, Village of Key Biscayne FEMA Flood Insurance Rate Map (FIRM) FEMA defines the flood zones as geographic areas that face heightened risks of flooding, most of which are located near bodies of water. Every zone is classified according to its level of risk and the potential severity of flood events. Prepared for: Village of Key Biscayne AECOM 16 K-8 Basin Basis of Design Report (BOOR) Village of Key Biscayne AECOM Project No.: 60690913 The Village is mapped as lying within AE zones with established base flood elevations ranging from elevations 7 and 8 feet, NGVD (5.44-6.44 feet NAVO) in the eastern areas of the Village, 9 and 10 feet, NGVD (7.44-8.44 feet NAVO) for the central and western areas of the Village, and up to a base flood elevation of 12 feet, NGVD (10.44 feet NAVO) in the extreme southwest portion of the Village. AE zones are defined as Regions with a 1 % annual chance, or 26% chance over the life of a 30-year mortgage of experiencing a flooding event. This flood insurance rate zone corresponds with flood depths greater than three (3) feet. Mandatory flood insurance purchase requirements apply within these zones. 2.1.4 Repetitive Loss FEMA reports repetitive loss for properties with two or more claims of more than $1,000 that have been paid by the NFIP within any 10-year period since 1978 (e.g., two claims during the periods 1978-1987, 1979-1988, etc.). FEMA maintains a list of repetitive loss properties for communities participating in the Community Rating Score ("CRS"). Each year, communities can obtain an updated list of repetitive losses that reflects the community's previously submitted changes, new properties that have been added due to recent floods, and changes resulting from other community updates. This list can be a valuable planning tool and source of information about the location and extent of flooding within the community. The FEMA data for repetitive losses shows several instances of repetitive losses in the vicinity of the School for which mitigation measures have been enacted, and one which, at present, still requires mitigation. These areas of repetitive losses as reported by FEMA are depicted on Figure 5_ Figure 5, Repetitive Losses 2.1.5 Frequently Flooded Areas Records maintained by the Village Public Works Department ("PWD ") of observed flooding and/or flooding complaints are numerous and reflect that the areas around the School are subject to frequent and prolonged flooding. Figure 6, depicts the areas in the vicinity of the School subject to recurring flooding. Prepared for: Village of Key Biscayne AECOM 17 K-8 Basin Basis of Design Report (BOOR) Village of Key Biscayne AECOM Project No.: 60690913 Figure 6, Frequently Flooded Areas 2.1.6 Existing Stormwater Collection System The existing stormwater collection and conveyance system serving the Village consists of multiple, largely non-interconnected, networks of culverts of various sizes and materials and inlets which collect and convey stormwater runoff to discharge locations at adjacent, or nearby water bodies via gravity fed outfalls. Most of the public drainage infrastructure within the Village is located within the single-family residential land use designations with some high-rise residential properties discharging into the public system. Figure 7 depicts the existing configuration of the stormwater management system serving the Village. Legend DIAMETER-IS DIAMETER-18 DIAMETER-24 DIAMETER-30 DJAMETER-36 ---> DIAMETER-38 DIAMETER-42 DIAMETER-48 SW-PIPES .. ./ ' ' \ - ' ).,.,. \ \ ' N A Figure 7, Existing Stormwater Management System Prepared for: Village of Key Biscayne AECOM 18 K -8 B a sin Ba sis of De sign R eport (B O O R ) Village of Key Biscayne AECOM Project No.: 60690913 An additional component utilized within the stormwater management system serving the Village is an exfiltration (seepage) system consisting of a series of 15-inch auger wells installed to a depth of 10 feet and backfilled with gravel. These wells were installed in mu It i p I e locations along the public rights-of-way throughout the Village. The soils in the Village at 10 feet of depth are very silty and thus the water infiltrates very slowly. Furthermore, these wells are not interconnected to a network with a positive outfall. The combination of which results in low effectiveness of these wells (Section 2.9- Ref#2). In some portions of the Village, shallow exfiltration trenches, or French Drains, have been utilized to provide water storage during m inor storm events. However, due to the low permeability of the soils within the Village, these trenches also have low efficiency. Tw o storm w ater pump stations discharging into twenty-eight (28) drainage wells are additionally used for stormwater m anagement. These stormwater components will not be considered for modeling alternatives for the Project since these systems are not within the vicinity of the School (Section 2.9 - Ref #2). 2.1.7 Stormwater Outfalls There are seventeen (17) storm water outfalls from individual drainage systems permitted by Miami-Dade Department of Regulatory and Economic Resources ("DRER") within the Village which ultimately discharge into Biscayne Bay. The outfalls range in size from 8-inches to 48-inches and were permitted and installed betw een 1969 and 1992. M any of the outfalls were constructed within easements between residential lots, which lim its access to them. It could not be determined, therefore, if all the outfalls are open and fully functioning. Some m ay have accumulated silt and sediment over time, thereby reducing capacity or otherw ise be inoperable. Figure 8 depicts the locations of the outfalls connected to the existing stormwater m anagement system. The current stormwater discharge capabilities to the Biscayne outfalls are limited due to the undersized outfall pipes, capacity of the existing pipe network, and increasingly adverse outfall tailw ater stages being higher than rim elevations of upstream inlets during high tide events -thereby leading to "sunny day flooding". IY' 0,.,. 0-11·· ·0•48""')~ 0-16: / , ,/ 0•18 Inch • • \ ; ..... "'-·°"'t. 0•08: 0-03: 0•36 Inch~ ii-~• O::it48 0 03: , ~OS: 0-04. ,nch_.D•48 inch, D=1Elnct!.a,D•l8 '-~-, .. o~ ~~ ·-•·- • • 'I. • 0•15 loch 0-0l,· ._ . • 0•361nch • ~n•~•·• • IJ .. ' i I \ ' -::- N A Figure 8, Village of Key Biscayne Outfalls P rep ared for: V illage of K ey Biscayne AECOM 19 K-8 Basin Basis of Design Report (BOOR) Village of Key Biscayne AECOM Project No.: 60690913 2.1.8 Project Study Area As shown on Figure 9, Existing Conditions Model Basinsthe Project study area consists of portions of Basins 6A, 68 and 98 of the existing conditions model and contains approximately 76.21 acres. Figure 9, Existing Conditions Model Basins The Project drainage area was delineated by reviewing the existing conveyance infrastructure and the topography of the area, and prior stormwater plans. In general, the project drainage basin contains the K- 8 School property and the lands immediately adjacent to, and westerly thereof and extending to the Biscayne Bay. Figure 10 depicts the limits of the modified drainage basin study area of the "stand-alone" K-8 School stormwater master plan and Project. It being understood that ultimately the study area will be interconnected with the ultimate improvements being developed concurrently with the Village-wide SWMP. For the purposes of this analysis, it is assumed that the project study area does not receive stormwater inflows from areas outside the study area. Figure 10, K-8 School Project Study Area Prepared for: Village of Key Biscayne AECOM 20 K -8 Ba sin Ba sis of D esign R eport (B O O R ) Village of Key Biscayne AECOM Project No.: 60690913 As it is situated in the existing storm water management system, and as mapped as part of the existing conditions m odel, the School pro perty consists of approximately 17.63 acres located in Basin 98 (see Fig ure 9). As shown on Figure 11, Basin 98 flows easterly to Basin 9, which extends north and south along Crandon Boulevard, with a likely majority of the stormwater runoff being discharged southerly to Outfall #3 in the vicinity of Knollw ood Drive (see Figures 7 & 8). Basin 98 is not hydraulically connected to Basin 6. As they are situated in the existing stormwater management system, and as mapped as part of the existing conditions m odel, Basins 6A and 68 together ("Basin 6") encompass approximately 58.58 acres and include the backbone drainage systems within West McIntyre Street (west of the School), West Enid Drive and Harbor Drive with connections to three (3) existing outfalls (the "Basin 6 Outfalls") discharging into Hurricane Harbor - being O utfall No.'s 12, 14 and 15. The three existing outfalls are small diameter pipes, being 18- inch, 30-inch, and 12-inch respectively. Further, they are situated within limited, side-lot drainage easements; the physical width of the side-lot easements for Outfalls 12 and 14 are uncertain and can only be assum ed at this time. The potential for improvement of these two outfalls is also uncertain. Figure 11 provides a detailed view of the existing stormwater network within the study area. Figure 11, K-8 School Project Existing Storm Sewer Network 2.2 Stormwater Planning Criteria Storm w ater m anagement systems m ust adhere to mandated water quality and quantity criteria set forth by various local, state, and federal agencies with jurisdiction within the State of Florida. As determined by these agencies, it m ay be necessary for existing systems when rehabilitated or retrofitted to comply with all regulatory requirements irrespective of the pre-existing conditions. The improvements that the Village will undertake will comply with the applicable regulatory requirements, codes, ordinances, and criteria. The Florida Air and Water Pollution Contro l Act, Chapter 403 sub-section 403.0891 of the Florida Statutes, authorizes the South Florida Water M anagement District (SFWM D) to develop and maintain a Stormwater M anagement Program. The SFWM D has delegated this authority to Miami-Dade County. This Stormwater M aster Plan Update is a component of the Stormwater Management Program and is consistent with the requirements set forth in Chapters 62-40 and 62-43 of the Florida Administrative Code (F.A.C.), EPA National Pollutant Discharge Elimination System (NPDES) requirements, SFWM D rules, Chapter 24 of the M iami-Dade County Code, and the Miami-Dade County Comprehensive Development Master Plan prepared pursuant to the requirements of Chapter 163 of the Florida Statutes. Prep ared for: V illage of Key Biscayne AECOM 21 K-8 Ba sin Ba sis of D e sign R eport (B O D R ) Village of Key Biscayne AECOM Project No.: 60690913 A dditionally, m itigation of quantity and quality im pacts to Biscayne Bay, which is designated as a State A quatic Preserv e and regulated according to Florida Statute 258.397, are authorized through Chapter 24 of the M iam i-D ade C ounty code. D ue to the coastal location of the V illage, jurisdiction for storm w ater m anagement ext ends across Federal, State and local agency criteria that m ust be followed. Depending on the complexity, ext ent and impact to inla nd and coastal/enviro nm ental resources, each design im pro vement will generate its own respective specific set of requirem ents. The fo llow ing agencies are expected to be involved with pro posed design im provem ents: 1) Florida Departm ent of Environm ental Pro tection ("FD EP") 2) Florida Departm ent of Transportation ("FOOT") 3) South Florida Water M anagem ent D istrict ("SFWM D ") 4) M iam i-D ade Departm ent of R egulatory and Econom ic Resources ("DRER") 5) Florida Fish and Wi ldlife C onserv ation C omm ission ("FF W CC") 6) U nited States A rm y C orps of Engineers ("USAGE") 7) U nited States Fish and Wi ldlife Serv ice ("USFW S") 8) U nited States Coast G uard ("U SC G ") 9) V illage of Key Biscayne Public W orks D epartment ("PW D") 10 ) V illage of Key Biscayne Building D epartment Water quality regulatory requirem ents govern the release of pollutants into water resources, including surface w ater and ground w ater. Wi thin the Village of Key Biscayne, the FDEP, SFWM D and DRER have jurisdiction over storm w ater quality criteria. All proposed stormw ater infrastructure systems to be constructed in response to defici encies and inadequacies w ithin the Village shall be designed and permitted to com ply w ith the relevant requirem ents. Waters of the Biscayne Bay A quatic Preserv e and Biscayne National Park are classified as Outstanding F lo rida Waters (O FW s), and as such are subject to special criteria. • A n O utstanding Florida Water, (O FW), is a w ater designated as such due to its natural attributes and im port ance. This special designation is applied to those water bodies to protect existing good w ater quality. M ost OFW s are areas m anaged by the state or federal govern ment. • System s discharging to a waterbody that has been identified as im paired by FDEP pursuant to 403.067, F.S ., or to an O utstanding Florida Water, shall be designed in accordance with the pro cedures established by the SFWM D . Specifically, systems which have a direct discharge to an O FW , m ust pro vide an additional fifty percent (50%) of the required water quality treatment. 2.3 Development of Alternative Scenarios D eveloping a storm w ater m anagem ent system for the Pro ject as a stand-alone project, which is to be designed in concert w ith how ever, constructed in advance of, the storm w ater infrastructure improvements w hich w ill be put fo rt h in the V illage-w ide SWM P presented a significant challenge. The Project m ay ultim ately require a connection to such altern ate "ext ra-neighborhood" discharge locations and capabilities w hich are not presently available in the K-8 School Project basin due to a lack of drainage easements. This com plicates the evaluation of the various design altern atives and presents a unique set of challenges. In February 2022, the V illage C ouncil adopted a roadway Level of Service (LOS) which includes a requirem ent to "keep ro ads passable" and allows for ponding to depths of 0-0.5 feet within swales for a m axim um duration of 6-12 hours. The design storm as adopted by the Village consists of a 10 -year recurrence, 24-hour duration storm event w ith a total rainfall of eight (8) inches in the vicinity of the Village. Prep ared fo r: V illage of K ey Biscayne AECOM 22 K-8 Basin Basis of Design Report (BO OR) Village of Key Biscayne AECOM Project No.: 60690913 The topography of the Village (in particular the elevation of the existing roadways), the stormwater level of serv ice adopted by the Village and the adoption of the NOAA intermediate-high sea level rise projection as the basis for determining the sea-level boundary conditions for use in design and planning of stormwater infrastructure impro vements for the Village through the 2060 planning horizon, led the AECOM team to focus on improvement projects to realize near-term benefits where possible and the development of a storm w ater m anagement system which pro vides adaptable solutions and strategies as the infrastructure im provements are implemented incrementally over time. Wh ile some of the ideas to be presented are unique in the approach to adaptation to sea level rise (SLR), others are not, including the universally recognized need to m ove away fro m a reliance on gravity-fed discharge to a mechanical, pump-based system to ensure the discharge capacity necessary to meet the drainage level of service. To avoid the "one size fits all scenario" and resulting issues with harmonization with adjacent private properties, and to provide the Village m aximum flexibility in the development of an adaptation and resiliency strategy to m itigate for the projected SLR, a strategy was developed to allow for incremental and scalable pro ject solutions. Wh ile the m ajor undergro und infrastructure would be installed with the initial project, this concept allows for an initial road raising within each zone project to a target elevation and subsequent increm ental raising of the roadway infrastructure over time. For the K-8 School Project the initial road raising is expected to be a m inimum of 6-inches, or that which is necessary to achieve a minimum road cro wn elevation of 2.33 feet, NAVO. An example incremental road raising would be a 2-inch lift of asphalt and corresponding adjustments to m anhole rims and inlet grates every 10-years, or as SLR dictates. The intent being that the incremental changes to landscaping and greenspace areas will allow for mature tree canopies to adapt and adjust to the changing surface and groundwater elevations which will occur over tim e. To fa cilitate adaptable and incremental solutions, the stage-storage component attributable to the public road rights-of-way within the Village has been removed from the proposed conditions stormwater model. The benefit of this m odeling technique is that the Village can implement improvements within the rights-of­ way in areas of deficient levels of service without affecting the results predicted by the proposed conditions storm w ater m odels and allowing for near-term localized solutions while the overall SWMP is implemented. The detrimental effect of this m odeling technique is that, in the absence of offline storage such as storm w ater ponds or detention areas, the storage component within the public road rights-of-way is often the lowest lying lands "seen" by the stormwater model, and therefore the first level that storage is available to the m odel to calculate the volumes and subsequent surface elevation of accumulated stormwater runoff. Wi th the removal of this storage component, once the model calculates a flood stage above the lowest inlet in the collection system, the above grade surface water stages predicted by the model can rise abruptly, and to a degree, the reported results are disproportionately high and it is to be expected that the results of the m odel will predict that several (to many) of the individual drainage sub-basins with low-lying roadways will fail level of service as defined by any amount of flooding occurring on the roadway. By default, depth and duration of roadway inundation becomes a function of pumping capacity. As discussed in Section 2. 1. 8, Project Study Area, the School property adds approximately 17 .63 acres to the contributory drainage area to the Basin 6 Outfalls as herein defined. The additional acreage represents a 30% increase in the size of the existing conditions model Basin 6 area, which thereby introduces additional storm w ater runoff into the existing drainage collection and conveyance system and ultimately to the Basin 6 O utfalls. It being understood, and as reflected in the results of the existing conditions model, that the existing collection and conveyance system and outfalls are undersized and deficient in meeting the desired level of service based on the existing drainage basin acreage and drainage infrastructure. To evaluate the proposed stand-alone Pro ject stormwater management system given the constraints discussed above, the AECO M team borrowed against prior work done for the Village related to the evaluation of existing outfalls and potential enhancements to the Village-wide discharge capabilities being evaluated concurrently with the m aster SWM P update. AEC O M developed six (6) design concepts to evaluate the options and effectiveness of a stormwater management system to serve the Project basin. As a base, all scenarios for the stand-alone Project include the follow ing: • An initial ro ad raising that is expected to be a minimum of 6-inches, or that which is necessary to achieve a m inimum road crown elevation of 2.33 feet, NAVO. Prepared for: Village of Key Biscayne AECOM 23 K -8 Ba sin Ba sis of D esign R eport (B O O R ) Village of Key Biscayne AECOM Pro ject No.: 60690913 • Identical storm w ater collection and conveyance system pipe sizing and locations. As this report is written, and in the initial phase of design development, to limit the hydraulic grade line between the School and the pump station, the trunkline or backbone of the stormwater collection and conveyance system ext ending fro m the eastern boundary of the School property and west to the pump station location and located within West McIntyre Street, Ridgewood Road and West Enid Drive contains step-wise increases in size from 48-inch, to 60-inch, and ultimately 72-inch diameter pipes, along with inlets, manholes and appurtenant structures. The systems within West McIntyre Street and W est Enid Drive are interconnected at Ridgewood and Glenridge Drives with a 48-inch pipe, and at Satinw ood Drive with a 60-inch pipe, and at the pump station via a 72 -inch pipe located within the Harbor Drive Park. However, these pipes should be considered to represent the "worst­ case" scenario, as refinement to the pipe sizes may be possible based on the ultimate pump station capacity and the extent to which ro adways within the Project area may be raised coincident with the final Project design. The details of the proposed stormwater basin layout and collection and conveyance system are discussed in more detail in Section 2.4, Proposed Drainage System. • Installation of a storm water pumping station to be located within Harbor Drive Park situated adjacent to, and east of the intersections of W. McIntyre Street and W est Enid Drive with Harbor Drive. This neighborhood pumping station is to be designed to utilize, to the extent practicable, the current and/or potential capacity of the Basin 6 Outfalls and have the reserve capacity and ability to connect, and pump, to a centrally located re-pumping station ("repump") and ultimately to an altern ative outfall - the location of which is being developed as part of the Village-wide SWM P. • The "design storm", which is defined and discussed in Section 2.5.1, Design Storm Hydrology and Routing. Discussion of the design storm is a worthy topic as a part of the Development of Modeling Scenarios to present a few facts, figures and values which are not inherent in the model results and reports. Wh ile this description is somewhat lengthy, it should prove beneficial in informing decisions which will need to be made regarding the overall capacity of the pumping station, levels of service as they relate to short-duration flooding of existing roads, the potential and/or need to perform roadway raising, and the trickle-down impacts to the size (and ultimately costs) of the necessary collection and conveyance systems. The design storm as adopted by the Village consists of a 10-year recurrence, 24-hour duration storm event with a total rainfall of eight (8) inches in the vicinity of the Village. As defined, such a storm has a ten percent (10 %) probability of occurring at a given location in any given year. It is a statistical average which is not synchronized to any point of beginning. A storm of a magnitude appro ximating the "design storm" can occur in any given year, more than once each year, and in the event of a close encounter with a major tropical weather system, any spin-off storm could easily generate rainfall amounts equal to or exceeding design storm values. Beyond total rainfall there is another component to the stormwater model, which is often overlooked, however, has m erit in the discussion of stormwater retrofits of low-lying, nearly to fully built out communities which are also having to deal with SLR (i.e., the Village). That is the rainfall distribution, or the pattern of rainfall over the duration of the design storm event. For coastal communities - particularly in South Florida - a rainfall distribution in which an intense period of rainfall is embedded is appropriate. For the Village-wide SWM P and the K-8 School Project, the USDA Natural Resources Conservation Service (NRCS) Type Ill Modified, rainfall distribution has been selected with a peaking factor of 150 to provide the best model simulation for high intensity rainfall events over relatively flat terrain. Inputs to the stormwater model are: 1) the total rainfall, 2) the rainfall distribution, 3) the runoff peaking factor, 4) the impervious surface coverage, 5) the relationship to the groundwater table, and 6) an estimate of the time it takes for a drop of rain to enter the stormwater collection system (known as the time of concentration). P rep ared for: V illage of K ey Biscayne AECOM 24 K-8 Basin Ba sis of D esig n R eport (B O O R ) Village of Key Biscayne AECOM Project No.: 60690913 Together, the m odel uses these inputs to generate a time sequence of the percentage of rainfall occurring and the subsequent surface water runoff for a designated time interval and distributes the rainfall and runoff from Hour "O" to Hour "24". After the rainfall ceases, the model continues the simulation until all the water which fell over the duration of the design storm has been collected and discharged. The peak rainfall intensity in the storm "simulation" occurs during the 12th hour, with the peak volume of runoff generated betw een hours 11.5 to 12. 5. For the K-8 Pro ject Basin, the Design Storm Peak Hour Runoff Rate ("DSPRR") is calculated to be approximately 247.2 cubic feet per second (cfs) or 3.24 cfs per acre, per hour {"cfs/ac/hr"), or 3.22 inches per acre, per hour. This is a significant volume of water (40% of the total design storm rainfa ll) occurring over a very short period. This is exacerbated by the intentional removal of storage from the public ro ad rights-of-way and the limited amount of useable ("seen" by the model) surface storage with the Pro ject Basin lying below the existing crown of road elevations. The result of which is: that any rate of model predicted stormwater runoff greater than the installed capacity of the collection system and pump station will rapidly manifest as surface waters, and the greater the deficit, the m ore quickly the elevation of the peak "flood" stage will increase. Based on the preceding discussion, and it being understood that any predicted "flood" elevation which would jeopardize any existing structure as unacceptable, given the intentional removal of roadway storage, it is to be expected that the results of the model will predict that several (to many) of the individual drainage sub-basins with low-lying roadways will fail level of service as defined by the existing cro wn of ro ad. In developing the scenarios discussed below, it is anticipated that a minimum pumping rate approximating the value of the DSPRR (3.24 cfs/ac/hr) will be necessary to meet the level of service fo r the Project. The salient point of this discussion is that magnitude of the required pumping rate which represents 40% of the total design storm rainfall (more than 3-inches per acre per hour) is a stro ng indication that "flood" elevations predicted by the stormwater model which indicate that roadw ays would be inundated above the existing crown of road should indeed be of short-duration. In the event there is a specific need to focus on specific areas as it relates to depth and duration of "flooding", the storm water m odel can generate that information for further discussion. In addition to the need to collect, convey and "lift" the water to the point of discharge via stormwater pumps, each of the scenarios have in common: • The need to evaluate the existing outfalls to determine: o the existing rate of discharge from the project study area - more particularly, the velocity of the existing discharges as it relates to the benthic environment in the vicinity of the outfall locations, and o the opportunities and limitations of improving the existing discharge culverts within the existing drainage easements while minimizing the impacts to the adjacent residents and the benthic environment. It is important to note that a benthic survey in the areas of the Basin 6 Outfalls is planned but has yet to be performed because it can only be conducted at certain times of the year. As such, the potential fo r further development or enhancement of the discharge pipes at the Basin 6 Outfalls is unclear. Therefore, the appro ach being taken is that, if the velocity of the proposed discharge at each of the three (3) outfall locations is equal to, or less than, the existing discharge velocity as predicted by the existing conditions m odel, or that which could cause erosion and scour, then any potential impact to the benthic enviro nment would be minimized, if not eliminated. The results of the benthic survey will be useful for the final design phase, as the potential enhancement of the Basin 6 Outfalls discussed in the scenarios below are further explored and evaluated. Also of note, in all envisioned scenarios, the existing outfalls would remain in some form. They could/would be cleaned and lined, replaced, upsized, and/or if not utilized for "discharge" fitted on the upstream end with an inlet with an appropriate rim elevation to provide a gravity-fed emergency overflow structure for the Project basin in the event of a mechanical failure. Prepared for: V illage of K ey Biscayne AECOM 25 K-8 Basin Basis of Design Report (BOOR) Village of Key Biscayne AECOM Project No.: 60690913 Absent the ability to install conventional stormwater best management practices which would attenuate a portion of the peak stormwater runoff, the differences between the scenarios essentially comes down to the amount of discharge available within the K-8 School basin, or that which can ultimately be made available to the K-8 School basin either by obtaining additional drainage easements within the basin, or interconnection to an as yet to be determined "extra-neighborhood" outfall to be developed with the Village­ wide SWM P. Scenarios 5 and 6 were developed to determine what would be necessary to develop adequate discharge capacity within the K-8 School Project basin, to reduce, if not eliminate reliance on future "extra­ neighborhood" improvements to be constructed as part of the Village-wide SWM P - and as such the results do not reflect any reliance on additional out of basin discharge and are based on local discharge capacity only. These scenarios envision the Village obtaining additional or enhanced drainage easements along the side lot lines and a "T" or "L" shaped easement configuration along the waterfront allowing for the installation of a larger side-lot line discharge pipe and the reconstruction of a seawall(s) incorporating both energy dissipation and increased capacity for the pump discharge. The development of these scenarios was somewhat subjective and were based on the best available information for the K-8 School basin, and prior experience with the design and permitting of energy dissipation and discharge structures for pumped systems. As such, the results of these scenarios should be considered reasonable parameters to evaluate what can be achieved locally, but not absolute values. 2.3.1 Scenario 1 Scenario 1 maintains or rehabilitates existing outfalls with a connection to the pumping station with provisions to regulate flows such that the existing peak discharge velocity within each outfall pipe (as calculated from the results of the existing conditions model) is limited to less than, or equal to the "existing velocity" to minimize disturbance to the benthic environment. In addition, this scenario provides additional baseline data which is helpful in the evaluation of the subsequent scenarios. Total pumping capacity and per acre discharge rates for this scenario are presented in Section 2. 6, Summary and Results. 2.3.2 Scenario 2 Scenario 2 maximizes the pipe carrying capacity inherent to the assumed width of each existing drainage easement for the Basin 6 Outfalls. This scenario assumes the installation of the largest possible pipe within each easement which are then connected to the pumping station with provisions to regulate flows such that the existing discharge velocity within each outfall pipe is limited to less than, or equal to the "existing velocity" to minimize disturbance to the benthic environment. The calculated maximum capacity of the rehabilitated outfalls was determined to be approximately 47.7 cfs. This solution provides a "partial solution" to the overall needs of the Project drainage basin. However, in the absence of some other resolution to the discharge limitations imposed by the capacity of the Basin 6 Outfalls, which are unknown at the time this analysis is being performed, this scenario most likely represents the predicted "near-term" performance of the K-8 School stormwater management system. Near-term being defined as, until such time as the Village-wide SWM P improvements are constructed and operational. Total pumping capacity and per acre discharge rates for this scenario are presented in Section 2. 6, Summary and Results. A discussion on the maximum capacity of the existing outfall is contained in Section 2.4.4, Rehabilitation of Existing Outfalls. 2.3.3 Scenario 3 Scenario 3 builds upon the results of Scenario 2 in which the pipe carrying capacity inherent to the width of each existing drainage easement for the Basin 6 Outfalls is maximized and connected to the pumping station with provisions to regulate flows such that the existing discharge velocity within each outfall pipe is limited to less than, or equal to the "existing velocity" to minimize disturbance to the benthic environment. This discharge component is then combined with the reserve capacity within the proposed pump station to provide an additional volume of discharge to an "extra-neighborhood" alternative discharge location to be developed and implemented as a part of the Village-wide SWM P. The DSPRR, as herein defined, is approximately 247.2 cfs. Prepared for: Village of Key Biscayne AECOM 26 K -8 Ba sin Ba sis of D e sig n R e port (B O D R ) Village of Key Biscayne AE C O M Pro ject No .. 60690913 For this scenario, the difference betw een the DSPRR and the improved discharge capacity of the Basin 6 O utfalls as described in Scenario 2 (199.5 cfs) forms the basis of the reserve capacity of the proposed pum ping station. Total pum ping capacity and per acre discharge rates for this scenario are presented in Section 2. 6, Summary and Results. 2.3.4 Scenario 4 Scenario 4 builds upon the results of both Scenarios 2 and 3 in which the pipe carrying capacity inherent to the width of each existing drainage easement for the Basin 6 Outfalls is m aximized and connected to the pum ping station with pro visions to regulate flows such that the existing discharge velocity within each outfall pipe is lim ited to less than, or equal to the "existing velocity" to m inimize disturbance to the benthic enviro nm ent. This discharge component is then combined with the reserve capacity within the proposed pump station to provide an additional volum e of discharge to an "ext ra-neighborhood" altern ative discharge location to be developed and im plemented as a part of the Vi llage-w ide SWM P. In this scenario, the reserve capacity of the pump station w as then adjusted as necessary to produce m odel results which meet the level of service standard of zero flooding above the existing cro w n of road in any sub-basin. This results in a combined pum ping rate of 275.7 cfs fo r the Project basin. Total pumping capacity and per acre discharge rates for this scenario are presented in Section 2. 6, Summary and Results. 2.3.5 Scenario 5 Scenario 5 is a variant building on both Scenarios 2 and 3 in which the Village, thro ugh community outreach to the affected landowners, can secure additional drainage easement(s) width along the side lot lines, and/or in a "T" or "L" shaped configuration along the waterfront allowing for the potential to install a larger side-lot discharge pipe and construction of a seaw all which will include both discharge and energy dissipation components within the newly secured easement. The proposed benefit to the landowner in exchange fo r the easement(s) is that the Village would reconstruct the landowner's seawall as part of the Pro ject. This scenario is not without practical limitations including the seawall configuration, the size of the pipe which can be placed in the side-lot easement, and the velocity of flows within the discharge piping which affects the amount of energy dissipation required - which in turn impacts the "effective discharge length" of the reconstructed seawall. These limitations, while anticipated, are yet indeterminate so an exact determ ination of the increase in the discharge rate that a scenario of this construct could/would provide is unknow able at this time. To conservatively develop this scenario, it was assumed that the discharge pipe within Outfall #15 (which has a known easement) could be up-sized to a m inimum diameter 48-inch conduit (with an aggressive discharge velocity of 13.4 fps). Further, it was envisioned in this scenario that a seawall with an "effective discharge length" of at least seventy (70) feet to provide the necessary energy dissipation could be constructed - and provide 168 cfs discharge capacity at a reduced velocity of approximately 1.25 fps. Further it was assumed that Outfall N o.'s 12 & 14 w ould also be enhanced as discussed in Scenario 2 - m aking the total combined discharge directed to the Basin 6 Outfalls and Hurricane Harbor equal to 193.1 cfs (or appro ximately 54.1 cfs lower than the D SPRR). Wh ile ultimately, and as desired, this scenario could still rely on additional discharge to an "extra­ neighborhood" altern ative discharge location to fully m eet the level of service requirements, the results fo r this scenario as presented below assum e that discharge occurs only to the Basin 6 Outfalls, as a baseline to see w hat could be possible within the local neighborhood and to reduce reliance on the "extra­ neighborhood" altern ative discharge location. Total pumping capacity and per acre discharge rates for this scenario are presented in Section 2. 6, Summary and Results. P re pa red for: V illa ge of Key Biscayne AECO M 27 K-8 Ba sin Ba sis of Design R eport (B O O R ) Village of Key Biscayne AECOM Project No .. 60690913 2.3.6 Scenario 6 Scenario 6 is a variant building on Scenarios 2 and 5 in which it is assumed the Village can secure additional drainage easement(s) width along the side lot lines, and/or in a "T" or "L" shaped configuration allowing for the potential to install a larger side-lot discharge pipe and a reconstructed seawall(s) which will include energy dissipation for the pumped discharge within the newly secured easement(s). This scenario is subject to the same practical limitations as Scenario 5. These limitations, while anticipated, are yet indeterminate so an exact determination of the increase in the discharge rate that a scenario of this construct could/would provide is unknowable at this time. To conservatively develop this scenario, it was assumed that discharge pipes in both Outfall No.'s 12 & 15 (which are the closest to the pump station location) could be up-sized to a minimum 36 and 48-inch diameter conduits, respectively (with a slightly less aggressive discharge velocity of 12.6 fps), and that a seawall with the necessary "effective discharge lengths" capable of providing minimum, combined 247.2 cfs discharge capacity coupled with the necessary energy dissipation could be constructed. Further it was assumed that Outfall No. 14 would also be enhanced as discussed in Scenario 2 - making the total combined discharge directed to the Basin 6 Outfalls and Hurricane Harbor equal to 261 cfs (or approximately 13.8 cfs greater than the DSPRR). C onsistent w ith Scenario 5, the results for this sc enario, as presented below, assum e that discharge occurs only to the Basin 6 Outfalls as a baseline to see what could be possible within the local neighborhood to reduce reliance on the "extra­ neighborhood" alternative discharge location. This scenario is not without its unknowns and relies heavily on the goodwill of a handful of the Village residents, however, it merits further evaluation for its potential. Total pumping capacity and per acre discharge rates for this scenario are presented in Section 2. 6, Summary and Results. 2.3.7 Additional Possible Scenarios Wh ile not evaluated as a part of the scope of the K-8 School Project, the cost-benefit of rehabilitating and/or improving existing neighborhood outfall locations versus the cost of developing larger "extra-neighborhood" alternative discharge locations to be developed and implemented as a part of the Village-wide SWMP should be developed. In such a scenario, the neighborhood pump stations would be sized with sufficient capacity to pump the DSPRR (similar to Scenario 3) which may still reflect some short-term roadway inundation, or likewise design the pumps to have sufficient capacity to pump in excess of the DSPRV to ensure all roads meet the level of service (similar to Scenario 4). To evaluate this scenario fully, the p ercen tag e of req uired level of service discharge volum e by basin attributable to the neighborhood ou tfalls w ould need to be calculated along w ith the costs associated with the im provem ents necessary to fully utilize the local discharge to the m axim um extent practicable, and a m etric develop ed to com p are those costs/unit volum e against the costs necessary to increm entally increase the Villag e-w id e altern ative locations being proposed with the Vi llage-w ide SWMP. Total pumping capacity and per acre discharge rates for this scenario were not calculated but are expected to be similar to those presented for Scenarios 3 and 4. In this alternative scenario, the existing local outfalls would be rehabilitated and converted to emergency overflow structures to provide a gravity-fed emergency overflow structure for the basin in the event of a mechanical failure. 2.3.8 Scenarios Summary To summarize, the scenarios build upon each other as follows: • Scenario 1: Utilize Existing Outfalls o Maintains existing outfalls and sizes, o Includes pump station of capacity equal to perm issible discharge rate, and o Discharge rate varies at each outfall location such that proposed flows do not exceed existing outfall velocity. Prep ared for: V illage of K ey Biscayne AECOM 28 K-8 Ba sin Ba sis of D e sign R eport (B O O R ) Village of Key Biscayne AECOM Project No.: 60690913 • Scenario 2: Rehabilitate and Improve Existing Outfall Locations o Install largest diameter pipe possible within the available easements, o Includes pump station of capacity equal to permissible discharge rate, and o Discharge rate varies at each outfall location such that proposed flows do not exceed existing outfall velocity. • Scenario 3: Rehabilitate and Improve Existing Outfalls. Install Reserve Capacity for Repump to Central Facility o Rehabilitates outfalls consistent with Scenario 2, o Includes m inimum pump station capacity equal to the DSPRR, o Discharge occurs to rehabilitated outfalls at permissible rates, and o An additional force m ain installed and pumps sized to repump significant excess runoff to centralized facility. • Scenario 4: Rehabilitate and Improve Existing Outfalls. Increased Reserve Capacity for Repump to Central Facility o Rehabilitates outfalls consistent with Scenario 2, o Includes m inimum pump station capacity exceeding the DSPRR, and sufficient to fully meet roadw ay LO S, o Discharge occurs to rehabilitated local outfalls at permissible rates, and o An additional force m ain installed and pumps sized to repump significant excess runoff to centralized facility. • Scenario 5: Rehabilitate Two Existing Outfalls and Constructs One New Outfall. Reduced Reserve Capacity for Repump to Central Facility o Rehabilitates outfall no. 's 12 and 14 consistent with Scenario 2, o Im pro ves outfall #15 discharge easements and includes a reconstructed seawall with an energy dissipater/discharge structure of approximately BO-feet in length. o Includes minimum pump station capacity equal to the DSPRR, o Discharge occurs to rehabilitated outfalls 12 and 14 at permissible rates, o Discharge to outfall 15 occurs at approximately 168 cfs at a discharge rate of 1.25 fps and, o As desired, an additional force main installed and pumps sized to repump greatly reduced excess runoff to centralized facility. • Scenario 6: Rehabilitate One Existing Outfall and Constructs Two New Outfalls. No Repump to Central Facility (Potential for excess capacity within the Project Basin) o Rehabilitates outfall #14 consistent with Scenario 2, o Impro ves outfall no.'s 12 and 15 discharge easements and at each location includes a reconstructed seawall with an energy dissipater/discharge structure of not less than 60- feet in length. o Includes minimum pump station capacity exceeding the DSPRR, o Discharge occurs to rehabilitated outfall #14 at permissible rates, o Discharge to outfall no. 's 12 and 15 occurs at a minimum rate of approximately the DSPRR (247.2 cfs) at a discharge rate of 1.25 fps, and, o Pumps sized for local discharge only - NO REPUMP o Configuration could also be one larger seawall with energy dissipation/discharge centered on either of the existing easement locations. P repared for: V illage of K ey Biscayne AECOM 29 K -8 Ba sin B asis of D esign R eport (B O O R ) Village of Key Biscayne AECOM Project No.: 60690913 The results of the proposed stormwater modelling for each of the scenarios discussed above are presented in Section 2. 6, Summary and Results. Table 1 shows the discharge rate simulated for each scenario, and the percentage of the overall required discharge provided by the local, Basin 6 outfalls. Table 1, K-8 School Basin Discharge Rates by Scenario K-8 School Project - Discharge Rates by Scenario Scenario Existing 1 2 3 4 5 6 Pum ping Rate (cfs) -0- 13.3 47.7 247.2 275.7 193.1 260.8 R e-Pum p R ate (cts) -0- -0- -0- 199.5 228.0 -0- -0- CFS/Ac/H r -0- 0.2 0.6 3.2 3.6 2.5 3.4 Inches/Ac/H r -0- 0.2 0.6 3.2 3.6 2.5 3.4 K -8 School Project - % of Total Discharge to Basin 6 Outfalls by Scenario Basin 6 Di scharge (cfs) 13.3 13.3 47.7 47.7 47.7 193.1 260.8 % Di scharge to Basin 6 O utfalls 100.0 100.0 100.0 19.0 17.3 100.0 100.0 N o tes: 1) Scenario 3 includes a re-pum p rate of 199.5 cfs. 2) Scenario 4 includes a re-pum p rate of 228.0 cfs. 3) Scenarios 5 & 6 rely excl usively on im proved Basin 6 Outfall structures with no re-pum ping included. 4) The K-8 School Project Area is 76.21 acres (9.7%) of the Village-w ide SW M P area of approximately 785.8 acres. 2.4 Proposed Drainage System The Village has adopted the NOAA intermediate-high sea level rise projection as the basis for determining the sea-level boundary conditions for use in design and planning of stormwater infrastructure improvements for the Village through the 2060 planning horizon to be used in conjunction with the 10-year / 24-hour design storm event as the acceptable drainage level of service for the Village. The drainage report details the stormwater management improvements proposed for the K-8 School Project as a stand-alone project, which is to be designed in concert with, but constructed in advance of, the stormwater infrastructure improvements which will be put forth in the Village-wide SWM P. The objective of the stormwater management system upgrades is to eliminate deficiencies in the existing system and effect the efficient collection and removal of stormwater runoff and to accommodate the increased demand of the system to address expected SLR. To provide the Village maximum flexibility in the development of an adaptation and resiliency strategy to mitigate for the projected SLR, the development of a SWM P for the K-8 School Project needs to provide adaptable solutions and strategies as the infrastructure improvements are implemented over time. However, given the low-lying topography and anticipated high groundwater conditions, the relatively slow rate of resilient redevelopment within the largely built-out Village, the undersized and largely non­ interconnected drainage system, and the limited number and size of potential discharge locations, there was a universally recognized need to move away from a reliance on gravity-fed discharge to a mechanical, pump-based system to ensure the discharge capacity necessary to meet the drainage level of service. More catch basins have been added to improve runoff collection from streets, drainage pipes and trunk lines have been upsized to increase the capacity and efficiency of the drainage networks, and to increase overall system reliability. The SWM P envisions the interconnection of the drainage systems within individual drainage basins to the extent practicable. The proposed water management system is designed to discharge at the predicted tailwater stages during high tide events and inclusive of the anticipated SLR. Prepa red for: V illa ge of K ey Biscayne AECOM 30 K-8 Basin Basis of Design Report (BO OR) Village of Key Biscayne AECOM Project No.: 60690913 O ne of the strategies implemented thro ughout the preparation of this report is that the stage-storage component attributable to the public road rights-of-way within the Village have been removed from the proposed conditions storm water m odel. The benefit of this modeling technique is that the Village can im plement 1) incremental, 2) scalable, and 3) adaptable improvements within the rights-of-way in areas of deficient levels of service without affecting the results predicted by the proposed conditions stormwater m odels and allowing for near-term localized solutions while the overall SWM P is implemented. Wh ile the m ajor underground infrastructure would be installed with the initial project, this concept allows for an initial road raising within each zone project to a target elevation and subsequent incremental raising of the ro adway infrastructure over time. For the K-8 School Project, the initial road raising is expected to be a minimum of 6-inches, or that which is necessary to achieve a minimum road crown elevation of 2.33 feet, NAVO - m aking the low edge of pavement 2.13. The roadway would be reconstructed with black base providing added structural support given the expected high groundwater conditions. It is envisioned that over time, the roadway would be over-built using three (3) 2-inch lifts of asphalt and corresponding adjustments to m anhole rims and inlet grates every 10-years, or as SLR dictates. Ultimately the combination of initial and incremental road raising will result in roadways with a minimum low edge of pavement at, or above 2.63 feet, NAVO - the target 2060 SLR projection. The intent being that the incremental changes to landscaping and greenspace areas will allow for mature tree canopies to adapt and adjust to the changing surface and groundwater elevations which will occur over tim e. 2.4.1 K-8 School Project Stormwater Collection and Conveyance Improvements As discussed in Section 2. 3, Development of Altern ative Scenarios, identical stormwater collection and conveyance system pipe sizing and locations were utilized in the development of each of the model scenarios. In the initial phase of design development and to limit the hydraulic grade line between the School and the pro posed Harbor Drive Park pump station, the trunkline or backbone stormwater collection and conveyance system ext ending from the easterly boundary of the School property and west to the pump station location and located within West M cIntyre Street and West Enid Drive contains step-wise increases in size from 48- inch to ultimately 72 -inch diameter pipes, along with north/south interconnecting pipes, inlets, manholes and appurtenant structures. However, these pipes should be considered to represent the "worst-case" scenario, as refinement to the pipe sizes may be possible based on the ultimate pump station capacity and the extent to which roadways within the Project area may be raised coincident with the final Project design. As show n on the Figure 12 , Pro posed K-8 Project Stormwater Collection System, the AECOM K-8 Basin design proposes to: • Replace the storm water collection and conveyance system within West McIntyre Street north of the School from G lenridge Road to Ridgewood Road, along Ridgewood Road and continuing westerly on West M cI ntyre Street to Harbor Drive Park - consisting of pipes increasing in size from 48- inches to 72-inches, • Replace the stormwater collection and conveyance system within W est Enid Drive south of the School from G lenridge Road to Ridgewood Road, along Ridgewood Road and continuing westerly on W est Enid Drive to Harbor Drive Park - consisting of pipes increasing in size from 48-inches to 72 -inches, • Construct/Replace the north/south interconnection pipes within Ridgewood and Glenridge Drives consisting of a 48-inch pipe, • Construct a north/south interconnection pipe within Satinwood Drive consisting of a 60-inch pipe, • Install a 72 -inch pipe within Harbor Drive Park connecting both West McIntyre Street and West Enid Drive to the proposed Harbor Drive Park pump station, and Prepared for: Village of Key Biscayne AECOM 31 K -8 Ba sin B asis of De sign Report (B O O R ) Village of Key Biscayne AECOM Pro ject No .. 60690913 • Constructing a discharge force main of varying size both north and south within Harbor Drive to the existing Basin 6 outfalls located along West Matheson Drive (#14), Harbor Drive (#15) and Sunset Circle (#12) and extending a forcemain from Harbor Drive easterly within West McIntyre Steet to a yet to be determined terminal point in the vicinity of Glenridge Road. This section of the force main is anticipated to be connected to a re-pump facility the location of which will be determined with the development of the Village-wide SWM P. + AS'COM Key Biscayne Village of Key Biscayne Conceptual Storm Sewer Layout Legend 0 P\.tmpStnllon --• .... • Forool'lla!n D Vllage ol Key 8iS(.8yrnt Sub-8Hln Boundary Figure 12, Proposed K-8 Project Stormwater Collection System 2.4.2 Stormwater Pump Station A stormwater pumping station will be constructed within the Harbor Drive Park situated adjacent to, and east of the intersections of W. McIntyre Street and West Enid Drive with Harbor Drive. This neighborhood pumping station is to be designed to utilize, to the extent practicable, the current and/or potential capacity of the Basin 6 Outfalls and have the reserve capacity and ability to connect, and pump, to a centrally located re-pumping station ("repump") and ultimately to an alternative outfall - the location of which is being developed as part of the Village-wide SWM P. At a minimum, the stormwater pump station will be installed with a firm pumping capacity equal to, or greater than the DSPRR of 247.2 cfs (3.25 cfs/aclhr). The proposed pump station will contain five (5) or six (6) duty pumps and one (1) redundant pump for emergency use in the event of a mechanical failure of one of the duty pumps. A representative pump curve for the Harbor Drive Park pump station consisting of five (5) duty pumps is shown in Figure 13, . Based on the physical characteristics of the pumps anticipated, the station will have a total firm pumping capacity of approximately 111,000 gpm or 247.2 cfs (49.50 cfs/pump). The capacity of the redundant pump is not utilized in the stormwater model and is not reflected in the model results presented herein. The pumps will be designed such that the pumps will start sequentially based on water levels within the pump wetwell. In addition, the pumps will feature variable frequency drives ("VFD") such that the pump starts at a slow speed and ramps up to maximum capacity. P re pa red for: V illage of K ey Biscayne AECOM 32 K-8 Ba sin Ba sis of D esig n R eport (B O O R ) Village of Key Biscayne AECOM Project No.: 60690913 This feature allows the pump station to gradually increase in capacity as rainfall and runoff conditions dictate, and significantly reduces power consumption of the alternative "all or nothing" scenario. Pum ped discharge will be directed to the Hurricane Harbor via one (1) or more of the three (3) existing Basin 6 O utfalls in their impro ved conditions as discussed in more detail in Section 2.4.4, Rehabilitation of Existing Outfalls. Excess pump station capacity will be reserved for connection to a yet determined "extra­ neighborhood" altern ative discharge location - although the necessary force main will be constructed as part of the pro ject. K-8 School » Harbor Drive Park Pump Station System Performance Model A:COM 1,p.,mp;-1 /:: / ; jsPu~sl ' Pumps: 5 OperDlirig + 1 Stnndby Rating Point: 22,20 0 gpm @ 31. 7 ft Flygt- 70811765 3-990N4Axial Flow Pump +----~--+--~-------------~---'---~Mo tor: 6 Pole/200kW /985rp m (V FD) !<o.ooo !~~~; ~:::,!~; 1 5d<J~;m discharge diameter TO.OW J/J,000 00.1.lOO 70.000 RA TE OF Ft.OW, GPM /j0,000 -Syslom Cuwo -fP,,mp 30Hz -1Pump-35H1 -t-Pvmp4QHl -1Pump -45Hz -fP11mp -lPvmps -:JP11mps 4Pvmps -5Pump.s Figure 13, Harbor Drive Pump Station System Performance Model 2.4.3 Water Quality and Stormwater Treatment Units To pro vide water quality treatm ent for the pumped discharge, the proposed design includes the installation of tw o (2) hydrodynamic treatm ent devices as manufactured by Contech Engineering Solutions ("Contech"). AECO M worked with Contech to develop the design and configuration of the stormwater quality treatment units ("SWf Us") and develop the methodology behind how the SWf Us were to be incorporated into the storm w ater system and hydraulically modeled to accurately account for head losses induced into the system by the swr us. SWf Us will be installed within each trunkline directing stormwater to the pumping station. Each swr u will have a maximum treatment flow capacity of 63 cfs, for a total of 126 cfs maximum flow treatment capacity, prior to high level flows bypassing the treatment units. The contributing drainage area served by the Harbor Drive Park pump station is 76.21 acres made up largely of single-family homes on m edium sized lots. Considering the discharge is into Biscayne Bay, an OFW , an additional ½-inch of water quality treatment (or a total of 1.5-inches) of the "first flush" of storm w ater runoff is required. The SWf Us are sized to provide this "rate" of treatment over a period of one hour. The required water quality treatment rate for the drainage basin served by the pump station is 9.53 acre-feet, or 115.3 cfs (1.5-inches/hour). Therefore, the proposed treatment capacity of the SWf Us exceed the water quality requirements for the basin. Wh ile the SWf Us provide continuous treatment for all water passing through them, flows exceeding the m axim um treatment flow capacity will bypass the treatment unit. Prepa red for: V illage of Key Biscayne AECOM 33 K -8 Ba sin Ba sis of D e sig n R e port (B O D R ) Village of Key Biscayne AE C O M Project No.: 60690913 However, the VFD or "soft start" component and sequential starting of the individual pumps act to ensure that full m easure of required water quality treatment is achieved prior to the pump station reaching its m axim um capacity coinciding with the peak runoff from the design storm. In addition, the pump station will be equipped with trash racks to screen and prevent large debris fro m entering the pum ps and being discharged to into Biscayne Bay. 2.4.4 Rehabilitation of Existing Outfalls It is anticipated that all the existing outfalls would remain in some form. They could/would be cleaned and lined, replaced, upsized, and/or if not utilized for "discharge" fitted on the upstream end with an inlet with an appro priate rim elevation to provide a gravity-fed emergency overflow structure for Project basin in the event of m echanical failure. The K-8 Project design needs to further evaluate the existing outfalls to determine the opportunities and lim itations of im proving the existing discharge culverts within the existing, or enhanced, drainage easem ents while m inim izing the impacts to the adjacent residents and the benthic enviro nment. Wi th the uncertainty of the m aximum potential of the existing outfalls and in the conceptual design phase, the appro ach being taken is that: if the velocity of the proposed discharge at each of the three (3) outfall locations is equal to, or less than, the existing discharge velocity as predicted by the existing conditions m odel, or that w hich could cause erosion and scour, then any potential impact to the benthic enviro nment would be m inim ized, if not elim inated. As applicable, the Altern ative Scenario m odels m aximize the pipe carrying capacity inherent to the assumed width of each existing drainage easement for the Basin 6 Outfalls. These scenarios assume the installation of the largest possible pipe within each easement which are then connected to the pump station discharge force main with provisions to regulate flows such that the existing discharge velocity within each outfall pipe is lim ited to less than, or equal to the "existing velocity". The results of the Existing Conditions m odel are used to provide the technical parameters for the evaluation discussed above, and a baseline to evaluate the effectiveness of a given discharge scenario. However, as shown in Table 2, Basin 6 G ravity Outfalls Discharge Capacities, m aximizing the existing outfalls provides only a "partial solution" to the overall needs of the Pro ject drainage basin. Table 2, Basin 6 Gravity Outfalls Discharge Capacities K-8 School Project - Basin 6 Gravity Outfalls Easement Existing Existing Existing Maximum Maximum Basin 6 Outfall Size Velocity Diameter Discharge Diameter Discharge (feet) (fps)<3> (inches) (cfs)<1> (inches) (cfs)11> 0-14 10(2) 1.95 12 1.53 36 13.80 0-15 15 1.81 30 8.89 48 22.60 0-12 10<2) 1.60 18 2.82 36 11.30 TOTALS -/- -/- -/- 13.24 -/- 47.70 Notes: (1) cfs = cubic feet per second (2) Easement width assumed as there are no official records to document width (3) fps = feet per second O ther possibilities w hich require further evaluation in the K-8 Project design, and which depend heavily upon comm unity outreach and the goodwill of the affected landowners, would involve successfully securing additional drainage easement(s) width along the side lot lines, and/or in a 'T' or "L" shaped configuration along the w aterfront allow ing fo r the potential to install a larger side-lot discharge pipe and construction of a seawall which will include both discharge and energy dissipation components within the newly secured easem ent. The pro posed benefit to the landowner in exchange for the easement(s) is that the Village would reconstruct the landowner's seaw all as part of the Pro ject. P repa re d fo r: V illa ge of Key Biscayne AEC O M 34 K-8 Basin Basis of Design Report (BO OR) Village of Key Biscayne AECOM Project No.: 60690913 2.5 Stormwater Design Methodology AECO M with its partner, GIT Consulting, LLC developed and evaluated stormwater models for the "Existing Conditions" and proposed Altern ative Scenario improvements using the Advanced Interconnected Channel and Pond Routing version 4 ("ICPR 4") computer pro gram developed by Streamline Technologies, Inc. This softw are program is a FEMA-approved model that can dynamically analyze complex interconnected drainage systems over extended time periods. The K-8 Project model was created using the traditional ICPR 4 m odel one-dimensional ("1 D") model features. The AECO M team updated the Existing Conditions model and performed calibration scenarios using know n, recent storm events to verify the predicted performance of the existing system against both physical and anecdotal evidence to ensure the reliability of the model construct. The AECOM team then prepared the baseline m odel for the simulation and evaluation of the proposed Alternative Scenarios. As noted in Section 2.3, Development of Altern ative Scenarios, all model scenarios contain the same hydrologic and hydraulic input parameters. The ICPR 4 model utilizes LiDAR data, Geographic Information System ("GIS") geodatabase files, and info rmation input from record drawings of existing conditions provided by the Village of Key Biscayne to define elevations of catch basins, existing pipe network locations and pipe sizes. The m odel platform provided flexibility to evaluate the performance of the system for different rain events, optim ize pipe sizes and pump operations. 2.5.1 Hydrology For reference, the entire ICPR 4 Input Report with Simulation Summaries for both the Existing Conditions and baseline Altern ative Scenarios model are included as Appendix A.1 and A.2, respectively. 2.5.1.1 Rainfall and Runoff The fo llow ing hydro logic parameters were used to generate the inputs for the ICPR 4 model: • Natural Resources Conservation Service (NRCS) Unit Hydrograph method, • An 8.00-inch rainfall for the 10 -Year, 24-Hour Design Storm was obtained from SFWM D data, • Rainfall amounts obtained from the National Weather Service for the calibration storm events are presented in Tables 3 and 4, below, • The NRCS Type Ill Florida M odified Distribution was used for the rainfall distribution, • A peaking factor of 150 was used for the models, • Curve numbers (CN) within the study area were assigned to 95. This number was determined based on the anticipated elevated water table, and soil compaction within the study area, and • Time of concentration (Tc) was set to be 10 minutes for the majority of the basins - with larger more complex basins evaluated based on the NRCS TR-55 method. 2.5.1.2 Model Calibration Rainfall Events Tw o rainfall events were selected to represent typical hydraulic stress on the stormwater system and include June 4, 2022, and September 26, 2022 (Hurricane Ian). The rainfall data was downloaded for three NEXRAD pixels (10038353, 100383354 and 10038828) which cover the area including the Village of Key Biscayne. Table 3, Existing Conditions Model June 2022 Calibration Storm Rainfall Data 10 038353 10 038354 10 038828 0, 0, I ,, I " o• I I I O.J I " OJ I - • • . - I - - ... ~ ... '\, "'~\'\' .. ,~ ... \ ... , .. ,"· .... t!'''\ ,,,\<,J. ........ ~"\ ... ,~ ... ,, ... ~, ... ,.,f,c\''\ ... ,...-.'I'"'- v,yv ... ·°"''"'\ ,JP,, ... ,¥.,,,,. ,,,./"" ... ~ ....... ,,,tf"' ,,,\,v ... ,..~, ... 'o~"' ,_,\'•"'""'" .. s•'"'"' .,.,-.'I,,,. Prepared for: Village of Key Biscayne AECOM 35 K-8 Basin Basis of Design Report (BO OR) Village of Key Biscayne AECOM Pro ject No.: 60690913 Table 4, Existing Conditions Model, September 2022 Calibration Storm Rainfall Data 10038353 10038353 10038353 '" 0, ()4~ I I " I ~ oe . " I tH ~ 0.35 t O'> ~- O J ~ I ~ 04 ! o:: ~ 0.1 I ~ Ol I ~1U S I C ·J'J ~ 0, 1 " J I '" 'J/N/U 'J/istn 'Jfl\,fn ,tl1/ll q/}8/n -tntn ?l'(l/l1. 9(14/)l •},')'>/11 fJ/'J"ln 9/H/n ?08/U ,,1l'JpJ "1,'¥)/1) <)fM/n '1/'J<./n 9iH./Jl 9/)1 i1} 'I/nm c;/Ylfn 9/10 /Jl 2.5.1.3 Basin Areas Multiple hydraulically distinct sub-basins were created within the ICPR 4 model to represent accurate runoff into the Village's stormwater management system. To determine basin boundaries, aerial photography, LiDAR and topographic surveys, and prior stormwater plans were evaluated. To determine likely contributing area to the municipal system, an offset area of 100 feet from the road rights-of-way was created in GIS and verified by aerial overlay to ensure all reasonable and "landlocked" areas were captured and areas of overlap were trimmed. Wh ile excluded from the providing storage within the model, the runoff from all road rights-of-way were included in the model. Figure 14, K-8 Project Drainage Sub-Basin Locations shows the physical locations of the K-8 Project drainage sub-basins. + '"' .. --==?!.".-:=, ... Key Biscayne Key Biscayne Sub .. Basin Locations Legend CJ ~~1;0:a:r::~u~~~:0 A:COM Fig ure 14 , K-8 Project D rainage Sub-B asin Locations Delineating the sub-basins via right-of-way offset and excluding the rear portion of waterfront lots results in a contributing drainage basin for the study area of 76.21 acres. Table 5 provides the contributing drainage areas associated with each sub-basin. {remainder of this page intentionally blank} Prepared for: Village of Key Bisca yne AECOM 36 K-8 B a sin Ba sis of D e sign R eport (B O O R ) Village of Key Biscayne AECOM Project No.: 60690913 Table 5, K-8 School Project Sub-Basin Areas Sub-Basin Contributing Area ID# (acres) VKB-06 (School) 17.63 VKB-12 8.61 VKB-26 10.11 VKB-31 6.17 VKB-32 6.35 VKB-33 11.45 VKB-34 15.89 Totals 76.21 2.5.2 Hydraulics For reference, the entire ICPR 4 Input Report with Simulation Summaries for both the Existing Condition and baseline Altern ative Scenarios model are included as Appendix A.1 and A.2, respectively. 2.5.2.1 Collection System AECO M has prepared a baseline model for the Alternative Scenarios based on the conceptual trunkline storm w ater collection system shown in Figure 12, and consistent with the improvements proposed for the Altern ative Scenarios. These improvements included modifications to the stormwater collection system, pump station capacity, and the stormwater treatment units. The ICPR 4 Nodal Diagram for the baseline Altern ative Scenario m odel is shown in Figure 15. Please refer to Appendix A.3 for larger scale versions of the ICPR 4 Nodal Diagram for both the Existing Conditions and baseline Alternative Scenario models. Key Biscayne Key Biscayne Alkrnatlvc Sccno1rlo Model Nodal Design 0 """"' -Wwl~ - Plpellnll -- R11W\gCuNft c::J Mod elllo11nt Figure 15, K-8 Project Alternative Scenario Model Nodal Diagram Prep ared for: V illa ge of K ey Biscayne AECOM 37 K -8 Ba sin Ba sis of D esign R eport (B O O R ) Village of Key Biscayne AECOM Project No.: 60690913 2.5.2.2 Nodal Stage vs. Storage In the Altern ative Scenario m odels, surface storage was assumed to be contained within the study area. Li DAR data was used to create a digital elevation model ("DEM") which the ICPR 4 program then uses to autom atically generate stage versus area relationships which are assigned to each node. As noted previously, storage within the road rights-off-way were removed. This is accomplished by creating an artificial plateau at a sufficiently high elevation within the LiDAR data along the road rights-of-way. Warn ing stages were set at the m inimum existing crown of road to establish the desired Level of Service. Li kew ise, peak predicted flood stages for the design storm event were compared against finished floor elevations ("FFE") to determine any potential impacts to structures. 2.5.2.3 Tidal Boundary Condition The tidal boundary condition for the Altern ative Scenarios model or "tailwater," are based on the Village PW D planning horizon of 2060 with emphasis on anticipated SLR. Therefore, the tidal boundary condition w as calculated to be M ean High Water plus 2060 SLR and used as the basis of design for the proposed drainage system for all design storm events in anticipation of worsening future conditions. Wh ile there are endless naturally occurring possibilities which could increase this value (onshore winds, seasonal high tides, and storm surge), the drainage system serving the K-8 Project is being converted to a m echanical, pumped system which can easily overcome moderate fluctuations in the system total dynamic head with m inimal loss of capacity. Therefo re, the tailwater conditions are more applicable to the modeling of existing gravity flow conditions fo r the various design storm events, and then only to provide a baseline to measure the effectiveness of the proposed designs. However, the functionality of the drainage system can only be maintained so long as the perimeter integrity of the drainage basin is preserved. Tidal elevations sufficient to overtop existing bulkheads and sheet flow between houses into the ro ad rights-of-way will incapacitate the system. Data from NO AA for Virginia Key Station ID 872 3214 were downloaded for the available period of record for years 1996-2020 grouped on annual basis and analyzed to determine current tide levels and historical changes of the sea level. Figure 16 depicts the Selected Probability Exceedance Curves Illustrating Sea Level Rise. 4 co co 2 0 > <( z .t::: 0 Q) > ~ m -2 (f) Probability exceedance Figure 16, Selected Probability Exceedance Curves Illustrating Sea Level Rise This data used m ore than 2,165,800 points to provide statistical analysis of the historical data, including nearly 86,000 observations per year. Pro bability Exceedance Values of 1, 5, 10, 25 50, 75 90, 95 and 99% w ere extracted and are show on Table 6. Note that, for the Virginia Key Tide Station, the "slack tide" or m ean sea level ("MSL") expressed as an elevation in NAVO 88 is (-)0.89 feet. The normal tidal amplitude (high to low tide) is 2.04 feet - making high tide (Mean High Water) approximately equal to 0. 13 feet, NAVO. Pre pa re d fo r: V illage of K ey B iscayne AECOM 38 K-8 Basin Basis of Design Report (BO DR) Village of Key Biscayne AECOM Project No.: 60690913 Table 6 Probability Exceedance Values of Observed Data at Virginia Key in ft NAVO 88 Total Annual Year Max 1% 5% 10% 25% 50% 75% 90% 95% 99% Min Observations 2015 2.05 1.41 0.87 0.58 0.11 -0.54 -1.20 -1.64 -1.81 -2.08 -2.46 87600 2016 2.09 1.35 0.82 0.57 0.12 -0.54 -1.18 -1.58 -1.74 -2.00 -2.39 85076 2017 3.86 1.32 0.82 0.55 0.09 -0.55 -1.20 -1.62 -1.81 -2.12 -2.52 87600 2018 1.60 1.07 0.68 0.44 0.01 -0.65 -1.26 -1.66 -1.84 -2.15 -2.55 87600 2019 2.19 1.66 1.14 0.80 0.33 -0.31 -0.98 -1.39 -1.60 -1.92 -2.52 87600 2020 2.18 1.52 0.99 0.71 0.23 -0.39 -1.05 -1.45 -1.66 -1.99 -2.66 87827 The data demonstrates that the 1 % exceedance for the current conditions ( as of December 31, 2020) is approximately 1.52 feet, NAVO. Therefore, in 2020, a 1 % exceedance means that for 3.65 days of the year the tidal water elevations were greater than 1.52 feet, NAVO. AECOM, in consultation with the Village and their Resiliency and Adaptation consultant team, determined that a reasonable planning horizon for public works projects was approximately 40 years. Therefore, the 2060 milestone year was targeted for the SWMP design. As shown on Figure 17, Southeast Florida Regional Compact for Climate Change Unified Sea Level Rise Projection for the NOAA Intermediate High Project (baseline year 2000, and consistent with the Virginia Key Station Tidal Epoch - 1983-2001 ), by milestone year 2060 sea levels are anticipated to rise approximately 30-inches. Based on this data, the equation for the tidal boundary condition for the design of the proposed SWMP improvements for the K-8 Project basin becomes: MHW (0.13 feet, NAVD) + 2060 SLR (30 inches) = 2.63 feet, NAVD 200 8180 _, 0 LL N tf ~ 160 ~~ > ·- 140 ~~ :0 ~ 120 QJ Ill C QJ QJ V) ~ ~ 100 - QJ ~ ~ ~ B 80 Ill QJ ~ ·E Go QJ Ill -~ & .!!1 "' 40 QJ QJ a: .c u ;§. 20 0 Unified Sea level Rise Projection (Southeast Florida Regional Climate Change Compact, 2019), NOAA IPCC Median 1 Intermediate (Inches) 1 High • 1 (inches) 204 0 l ±10 1 17 2070 ~ 21 40 2120 40 92 _ __L.._ Year Observed 5-Year Average Mean Sea Level NOAA High I (Inches) , 136 .·• NOAA High NOAA 1990 2000 2010 2020 2030 2040 205~e~ 2070 2080 2090 2100 2110 2120 ~lu FIGURE 1, Unified Sea Level Rise Projection Figure 17, Southeast Florida Regional Compact for Climate Change Unified Sea Level Rise Projection Prepared for: Village of Key Biscayne AECOM 39 K-8 Basin Ba sis of D esign Report (B O O R ) Village of Key Biscayne AECOM Pro ject No.: 60690913 2.5.3 Model Limitations and Assumptions The pro posed project includes the replacement of the existing pipes with larger diameter pipes and construction of a new pump station within the K-8 Project study area. The major assumptions were made in updating the existing conditions and Altern ative Scenario models. 2.5.3.1 Existing Conditions Model The follow ing relevant limitations and assumptions were used in the development of the Existing Conditions m odel: • The storm water m odel assumes the existing stormwater system in the Project area is fully operational. The m odel does not account for blocked or silted-in pipes, catch basins, and/or failing pipes or structures. • The storm w ater m odel is based on the best available data from surveys, as-builts, the Village GIS database, CCTV inspections, and field reconnaissance provided by the Village. • Information was not available for multiple existing stormwater pipe invert elevations and pipe sizes; the AECO M team used known information of upstream or downstream pipes to extrapolate unknow n values. 2.5.3.2 Alternative Scenario Baseline Model The following relevant limitations and assumptions were used in the development of the Alternative Scenario m odel: • There are no offsite inflows into the K-8 Basin from the adjacent areas. • Existing seaw alls are at sufficient heights to prevent overtopping to a minimum elevation of 2.63 feet, NAVO. • Any gravity outfalls remaining within the basins will be fitted with a backflow prevention device or upstream inlet with a rim elevation not less than 2.63 feet, NAVO. • Existing drainage infrastructure to be incorporated into the project work will be inspected and determined to be of sound construction and free of obstructions, which would otherw ise limit the hydraulic efficiency of the system. • Initial road raising is expected to be a minimum of 6-inches, or that which is necessary to achieve a m inimum road crown elevation of 2.33 feet, NAVO. 2.6 Alternative Scenario Modeling Summary and Analysis Results of the m odel runs for the 10-Year / 24-Hour Design Storm Event for the Existing Conditions model and those of the six (6) Altern ative Scenarios developed are presented below. Compared to the results from the Existing Conditions m odel, except for Scenario 1, with the inclusion of the pumped system and improved outfalls, the m odel results for all Scenarios demonstrates significant improvements to the inundation depths and duration of flooding for the design storm event. For ease of comparison, a compilation of the model results for the Existing Conditions and each of the various Altern ative Scenarios for the design storm event at select points within the modeled stormwater network are presented in Table 7. These points have been chosen as they represent locations which: 1) are representative of the locations where larger pipe networks would join the main trunk line within McIntyre Street or West Enid Drive, 2) they are located within the lowest lying areas within the K-8 School Basin, or 3) represent areas containing structures with the lowest identified FFE's. Complete ICPR 4 Reports for the "Nodal Min/Max Stage" and "Link Maximum Flow" for all nodes and m odel links (pipes, weirs, pumps, etc.) contained in the model for the design storm event - for both the Existing Conditions and each of the six (6) Altern ative Scenarios developed are included in this report as Appendix A.4 and Appendix A.5, respectively. Prepa red for: V illage of Key Biscayne AECOM 40 K-8 Basin Basis of Design Report (BOOR) Village of Key Biscayne AECOM Project No.: 60690913 Simulation Summaries are included with the respective input reports included as Appendix A.1 and A.2 for the existing conditions and baseline Alternative Scenario models, respectively. Table 7, K-8 School Project Alternative Scenarios Design Storm Model Summary K-8 School Project -Alternative Scenarios Model Summary with Initial Road Raising(1) Existing Lowest Initial Target Model Scenario Peak Stage<•! Project Low Road Floor Road Road Existing Basin Basin Area Crown Elevation Raise121 Crown Conditions 1 2 3 4 5 6 ID# (acres) (feet) (feet) (inches) (feet) (feet) (feet) (feel) (feet) (feel) (feet) (feet) School (VKB-06) 17.63 1.65 3.29 8.16 2.33 4.20 4.47 4.06 2.63 -1.18 3.27 0.23 VKB-12 8.61 1.97 3.90 6.00 2.47 4.18 4.60 4.14 2.41 -1.53 3.15 -0.08 VKB-26 10.11 1.95 3.62 6.00 2.45 4.19 4.60 4.14 2.4<1 -1.48 3.16 -0.04 VKB-31 6.17 1.50 4.06 9.96 2.33 4.07 4.58 4.10 1.92 Ii -2.24 2.89 -0.68 VKB-32 6.35 1.83 2.70 6.00 2.33 3.79 4.56 4.08 1.68 -2.59 2.75 -0,95 VKB-33 11.45 1.94 4.14 6.00 2.44 4.09 4.59 4.12 2.14 -1.90 3.01 -0.42 VKB-34 15.89 1.52 3.40 9.72 2.33 3.81 4.57 4.08 1,.78 -2.35 2.80 -0.86 Totals 76.21<•1 "''"" ~S000,00 M- """" ffE "" "'"' Crown LOS #.## Scenario Meets FFE LOS, but not Road Crown LOS #.## Scenario Meets both FFE and Road Crown LOS Notes: 1) All Elevations are referenced to NAVO, 88. 2) Roads Assumed to be Raised a Minimum of 6-inches or as Required to get to Low Crown of Road of 2.33 feet NAVO. 3) The K-8 School Project Area is 76.21 acres (9. 7%) of the Village-wide SWMP area of approximately 785.8 acres. 4) Scenario 3 includes a re-pump rate of 199.5 cfs. Scenario 4 includes a re-pump rate of 228 cfs. Scenarios 5 & 6 rely exclusively on improved Basin 6 Outfall structures with no re-pumping included in the reported results - although re-pumping would be included as necessary. 2.6.1 Alternative Scenario 1 Utilize Existing Outfalls: Scenario 1 maintains or rehabilitates existing outfalls and pipe sizes with a connection to the pumping station with a capacity equal to sum of the existing peak discharge rate at each outfall location while matching existing discharge velocity. This scenario is not a viable solution and would be the least preferred option. Due to the additional of the School property to the study area drainage basin, the model results show minimal, to no, benefits as compared to the results of the existing conditions model. However, the recovery time for inundation over the crown of road (36-hours) is one-half that of the existing conditions. 2.6.2 Alternative Scenario 2 Rehabilitate and Improve Existing Outfall Locations: Scenario 2 installs the largest diameter pipes possible within the available easements comprising the Basin 6 Outfalls and includes a pump station of a capacity equal to the sum of maximum discharge rate achievable at each outfall location such that proposed flows do not exceed existing outfall velocity. This Scenario provides a "partial solution" to the overall needs of the Project drainage basin. However, in the absence of some other resolution to the discharge limitations imposed by the capacity of the Basin 6 Outfalls, which are unknown at the time this analysis is being performed, this scenario most likely represents the predicted "near-term" performance of the K-8 School storm water management system. Near-term being defined as, until such time as the Village-wide SWM P improvements are constructed and operational. As a stand-alone solution, Scenario 2 fails to meet Levels of Service for both FFE and road crown. Model results indicate that flooding over the crown of road would occur up to approximately 1.75 feet which approximates the existing conditions. Prepared for: Village of Key Biscayne AECOM 41 K -8 B a sin Ba sis of D e sign R eport (B O O R ) Village of Key Biscayne AECOM Project No.: 60690913 How ever, the evaluation of the recession times for flooding performed for the area in the vicinity of the School indicates that the ro ad is submerged for appro ximately 7.75 hours as compares to over 3-days for the existing conditions. G iven the current state of available op tions, Scenario 2 becom es an essential com ponent of the K­ B S ch ool Project and represents a foundation for the adaptation and im plem entation of future im p rovem ents and enhan cem ents to the overall drainage system to supplem ent the K-8 School P roject. The im pro vem ents to be im plem ented with Scenario 2 would is envisioned to be combined with additional w ork w hich w ould be im plem ented and supplem ented by one of Scenarios 3-6, as part of an adaptable and increm ental solution. 2.6.3 Alternative Scenario 3 Rehabilitate and Impro ve Existing Outfall Locations and Provide Reserve Pump Station Capacity to Transfer Flows to a Central Facility to be Repumped to a Master Outfall: Scenario 3 m aximizes the capacity of the existing outfalls as described in Scenario 2 however, includes a pum p station of a capacity capable of pumping the design storm peak hour runoff (3.22 inches per hour). Stormw ater runoff exceeding the capacity of the local outfalls being pumped to a central re-pump facility (w hen available) and ultimately to a future Village-wide master outfall. Scenario 3 represents an enhancement of the essential and successful implementation of Scenario 2. Initially, pumps of sufficient capacity to utilize the Basin 6 Outfalls would be installed. Scenario 3 would include a storm w ater force m ain to be constructed in West McIntyre Street from the pump station to a yet to be determined terminal location near the eastern property boundary of the K-8 School. This force main w ould then be connected to a centralized re-pump facility and ultimately an alternative discharge location(s) developed with the Village-wide SWM P. The reserve pump station capacity will be utilized at some point in the future as the altern ative discharge becomes available. S cen ario 3 shows sig nificant benefit to the Project drainage basin. It achieves the param ount goal of p rod ucing p eak flood stag es low er than any know n FFE. Scenario 3 does not fully achieve the des ired roadway level of serv ice as it relates to the inundation of the existing crown of road elevations within the P roject basin. In the low est lying areas in the vicinity of the School, the m odel res u lts p redict that the m axim um flooding over the crow n of road w ould occur up to 0.30-feet. H o wever, the evaluation of recession tim es for flooding indicates that the roadway would be inu n dated abo ve the crow n for approxim ately 15 m inutes to one-half hour. Scenario 3 produces peak stages within the Basin (exclusive of roadway storage) which are at or below the 2060 SLR projection of 2.63 feet, NAVD. Presented differently, because the roadway storage has been removed, the Village could conduct incremental road raising to an elevation of 2.63 feet, NAVD to alleviate areas of localized level of service failures predicted by the model without affecting the model results. In addition, any inundation above the crown of road would be of short duration. 2.6.4 Alternative Scenario 4 Rehabilitate and Impro ve Existing Outfall Locations and Provide Significant Reserve Pump Station Capacity to Transfer Flows to a Central Facility to be Repumped to a Master Outfall: Like Scenario 3, Scenario 4 m aximizes the capacity of the local outfalls as described in Scenario 2. Scenario 4 includes a pump station of a capacity such that the roadway level of service is met, and no flooding of the ro adw ay occurs. Pumping capacity required in excess of the capacity of the local outfalls is to be pumped to a central re-pump facility (when available) and ultimately to a Village-wide master outfall. Scenario 4 represents an enhancement of the essential and successful implementation of Scenario 2. Initially, pum ps of sufficient capacity to utilize the Basin 6 Outfalls would be installed. Scenario 4 would include a storm w ater force m ain to be constructed in West McIntyre Street from the pump station to a yet to be determined terminal location near the eastern property boundary of the K-8 School. This force main would then be connected to a centralized re-pump facility and ultimately an alternative discharge location(s) developed with the Village-w ide SWM P. P rep a red fo r: V illage of Key B iscayne AECOM 42 K-8 Ba sin Ba sis of Design R eport (B O O R ) Village of Key Biscayne AECOM Project No.: 60690913 The reserve pump station capacity will be utilized at some point in the future as the alternative discharge becomes available. In this scenario, the reserve capacity of the pump station was adjusted as necessary to pro duce m odel results which meet the level of service standard of zero flooding above the existing crown of road in any sub-basin. Scenario 4 protects FF E s and fully m eets the currently adopted roadw ay LO S with no flooding of the roadw ay occurring . The pump capacity in Scenario 4 is approximately 115% greater than that of Scenario 3. Wh ile this scenario shows compliance with the Level of Service for the Project area, the model is very sensitive, and the scenario requires significant pumping capacity. The associated force main required to pump to a central facility being developed as a part of the Village-wide SWM P would have to be increased in size accordingly, which poses spatial challenges within the crowded right-of-way and the benefits will not be realized until such time as these improvements are constructed and operational. The m odel results for scenario were very sensitive. At the combined pumping rate of 275.7 cfs modeled for the Project basin, the m odel produced results which demonstrated compliance with the levels of service for the Pro ject Area. Any increase in pump capacity demonstrated little or no improvement, as the pump capacity equaled, or exceeded the rate of rainfall runoff (basically the pump runs out of water). However, any less pumping capacity and the model produced results which failed to meet the level of service and w ere comparable to the results for Scenario 3. 2.6.5 Alternative Scenario 5 Rehabilitates and Improves tw o of the Existing Outfall Locations and Reconstructs the Remaining Existing O utfall and Adjoining Seawall to Include both Energy Dissipation and Increased Discharge Capacity: Scenario 5 is a variant building on Scenarios 2 and 3 in which the Village, through community outreach to the affected landow ners, can secure additional drainage easement(s) width along the side lot lines, and/or in a "T" or "L" shaped configuration along the waterfro nt allowing for the potential to install a larger side-lot discharge pipe and construction of a seawall which will include both discharge and energy dissipation components within the new ly secured easement. This Scenario assumes the Outfall #15 discharge pipe could be increased and that a seawall with an "effective discharge length" of at least seventy (70) feet and providing 168 cfs discharge capacity and the necessary energy dissipation could be constructed. Further it was assumed that Outfall No.'s 12 and 14 would also be enhanced as discussed in Scenario 2 - making the total combined discharge directed to the Basin 6 Outfalls and Hurricane Harbor equal to 193.1 cfs (or approxim ately 54.1 cfs lower than the DSPRR). The pump station capacity for Scenario 5 would be equal to the DSRPR (same as Scenario 3) and ultimately this scenario could, if desired, rely on additional discharge to an "extra-neighborhood" alternative discharge location to fully m eet the level of service requirements, it does so at a significantly lower volumetric rate, thereby reducing reliance on an "extra-neighborhood" alternative discharge location. Scenario 5 show s significant benefit to the Pro ject drainage basin. Depending upon the ultimate size of the reconstructed outfall structure, the m odel results indicate that some re-pumping may be necessary to pro duce peak flood stages lower than any know FFE. Additionally, Scenario 5 does not fully achieve the d e sired roadw ay level of serv ice as it relates to the inundation of the existing crow n of road ele vatio ns w ithin the Project basin. In the lowest lying areas in the vicinity of the School, the model results predict that the maximum flooding over the crown of road throughout the project basin would range from 0.4 to 0. 94-feet. However, the evaluation of recession times for flooding indicates that the roadway would be briefly inundated above the crown for approximately 45 minutes. As a "stand-alone solution", and as compared to Scenario 2, this Scenario would provide significant im provement to the "near-term performance of the K-8 School stormwater management system. Scenario 5, in conjunction with a connection to an "extra-neighborhood" alternative discharge location would fully m eet the level of serv ice requirements, merits more evaluation for its potential and may require further discussion and refinement to the definition of Level of Service as it relates to maximum depth and duration of inundation above the existing crown of ro adway elevation. 2.6.6 Alternative Scenario 6 Rehabilitates and Improves one Existing Outfall Location and Reconstructs Two of the Existing Outfalls and Adjoining Seawalls to Include both Energy Dissipation and Increased Discharge Capacity: P re pa red for: V illage of Key Biscayne AECOM 43 K-8 Basin Basis of De sign R eport (B O O R ) Village of Key Biscayne AECOM Project No.: 60690913 Scenario 6 is a variant building on Scenarios 2 and 5 in which it is assum ed the Village thro ugh community outreach can secure additional drainage easem ent(s) w idth along the side lot lines, and/or in a "T" or "L" shaped configuration allow ing fo r the potential to install a larger side-lot discharge pipe and seawall which w ill be incl ude and provide energy dissipation fo r the pum ped discharge within the new ly secured easement. F or Scenario 6, it w as assum ed that discharge pipes in both Outfall No.'s 12 & 15 (w hich are the closest to the pum p station location) could be upsized, and that a seawall with the necessary "effective discharge le ngths" capable of providing m inim um , com bined 247.2 cfs discharge capacity coupled with the necessary energy dissipation could be constructed. Further it was assum ed that Outfall No. 14 would also be enhanced as discussed in Scenario 2 - m aking the total combined discharge directed to the Basin 6 Outfalls and H urricane H arbor equal to 261 cfs (or approxim ately 13.8 cfs greater than the DSPRR). The pump station capaci ty for Scenario 6 w ould be equivalent to com bined design discharge capacity of the reconstructed outfalls or appro xim ately 106% greater than that of Scenario 3. Scenario 6 would not require re-pum p to a central re-pum p facility and fully meets level of service requirements. Scenario 6 shows significant benefit to the Project drainage basin. The model results indicate that this Scenario protects FFEs and fully m eets the currently adopted roadway LOS with no flooding of the roadway occurring. Scenario 6 dem onstrates that it is possible to develop a stormwater m anagem ent system for the K-8 School Project which does not rely upon a yet to be determined altern ative outfall location being developed as a part of the Village-wide SW MP. Furt her, the results of Scenario 6 dem onstrate that it is possible to generate "excess capacity" within the Project Basin which with the developm ent of the Village-wide SWMP could be "shared" with adjacent basins via storm water piping interconnections. Should this scenario be successfully im plem ented in other basins within the Village, the reliance on the development of an "extra­ neighborhood" altern ate discharge location could be greatly reduced. 2.7 Evaluation of Flooding Depth & Duration - K-8 School Vicinity T he follow ing section incl udes both tabular and graphic representations of select altern ative design scenarios to bett er illustrate the m odeling results in the vicinity of the K-8 School. As shown in Figure 18, the area evaluated is located along West M cI ntyre Street along the northern boundary of the school, and just to the w est of the student dro p-off zone. Figure 18, A ltern ative Scenarios C ross Section Location Table 8, School Basin (V K B -06) Flood Depth and Duration Sum m ary presents the m odel results of the various altern ative scenarios fo r the basin containing the School site (VKB-06) including an initial project road raising of 6-inches and provides colum nar data for existing and target road crow ns, peak stage, m axim um depth of flooding over crow n, and hourly tim estamp data fo r the tim e required for flooding to: 1) reach the ro ad cro w n, 2) reach a peak, and 3) recede to elevations of the road cro w n +6-inches, the road crow n +3-inches, and the road cro w n. The last colum n indicates the total tim e the flood water is predicted to be above the road crow n. Prep ared for: V illa ge of Key Biscayne AECOM 44 K-8 Ba sin Ba sis of D e sign R eport (B O D R ) Village of Key Biscayne AECOM Project No.: 60690913 The tabular results (shown graphically in Figures 19 - 22) indicate only Scenarios 4 and 6 fully meet the adopted level of service for Basin VKB-06 which requires that no ponding shall occur on the roadway and fully protect FFE elevations within the basin. However, as compared to the existing conditions, the data also reflect that the Scenarios 2, 3 and 5 dramatically reduce the time flood waters exceed the road roadway crown from >77-hours to 7.75-hours, 0.25 hours and 0.75-hours, respectively. Table 8, School Basin (VKB-06) Flood Depth and Duration Summary K-8 School Basin (KVBOG) -Altern ative Scenarios Model Summary with Initial Road Raising" Maximum Recession Time to Existing Lowest Target Depth Time to To tal Basin Road Floor Initial Road Peak over Reach Time to Crown Crown Time to Duration> Model Scenario<4l Area Cro wn Elevation Raise<2> Cro wn Stage Crown Crown Peak +6 Inches +3 Inches Crown Crown ID # (acres) (feet) (feel) (Inches) (feel) (feel) (feet) (hours) (hours) (hours) (hours) (hours) (hours) Existing Conditions 17.63 2.28 3.29 0.50 2.78 4.20 1.92 3.00 23.00 >77 >77 >77 >77131 Scenario 1 17.63 2.28 3.29 0.50 2.78 4.47 1.69 11.50 23.00 44.50 45.75 46.50 35.00 Sce nario 2 17.63 2.28 3.29 0.50 2.78 4.06 1.28 12.00 14.75 19.00 19.50 19.'75 7.75 Sce nario3 17.63 2.28 3.29 0.50 2.78 2.63 (0.15) NIA 12.50 N/A N/A <0.25 <0.25 Scenario 4 17 .63 2.28 3.29 0.50 2.78 -1.18 (3.96) NIA 12.25 N/A NIA NIA NIA Scenario 5 17.63 2.28 3.29 0.50 2.78 3.27 0.49 12.35 12.75 N/A 12.85 13.00 <0.75 Scenario 6 17.63 2.28 3.29 0.50 2.78 0.23 (2.55) N/A 12.50 NIA NIA N/A NIA Notes: 1) All Elevations are referenced to NAVO, 88. 2) Initial Road Raising shall be 6~inches, or as required to achieve a minimum road crown of 2.33 feet, NAVO 3) Simulation term inated at 80 hours after onset of storm evenl. 4) Scenario 3 includes a re -pum p rate of 199.5 cfs. Scenario 4 includes a re-pump rate ol 228 cfs. Scenarios 5 & 6 rely exclusively on Improved Basin 6 Outfall structures with no re-pumping Included In the reported results - although re-pumping would be Included as necessary. K-8 School Basin (KVBOG) -Altern ative Scenarios Model Summary with Initial Road Raising Figure 19, School Basin (VKB-06) Time-Stage Hydrograph presents the model data as a time-stage hydrograph for the Existing Conditions and Scenarios 2, 3 and 5 at the student drop off on the West McIntyre Street location along with a representation of the existing and hypothetical proposed cross section - with both a crowned and inverted crown section. <.00 4.00 .. __ ... _ g ].00 . C: .g j "0 2: 100 "' ,,,,,-' ' ' ' ' I ' ' , ' l.00 I ' 0.00 ,, I : : ~ t I It 1 I I• :: :l t I I\ ,, lj ,. ,. ,, 1: fl I• ,, ,, ,, ,: .... •• 1: :: ii :: I I ti I: :; ; l ; Relative Time of Flooding (hrs) ---E1t.1 ~tm •Cond1tlons ---Sc en;uio2 ---~eria,10 J - -Sc eN 110!1 - [,lumaRoad - fa1aetRoad C,o\\-n - T,ujlt'lRoad-ln\i!fled Stage Hydrograph of Alternative Scenarios Figure 19, School Basin (VKB-06) Time-Stage Hydrograph Prep ared for: V illage of Key B iscayne AECOM 45 K-8 Basin Basis of Design Report (BOOR) Village of Key Biscayne AECOM Project No.: 60690913 Figure 20, Existing Conditions - Peak Stage and Flood Durationis a graphical representation of the peak stage and flood duration of the Existing Conditions at the student drop-off zone on West McIntyre Street. Total Flood Duration at Crown Elevation - > 77 .00 hrs Existing Road Section A-~ 7' Sidewalk 9'-6" Drop-off Area 14' Drive Lane 50'R.O.W. Figure 20, Existing Conditions - Peak Stage and Flood Duration Figure 21, Scenarios 2, 3 & 5 Peak Flooding and Duration - Crown Section is a graphical representation of the peak stage and flood duration for Scenarios 2, 3 & 5 at the student drop-off zone on West McIntyre Street, for a conventional centerline crown roadway section - including an initial roadway raising of 6- inches. Figure 22, Scenarios 2, 3 & 5 Peak Flooding and Duration - Inverted Crown Section is a graphical representation of the peak stage and flood duration for Scenarios 2, 3 & 5 at the student drop-off zone on West McIntyre Street, for an inverted crown roadway section - in this design alternative, the initial roadway raising of the centerline grade, is "as necessary" to achieve a minimum centerline elevation of 2.33 feet, NAVO. While these sections depict a moderate increase in the depth of flooding, due to the addition of the pump station, they recover within similar timeframes to the conventional centerline crown versions. {remainder of this page intentionally blank} Prepared for: Village of Key Biscayne AECOM 46 K-8 Basin Basis of Design Report (BO OR) Village of Key Biscayne AECOM Project No.: 60690913 Total Flood Duration at Crown Elevation - 7.75 hrs <' . - >' \ \ ) ) S ce na rio 2 : Proposed Road Section - Centerline Crown ' ' ' ' ' ' ' ' ' ' ' /-•\..,,_,-- ...... r,, '\...,.r -• .. Total Flood Duration at Crown Elevation • <0.26 hrs < .•· \,. 9"-6" Drop-off Area Sce na rio 3 : Proposed Road Section - Centerline Crown ' ' ' ' ' ' ' ' ' ' ' / / / / / / / / / / / / Total Flood Duration at Crown Elevation • <1.00 hrs \ ) ,-1" Sc e na rio 5 : Proposed Road Section - Centerline Crown ' ' ' ' ' ' ' ' ' ' ' Figure 21, Scenarios 2, 3 & 5 Peak Flooding and Duration - Crown Section Prepared for: Village of Key Biscayne AECOM 47 K-8 B asin Basis of Design R eport (B O O R ) Village of Key Biscayne AECOM Project No.: 60690913 Total Flood Duration at Crown Elevation • 7.75 hrs _/ < Scenario 2 : Proposed Road Section • Inverted Crown ,1 ...... \.,.,---­ , Total Flood Duration at Crown Elevation • <0.26 hrs \ \ \ .i_/ I I I - Scenario 3 : Proposed Road Section • Inverted Crown Total Flood Duration at Crown Elevation • < 1.00 hrs \ \ \ <i <1 d6 r1 ) j''< ;,,,t_., ,Y ---~ .f\M\j \( // C. ,.J ~ -v "'--~- J \V/ "'-'" - ~ ;/ ~i( I/ j Peak Stage Flooding • 3.27 ft , 2.57 - Scenario 5 : Proposed Road Section - Inverted Crown Figure 22, Scenarios 2, 3 & 5 Peak Flooding and Duration - Inverted Crown Section Prepared for: V illa ge of Key Biscayne AECOM 48 K-8 Ba sin Ba sis of D esign R eport (B O O R ) Village of Key Biscayne AECOM Pro ject No .. 60690913 2.8 Drainage Design Report Conclusion The pro posed Altern ative Scenarios for the K-8 Basin Project drainage improvements are all effective at reducing both the depth and duration of flooding within the project drainage basin. As such, it can be unequivocally stated that the pro posed K-8 Basin drainage improvements will be just that - providing improvements to both depths of inundation and recovery times for the design storm event and introducing an element of water quality treatment lacking fro m a basin which discharges into Biscayne Bay, which is both an Outstanding Florida Waterbody and an impaired water body. As proposed, the capacity of the proposed SWT Us exceed the one-hour water quality treatment volume. Regardless of Scenario ultimately chosen, the installed pump station should have the necessary capacity of not less than the design storm peak hourly runoff rate of247.2 cfs (~111,000 gpm). Given the uncertainties associated with Scenarios 5 and 6, based on the results from the stormwater modeling, and the varying degree to which each of the other scenarios protect FF Es within the basin and conform to the adopted roadway level of service, Scenario 3 is recommended as the Preferred Alternative Scenario. Based on the current project status, Scenario 3 represents the most likely scenario to be im plemented long term. However, should either Scenario 5 or 6 become a possibility, given the decreased reliance of "extra-neighborhood" discharge facilities and associated construction costs, then either Scenario would become the recommended preferred alternative. Subject to the gainful negotiations with affected stakeholders in securing additional easements necessary to implem ent Scenarios 5 and 6, and the time lag to construct the Village-wide SWM P improvements to support Scenario 3, in the interim , Scenario 2 becomes the default scenario to be implemented. Both Scenario 2 and 3 represent significant improvements within the basin. Scenario 2 produces flood stages m arginally better than the existing conditions but demonstrates a ten-fold decrease in inundation times. Scenario 3 pro duces dramatic reductions in both flood stage and inundation time. At present, Scenario 3 protects FFE of structures within the project basin; however, it fails drainage Level of Serv ice - defined as no allowable flooding above the road crown - but achieves a peak flood elevation of 2.63 feet, NAVO which, based on 2060 SLR projections, by default becomes the required future minimum road edge of pavement. It is anticipated that there would be an initial raising of the roadways during the neighborhood improvements, and subsequent incremental raising to be implemented over time. Approval of Scenario 2 as the interim preferred altern ative and ultimately Scenario 3 (or Scenario 5) as the Preferred Altern ative Scenario would require Village Council to reconsider the definition of roadway level of service, to allow for ponding on the roadways and over the roadway crown to a reasonable depth and duration. 2.8.1 Follow-Up Issues During intern al team discussions regarding the development of the Alternative Scenarios, several issues need to be explored further to fully develop the alternative scenarios and/or to obtain information to implement m easures that m aximize the potential and improve the overall performance of the stormwater system . • Determine actual easements available for discharge to Hurricane Harbor, • Complete benthic and bathymetric surveys, • Negotiate with affected stakeholders regarding additional easements, and • Determine location of central re-pump facility to enable final design of pump station. 2.9 Drainage Design Report References 1. Wi lliams, Hatfield and Stormer, Inc, 1993 Stormwater Master Plan, Village of Key Biscayne 2. Tetratech, 2011 Stormwater Master Plan Update, Village of Key Biscayne 3. EAC, 2015, VKB Implementation of SWM P Prepared for: V illage of K ey Biscayne AECOM 49 K-8 Basin Basis of Design Report (BO OR) Village of Key Biscayne AECOM Project No.: 60690913 3 Streetscape Toolkit and Harbor Park Conceptual Design Ideas As part of this BOOR, AECOM created a streetscape toolkit with different options to establish the design criteria for the Project. Conceptual design ideas for Harbor Park were developed in collaboration with Village staff. The streetscape toolkit and conceptual design ideas for Harbor Park were developed with the philosophy of maintaining and enhancing the aesthetic character of the community. On April 4, 2023, AECOM and Village staff presented a progress update on the K-8 BOOR and the Village­ wide SWM P projects to the Village Council. At this meeting, Councilmembers were concerned with the delivery method for the K-8 Basin project (design-bid-build vs. design-build). If the Village decided to pursue implementation of the K-8 Basin project via the design-bid-build delivery method, the detailed design phase could commence using the design parameters set forth in this BOOR. Alternatively, if the Village decided to pursue implementation of the K-8 Basin project via the design-build delivery method, a Design-Build Criteria Package (DCP) would need to be developed to procure a Design-Builder. Additionally, AECOM clarified that the selected level of service for the Village-wide Integration and Implementation Plan (IIP) could be modified, if required by the Village Council, and adapted accordingly to the K-8 Basin project during the detailed design phase. On April 6, 2023, AECOM and Village staff hosted a community meeting to provide a progress update on the K-8 BOOR and the Village-wide SWM P projects to Village residents. The community meeting flyer is presented in Figure 18. COM MUNITY · MEETING: Update on KBK8 Basin Stormwater System Design Join Village staff and AECOM lor a community meeting to rnscuss tho upcoming ResiUem tnnastrucrure & Adnprauon Program as it relates 10 the Key Biscayne t<.8 scneor nasm and Harbor Park The purpose of this meeung ,s 10 discuss,., upqradas 10 the stormweter system and mcdiucauons to Harbo, Park thal will bolance · rccreauonal space and the Village's smnuwetet system neens. MONDAY, MARCH 6, 2023 6:00 - 7:00 PM KEY BISCAYNE COMMUNITY CENTER Figure 23, Community Meeting Flyer At the community meeting, Village residents provided feedback on the streetscape toolkit and Harbor Park conceptual design ideas. The following conceptual street sections were presented and displayed in boards at the community meeting: Prepared for: Village of Key Biscayne AECOM 50 K-8 Basin Basis of Design Report (BO O R) Village of Key Biscayne AECOM Project No.: 60690913 I I I 50' R.0.W. i I I : E•lstlng Elevation ·-9' Drive LaneJ Section A-A' - Existing Street Figure 24, Existing Street ) ( ·, , \ I I \._ \.__' '- ' Option 1 A- Proposed Two -Way ", '' . .__ Street; Centered Centerline Crown '' ....._ ', ..._ Figure 25, Proposed Street (Option 1A): Two-Way Street with Centered Centerline Crown \ -- 'l r \,- j) \r,..,.. V 1-18' P.irkinc-- ---12' Drive Lane­ ,.1-------------+-t 50' R.O.W . Option 1 B - Proposed One -Way Street ',', wilh Parking; Centered Centerline , ' Crown ',' ,,, ,_. /.' • I,/ I ,1 ( Figure 26, Proposed Street (Option 1 B): Proposed One-Way Street with Streetside Parking and Centered Centerline Crown Prepared for: Village of Key Biscayne AECOM 51 K-6 Ba sin Ba sis of D esign R e p ort (B O O R ) Village of Key Biscayne AE C O M Project No.: 60690913 I I Option 1 C - Proposed One -Way Street with Parking; Off-Centered Centerline Crown Figure 27, Proposed Street (Option 1C): Proposed One-Way Street with Streetside Parking and Off-Centered Centerline Crown Option 2A - Proposed Two -Way Street; Centered Inverted Crown Figure 28, Proposed Street (Option 2A): Proposed Two-Way Street with Centered Inverted Crown 5 ',_,J \ \ I Option 28 - Proposed One -Way Street with Parking; Centered Inverted Crown Figure 29, Proposed Street (Option 28): Proposed One-Way Street with Parking and Centered Inverted Crown P rep are d fo r: V illa ge of K ey Biscayne AEC O M 52 K-8 Ba sin Ba sis of D esign R eport (B O O R ) Village of Key Biscayne AECOM Project No.: 60690913 \ I ,,. // \ ; , / \ I / / \ I ' ) ': I i ,~-'.-=- :- - -= -- -·---.:,. /~-;;-= .. --:~ 1 I Option 2C - Proposed One -Wriy Street with Parking; Off-Centered Inverted Crown Figure 30, Proposed Street (Option 2C) Proposed one-Way Street with Parking and off-Centered Inverted Crown T he fo llow ing H arbor Park conceptual design ideas were presented and displayed in boards at the com m unity m eeting: Figure 31, Harbor Park - Existing Site P repared for: V illage of Key Biscayne AECOM 53 K-8 B asin Ba sis of D e sig n R e po rt (B O O R ) Village of Key Biscayne A EC O M Project No.: 60690913 G) Water Quality Treatment @ Pump Station --1-~ I • •!. .. ) ~, I -1 I ::;=,_ I JI I I ~ ~ L - J --.--• ! I @ I ._ @. Civic-Style Equipment Building with Removable Roof @ Transformer (z) Service Entrance @ Pathway Connections @ Dense Screen Planting Figure 32, Harbor Park Site - Reference Images Prep ared fo r: V illa ge of Key Biscayne AEC O M 54 K-B Basin Basis of Design Report (BO OR) Village of Key Biscayne AECOM Project No.: 60690913 Figure 33, Conceptual Design - Architectural Elements Figure 34, Conceptual Design - Hardscape Materials Prepared for: Village of Key Biscayne AECOM 55 K-8 Ba sin Ba sis of D e sig n R e po rt (B O O R ) Village of Key Biscayne AEC O M Project No.: 60690913 Figure 35, Conceptual Design - Paving Materials •High efficiency LED lights ·Full cut-off, no glare lighting ·Pedestrian scale , .. ,.' '· ' '• ',, ; .. :·, .. } 1··. ' '; - ' -.,,_ . I !~ ' l Figure 36, Conceptual Design - Lighting Typologies P rep ared fo r: V illa ge of Key Bisca yne A EC O M 56 K-8 Ba sin Basis of D esign R eport (B O O R ) Village of Key Biscayne AECOM Project No.: 60690913 Figure 37, Conceptual Design - Site Amenities Figure 38, Conceptual Design - Landscaping Prep ared fo r: V illage of K ey Biscayne AECOM 57 K-8 Basin Basis of Design Report (BODR) Village of Key Biscayne AECOM Project No.: 60690913 4 Utilities The K-8 Basin project is Zone 1 of the Village's Resilient Infrastructure and Adaptation Program to protect its shorelines, upgrade its stormwater system, improve its roadways, and underground its utilities in an integrated, "dig once" approach. The K-8 Basin project needs to be designed and constructed with the "dig once" approach; for this reason, utility undergrounding design and coordination will be paramount to the project's success. As part of this BOOR, AECOM requested a Sunshine 811 Design Ticket and coordinated with utility providers in the project area. Sunshine Design Ticket #016302162 was requested on January 16, 2023; the utility providers included in the ticket are shown in Figure 39. * Responses are current as of 01/16/2023 12:33 PM ~ Service Acea Utili!}'Jy~(~l ~ 6111:caati: !:12a1ai;1 ~en!;)! Contact Positive Res~ No COMCAST CABLE CATV, FIBER RICARDO HFC HELP DESK ((1279 DAVIDSON (855) 962-8525 (786) 586-8505 No DADE COUNTY STREET LIGHTS, OCTAVIO VIDAL OCTAVIO VIDAL FRANK AIRA P.E. PUBLIC WORKS AND TRAFFIC SIGNALS (305) 412-0891 x201 (305) 412-0891 x201 (305) 592-3580 x233 TRAFFIC DCPWT No FLORIDA POWER & ELECTRIC EDGAR AGUILAR USIC DISPATCH LIGHT--DADE (386) 586-6403 CENTER FPLDAD (800) 778-9140 No HOTWrRE CATV. FIBER, WALTER DAVILA RALPH HERRERA NOC/ OAIS COMMUNICATIONS TELEPHONE (954) 699-0900 (954) 628-7023 HASSANZADA (CALL HC1660 lF NO RESPONSE FROM NOC) (561) 288•9188 x6 Yes MIAMI-DADE WATER SEWER, WATER LAZARO GUERRA HENRYCUIK RADIO Extraordinary circu &SEWER (786) 268-5273 (786) 268-5369 COMMUNICATION mstances per 556.10 'vlDWS CENTER 5(8)(a), F.S. exist, cal (305) 274-9272 I utility owner/ aper ator provider for thi s location. No AT & T/ TELEPHONE DINO FARRUGGIO UTILIQUEST LLC * AT&T NETWORK DISTRIBUTION G27896@ATT.COM (888) 357-1922 OPERATIONS snrzs CENTER (800) 247-2020 Figure 39, Sunshine Design Ticket 4.1 Hotwire Communications On January 16, 2023, Walter Sancho-Davila (walter.sancho-davila@hotwirecommunication.com; Outside Plant Engineering Project Manager) confirmed via email that Hotwire Communications does not have facilities within the K-8 Basin project area. 4.2 Florida Power & Light On January 26, 2023, Florida Power & Light ("FPL") representative Jamie Purnell (jamie.purnell@fpl.com; FPL Land Survey/Cable Locations) provided FPL utility maps for the K-8 Basin project area. Village staff confirmed that OzzieAlvarodiaz (ozzie.alvarodiaz@fpl.com; FPL Lead Project Manager) will serve as FPL's undergrounding project manager for the K-8 Basin project. Additionally, Joseph Padron (joey.padron@fpl.com; FPL Central/West Miami-Dade External Affairs Manager) will serve as FPL's external affairs manager for the K-8 Basin project. On March 20, 2023, Ozzie Alvarodiaz provided preliminary FPL undergrounding plans for the K-8 Basin project area (in CAD and PDF formats) to AECOM; FPL's design was incorporated into AECOM's preliminary design plans for this BOOR which are included as Appendix A.7. Prepared for: Village of Key Biscayne AECOM 58 K-8 Basin Basis of Design Report (BO OR) Village of Key Biscayne AECOM Project No.: 60690913 The final design of the K-8 Basin project needs to incorporate/ coordinate FPL's undergrounding design to fulfill the "dig once" approach. FPL's existing utilities within the K-8 Basin project area are shown in Figures 40 and 41. Callbt!fore cu rf 11-800432-4770 2.0234 Couot :Dade mt Area : Central Dade Svc Ctr: Central Dade Z-0232 Figure 40, Existing Utilities: FPL (1/2) ---~---, ...... , I--~-1~ g ii ".,......___.,,._,._,.__ ,--,_,. . '-' (I) 0 :1,,.--........ i \_../~ Coun .Dade Svc Ctr; Central Dade Figure 41, Existing Utilities: FPL (2/2) Prepared for: Village of Key Biscayne AECOM 59 K-8 Basin Basis of Design Report (BODR) Village of Key Biscayne AECOM Project No.: 60690913 4.3 Comcast Cable On January 24, 2023, Ricardo Davidson (ricardoa davidson@cable.comcast.com; Comcast Construction Supervisor) provided a Comcast Cable existing utilities map for the K-8 Basin project area. Village staff indicated that Comcast Cable's undergrounding design will follow FPL's design. Comcast Cable's existing utilities within the K-8 Basin project area are shown in Figure 42. l_l_l_l I 1-1-1 I 4 Strand Strand Aer al Messenger Aer,al Slac Aerial Span Underground rench U derground Conduit - U known Figure 42, Existing Utilities: Comcast Cable 4.4 AT&T On January 24, 2023, Damian Bas (db022t@att.com; AT&T) provided an AT&T existing utilities map for the K-8 Basin project area. Village staff indicated that AT&T's undergrounding design will follow FPL's design. AT&T's existing utilities within the K-8 Basin project area are shown in Figure 43. Prepared for: Village of Key Biscayne AECOM 60 K -8 Ba sin Ba sis of D e sign R eport (B O O R ) Village of Key Biscayne AECOM Project No.: 60690913 External Map Request for Aecom Design Ticket 016302162 Project I -i=-j r--: MfilAI 1:4,096 N I • Poles ! MiinhOIH /'-../Conduit ,.. , ., S110e1Ce1110rtinft9 ,-_;Mapl)lnulndv11 t • j \'Yll'OG(lnU)f Bound111-y Pa1C(Jls LJ..lobAOI Date: 1/24/2023 Index Map ~•,"1JOM~r.,.. .... ..,..._..,,...,,...,..,..., .. ~ru....,,.,.,.u,_ .. , .,,_..,.,,_.M&T~-.;,,.r..,ot,.,,. , ... _. .... ~ • ..__,, .,.....,-..,,.,._,, r,o;,,M ,..,_,....,._ • .,..,~•-olA!-,.L-1,,_ ... Figure 43, Existing Utilities: AT&T Prep ared fo r: V illage of K ey Biscayne AECOM 61 K-8 Basin Basis of Design Report (BOOR) Village of Key Biscayne AECOM Project No.: 60690913 4.5 Miami-Dade Water and Sewer Department On January 31, 2023, Miami-Dade Water and Sewer Department ("WASD") representative Lisel Suarez Toledo, PE (lisel.suareztoledo@miamidade.gov; WASD Utility Engineering) provided WASD potable water and sanitary sewer as-builts for the K-8 Basin project area. WASD's as-builts incorporated into AECOM's preliminary design plans for this BOOR included as Appendix A.7. WASD and the Village have a Joint Powers Agreement ("JPA") in place; this agreement enables the Village to include WASD's capital and maintenance/repair projects in the K-8 Basin project and fulfill its "dig once" approach. Coordination with WASD for potential potable water and sanitary sewer improvements within the K-8 Basin project area is ongoing. 5 Maintenance of Traffic and Construction Phasing The sequence of construction needs to be planned to minimize traffic delays. The K-8 Basin project will involve the development and use of a Maintenance of Traffic ("MOT") Plan. This Plan would include traffic management and signage, access to residences and the K-8 School, detour routes, public notification of alternative routes, emergency services coordination, and project scheduling. Evaluation of the current traffic flow and the timing of construction would be required to develop the Plan. The Maintenance of Traffic will need to be coordinated with the Village. The local news media would be notified in advance of road closings and other construction-related activities which could excessively inconvenience the community to allow residents and/or tourists in the area to plan travel routes in advance. A sign providing the name, address, and telephone of the Village's contact person for the K-8 Basin project needs to be displayed on-site to assist the public in obtaining answers to questions or report complaints regarding the project's construction. The roadway reconstruction and drainage system improvements need to be completed in phases to avoid disrupting residents within the entire project area at the same time; the limits of construction would need to be coordinated with the Village. The preliminary phases of construction would be the following: 1. Phase 1: Construction at the three drainage outfalls into Hurricane Harbor, construction of the stormwater pump station at Harbor Drive Park, and the discharge force mains from the pump station to the drainage outfalls. 2. Phase 2: Construction of the stormwater collection and conveyance system within West McIntyre Street from Harbor Drive to Glenridge Road. The construction of the new drainage system should be performed in sections (west to east) to minimize access disruption for the residents and the K-8 School stakeholders. This phase needs to include construction of the side streets drainage system that would connect to the drainage trunkline on West McIntyre Street. 3. Phase 3: Construction of the stormwater collection and conveyance system within West Enid Drive from Harbor Drive to Glenridge Road. The construction of the new drainage system should be performed in sections (west to east) to minimize access disruption for the residents and the K-8 School stakeholders. This phase needs to include construction of the side streets drainage system that would connect to the drainage trunkline on West Enid Drive. 6 Permitting Evaluation Environmental resources management is of primary concern during the implementation of permitting, monitoring, education, restoration, regulatory, and land management programs to protect water quality and the natural resources that are vital to the health and well-being of the Village and the surrounding ecosystem. Regulations enforced by the agencies and applicable to the Project state that the following permits are to be obtained prior to the proposed infrastructure improvements and the associated rules be implemented per the issued permits and conditions. The following permits are recommended as part of the proposed stormwater improvements. Prepared for: Village of Key Biscayne AECOM 62 K-8 Basin Basis of Design Report (BODR) Village of Key Biscayne AECOM Project No.: 60690913 6.1 United States Army Corps of Engineers 6.1.1 Section 404 Authorization or Section 1 O Authorization Section 404 of the Clean Water Act requires a permit from the US Army Corps of Engineers ("USAGE") for any dredge or fill in waters of the United States, including all tidal waters and any wetlands adjacent to tidal waters. For projects impacting wetlands, compensatory mitigation is required to offset impacts associated with the proposed work. Projects in navigable waters, including all tidal waters, also require authorization from the USAGE under Section 10 of the Rivers and Harbors Act. Authorization under Section 404 and Section 10 can be obtained with a single application to the USAGE. During a preliminary inspection of the outfall locations, mangroves were identified within the proposed project footprint at two of the three proposed outfall locations. The mangroves identified will be required to be permitted for removal through the USAGE Section 404 permitting section. Compensatory mitigation for the mangrove impacts will be obtained through the purchase of mitigation credits from the Everglades Mitigation Bank, owned by FPL. As of April 2023, the Everglades Mitigation Bank offers joint state and federal mangrove mitigation credit at the cost of $150,000 per credit. Following a complete site inspection documenting the proposed impacts to mangroves and coordination with the regulating agencies, the Uniform Mitigation Assessment Method ("UMAM") will be used to determine the amount of credit that will be required to offset any proposed mangrove impacts. 6.2 South Florida Water Management District 6.2.1 Environmental Resource Permit - Individual Section 62-330 of the Florida Administrative Code requires an Environmental Resource Permit (ERP) be obtained for all work within wetlands or surface waters within the state of Florida. For the proposed stormwater improvements, an Individual ERP would be required from the South Florida Water Management District ("SFWM D"). A desktop analysis of the area proposed for impacts did not indicate a permit has been previously issued in the area, therefore a new Individual ERP will be required. During a preliminary inspection of the outfall locations, mangroves were identified within the proposed project footprint at two of the three proposed outfall locations. If the proposed work results in impacts to mangroves, compensatory mitigation will also be required at the state level. Mitigation banks can offer state, federal, or joint state-and-federal mitigation credit depending on the authorizations they have obtained from the federal and state regulators. Compensatory mitigation for the mangrove impacts will be obtained through the purchase of mitigation credits from the Everglades Mitigation Bank, owned by FPL. As of April 2023, the Everglades Mitigation Bank offers joint state and federal mangrove mitigation credit at the cost of $150,000 per credit. Following a complete site inspection documenting the proposed impacts to mangroves and coordination with the regulating agencies, the Uniform Mitigation Assessment Method (UMAM) will be used to determine the amount of credit that will be required to offset any proposed mangrove impacts. 6.3 Florida Department of Environmental Protection 6.3.1 National Pollutant Discharge Elimination System - Conceptual Generic Dewatering Permit Discharge of groundwater and stormwater from a noncontaminated site or a site outside of 500 feet from a contaminated site qualifies for a Conceptual Generic Dewatering Permit. If the site is determined to have contamination present or within 500 feet of a contaminated site, a Dewatering Permit from the FDEP Southeast District Office will be required in conjunction with the Conceptual Generic Dewatering Permit. A Dewatering Permit will be required from the FDEP Southeast District Wastewater Section if contamination is present or if the site is found to be within 500 feet of contamination. Prepared for: Village of Key Biscayne AECOM 63 K-8 Basin Ba sis of De sign R eport (B O O R ) Village of Key Biscayne AECOM Pro ject No.: 60690913 6.4 Miami-Dade County DRER - Department of Environmental Resources Management 6.4.1 Class I Permit Chapter 24-48(1 )(a) of the Miami-Dade County Code of Ordinances requires any work in, on, over, or upon tidal waters in M iami-Dade County to obtain a Miami-Dade County Class I Permit. Replacement of the existing headw alls, and any other in-water work, will therefore require authorization under a Miami-Dade County Class I Permit. During a preliminary inspection of the outfall locations, mangroves were identified within the proposed project footprint at tw o of the three outfall locations. If the seawalls are reconstructed at the existing outfall locations, the mangroves identified would be required to be permitted for removal through the Class I permitting section. It is anticipated that joint state-and-federal credit from the Everglades Mitigation Bank operated by FPL will also fulfill any local mitigation requirements. 6.4.2 Class II Permit Chapter 24-48(1 )(b) of the Miami-Dade County Code of Ordinances requires a Miami-Dade County Class II Permit for the construction, installation and/or alteration of any outfall or overflow system in, on, under or upon any water body of M iami-Dade County. A Miami-Dade County Class II Permit will therefore be required if stormw ater is proposed to discharge into any surface water in Miami-Dade County to control the pollution inherent in stormw ater runoff. In addition, any improvements to the stormwater system will need to be reviewed and appro ved by the M iami-Dade County Class II Permitting Section. 6.4.3 Class V Permit Chapter 24-48.(1 )(e) of the M iami-Dade County Code of Ordinances requires a Miami-Dade County Class V permit for any dewatering of groundwater, surface water or water which has entered into an underground facility, excavation or trench. The pro posed work will require a Miami-Dade County Class V Permit if the temporary dew atering of groundwater is required as part of construction to ensure that sediment, turbidity, and contaminants are removed before discharge. 6.4.4 Pollution Remediation Section Chapter 24-42 of the Miami-Dade County Code of Ordinances prohibits discharge of contaminated water or m atter into any waters in M iami-Dade County. If an area previously identified as contaminated is identified w ithin the limits of the proposed storm water improvements, an Authorization from the Miami-Dade County Pollution Remediation Section will be required prior to the issuance of the Class V dewatering permit. 6.4.5 Tree Program Section 18A-5 of the Miami-Dade County Code of Ordinances requires a Tree Removal/Relocation Permit for removal or relocation of any trees in Miami-Dade County. Impacts to trees within the proposed work area not specifically exempt under the Enviro nmental Code of Miami-Dade County will require a Tree Removal/Relocation Permit. Information to be submitted as part of the application process consists of species identification, global positioning system location on an aerial map, dimensions, a conditional rating, photos of the trees proposed for relocation or removal, details indicating whether the tree is to be relocated or removed, and potentially an arborist report if the processing biologist requires it. 6.5 Miami-Dade County Water and Sewer Department 6.5.1 Revision to the Existing Water and Sewer Permits Improvements to the M iami-Date County Water and Sewer Department ("WASD") potable water and sanitary sewer infrastructure will require a revision to the existing WASD Permit. P repare d for: V illage of K ey Biscayne AECOM 64 K-8 Basin Basis of Design Report (BOOR) Village of Key Biscayne AECOM Project No.: 60690913 6.5.2 Right-of-Way Permit Potential impacts within the vicinity of WASD's water and sanitary sewer infrastructure will require a WASD Right-of-Way Permit. 6.6 Village of Key Biscayne - Internal Departments 6.6.1 Public Works Department A Right-of-Way Permit will be required for the proposed improvements to the Village's stormwater system. In addition, an approval stamp from the Village of Key Biscayne PWD will be needed prior to submittal of the permit set/drawings to the applicable regulatory agencies. 6.6.2 Building, Planning, and Zoning Department A Building Permit will be required for the proposed improvements to the Village's stormwater system. In addition, approval from the Building, Zoning, and Planning Department's Tree Section verifying that the DERM Tree Program has issued a Tree Removal/Relocation Permit will be required prior to the issuance of a Building Permit. 7 Preliminary Marine Benthic Review 7.1 Introduction On March 20, 2023, qualified biologists from AECOM performed a preliminary marine benthic review of the three (3) proposed outfall locations within the Hurricane Harbor basin on the western side of the Village. This preliminary review was performed to identify potential resources within the immediate area of the proposed outfalls associated with the K-8 Basin project. A formal Benthic Resource Survey is scheduled to be performed between June 1, 2023 and September 30, 2023, in accordance with the Guidance on Surveys for Potential Impacts to Submerged Aquatic Vegetation as defined by the FDEP. The preliminary marine benthic review was performed by two snorkeling biologists. The biologists entered the Hurricane Harbor from a boat and began the survey at the proposed outfall locations. At each site, a 25-foot by 25-foot area was surveyed with the proposed outfall location as the center point of one edge of the survey area. For Outfalls 1 and 3, it was not possible to start the survey against the shore/seawall due to the presence of red mangroves (Rhizophora mangle); the survey was initiated as close to the mangroves as safely possible. The survey proceeded from the proposed outfall location along the shoreline for 12.5 feet in each direction from the center, then the diver turned waterward, traveled 5 feet, and then returned to the center line (see Figure 44) with the survey extending to a distance of 25 feet from shore at the proposed outfall locations. Observed resources and approximate locations were recorded and representative photos were taken. Visibility was limited to less than half a foot due to the suspended sediments in the water column caused by ongoing winds. Results of the preliminary benthic investigation are detailed below. Figure 44, Search Pattern Used to Observe Resources at the Existing Outfall Locations Prepared for: Village of Key Biscayne AECOM 65 K-8 Basin Basis of Design Report (BOOR) Village of Key Biscayne AECOM Project No.: 60690913 7.2 Results 7 .2.1 Outfall 1 - South (VKB Outfall #12) Outfall 1 is in an area dominated by mature red mangroves. The survey area waterward of the mangroves was comprised of predominantly a silt size sediment substrate with no resources apparent within the survey area, which ranged in depth from approximately 5 feet at the mangrove fringe to a depth of greater than 10 feet at the outer limits of the survey area. Approximately five hard corals (Siderastrea spp.) were found to exist within the survey area and were situated on boulders located approximately 10 feet north and 15 feet waterward of the proposed outfall location and beneath an existing dock structure. These hard corals were small in size measured at less than 10 centimeters. Oysters and macroalgae we observed binding to the mangrove prop roots and the existing dock pilings. Seagrasses were not found to exist within the survey area footprint. It is suspected that the mangrove canopy cast a significant shadow over the survey areas, which is not conducive to the growth of seagrass. Additional roving by the biologist identified seagrass to be present north and waterward of the survey area with low density patches of paddle grass (Halophila decipiens) and turtle grass (Thalassia testudinum) at less than 1 %. Green algae (Halimeda sp.) were observed outside the survey footprint. 7.2.2 Outfall 2 - East (VKB Outfall #15) Outfall 2 is on an existing seawall that contains a mosaic of vegetative species dominated by landscaped palm trees. The depth of water along the seawall was observed to be approximately 4 feet sloping significantly waterward to a depth of approximately 10 feet over a predominantly bare silt substrate. Hard corals were observed along the seawall and bound to the rocks and piping observed at the base of the seawall. The hard corals observed were limited to Siderastrea spp. with smaller size classes and some corals up to 10 centimeters in diameter. More than eight hard corals were observed. Minimal amounts of macroalgae were observed along the seawall and rock rubble. No other resources were identified in the area. Four West Indian manatees were observed loafing adjacent to the site. 7.2.3 Outfall 3 - North (VKB Outfall #14) Similar to the results stated above for Outfall 1, Outfall 3 is in a location currently dominated by mature red mangroves. At the base of the mangroves and along the seawall to the west, large boulders were observed on the substrate. The depth from the water's surface to the top of the boulders was approximately 2 feet. The depth to the substrate adjacent to the boulders was approximately 5 feet and sloped significantly waterward to a depth of greater than 10 feet over a predominantly bare silt substrate. Macroalgae and hard corals (Siderastrea spp.) were observed bound to the seawall and boulders. Six hard corals were observed and measured to be less than 10 centimeters in diameter. Macroalgae of various species were observed bound to the mangrove prop roots and in small patches random situated on the substrate of the survey area. No other resources were identified in the area. 7.3 Summary Based on the preliminary marine benthic review conducted in March 2023, seagrasses are not present within a 10-foot radius of any of the proposed outfall sites. Hard coral (Siderastrea sps.) of small size classes were observed at each of the three proposed outfall locations. The substrate consists of unconsolidated sediments of silt size grains. Potential modifications to Outfalls 1 and 3 would require impacts to the existing mangroves if the seawalls are reconstructed. Lastly, manatees were observed in close proximity to the site. No other protect flora or fauna were observed. Prepared for: Village of Key Biscayne AECOM 66 K-8 Basin Basis of Design Report (BOOR) Village of Key Biscayne AECOM Project No .. 60690913 7.4 Photo Log Site Location: Outfall 1, Hurricane Harbor, Key Biscayne Photo No.: 1 Date: 20 Mar 2023 Direction Photo was taken: East NE E SE 5 60 90 120 150 180 210 • I • I • I • I • I • I • I • I • I • I • I • I • I • I • I • I • I • I • I LAT: 25.690364 ILON: -80.174194 ±13ft • 13it Description: View of the existing red mangroves and dock structures at Outfall 1. Site Location: Outfall 1, Hurricane Harbor, Key Biscayne Photo No.: 2 Date: 20 Mar 2023 Direction Photo was taken: East Description: View of the existing red mangroves at Outfall 1. Prepared for: Village of Key Biscayne AECOM 67 K-8 Basin Basis of Design Report (BOOR) Village of Key Biscayne AECOM Project No.: 60690913 Site Location: Outfall 1, Hurricane Harbor, Key Biscayne Photo No.: 3 Date: 20 Mar 2023 Direction Photo was taken: North Description: View of boulders under the existing dock at Outfall 1 with several hard corals (Siderastrea spp.). Site Location: Outfall 2, Hurricane Harbor, Key Biscayne Photo No.: 4 Date: 20 Mar 2023 Direction Photo was taken: East Description: View of the existing seawall and docks at Outfall 2. N NE i E SE o 30 Go l so 120 iso I • I • I • I • I • I • I • I • I • I • I • I • I • I • I • I • I • I • I • Prepared for: Village of Key Biscayne AECOM 68 K-8 Basin Basis of Design Report (BOOR) Village of Key Biscayne AECOM Project No.: 60690913 Site Location: Outfall 2, Hurricane Harbor, Key Biscayne Photo No.: 5 Date: 20 Mar 2023 Direction Photo was taken: East Description: View of hard corals (Siderastrea spp.) observed on the existing seawall. Site Location: Outfall 3, Hurricane Harbor, Key Biscayne Photo No.: 6 Date: 20 Mar 2023 Direction Photo was taken: North Description: View of the existing red mangroves at Outfall 3. W NW i N NE 270 300 330 j 0 30 60 I • I • I • I • I • I • I • I • I • I • I • I • I • I • I • I • I • I • I LAT: 25.691147 LON: -80.173602 ±13ft A 10ft 'ffll Prepared for: Village of Key Biscayne AECOM 69 K-6 Basin Basis of Design Report (BOOR) Village of Key Biscayne AECOM Project No.: 60690913 Site Location: Outfall 3, Hurricane Harbor, Key Biscayne Photo No.: 7 Date: 20 Mar 2023 Direction Photo was taken: Northeast Description: View of the existing red mangroves at Outfall 3. Site Location: Outfall 3, Hurricane Harbor, Key Biscayne Photo No.: 8 Date: 20 Mar 2023 Direction Photo was taken: North Description: View of hard corals (Siderastrea sp.) observed on the existing boulders. Prepared for: Village of Key Biscayne AECOM 70 K-8 Basin Basis of Design Report (BOOR) Village of Key Biscayne AECOM Project No .. 60690913 Site Location: Outfall 3, Hurricane Harbor, Key Biscayne Photo No.: 9 Date: 20 Mar 2023 Direction Photo was taken: South Description: Green macroalgae and unconsolidated sediments seen waterward of Outfall 3 at ~7-feet depth. 8 Essential Fish Habitat Assessment The purpose of this section is to present the findings of an Essential Fish Habitat ("EFH") Assessment for the Proposed Action, as required by the Magnuson-Stevens Fishery Conservation and Management Act of 1976, as amended through the 1996 Sustainable Fisheries Act (Magnuson-Stevens Act ["MSA"]). The objective of this EFH Assessment is to evaluate whether the Proposed Action may affect EFH designated by the National Marine Fisheries Service ("NMFS"), also known as National Oceanic and Atmospheric Administration ("NOAA ") Fisheries, the South Atlantic Fisheries Management Council ("SAFMC") for the project area or Zone of Influence ("ZOI"), and Habitat Areas of Particular Concern ("HAPC"). The ZOI for the proposed project is located within both EFH habitat and HAPCs. This EFH Assessment includes a description of the Proposed Action; an analysis of direct, indirect, and cumulative effects on EFH for federally managed fish species and their prey; the potential effects of the Proposed Action; proposed mitigation measures to minimize expected project effects if applicable; and a summary of potential impacts. 8.1 Action Area The action area includes three existing outfalls in an area within the Village of Key Biscayne, Florida, known as Hurricane Harbor, centered at 25.6908°, -80.1736°. Hurricane Harbor is an area on the western side of Key Biscayne which encompasses approximately 3.8 acres of surface waters. Water depths range from 3- 15 feet within the basin. The Hurricane Harbor is of irregular shape with a mouth to the harbor measured at approximately 150-foot in width and leading to a basin width of dimensions 425-foot east to west and 235-foot north to south. The area is surrounded by single family homes with a shoreline that consists of vertical seawalls, concrete bags, or earthen edges sloped toward the basin. An aerial map showing the approximate locations of the existing structures is provided as Figure 45. Prepared for: Village of Key Biscayne AECOM 71 K-8 Basin Basis of De sign R eport (B O O R ) Village of Key Biscayne AECOM Pro ject No.: 60690913 0 75 150 I I 300 Feet I Biscayne Bay Legend t) Existing Outfall Figure 45, Existing Outfall Locations 8.1.1 EFH Consultation History AECO M , on behalf of the Village, completed a Biological Assessment ("BA"); refer to Section 10, Marine Species Biological Assessment of this BO OR. 8.2 Proposed Action The pro posed action will implement stormwater drainage improvements surrounding the K-8 School and street im pro vements within the vicinity of the school and along West McIntyre Drive and West Enid Drive. Drainage features include pipes, a proposed pump station and generator with raised electrical panels to be installed at Harbor Drive Park between West McIntyre Drive and West Enid Drive and force mains to three existing outfalls. If the existing outfalls were to be rehabilitated, manatee exclusion grates and dissipater structures in the form of rip rap rubble would need to be installed on a ten-foot by ten-foot area of the benthic substrate below each of the outfall locations. If additional easements along the shoreline are obtained by the Village, the existing outfalls would require the construction of a vertical seawall at each of the locations to support the new outfall pipes. Habitat supporting mature mangroves were identified at each of these locations during a preliminary investigation within the area. The mangroves may be required to be impacted · to support the proposed project. The drainage features will serve the immediate area as well as areas adjacent to the site for future needs. Pro posed street improvements will be designed to the Village's level of serv ice requirements. 8.3 EFH, Managed Fisheries, and Fishery Management Plans 8.3.1 Background M arine fisheries in the United States ("U.S.") are managed within a framework of overlapping federal, state, interstate, and tribal authorities. NOAA Fisheries and its eight regional Fishery Management Councils ("FMC") are responsible for the m anagement and protection offi sheries and habitat essential for the survival of m anaged species. In the southeastern U.S., the U.S. Secretary of Commerce, acting through NOAA Fisheries and in coordination with the SAFMC, has been delegated this authority under the provisions of the M SA (Public Law 104-208). Prep ared for: V illage of Key B iscayne AECOM 72 K-8 Basin Basis of Design Report (BOOR) Village of Key Biscayne AECOM Project No.: 60690913 The SAFMC is responsible for the management of fish stocks and areas of EFH within the federal 200- mile limit of the Atlantic Ocean coastline from North Carolina through Florida. The MSA, as amended by the Sustainable Fisheries Act of 1996, sets forth several mandates for NOAA Fisheries and the SAFMC to identify and protect important marine and fish habitat, and to delineate EFH for managed species within the Exclusive Economic Zone ("EEZ"), including highly migratory species (e.g., billfish, sharks, and tuna) that make extended migrations beyond the EEZ. The U.S. Congress ("U.S.C.") defined EFH as "those waters and substrate necessary to fish for spawning, breeding, feeding, or growth to maturity" [16 U.S.C. 1802 (1 O)]. The EFH definition is further interpreted as follows (Federal Register [FR] 62, 244, December 19, 1997): • Waters include aquatic areas and their associated physical, chemical, and biological properties that are used by fish and may include aquatic areas historically used by fish where appropriate, • Substrate includes sediment, hard bottom, structures underlying the waters, and associated biological communities, • Habitat required to support a sustainable fishery and the managed species contribution to a healthy ecosystem, and • Spawning, breeding, feeding, or growth to maturity covers a species' full life cycle. Section 303(a)(7) of the amended MSA directs NOAA Fisheries and the SAFMC, under the authority of the Secretary of Commerce, to describe and identify EFH within each Fishery Management Plan ("FMP"); minimize to the extent practicable, the adverse effects of fishing on EFH; and identify other actions to encourage the conservation and enhancement of EFH. The SAFMC has since designated EFH for many species under its jurisdiction and has identified ways to minimize adverse impacts to EFH in the FMPs provided within the Final Habitat Plan for the South Atlantic Region (SAFMC, October 1998). Additionally, the SAFMC has designated several Habitat Areas of Particular Concern (HAPCs; subsets of EFH), which include areas that hold an especially important ecological function, are sensitive to human-induced environmental degradation, are particularly vulnerable to development activities, or are particularly rare. Section 305(b)(2) of the MSA "requires federal action agencies to consult with NOAA Fisheries on all actions, or proposed actions, authorized, funded, or undertaken by the agency, that may adversely affect EFH." An adverse effect is defined as "any impact which reduces the quality and/or quantity of EFH," which includes physical, chemical, or biological effects (NMFS, 2004). Effects may manifest in several ways, either directly or indirectly, and on any spatial scale, including areas beyond EFH. For example, changes in water quality, benthic communities, or prey availability may constitute adverse effects on EFH. An impact that reduces the quality or quantity of EFH is an adverse effect. Effects are evaluated on a spatial scale from site-specific to habitat-wide, and on a temporal scale that includes the cumulative effects of multiple actions on EFH. The EFH Guidelines (50 Code of Federal Regulations [CFR] 600.05-600.930) outline the process for federal agencies, NOAA Fisheries, and the FMC to satisfy the EFH consultation requirement under Section 305(b)(2)-(4) of the Magnuson-Stevens Act. As part of the EFH consultation process, the guidelines require federal action agencies to prepare a written EFH Assessment describing the effects of that action on EFH (50 CFR 600.920(e)(1 )). An EFH Assessment is a critical review of a proposed project and its potential impacts to EFH. As set forth in the rules, EFH Assessments need to include: (1) a description of the proposed action; (2) an analysis of the effects, including cumulative effects, of the action on EFH, the managed species, and associated species by life history stage; (3) the federal agency's views regarding the effects of the action on EFH; and (4) proposed mitigation, if applicable. The level of detail in an EFH Assessment should be commensurate with the complexity and magnitude of the potential adverse effects of the action. EFH Assessments are needed for efficient and effective consultations between a federal action agency and NOAA Fisheries. Under the MSA, federal agencies are required to consult with the NOAA Fisheries Service when their proposed activities may have an adverse effect on EFH. The MSA defines an adverse effect as "any impact which reduces quality and/or quantity of EFH." Adverse effects may include direct or indirect physical, chemical, or biological alterations of the waters or substrate and loss of, or injury to, benthic organisms, prey species and their habitat, and other ecosystem components, if such modifications reduce the quality and/or quantity of EFH. Adverse effects to EFH may result from project activities occurring within EFH or outside of EFH and may include site-specific or habitat-wide impacts, including individual or synergistic consequences of actions. Prepared for: Village of Key Biscayne AECOM 73 K-8 Ba sin Ba sis of D esign R eport (B O O R ) Village of Key Biscayne AECOM Pro ject No.: 60690913 T his assessm ent of EFH for the Vi llage of Key Biscayne Im provements Project is being provided in conform ance w ith the 1996 A m endm ents to the M SA. Section 2.0 discusses the proposed action. Section 3.0 (E F H , M anaged Fisheries, and Fishery M anagement Plans) of this assessment pro vide a general de scription of the EFH and H A P Cs found w ithin the project area as well as a description of the SAFMC m a naged species that m ay potentially utilize EFH within the pro ject evaluation area. Section 4.0 (A ssessm ent of Potential Im pacts) evaluates avoidance and m inim ization m easures to eliminate and/or reduce EFH im pacts resulting fro m the pro posed pro ject. Section 5.0 (Mitigation) and Section 6.0 (The Eff ects of the A ction), provide our concl usions and pro posed m itigation m easures. 8.3.2 Essential Fish Habitat T he 19 96 am endm ents to the M S A set fo rth a m andate fo r NO AA Fisheries, regional FMC, and other federal agencies to identify and protect EFH of econom ically im portant m arine and estuarine fisheries. To achieve this goal, suitable fisheries habitat needs to be m aintained. A pro vision of the M SA requires FMC to identify and protect EFH fo r every speci es m anaged by an FM P (USC 1853(a)(7)). In general, EFH is designated based on tw o com ponents: the life-stage of the species and the habitat type required during that life-stage. U sing this approach, the SA FM C identifies categories of EFH based on the biological requirements of a m a naged species during each life-stage (eggs, larv ae, post-larv ae, early juveniles, late juveniles, adults, and spaw ning adults). Eggs are the fertilized pro duct of individuals that have spaw ned, individuals de pending com pletely on their yolk-sac fo r nutrition in this unhatched phase. Larvae are individuals that have hatched and can generally capture prey. Juveniles are individuals that are not sexually mature but have fully fo rm ed organ system s, like those of adults. Adults are sexually m ature individuals that are not necessarily in spaw ning condition, w hile spawning adults are those individuals capable of pro ducing offspring. The SA FM C m anages com m ercial and recreational fisheries resources in federal waters under the following eight FM P s: C oastal M igratory Pelagic (m ackerel and cobia); Dolphin and Wahoo; Sargassum; Golden C rab; S hrim p; Snapper Grouper; C oral and Live Bottom Habitat; and Spiny Lobster. It should be noted that hig hly m igratory species (sharks, billfish, and tuna) are directly m anaged by the Atlantic Highly M igratory Speci es D ivision of N O AA Fisheries under the incidental harassm ent authorization consolidated FMP, which includes the A tlantic w aters and fisheries. G iven the geographical location of the Proposed Action, the SAFMC has designated EFH for various species/m anagem ent groups and associated species at various life-stages that m ay be found in the area. Table 9 provides a list of the federally m anaged species with designated EFH and HAPC that use or m ay use the project area at any tim e, given their geographical distribution, life-history, and physiological tole rances (N O AA , 2023). Table 9, FM P Species w ith EFH and HAPC that may be within the Vicinity of the Proposed Action Life-Stage Common name Scientific name (Eggs, Larvae, Juvenile, and Adult) Spiny Lobster Spiny lobster Panulirus argus All Slipper lobster Scyllarides nodifer All P rep ared for: V illage of Key Biscayne AECOM 74 K-8 Basin Basis of Design Report (BOOR) Village of Key Biscayne AECOM Project No.: 60690913 Life-Stage Common name Scientific name (Eggs, Larvae, Juvenile, and Adult) Reef Fish Almaco jack Serio/a rivoliana All Anchor tilefish Caulolatilus intermedius All Atlantic Spadefish Chaetodipterus faber All Banded rudderfish Serio/a zonata All Bank Sea Bass Centropristis ocyurus All Bar Jack Caranx ruber All Black grouper Mycteroperca bonaci All Black Sea Bass Centropristis striata All Blackfin snapper Lutjanus buccanella All Blackline tilefish Caulolatilus cyanops All Blue runner Caranx crysos All Blueline tilefish Caulolatilus microps All Bluestriped grunt Haemulon sciurus All Coney grouper Cephalopholis fulva All Cottonwick grunt Haemulon melanurum All Crevallejack Caranx All Cubera snapper Lutjanus cyanopterus All Dog snapper Lutjanus jocu All Dolphin/Dorado/Mahi Coryphaena hippurus All Dwarf sand perch Diplectrum bivittatum All Prepared for: Village of Key Biscayne AECOM 75 K-8 Basin Basis of Design Report (BOOR) Village of Key Biscayne AECOM Project No .. 60690913 Life-Stage Common name Scientific name (Eggs, Larvae, Juvenile, and Adult) French grunt Haemulon flavolineatum All Gag grouper/Charcoal belly Mycteroperca microlepis All Golden tilefish Lopholatilus chamaeleonticeps All Goliath grouper Epinephelus itajara All Grass porgy Calamus arctifrons All Gray snapper Lutjanus griseus All Gray triggerfish Batistes capriscus All Graysby grouper Cephalopholis cruentata All Greater amberjack Serio/a dumerili All Hogfish Lachnolaimus maximus All Jolthead porgy Calamus bajonado All Knobbed porgy Calamus nodosus All Lane snapper Lutjanus synagris All Lesser amberjack Serio/a fasciata All Longspine porgy Stenotomus caprinus All Mahogany snapper Lutjanus mahogoni All Marbled grouper Epinephelus inermis All Margate grunt Haemulon album All Misty grouper Epinephelus mystacinus All Mutton snapper Lutjanus analis All Nassau grouper Epinephelus striatus All Prepared for: Village of Key Biscayne AECOM 76 K-8 Basin Basis of Design Report (BOOR) Village of Key Biscayne AECOM Project No .. 60690913 Life-Stage Common name Scientific name (Eggs, Larvae, Juvenile, and Adult) Ocean triggerfish Canthidermis sufflamen All Porkfish Anisotremus virginicus All Puddingwife Halichoeres radiatus All Queen snapper Etelis oculatus All Queen triggerfish Batistes vetula All Red grouper Epinephelus morio All Red hind grouper Epinephelus guttatus All Red porgy Stenotomus chrysops All Red snapper Lutjanus campechanus All Rock Hind grouper Epinephelus adscensionis All Rock sea bass Centropristis philadelphica All Sailors choice grunt Haemulon parra All Sand tilefish Ma/acanthus plumieri All Sand perch Diplectrum formosum All Saucereye porgy Calamus All Scamp Mycteroperca phenax All Schoolmaster Lutjanus apodus All Sheepshead Archosargus probatocephalus All Silk snapper Lutjanus vivanus All Smallmouth grunt Haemulon chrysargyreum All Snowy grouper Epinephelus niveatus All Prepared for: Village of Key Biscayne AECOM 77 K-8 Basin Basis of Design Report (BOOR) Village of Key Biscayne AECOM Project No.: 60690913 Life-Stage Common name Scientific name (Eggs, Larvae, Juvenile, and Adult) Spanish grunt Haemulon macrostomum All Speckled hind Epinephelus drummondhayi All Tiger grouper Mycteroperca tigris All Tomatate grunt Haemulon aurolineatum All Vermilion snapper Rhomboplites aurorubens All Warsaw grouper Epinephelus nigritus All Whitebone porgy Calamus leucosteus All White grunt Haemulon plumierii All Wenchman Pristipomoides aquilonaris All Yellowedge grouper Epinephe/us flavolimbatus All Yellowfin grouper Mycteroperca venenosa All Yellow jack Carangoides barthoomaei All Yellowmouth grouper Mycteroperca interstitialis All Yellowtail snapper Ocyurus chrysurus All Coastal Migratory Pelagics Cobia Ling, Rachycentron canadum All King Mackerel Scomberomorus cavalla All Spanish Mackerel Scomberomorus maculatus All Golden crab Golden crab Chaceon fenneri All Jonah crab Cancer borealis All Prepared for: Village of Key Biscayne AECOM 78 K-8 Ba sin Ba sis of Design R eport (B O D R ) Village of Key Biscayne AECOM Pro ject No.: 60690913 Life-Stage Common name Scientific name (Eggs, Larvae, Juvenile, and Adult) Red crab Chaceon quinquedens All Sargassum Sargassum Sargassum All Sharks Blacknose shark Carcharhinus acronotus Juvenile, Adult Blacktip shark Carcharhinus /imbatus Larvae, Juvenile, Adult Bonnethead shark Sphyrna tiburo Larvae, Juvenile, Adult Bull shark Carcharhinus leucas Juvenile, Adult Great hammerhead shark Sphyrna mokarran All Lemon shark Negaprion brevirostris Larvae Nurse shark Ginglymostoma cirratum Juvenile, Adult Smooth hammerhead shark Sphyrna lewini Juvenile, Adult Spinner shark Carcharhinus brevipinna Larvae Tiger shark Galeocerdo lewini Larvae, Juvenile, Adult Shrimp Brown shrimp Penaeus aztecus All Pink shrimp Penaeus duorarum All White shrimp Penaeus setiferus All Rock shrimp Sicyonia brevirostris All Royal Red shrimp Pleoticus robustus All P rep ared for: V illage of Key Biscayne AECOM 79 K-8 Basin Basis of D esign R eport (B O D R ) Village of Key Biscayne AECOM Pro ject No.: 60690913 NO AA Fisheries also designates specific habitat for managed species that may influence SAFMC food w ebs and connectivity should they be negatively impacted by anthropogenic activities, such as coastal development. NO AA Fisheries divides EFH into estuaries, nearshore, and offshore. In addition, the agency separates EFH into estuarine and marine components because they each support specific life-stages. The estuarine component is defined as "all estuarine waters and substrates (mud, sand, shell, rock and associated biological communities), including the sub-tidal vegetation (grasses and algae) and adjacent inter-tidal vegetation (marshes and mangro ves)." The marine component is defined as "all marine waters and substrates (mud, sand, shell, ro ck, hard bottom, and associated biological communities) from the shoreline to the seaward limit of the EEZ." The MSA, thro ugh the EFH provision, protects substrate needed for federally managed fisheries. In this context, "substrate" includes the associated benthic communities that make these areas suitable fish habitat. Water colum n habitat (estuarine and marine) is defined in terms of preferred levels in the physiochemical factors for m arine species, such as temperature, salinity, density, nutrients, and light availability. M ost m arine species rely on certain habitat during a specific life-stage or for their entire life cycle (eggs-adult stage). Designated EFH for the managed fisheries is often based on the seasonal and year­ round occurrence of species, which is generally linked to their life-stage. In estuaries, the EFH of each species is based on their relative abundance (common, abundant, highly abundant). In offshore areas, EFH consists of those areas depicted as "adult areas," "spawning areas," and "nursery areas." The project area contains four types of habitats that are essential for fish species managed in the South Atlantic region: Estuarine Intertidal Scrub-Shrub Wetland, Marine and Estuarine Water Column Habitat, Seagrass Habitats and Coral Reefs Live/Hardbottom. This following section provides a general description of these habitat types and potential use by SAFMC managed species. 8.4 EFH Habitat Types within the Proposed Action Area 8.4.1 Estuarine Intertidal Scrub-Shrub Wetland Estuarine intertidal scrub-shrub (mangrove) wetlands generally have high rates of primary production and are widely recognized for pro viding a variety of beneficial biological and physical functions. This habitat is know n to pro vide important nursery, feeding, and refuge habitat for both recreationally and commercially im portant fisheries and their prey resources (SAFMC, 1998a). It also plays an important part in the estuarine fo od web by providing particulate organic detritus to the water column, providing rookery habitat for a variety of bird species, and contributing to sediment stabilization for shoreline protection. Mangroves are known to provide nursery habitat for a variety of species, such as spiny lobster, pink shrimp, mullet, tarpon, snook, and m angrove snapper (Lewis et al., 1985). M angroves located along the seawall directly abuts Biscayne Bay within the project area and receives tidal flow via a direct connection during ext reme high tide events. The mangroves within the project area are considered m angro ve fringe forests. Mangrove fringe forests typically occur along sheltered shorelines with exposure to open water of lagoons and bays. The mangrove areas are isolated and do not demonstrate hydro logic connectivity to the surro unded upland area features. 8.4.2 Marine and Estuarine Water Column Habitat M arine and estuarine water column habitat traditionally comprises four salinity categories: oligohaline (< 8 ppt), m esohaline (8 -18 ppt), polyhaline waters (18 - 30 ppt), and some euhaline water (>30 ppt) around inlets. P rep ared for: V illage of Key Biscayne AECOM 80 K-8 Ba sin Ba sis of D e sign R eport (B O O R ) Village of Key Biscayne AECOM Project No.: 60690913 Saline environments have m oving boundaries but are generally maintained by sea water transported through inlets by tide and wind m ixing with fresh water supplied by land runoff. Particulate materials settle fro m these m ixing waters and accumulate as bottom sediments. Coarser-grained sediments, saline waters, and m igrating organisms are introduced from the ocean, while finer grained sediments, nutrients, organic m atter, and fresh water are input from rivers and tidal creeks. The sea water component stabilizes the system , with its abundant supply of inorganic chemicals and its relatively conservative temperatures. Closer to the sea, rapid changes in the enviro nmental variables generally occurs, such as water temperature; water temperature is m oderate compared to shallow upstream waters. Wi thout periodic additions of sea water, seasonal thermal extremes would reduce the biological capacity of the water column, including reducing the recruitment of m arine fauna fro m the ocean. Wh ile nearby wetlands contain some assimilative capacity abating nutrient enrichment, freshwater inflow and tidal flushing are important for circulation and removal of nutrients and wastes from the estuary (SAFMC, 1998a). The water column is the lifeblood of aquatic ecosystems. In many ways, it is the medium through which all other aquatic habitats are connected. As such, the water column provides a basic ecological role and function fo r organisms within it. The water column also provides other functions, both by itself and through benthic-pelagic coupling. Benthic-pelagic coupling refers to the processes that affect the connectivity betw een the benthic zone and pelagic zone through the exchange of and sediments, energy and nutrients w ithin the water colum n and play a critical function to food web nutrient cycles. The potential pro ductivity of fish and invertebrates in a system is determined by the assimilation of energy and nutrients by green plants and other life at the base of the food chain. The potential productivity of a habitat can indicate its relative value in supporting fish populations. Although productivity in the water colum n is derived m ostly fro m phytoplankton, it can also come from bacterial decomposition of plants (detritus), floating plants, and m acro algae (SAFMC, 1998a). In general, water column habitat exists wherever there is estuarine, nearshore, or offshore habitat. NOAA Fisheries describes the water column for EFH by water depth. Water column habitat is loosely defined as 'the water m ass between the surface and the bottom" of marine and estuarine waters. Estuarine water colum n habitat supports numerous species depending on their specific requirements, which can change thro ughout their life cycle. Typically, there is a mixing of seawater and fresh water within estuarine enviro nm ents, and the influx of nutrients fro m both sources results in high productivity (SAFMC, 2004). M ost m arine-spawning species use the water column during their egg and larvae life-stages; the estuarine w ater column transports eggs and larvae since they are unable to swim. This habitat provides nursery, foraging, and refuge for m any ecologically and commercially important shellfish and finfish. Differences in the chemical and physical properties of the water affect the biological components of the water column, including fish distribution. Water column properties that may affect fishery resources include temperature, salinity, dissolved oxygen ("DO "), total suspended solids ("TSS"), nutrients (nitrogen, phosphorus), and chloro phyll a (SAFMC, 1998a). Other enviro nmental factors also affect the distribution of aquatic organisms, such as depth, pH, water velocity and movement, and water clarity. Salinity levels (18-30 parts per thousand [ppt]) are wide ranging and depend on the geographical distance to marine waters, water flow, and tides. Saline enviro nments have moving boundaries but are generally maintained by sea water transported through inlets by tide and wind mixing with fresh water supplied by land runoff. The water column has both horizontal and vertical components that cause seasonal variations in salinity, phytoplankton, oxygen content, and nutrients conditions (SAFMC, 1998a). 8.4.3 Soft Bottom (Mud, Sand, Clay) Soft bottom habitats include sediments composed of loose rock, gravel, cobble, pebble, sand, clay, mud, silt, and shell fragments. Soft bottom sediments range in size from gravel (larger than 2.0 millimeters [mm]) to sand (0.05 to 2.0 m m), silt (0.002 to 0.05 mm), and clay (less than 0.002 mm). Prepared fo r: V illage of K ey Biscayne AECOM 81 K-8 Basin Basis of Design Report (BOOR) Village of Key Biscayne AECOM Project No.: 60690913 Surface sediments may affect shrimp and fish distributions directly in terms of feeding and burrowing activities or indirectly through food availability, water column turbidity, and related factors. Quartz sand predominates the nearshore environment, to a depth of 10 m to 20 m, from the Everglades northward along the coast of Florida (GMFMC. 2004). Sediment quality is influenced by physical, chemical, and biological components; its deposit location; the properties of seawater; contaminants; and other factors. Because these factors interact to some degree, sediments tend to be dynamic and are not easily generalized. Benthic fauna and infauna often rework sediments in the process of feeding and burrowing. In this way, marine organisms can influence the structure, texture, and composition of sediments, including the horizontal and vertical distribution of substances in the sediment (Boudreau, 1998). Soft bottom habitat is sometimes associated with loose shell fragments; this habitat type can be inhabited by various infauna (e.g., worms and crustaceans) and epifauna (e.g., sea pens), which act as ecosystem engineers and modify these habitats by the presence of their physical structure or burrowing in the substrate (GMFMC, 2004). 8.4.4 Seagrasses Seagrass habitats throughout the tropics directly benefit multiple fishery resources by providing important nursery and forage habitat for many valuable commercial and recreational fishes. Seagrass is part of a habitat complex that includes mangrove and hardbottom, which is historically abundant throughout Biscayne Bay. Seagrasses support a diverse community of fish and invertebrates within the Biscayne Bay Aquatic Preserve ("BBAP") area and provide critical water quality maintenance functions, including stabilizing sediments, diminishing wave action, and producing and exporting detritus materials, which is a key component to several estuarine and marine ecosystems. Several species of seagrass are found within Biscayne Bay: paddle grass (Halophila decipiens), shoal grass, turtle grass (Thallassia testudinum), manatee grass (Syringodium filiforme), star grass (Halophi/a engelmanni1) and Johnson's seagrass (Halophila johnsonii). This region of BBAP was previously designated as critical habitat for Johnson's seagrass however the NMFS issued a final rule to remove Johnson's seagrass from the Federal List of Threatened and Endangered Species effective on May 16, 2022. These actions also remove the critical habitat designation since it no longer qualifies for listing under the Endangered Species Act ("ESA"). In the South Atlantic region, all seagrasses are found on unconsolidated sediments in a wide range of physical settings and different stages of meadow development leading to a variety of cover patterns from patchy to continuous. Seagrass patches form and migrate across the sea bottom, and in high current environments, movement is considerable, and beds tend to remain in a continuously patchy state (SAFMC A14 2016). In contrast, contiguous perennial beds will tend to form in low energy embayments and protected areas. The SAFMC identifies seagrass habitat as EFH HAPC for several species managed under the Snapper Grouper FMP, such as adult white grunt (Haemu/on plumier,); juvenile and adult gray snapper (Lutjanus griseus) and lane snapper (Lutjanus synagris); juvenile mutton snapper (Lutjanus analis), schoolmaster (Lutjanus apodus), dog snapper (Lutjanus jocu); and goliath grouper (Epinephelus itajara). The seagrass composition within the proposed action area will be formally evaluated during the 2023 seagrass season and observations will be presented in a benthic resource report. A preliminary presence/absence evaluation conducted on March 20, 2023 identified that seagrass are located beyond the anticipated project boundaries and complete avoidance is feasible during construction. 8.4.5 Coral Reefs and Live/Hardbottom The coral, coral reefs, and live/hardbottom habitats located off the southeast coast of Florida are the primary natural reef builders in the region (SAFMC 2017). These habitats provide shoreline stabilization that protects nearby beaches and are utilized by over 500 species of fishes, invertebrates, and plants. Live/Hardbottom habitats are often centrally located between mid-shelf reefs to the east and estuarine habitats within inlets to the west. Prepared for: Village of Key Biscayne AECOM 82 K-8 Basin Basis of Design Report (BO OR) Village of Key Biscayne AECOM Project No.: 60690913 A s such, they serv e as settlem ent habitats for larv ae or as intermediate nursery habitats for juveniles m igrating in/out of coastal inlets. N earshore reefs abate w ave and current energy and are vital in the protection against coastal erosion. T he SA FM C has designated coral, coral reefs, and live/hardbottom habitat as a HAPC for species within the C oral FM P and the Spiny Lobster FM P. The project action area does not contain reef, however isolated ha rdbott om substrate m ay be present. The live/hardbottom habitat provides habitat for corals and possibly spiny lobster. A prelim inary benthic resource evaluation was conducted on M arch 20, 2023 and did not ide ntify the presence of coral. A fo rm al surv ey w ill be conducted in June 2023 to further identify if coral resources are w ithin the project footprint. Im pact avoidance to corals will be implemented prior to construction com m encem ent and w ill be further addressed during the enviro nm ental permitting process. 8.5 Federally Managed Species N O AA Fisheries authority to m anage EFH is directly connected to species covered under FMPs in the U nited States, incl uding A laska, Haw aii, the U .S. Virgin Islands, and Puerto Rico. EFH sections of FMPs incl ude detailed life-history and habitat inform ation used to describe and identify EFH for each FMP's federally m anaged species. The FM P s and Am endm ents m anaged by the SAFMC describe EFH for species under the agency's jurisdiction. NO AA Fisheries m anages EFH on the basis it can support the life­ stages of m anaged species, not the actual presence of those life-stages or species. NO AA Fisheries also has the authority to separately protect, conserv e, and m anage various protected species under the ESA. Of the 80 fish and m acroinvertebrate species that are federally m anaged, two (2) species of spiny lobster and S napper-G ro uper fish species have designated EFH , indicated they are know n to occur, or may potentially occur, perm anently or seasonally w ithin the Biscayne Bay area in close proximity to the Key Biscayne H urricane Harbor. A s such, the planned outfall construction activities could potentially impact EF H . T hese species are considered likely to utilize EFH w ithin the pro ject area based upon their known geographical distribution, life history inform ation, and physiological tolerances (SAFMC 1998a; SAFMC 1998b). 8.5.1 Spiny Lobster EFH fo r the spiny lobster in the G ulf of M exico ("G O M ") are w ater depths between 5 and 10 fathoms fro m Tarpon S prings, Florida to Naples, Florida, and out to depths of 15 fathoms from Cape Sable, Florida, to the boundary betw een the areas covered by the SAFM C and the Gulf of M exico FMC ("GMFMC"). In general, the spiny lobster is fo und in offshore coral reefs and seagrasses how ever, the South Florida Reef T ract appears to be the m ost im portant habitat for this species (G M FMC, 2004). Areas of high relief on the continental shelf provide habitat and incl ude coral reefs, artifici al reefs, ro cky hard bottom substrates, ledges and caves, sloping soft bottom areas, and lim estone outcroppings pro vide the ideal habitat conditions. R epro ductive fem ales m igrate to deeper w aters (15-30 m ) to release eggs. Larvae are water colum n associated and occur throughout the south Florida coastli ne in offshore waters. Juvenile spiny lo bsters are know n to use subm erged aquatic vegetation, reefs, and hard bottom habitats (NMFS, 2016). 8.5.2 Reef Fish R eef fish EFH in the SA FM P incl udes all estuaries. The R eef Fish FM P includes various species of snapper, grouper, and sea bass, w hich are com m only found in the warm , temperate waters of Biscayne Bay. Some of these speci es m ay also occur in the eastern Atlantic, and a few have representative populations within the eastern Paci fic. A dults are know n to use offshore coral reef, limestone, hard bottom, and artificial reef ha bitats, w hile juveniles occupy shallow , inshore areas associated with seagrass beds, m angro ves, and inshore reefs (G M FM C , 1981 ). Wh ile m ost reef fish species occur within deeper offshore waters as adults, so m e use nearshore estuarine habitats during juvenile life-stages. Prepared for: Village of Key Biscayne AECOM 83 K-8 Basin Basis of Design Report (BODR) Village of Key Biscayne AECOM Project No.: 60690913 Based on the presence of estuarine habitats, juvenile reef fish species may be found within the Proposed Action Area, including gray snapper, lane snapper, black grouper, and gag grouper. Of these species, the gray snapper and lane snapper are known to occupy nearshore estuarine habitats, such as mangroves, soft bottom, and sand/shell substrate, throughout their entire life cycle. The remaining species use nearshore estuarine habitats during juvenile life-stages only; adults migrate offshore to deeper hard bottom and reef habitats (GMFMC and NMFS, 2016). 8.5.3 Sharks Within the project area, EFH is present for ten species of sharks including blacknose, blacktip, bonnethead, bull, great & smooth hammerhead, tiger, spinner, nurse, and lemon sharks. These species of small and large coastal sharks use inshore and coastal habitats within the coast of Florida as nursery and foraging grounds. For instance, blacktip shark EFH for neonates and young of the year includes coastal areas, including estuaries and is one of the most productive blacktip shark nurseries. Blacktip shark neonate EFH is associated with water temperatures ranging from 20.8 to 32.2°C, salinities ranging from 22.4 to 36.4 ppt, water depth ranging from 3 to 25 feet, and DO ranging from 4.32 to 7.7 milligrams per liter (mg/L) in silt, sand, mud, and seagrass habitats. The blacknose shark is found at various water depths up to 45 m, bonnethead shark is found at various water depths up to 80 m, lemon shark is found at various water depths up to 91 m, and the bull, tiger, nurse, and blacktip shark are found at many water depths (Grace and Henwood, 1997). The larger coastal sharks include tiger, blacktip, bull, nurse, and lemon; smaller coastal sharks include blacknose, and bonnethead. Although each species has its own spatial and temporal patterns of habitat, general trends are observed among them and include utilization of inshore and estuaries as primary and/or secondary habitat; pupping activity primarily occurs in late spring and early summer, and newborn and juvenile sharks inhabit these primary nurseries throughout summer and into fall; these species migrate south, or offshore, when water temperatures begin to decline; and annual migratory cycles in which juveniles and adults move back and forth each year are seen in large and small coastal sharks (Hueter & Tyminski, 2007). 8.5.4 Coastal Migratory Pelagics The Coastal Migratory Pelagics Management Unit comprises three fish species: king mackerel, Atlantic Spanish mackerel, and cobia. The king mackerel, the largest of the three species, occurs throughout the Gulf of Mexico and the Caribbean Sea and along the western Atlantic Ocean from the Gulf of Maine to Brazil. Adults are water column associated and are found over reefs and in coastal waters, although they rarely enter estuaries. Spawning occurs over the outer continental shelf, and larvae are typically found over the middle and outer continental shelves (GMFMC and NMFS, 2016). Juveniles occupy inshore areas outward to the middle continental shelf (GMFMC, 1983). Atlantic Spanish mackerel occur throughout the coastal zones of the western Atlantic, from southern New England to the Florida Keys, and in the GOM, where they are centered off the Florida coast. Adults reside in coastal waters over the inner continental shelf and may enter estuaries in pursuit of baitfish and larvae occur over the inner continental shelf. Juveniles prefer estuarine habitats and nearshore waters; late juveniles can also occupy offshore waters to a depth of 50 m. Cobia are found in coastal and offshore waters from bays and inlets to the continental shelf. This species is primarily associated with the water column but also use hard bottom habitat in nearshore and offshore waters to a depth of 70 m. Spawning occurs offshore; however, larvae can occupy estuarine, nearshore, and offshore waters while the juvenile cobia occupy in nearshore and offshore waters. 8.5.5 Shrimp Five federally managed shrimp species are included in the Shrimp Fishery Management Plan. Of these, three are known to occur, or may potentially occur within the project area at some stage in their life history, including the pink shrimp, white shrimp, rock shrimp, royal red shrimp, and brown shrimp. Prepared for: Village of Key Biscayne AECOM 84 K-8 Basin Ba sis of D e sign R e port {B O O R ) Village of Key Biscayne AECOM Project No.: 60690913 Each of these five species has a similar range along the Atlantic coast. Pink shrimp occur from the Chesapeake Bay to the Florida Keys. W hite shrimp range from Fire Island, New York, to the St. Lucie Inlet in Florida. Brow n shrimp occur from Martha's Vineyard south to the Florida Keys. Wi thin the ICW and BBAP, pink shrimp and brown shrimp have been identified as the most common species. All penaeid shrimp have a life cycle that requires both inshore (post larvae and subadults) and offshore (adults and larv ae) m arine and estuarine habitats. Offshore, adult pink shrimp are most abundant near hard sand and calcareous substrates in waters of 11 to 37 meters (36-121 feet) in depth. They are also common in shallower estuaries and m arine waters surrounding the Florida Keys. Wh ite shrimp are generally found on soft, muddy bottoms within waters less than 27 meters (89 feet) in depth. Adult brown shrimp appear to prefer a similar substrate and are m ost abundant in waters less than 55 meters (180 feet) in depth. All species spaw n offshore, and spawning times varies slightly over space and time. Post larv al penaeid shrimp migrate to inshore habitats such as Biscayne Bay, which is considered nursery areas fo r post larval shrimp because they offer abundant food, suitable substrate, and shelter from predators. All species are omnivorous bottom feeders and are mostly active at night. As shrimp increase in size, they begin migrating toward high salinity oceanic waters either in the fall or the following spring (overw intering stock). According to the SAFMC, EFH for shrimp includes inshore nursery areas, offshore marine habitats used for spaw ning and gro wt h to m aturity, and all interconnecting water bodies. The SAFMC has further designated the follow ing areas as HAPC for penaeid shrimp: 1) all coastal inlets, 2) all state-designated nursery habitats of particular importance to shrimp, and 3) state-identified overw intering areas. Wi thin the pro posed project action area, EFH for penaeid shrimps include the fringing mangroves, and the water colum n. Based upon their typical life cycle, shrimp found within the project area are likely to be post larvae, juveniles, or overw intering stock. 8.6 Habitat Areas of Particular Concern As defined by the MSA, HAPC are subsets of EFH that include areas that hold a particularly important ecological function, and are sensitive to human-induced environmental degradation, particularly vulnerable to development activities, or particularly rare. The SAFMC designated HAPC broadly to include both general habitat types (i.e., seagrass beds) and specific geographic areas (i.e., Biscayne Bay) of ecological importance. HAPCs typically include high value intertidal and estuarine habitats, offshore areas of high habitat value or vertical relief, and habitats used for migration, spawning, and rearing of fish and shellfish. Wi thin the proposed project action area, three habitats are federally classified as HAPC by the SAFMC (1998a) for fishes within the Coral reef and Hardbottom, Snapper-Grouper Complex and the Spiny lobster. The project area is located within Biscayne Bay, which is a geographically defined HAPC. 8.7 Assessment of Potential Impacts Construction-related activities have the potential to impact managed species and/or EFH. Potential effects to fish and fish habitat directly related to the construction activities include water quality impairment, alteration of bottom habitat, elevated underw ater sound, and displacement. Various potential impacts considered negligible or non-existent are not analyzed in this EFH, such as permanent changes to bathymetry. 8. 7 .1 Construction Methods Construction is anticipated to primarily occur from upland areas. Equipment staged on landside would augment barge and support construction when needed. The need for an in-water barge will be assessed during the final design phase and is currently not anticipated to be warranted. Prepa red fo r: V illage of Key Biscayne AECOM 85 K-8 Ba sin Ba sis of D esign R eport (B O D R ) Village of Key Biscayne AECOM Project No.: 60690913 C o nstruction activities w ill be m itigated through use of Best M anagement Practices ("BMPs") throughout renovation construction activities. M eans and m ethods will be determined by the awarded contractor prior to construction com m encem ent. 8.7.2 Water Quality, Sediment Resuspension and Turbidity C o nstruction activities m ay tem porarily low er surface w ater quality from sediment being resuspended during pile installation activities. Pile installation m ay briefly cause sediment resuspension and turbidity, increasing total suspended solids (TS S ) w ithin the pro ject area, which could lower dissolved oxy gen (DO) levels. TS S are particl es that are larger than 2 m icro ns. Construction-related activities may reduce water quality in the form of elevated turbidity plum es that could potentially last from a few m inutes to several hours de pending on various factors, such as sedim ent type and w ater hydro logy. Elevated turbidity can so m etim es adversely im pact m arine species by lowering DO and other related water quality issues; how ever, potential im pacts vary w idely depending on duration, concentration, sediment type, specific species, and life-stage (Wi lber and C larke, 2001 ). For instance, TSS can adversely impact (e.g., elevated T S S can adversely im pact (e.g., bury) benthic com m unities when concentrations exceed 390 m g/L (USEPA, 19 86). N O AA Fisheries (2020) reported pile driving activities in the Hudson River caused TSS concentrations to tem porarily increase betw een 5.0 and 10.0 mg/L above background levels within approxim ately 300 feet (91.4 m ) of the pile being driven. D espite this m odest increase, turbidity levels were expected to return to norm al w ithin a few hours. In New Bedfo rd, M assachusetts, Battelle (2015) found turbidity readings in the active w ork zone ranged from near background levels to approximately 70 N e phelom etric Turbidity U nits ("N TU s") during a hydraulic dredging operation. Turbidity readings were hig hest w ithin 100 feet of dredging operations and decreased with increased distance from the source. D redging operations increase turbidity m ore than pile driving operations, such as the Pro posed Action, since pile driving im pacts usually have a sm aller fo otprint. T urbidity and D O are inversely related. Thus, the D O m ay decrease temporarily when bottom sediments are resuspended by the Proposed A ction but should return to ambient levels shortly after construction because pile driving activities are lim ited. In general, changes in turbidity and DO are expected to be m inim al because this w ill occur during low tide; however, levels could be elevated during construction and pile driving activities. Based on w ater hydro logy (tidal range) within the project area, the potential sediment plum e caused by construction activities w ould likely settle out of the water colum n within a day or sooner aft er operations are com pleted. R esuspended sedim ents are anticipated to disperse and dilute rapidly due to tidal m ixing. Elevated turbidity is anticipated to return to am bient conditions within 24 hours of the cessation of sedim ent disturbing activities. Also, the use of BM Ps and adherence to permit conditions will reduce potential im pacts. A n increase in turbidity and associated low er D O have the potential to have direct effects on fish behavior, such as avoidance. How ever, estuarine fish are subject to periodic short-term pulses of high suspended sed im ent, given the estuarine tidal enviro nm ent. M ost fish can tolerate some increases in turbidity, which so m etim es occurs aft er rain events. In fact, sensitive fish can tolerate turbidity around 580.0 m g/L, with a typical value of 1,000.0 m g/L fo r durations of one to tw o days (Burton, 1993; Wi lber and Clarke, 2001 ). T he refore, physical im pairm ent and injury to EFH species fro m increased turbidity associated with construction and dem olition activities are not anticipated. Turbidity would temporarily decrease water clarity, w hich m ay alter fish fo raging behavior and success (Breitburg, 1988); however, turbidity is predicted to return to pre-construction levels w ithin 24 hours follow ing disturbance. An increase in turbidity and lower D O levels are antici pated to be short-term and localized. F e rt ilization success of individual pelagic spaw ners and surv ivorship of individual pelagic larvae within the project area m ay be affected by turbidity; however, fish spaw ning occurs over broad areas and the construction footprint is sm all. Therefore, population-level adverse impacts to pelagic spawners are not anticipated. P rep a red for: V illage of K ey Biscayne AECOM 86 K-8 Basin Basis of Design Report (BO OR} Village of Key Biscayne AECOM Project No.: 60690913 Pelagic species and life-stages are expected to continue using unaffected portions of the water column during and after construction. Pelagic larval and egg life-stages would carry through the active project area on prevailing currents and tides, resulting in limited exposure to construction-disturbed areas, with no im pact anticipated. Despite these potential consequences associated with project activities, most fish are m obile and will likely temporarily avoid the project area and relocate to a similar habitat within the general area, which should m inimize potential impacts. The pro ject activities will not alter the salinity, tidal height, or water temperature, or permanently impact DO. Also, project activities will not impact other water column properties such as temperature, salinity, nutrients (nitro gen, phosphorus), and chlorophyll a. Therefore, no permanent impacts to water column habitat due to increased turbidity are anticipated within or adjacent to the project area. 8.7.3 Benthic Habitat A prelim inary benthic survey was conducted March 20, 2023. The benthic survey report is included as Section 7, Preliminary Marine Benthic Review. W hile direct impacts to the benthic habitat from in-water construction are not anticipated at this time, if dredge and/or fill are warranted to prevent outfall scour, impacts will be m inor. Direct impacts to the benthic community resulting from the placement of riprap at the outfall face would likely occur during construction. However, once the project is complete, the unaffected benthic community adjacent to the project area would be disturbed. Indirect im pacts on benthic habitat and organisms during construction are likely to result from turbidity and resuspended sediments caused by the floating turbidity barrier installation and excavation. Suspension feeders (i.e., bivalves) and surface deposit feeders (i.e., polychaetes) would be the most susceptible to burial. Re-colonization of the substrate within the buried areas would occur via larval recruitment and m ovement of benthic organisms from the surro unding area (U.S. Navy, 2019). Soft bottom benthic comm unities are very resilient to habitat disturbance from anthropogenic activities (Diaz et al., 2004; Brooks et al., 2006). Therefore, indirect impacts from turbidity and resuspended sediments may temporarily, but not permanently, affect benthic habitat. 8.7.4 Corals No corals were observed during the survey area. Prior to construction commencement the zone of direct im pact and secondary area will be re-evaluated for the presence of corals. The secondary area footprint will cover the m aximum extent to address temporary impacts that may potentially result from localized elevated turbidity. 8.7.5 Underwater Noise Construction activities are anticipated to occur from upland areas. If the need for an in-water barge is determined to be required, the installation of riprap below the outfalls will not result in a sound exposure level (SEL) that would impact estuarine fish. The project does not propose the utilization of an impact hamm er nor is it anticipated that construction-related noise will permeate aquatic (underw ater) and terrestrial (in-air) environments. Underw ater noise can cause a variety of impacts and injuries to marine fauna depending on sound level, duration, and other factors (Hastings and Popper, 2005). Also, sensitivity to underw ater sound differs among fish, and impacts can vary depending on body size; smaller fish are more vulnerable (Caltrans, 2009). Underw ater sound can cause a variety of direct impacts, such as barotrauma injury, and indirect impacts (hemorrhage, embolism, visceral damage, and stress); barotrauma injury is the physical damage to an organ from quick changes in the ambient pressure (Hastings and Popper, 2005). Swim bladders are the m ost common organ damaged because most fish have swim bladders that are filled with gas and thus a rapid change in pressure (pressure wave) from a blast can directly damage it (e.g., tear, rupture, and over inflate), forcing it to burst outw ard (Hastings and Popper, 2005). Prepared for: Village of Key Biscayne AECOM 87 K -8 Ba sin B asis of De sign R eport (B O D R ) Village of Key Biscayne AECOM Pro ject No.: 60690913 High intensity impulsive sounds can cause tissue damage, and behavioral changes. Underwater sound threshold limits for fish are limited; therefore, federal agencies often agree on different decibel (dB) values. Construction activity for the proposed action does not indicate the SEL generated from the placement of rip rap or barge spudding will exceed the thresholds that would impact fish. Thus, it is anticipated the underwater sound generated from minor activities will not adversely impact marine fish (juvenile and adult life-stages) because it is anticipated they will temporarily move away from any potential underwater sound. As indicated previously, construction will follow the project design criteria presented in JAXBO. Construction activities will be limited to daylight hours and noise abatement measures will be used. Therefore, the construction will be conducted in adherence to JAXBO; and noise impacts will be temporary. Adverse underwater noise impacts to managed species are not expected. 8.7.6 Displacement Underwater sound will likely cause behavioral changes to marine fish, which can vary from impaired startle response, freeze response, and increased swimming speed for avoidance. Construction-related activities may temporarily cause marine fish to move away or avoid the area and could have short-term effects on the ecological dynamics within the existing habitat. However, these potential changes would likely be short­ term and would not create long-term or permanent effects following project completion. Most of the aquatic organisms are highly mobile and will move away or avoid the impacted area during periods of elevated underwater sound. Potential indirect effects from in-water construction disturbances are predominantly related to short-term predator-prey relationships, with altered fish behavior potentially occurring within the action area during the project activities. Benthic foraging species would likely be displaced from the project area, but it is anticipated they would find suitable foraging habitat in adjacent areas. It is anticipated that fish displaced temporarily from the area due to construction activities will return to this habitat post construction (~30 days). Overall, the proposed action may have some potential impacts on marine resources; however, anticipated impacts are likely to minimal and proposed construction activities are likely to be temporary. Marine resources are anticipated to recover quickly based on the impact. Proposed mitigation measures are also expected to reduce potential impacts. Potential effects of project activities on FMP species are presented in Table 10. Table 10, Potential Effects of the Proposed Activities on FMP Species Project Activity Impact Assessment Placement of Riprap Water Column Underwater Noise Scour protection at Displacement from Water Column Outfall face Displacement from Benthic Foraging Habitat General Construction Displacement P repa red for: V illa ge of Key B iscayne AECOM 88 K-8 Basin Basis of Design Report (BOOR) Village of Key Biscayne AECOM Project No .. 60690913 8.8 Proposed Mitigation Measures Development of construction activities was designed to minimize and avoid impacts to EFH and managed species, to the fullest extent possible. State and federal requirements for use of BMPs will be implemented. Those BMPs are as follows: • Corals will be rescued/relocated from direct impact area prior to commencement of construction activities. • The limits of construction will be identified with a turbidity barrier. The turbidity barrier will move with the construction barge. The protection measures will be clearly stated in the construction specifications, and workers will be instructed to avoid conducting activities and disturbing areas beyond construction limits. • Tools, equipment, barricades, signs, surplus materials, demolition debris, and rubbish will be removed from the project work limits upon project completion. • Equipment on the project will be maintained in a clean and well-functioning state to avoid or minimize contamination from automotive fluids. Equipment will be checked daily. • Material will be stored, used, and disposed of in an appropriate manner. • A hazardous spill plan will be prepared prior to construction. • BMPs for drainage and sediment control will be implemented to prevent or reduce nonpoint source pollution and minimize soil loss and sedimentation in drainage areas. BMPs will include all or some of the following actions, depending on site-specific requirements and the Clean Water Act (CWA) Section 401 and 404 and National Pollutant Discharge Elimination System (NPDES) permit requirements: o Regular site inspections will occur during construction to confirm that BMP measures are properly installed and are functioning effectively. o Use temporary secondary containment equipment during construction, where practicable, so that accidental releases of hazardous material are prevented or limited in scope. o Use portable catch basins, containment berms, and other similar equipment for refueling equipment where feasible. o Keep spill kits on-site to provide easily accessible cleanup materials should a spill occur. o Handle hazardous materials/waste used or generated during proposed activities according to applicable laws and regulations. Personnel involved in project activities will receive training on sensitive biological resources that may be encountered in the action area. Personnel will be reminded that harassment, handling, or removal of wildlife and/or other sensitive resources from the action area is prohibited by law. Personnel will be instructed that in the event a special status species is identified within an immediate work area, work will cease until appropriate personnel are notified and further instructions are provided. Prepared for: Village of Key Biscayne AECOM 89 K-8 Basin Basis of Design Report (BO OR) Village of Key Biscayne AECOM Project No.: 60690913 8.9 The Effects of the Action: Summary and Conclusions The potential for adverse impacts to fish with EFH designated in the action area is likely to differ from species to species, depending upon life history, habitat use (demersal vs. pelagic), and distribution and abundance. However, it is anticipated that short-term impacts to older life-stages of fish (both pelagic and demersal) will be limited to temporary displacement. It is anticipated this displacement will not be significant because pelagic larvae and eggs will continue be carried through the project area with prevailing tides, currents, and wave action should spawning occur during project construction. Potential impacts could be m ore severe to m arine resources with demersal eggs/larvae. Juvenile and adult stages would likely leave the construction areas and move to nearby unaffected habitat during construction given the minimal increase in turbidity, sedimentation, and underw ater sound. Impacts to these life-stages would consist of a temporary displacement and a tempor ary loss of a very small portion of food/foraging area. Although SAV were fo und in the action area, they are not anticipated to be within the direct impact areas and will be re­ evaluated during the 2023 seagrass season as well as prior to construction. O verall, the Village of Key Biscayne anticipates the Proposed Action may affect but is not likely to adversely affect EFH. The proposed action m ay cause minimal and temporary impacts, but activities associated with the project would not have lasting direct or indirect effects upon the status or sustainability of the fisheries or their habitat. 9 Marine Species Biological Assessment 9.1 Introduction The purpose of this document is to present the findings of a Biological Assessment ("BA") for the Proposed Action. This BA includes a description of the Proposed Action; an analysis of direct, indirect, and cumulative effects for federally m anaged m arine species; the potential effects of the Proposed Action; proposed mitigation m easures to m inimize expected project effects if applicable; and a summary of potential impacts. 9.2 Protected Species and Habitats 9.2.1 Introduction The project study area was evaluated for potential occurrences of federally listed and state listed marine anim al species in accordance with Section 7 of the Endangered Species Act of 1973, as amended; the Fish and W ildlife Conservation Act; the M igratory Bird Treaty Act ("MBTA"); and Chapters 58-40 and 68A-27, F.A.C . It is important to note that all federally listed species are also considered state listed species. Federally listed species fall under the jurisdiction of the USFW S. However, species only listed at the state level are not considered federally listed and fall under the jurisdiction of the FFW C. The project study area w as also evaluated for the occurrence of federally-designated Critical Habitat as defined by Congress in 50 C.F.R. 17. Based on this evaluation, it was determined that federally-designated Critical Habitat for the West Indian m anatee (Trichechus manatus latirostris) is present within the limits of the project. The species referenced above, along with additional state and/or federal- listed wildlife species that may be affected by the project, are detailed in the following sections. 9.2.2 Assessment Methodology In accordance with Section 7 of the ESA of 1973, as amended, and Chapter 68 of the F.A. C, the project study area was evaluated for the potential occurrence of federal and state listed protected plant and animal species. Li terature reviews, agency database searches and coordination, and a habitat field review (performed on M arch 20, 2023) were conducted to identify protected species that might occur within the study area. Literature reviews and databases searches included the following: Prepared for: Village of Key Biscayne AECOM 90 K-8 Basin Basis of Design Report (BODR) Village of Key Biscayne AECOM Project No.: 60690913 • ESRI aerial photographs (2022) • USFWS Environmental Conservation Online System, Miami-Dade County (2023) • USFWS Critical Habitat Portal (2023) • FFWC Florida's Endangered and Threatened Species (2023) • USFWS IPaC Resource List (2023) • FFWC Waterbird Colony Locator Database (2023) • Miami-Dade County GIS data (2023) Aerial photographs from the ESRI were interpreted to determine habitat types occurring within Hurricane Harbor and the potential presence of any listed marine species. The USFWS lists are specific to Miami­ Dade County, but they are not site specific to the project study area. This list includes categorizations of species as endangered (E), threatened (T), and candidate (C). The FWC list covers the entire state of Florida and includes categorizations of species as federally-designated endangered (FE), federally­ designated threatened (FT), state threatened (ST), and species of special concern (SSC). 9.3 Species Occurrence and Effect Determinations Table 11 lists the state and federally listed wildlife species that occur in Miami-Dade County based on the databases and documents previously referenced. Each species listed in the table below was assigned a potential for occurrence within the project study area based on data reviews, field observations, presence and quality of suitable habitat, and the species' known ranges. Each species was assigned a none, low, moderate, or high likelihood for occurrence within the project study area based on the following: • None - The project is outside of the species' known range or the project is within the species' range; however, no suitable habitat for or previous documentation of this species occurs within or adjacent to the project study area, and it was not observed during the field reviews. • Low - The project is within the species' range, and minimal or marginal quality habitat exists within or adjacent to the project study area; however, there are no documented occurrences of the species in the vicinity of the project, and it was not observed during the field reviews. • Moderate - The project is within the species' range and suitable habitat exists within or adjacent to the project study area; however, there are no documented occurrences of the species, and it was not observed during the field reviews. • High - The project is within the species' range, suitable habitat exists within or adjacent to the project buffer, there is at least one documented occurrence of the species within the project study area, and/or the species was observed during the field reviews. Table 11, Listed/Protected Wildlife Species, Designation, and Potential for Occurrence Common Name Scientific Name Federal State Occurrence Effect Status Status Potential Determination Mammals West Indian Trichechus May Affect, Not Manatee(1l manatus T FT High Likely to Adversely latirostris Affect Reptiles American Alligator T FT Low No effect Alliaator mississiooietisis American Crocodylus T FT Low No effect Crocodile acutus Green Sea Turtle Chelonia mvties T FT Low No effect Prepared for: Village of Key Bisca yne AECOM 91 K-8 Ba sin Ba sis of D e sign R eport (B O O R ) Village of Key Biscayne AECOM Pro ject No.: 60690913 Common Name Scientific Name Federal State Occurrence Effect Status Status Potential Determination Hawksbill Sea Eretmochelys E FE Low No effect Turtle imbricata Leatherback Sea Dermochelys E FE Low No effect Turtle coriacea Loggerhead Sea Caretta T FT Low No effect Turtle Fishes Acipenser Gulf Sturgeon oxyrinchus T FT Low No effect (=oxyrhynchus) desotoi Smalltooth May Affect, Not Sawf sh Pristis pectinate E FE Low Likely to Adversely Affect Birds Audubon's Puffinus BCC Low No effect Shearw ater lherminieri Black Seater Melanitta niare BCC Low No effect Brown Pelican Pelecanus BCC Low No effect occidentalis Common Eider Somateria BCC Low No effect mollissima Common Loon Gavia immer BCC Low No effect Great Puffinus gravis BCC Low No effect Shearwater Pomarine Jaeger Stercorarius BCC Low No effect pomarinus Razorbill Alea torda BCC Low No effect Red-breasted Mergus serrator BCC Low No effect Merqanser Ring-billed Gull Larus BCC Low No effect delawarensis Roseate Tern Sterna dougallii BCC Low No effect Royal Tern Thalasseus BCC Low No effect maximus Sooty Tern Onychoprion BCC Low No effect fuscatus Wh ite-winged Melanitta fusca BCC Low No effect Seater Wi lson's Storm- Oceanites BCC Low No effect petrel oceanicus Fe de ral S tatus: E = Endangered, T = Threatened, C = Candidate, NL = Not Listed S tate S tatus: FE = Federally-designated Endangered, FT = Federally-designated threatened, NL= Not Listed, ST = State threatened. B C C = B ird of C onserv ation C oncern 1 The W est Indian m anatee, including the Florida m anatee subspecies, is federally pro tected by the Marine Mammal Protection Act. 9.3.1 State and Federally Listed/Protected Wildlife Species 9.3.1.1 Federally Listed Species Mammals West Indian Manatee (Trichechus m anatus latirostris): The West Indian manatee a fully aquatic herbivorous mammal. These gentle, aquatic mammals move slowly through the water as they feed on plants, and often are unable to move out of the way of fast-moving boats, whose propellers can wound or even kill them. Prepared fo r: V illage of K ey Biscayne AECOM 92 K-8 Basin Basis of Design Report (BOOR) Village of Key Biscayne AECOM Project No.: 60690913 They are typically found in coastal or estuarine waters, bays, rivers, and lakes, but may be found in inland canals during winter months as they search for warmer waters (USFWS 2016d). Manatees are grazers and require sheltered coves for feeding, resting, and calving. Manatees spend about 5 hours a day feeding primarily on submerged aquatic vegetation, such as seagrasses. Although manatees appear to tolerate marine and hypersaline conditions, they are most frequently found in fresh or brackish waters. Changes in water flow and salinity patterns, submerged vegetation, and the overall quality of the foraging habitat in Biscayne Bay and elsewhere are, along with water temperature, important influences on the distribution and abundance of manatees in the area (USFWS 2016d). Increases in salinity are generally considered to result in less favorable conditions for manatees, although manatees move freely through a wide range of salinities. Manatees are frequently reported drinking freshwater from natural sources as well as hoses, sewage outfalls, and culverts in marine and estuarine areas. The potential for manatees exists within Hurricane Harbor, which are tidally connected to the waters of Biscayne Bay and the Atlantic Ocean. Reptiles American Alligator (Alligator mississippiensis): The American alligator is federally listed as threatened due to similarity of appearance to the American crocodile. The American alligator is a large, semi-aquatic, armored reptile that is related to crocodiles. Their body alone ranges from 6 - 14 feet long. Almost black in color, it has prominent eyes and nostrils with coarse scales over the entire body. It has a large, long head with visible upper teeth along the edge of the jaws. Its front feet have 5 toes, while rear feet have 4 toes that are webbed. American Crocodile (Crocodylus acutus): The American crocodile is federally listed as threatened due to human activities and coastal development. A large lizard-shaped reptile, the crocodile closely resembles the alligator. Hatchlings are about 23 centimeters in length; adults may grow to 4.5 meters or larger. Florida crocodiles may be distinguished from alligators by their more slender build and their difference in snout shape. The crocodile's snout tapers forward from the eyes while the alligator's snout is untapered and rounded at the end. When the mouth is closed, the fourth tooth in the lower jaw is exposed in the crocodile but concealed in the alligator. American crocodiles inhabit brackish or saltwater, and can be found in ponds, coves, canals, and creeks in mangrove swamps in southern Florida. The project area within Hurricane Harbor contains very little suitable habitat for this species; no nests have been documented within one mile of the project study area and none were observed during the field reviews. The project area is also highly urbanized and far from known crocodile habitat making it unlikely that the project will affect crocodile nesting areas. However, the project area is within the American crocodile consultation area. Therefore, this species was assigned a 'low' probability of occurrence within the project study area. Green Sea Turtle (Chelonia mydas): The green sea is federally listed threatened and is likely to become endangered within the foreseeable future throughout all or a significant portion of its range. The green seas turtle grows to a maximum size of about 4 feet and a weight of 440 pounds. It has a heart-shaped shell, small head, single-clawed flippers, and its color varies. The nesting season is approximately June to September (USFWS 2016g). The green sea turtle is dependent upon three basic habitat types: high-energy beaches for nesting; open sea habitats as juveniles, and benthic feeding grounds (i.e., seagrass meadows) as adults. In the southeastern US, green sea turtle forage in shallow coastal and estuarine waters with an abundance of macroalgae or seagrass. Green sea turtles have strong nesting site fidelity and often make long distance migrations between feeding grounds and nesting beaches. Threats to this species include loss or degradation of nesting habitat from coastal development and beach armoring; disorientation of hatchlings by beachfront lighting; excessive nest predation by native and non-native predators; degradation of foraging habitat; marine pollution and debris; watercraft strikes; and incidental take from commercial fishing operations (USFWS 2016g). No suitable nesting habitat exists within the project limits. Sea turtle protection measures have been established by NOAA Fisheries for construction projects. Prepared for: Village of Key Biscayne AECOM 93 K-8 Basin Basis of Design Report (BO OR) Village of Key Biscayne AECOM Project No.: 60690913 Hawksbill Sea Turtle (Eretmochelys imbricata): The hawksbill sea turtle is federally listed as endangered and is in danger of ext inction throughout all or a significant portion of its range. The green sea turtle is a small to m edium-sized animal with an elongated oval shell, a relatively small head, a distinctive hawk-like beak, and flippers with two claws. General coloration is brown with numerous splashes of yellow, orange, or reddish-brow n on the shell. Nesting typically occurs betw een April and November and may occur on alm ost any undisturbed deep-sand beach in the tropics (USFW S 2016h). In contrast to all other sea turtle species, haw ksbills nest in low densities on scattered small beaches. Hawksbills inhabit coastal reefs, bays, ro cky areas, estuaries, and lagoons and are generally found at depths of 70 feet or less. They typically forage on coral reefs, although hawksbills may also occupy other hard-bottom communities and occasionally m angrove-fringed bays (USFW S 2016h). Threats to this species include loss or degradation of nesting habitat from coastal development and beach armoring; disorientation of hatchlings by beachfront lighting; excessive nest predation by native and non-native predators; degradation of foraging habitat; m arine pollution and debris; watercraft strikes; and incidental take from commercial fishing operations. No suitable nesting habitat exists within the project limits. Sea turtle protection measures have been established by NOAA Fisheries for construction projects. Leatherback Sea Turtle (Dermochelys coriacea): Leatherback sea turtles are federally listed as endangered and are in danger of ext inction throughout all or a significant portion of its range. Leatherback sea turtles are the largest, deepest diving, most migratory, and widest ranging of all sea turtles. Adults reach fo ur to eight feet long and 500 to 2,000 pounds in weight. Nesting occurs from February to July with sites located from G eorgia to the US Virgin Islands. Of all the sea turtles, the leatherback spends the most time in the open ocean, entering coastal waters only when nesting and/or feeding. Adult females require sandy beaches for nesting backed with vegetation and sloped sufficiently so the crawl to dry sand is not too far. The preferred beaches have proximity to deep water and generally rough seas (NOAA Fisheries 2007a). Threats to this species include loss or degradation of nesting habitat from coastal development; disorientation of hatchlings by beachfront lighting; excessive nest predation by native and non-native predators; degradation of foraging habitat; marine pollution and debris; and watercraft strikes. No suitable nesting habitat exists within the project limits. Sea turtle protection measures have been established by NOAA Fisheries for construction projects. Loggerhead Sea Turtle (Caretta caretta): Loggerhead sea turtles are federally listed as threatened and are likely to become endangered within the foreseeable future throughout all or a significant portion of its range. Loggerhead sea turtles are characterized by a large head with blunt jaws. Their shell and flippers are a reddish-brown color. Loggerhead sea turtles typically occur over the continental shelf and in bays, lagoons, salt m arshes, creeks, ship channels, and the mouths of large rivers (NMFS and USFWS 2008). Nesting primarily occurs from about M ay to August on barrier islands adjacent to continental landmasses in warm-temperate and sub-tropical waters (NMFS and USFW S 2008). Nest sites are typically located on high-energy, open sandy beaches above the mean high tide and seaward of well-developed dunes (NMFS and USFW S 2008). Threats to this species include loss or degradation of nesting habitat from coastal development and beach armoring; disorientation of hatchlings by beachfront lighting; excessive nest predation by native and non-native predators; degradation of foraging habitat; marine pollution and debris; w atercraft strikes; disease; and incidental take fro m commercial trawling, long line, and gill net fisheries. These sea turtles nest on the beaches at Cape Sable, but no suitable nesting habitat exists within the project lim its. Sea turtle pro tection m easures have been established by NOAA Fisheries for construction projects. Gulf Sturgeon (Acipenser oxyrinchus (=oxyrhynchus) desoto1): Gulf sturgeon are federally listed as threatened and are likely to become endangered within the foreseeable future throughout all or a significant portion of its range. Gulf sturgeon are large fish that can exceed a length of eight feet (2.4 meters), a weight of over 300 pounds (137 kilograms) and possess strength to leap nine feet (2.7 meters) into the air. Prepared for: Village of Key Biscayne AECOM 94 K-8 Basin Basis of Design Report (BO OR) Village of Key Biscayne AECOM Project No.: 60690913 Smalltooth Sawfish (Pristis pectinate): Smalltooth sawfi sh are federally listed as endangered. The smalltooth sawf ish is a cartilaginous fish that belongs to the Subclass Elasmobranchii, which also includes all sharks and rays. This dorsally tannish-brown fish can reach a total length of up to 18 feet (5.5 meters) including the saw (Bigelow and Schroeder 1953). The species' common and scientific names are derived from its long, flattened, toothed ro strum (nose or beak structure) that extends outw ard from its flattened head. The rostrum resembles a saw because it has 24-32 unpaired saw teeth on each side. Rostral teeth that are lost will not gro w back; however, chipped teeth will continue to grow as long as the base is intact (Slaughter and Springer 1968). The m outh teeth are small and flat like other rays. The smalltooth sawfi sh is considered a type of ray, in part because the gill slits are located on the bottom of the body and the pectoral fins are attached to the head. Birds Audubon's Shearwater (Puffinus lherminien): Audubon shearw ater are listed as Bird of Conservation Concern (BCC). Audubon shearw ater are small black-and-white shearw ater with relatively long tail and somewhat rounded wings. Usually flies low to the water with fluttering wingbeats, but in strong winds it can fly with high wheeling arcs. Undertail coverts are typically dark, but this can be very difficult to see in the field. Compare with M anx Shearw ater, which is larger with longer, more pointed wings, light undertail coverts, and a darker face. Found over warm tropical waters, especially around floating mats of Sargassum weed. Often seen singly or in pairs but can gather in loose flocks, sometimes loafing with other shearw ater species. Black Seater (Me/anitta nigra): Black seater are not listed as a BCC. Black seater are plump diving duck, typically seen in flocks in coastal areas. Males are completely black with bright orange knob on the bill. Females are bro wn overall with pale cheek and contrasting dark cap. Note potbellied shape and rounded head in flight. Typically coastal but migrates over land especially in the Northeast U.S. Often gathers in tight flocks. Dives frequently, feeding on aquatic invertebrates. Breeds on ponds in Arctic tundra. Brown Pelican (Pelecanus occidentalis): Brown pelican are not listed as a BCC. Brown pelican are not listed as a BCC. Large and conspicuous, gray-brown bird of saltwater habitats. Strictly coastal; rarely seen on inland lakes. Very long bill with pouch for scooping up fish. Forages mainly by diving on fish from above. Frequently cues into fishing activity looking for handouts. Often flies in long lines close to water's surface. Brow n pelican forage by diving from the air, from as high as 60' above water, plunging into water headfirst and coming to surface with fish in bill. Tilts bill down to drain water out of pouch, then tosses head back to swallow. Wi ll scavenge at times and will become tame, approaching fishermen for handouts. Common Eider (Somateria mollissima): Common elder are not listed as a BCC. Common elder are big, lethargic, heavy-bodied duck of northern coastlines. Often seen floating offshore in flocks of up to several thousand birds. Sociable in breeding season also, and often nests in colonies. Eider down, famous for its insulating qualities, is used in large amounts in the nest lining of these ducks, helping to keep the eggs warm in frigid northern climates. In some places, such as Iceland, the down is harvested commercially at coastal 'eider farms,' where the wild birds are encouraged to nest in sheltered nooks built for them. Common Loon (Gavia immer): Common loon are not listed as a BCC. Common loon are long-bodied, low-slung diver. M any people consider the loon a symbol of wilderness; its rich yodeling and moaning calls, heard by day or night, are characteristic sounds of early summer in the north woods. In winter, silent and more subtly m arked, Common Loons inhabit coastal waters and large southern lakes. In such places they are solitary while feeding but m ay gather in loose flocks at night. Prepared for: Village of Key Biscayne AECOM 95 K-8 Basin Basis of Design Report (BOOR) Village of Key Biscayne AECOM Project No.: 60690913 Great Shearwater (Puffinus gravis): Great shearwater are not listed as a BCC. Great shearwater with a crisp dark cap. Long, narrow wings are held quite straight when flying; wingbeats are stiff. Also look for messy brown patch on belly and dark markings on underwings. Notably larger and proportionally longer winged than Manx Shearwater, and wingbeats are not as snappy. Also compare with Cory's Shearwater, but note all-black bill, dark cap, and slightly quicker wingbeats and straighter wings on Great Shearwater. Primarily an Atlantic species, breeding mainly on remote Tristan Island group in the Southern Hemisphere. Spends the nonbreeding season (May to November) in cool water in the North Atlantic, where it can gather in large flocks, often mixed with other shearwater species. Occasionally seen from land but prefers to stay offshore. Pomarine Jaeger (Stercorarius pomarinus): Pomarine jaeger are not listed as a BCC. Pomarine jaeger are bulky gull-like seabird; the largest and most barrel chested of the three jaegers. Breeds on Arctic tundra and spends the rest of the year at sea. Breeding adults are unique with elongated spoon-shaped central tail feathers. Also note blackish-brown upperparts, messy black cap that extends below the bill, and extensive white flash on upper and underside of outer wing. Rare dark morph adult is entirely blackish­ brown but still has white wing flashes. Immature birds are variable, but in general, they are barred with brown above and have bold black-and-white bars on the underwing and undertail coverts. Difficult to separate from other jaegers, especially Parasitic. At all ages, note powerful direct flight and broad wings. Typically shows white shafts on six to eight outer wing feathers (more than other jaegers) and more obvious white flash on underwing. Bill is also thicker than other jaegers. All jaegers chase other birds and steal their food. Razorbill (Alea torda): Razorbill are not listed as a BCC. Razorbill are black-and-white seabird with a thick and blunt bill. Breeds in colonies on rocky islands; winters on the ocean. Black above and white below with thin white line in front of eye. In winter, white throat wraps up behind eye, but pattern is less crisp than on Common Murre. Similar to other murres but note different bill shape and longer tail that is sometimes held up. Found singly or in flocks. Sometimes seen from shore in large numbers following the passage of a winter storm. Frequently dives underwater searching for fish. Red-breasted Merganser (Mergus serrator): Red-breasted merganser are not listed as a BCC. Red­ breasted merganser are long-bodied duck with a thin bill and shaggy crest. Breeding males have a dark green head, brown breast, and gray sides. Females and immature males have a brown head and gray body. Bill is dull red. Separated from Common Merganser by thinner bill, shaggier crest, and slimmer shape overall. Dives to catch fish on large bodies of water, including freshwater lakes and coastal regions. Favors saltwater more than Common Merganser. Ring-billed Gull (Larus delawarensis): Ring-billed gull are not listed as a BCC. Ring-billed gull are fairly small gull, common and widespread throughout most of North America. Breeding adults are white-headed with a bold black ring around the bill; nonbreeding adults have smudgy brown markings on the head. Note pale eye and yellow legs. Immatures are mottled brownish overall; note pink bill with black tip. Found along lakes, rivers, ponds, and beaches. More common inland than most other gull species, and quite fond of parking lots and urban areas. Often in flocks. Most similar to Short-billed Gull, but larger and larger-billed. Immatures of the two species are especially difficult to differentiate, but Ring-billed is usually more coarsely mottled. Roseate Tern (Sterna dougallil): Roseate tern are not listed as a BCC. Roseate tern are graceful pale tern with extremely long forked tail. Named for faint rosy wash on belly. Bill color varies geographically; Old World birds arrive on breeding grounds with a black bill that turns to red, while New World birds arrive with a red bill that turns darker. Similar to Common Tern, but notably whiter wings. Prepared for: Village of Key Biscayne AECOM 96 K -8 B asin Ba sis of D e sign R eport (B O O R ) Village of Key Biscayne AECOM Pro ject No.: 60690913 Wi th practice, look for shallow, choppier wingbeats to distinguish from other tern species. Wi despread across the globe but local, breeding in scattered colonies, often on offshore islands. Can be found mixed in flocks with other tern s on beaches, mudflats, or estuaries. Listen for harsh two-parted call "chivick." Royal Tern (Thalasseus maximus): Royal tern are not listed as a BCC. Royal tern are large tern, found strictly in coastal areas. Feeds in open ocean and saltwater bays, where it flies high above the water looking for small fish. Rests on beaches, often in groups with other species. Separated from many terns by large size; only slightly smaller than Caspian. Look for the thinner orange bill (usually not deep red) and shaggier crest compared with Caspian. Also, forehead whiter than Caspian Tern in the nonbreeding season; this can show as early as m idsummer. Sooty Tern (Onychoprion fuscatus): Sooty tern are not listed as a BCC. Sooty tern is a tropical seabird is distinctive among tern s with its jet-black back, black cap, and neat white forehead. Immature birds are entirely dark blackish with white spots on wings and a white undertail. Most similar to Bridled Tern, but darker black back, dark undersides of flight feathers, and narrower white edges on tail. Sooty Tern is found in w arm tropical waters worldwide. It breeds in colonies on sandy islands, but otherw ise usually stays far offshore, and is rarely seen near land except when blown off course by a hurricane. White-winged Scoter (Melanitta fusca): Wh ite-winged seater are not listed as a BCC. Wh ite-winged seater are a large seater with distinctive white patch on wing. Dark chocolate-brown overall; males are darker than females and have small white mark under eye, dark knob on the bill, and pink bill tip. Females have two rounded white patches on face. At a distance, separated from Surf seater by more sloping head shape and white in the wing. Wi nters on coastal waters and large freshwater lakes. Occasionally found on large inland lakes during migration. Dives frequently, feeding on mollusks and crustaceans. Wilson's Storm-petrel (Oceanites oceanicus): Wi lson's storm-petrel are not listed as a BCC. Wi lson's storm -petrel are small and fluttery. Dark blackish-brown overall with even-width white rump patch and conspicuous pale wing panels. Long legs extend past the tail in flight; difficult to spot unless close. Frequently hovers and patters feet on surface of water when feeding. Most often seen in small, loose groups; sometimes feeds or rests on the water in a dense flock. Eats plankton from the surface of the water. Vexed taxonomy m ight include several cryptic species. Breeds in Antarctica and islands in the southern oceans. Ranges across all oceans when not breeding, mainly from May to October, typically staying offshore but sometimes seen from land. Most common in North Atlantic. 9.3.2 Critical Habitats Critical Habitat is a specific, federally-designated, geographic area that is essential for the conservation of a threatened or endangered species that may require special management and protection. Critical Habitat m ay include an area that is not currently occupied by the species, but that will be needed for its recovery. An area is designated as Critical Habitat after the USFW S publishes a proposed federal regulation in the Federal Register and then receives public comments on the proposal. The final boundaries of the Critical Habitat areas are also published in the Federal Register. Federally-designated Critical Habitat for the West Indian manatee exists within Biscayne Bay and Hurricane Harbor. Although the construction activities associated with retrofitting existing outfalls will result in minor impacts to the overall Critical Habitat area within the project study area, these impacts will not inhibit m anatee m ovement or water/air quality. Therefore, no destruction of adverse modification will occur to these waterw ays (i.e. Critical Habitat) as a result of this project. Prepa red fo r: V illa ge of K ey Biscayne AECOM 97 K-8 Basin Basis of Design Report (BO OR) Village of Key Biscayne AECOM Project No.: 60690913 9.4 Assessment of Potential Impacts Construction-related activities have the potential to impact marine species and/or their habitat. Potential effects directly related to the construction activities include water quality impairment, alteration of bottom habitat, elevated underw ater sound, and displacement. 9.4.1 Mammals West Indian Manatee (Trichechus manatus latirostris): In-water work is anticipated to occur as a result of this project. Numerous m anatees were observed in Hurricane Harbor during a March 20, 2023 field review and as a result this species was assigned a 'high' probability of occurrence within the project study area. In addition, federally-designated Critical Habitat exists within the project limits for the West Indian m anatee. The pro posed outfall retro fitting activities will result in minor impacts to the overall Critical Habitat area within the project corridor, however, these impacts will not inhibit manatee movement. Therefore, the project will not result in destruction of adverse modification to Critical Habitat for the West Indian Manatee. M inor impacts to West Indian m anatee potential foraging is anticipated to occur during in-water work. How ever, in-water work will not inhibit manatee movement between foraging areas. In addition, the installation of culverts will result in the alteration of canal substrate within the area of the culvert, which may result in m inor impacts to overall potential foraging area. To increase the protection of this species during construction, the Village will adhere to the most current version of the Standard Manatee Conditions for In­ Water Work (Appendix A.6). Therefore, the Village has determined that the proposed project, regardless of the Build Altern ative, "May Affect, Not Likely to Adversely Affect" the W est Indian Manatee. 9.4.2 Reptiles American Crocodile (Crocodylus acutus): Although there is a very low probability of occurrence for the American Cro codile, construction activities could affect the American crocodile's behavior, causing them to avoid the areas of proposed construction. Such impacts would be minimal and localized to the construction area, temporary (lasting only for the duration of construction) and are not expected to jeopardize the continued existence of the American cro codile. No net loss of functions and values to wetlands and other surface waters that may provide suitable habitat for this species will occur. Unavoidable impacts to the existing stormwater features are anticipated to be com pensated through construction of the new stormwater system. The project area is highly urbanized and far enough north from know n crocodile habitat that it is unlikely to affect crocodile nesting areas. Therefore, the proposed pro ject will have no effect on the American crocodile. The contractor will be advised of state and local law regarding the harassment of crocodiles prior to the com m encement of and during construction activities. Best Management Practices (BMPs) would be implemented in accordance with the latest edition of specifications in order to satisfy any permit requirements and m inimize potential impacts from construction activities. Green Sea Turtle (Che/onia mydas): Green sea turtles might temporarily utilize habitat within the project area; however, no suitable nesting habitat exists within the project limits. Because the project location lacks suitable nesting habitat, there is a relatively low potential for this project to impact the green sea turtle. Also, sea turtle protection m easures established by NOAA Fisheries would be employed during all in-water construction activities to ensure that no adverse impacts to this species would occur. As a result of these precaution m easures, is not anticipated to adversely affect this species. Therefore, the Action Alternatives may affect, but is not likely to adversely affect the green sea turtle. Hawksbill Sea Turtle (Eretmochelys imbricata): No suitable nesting habitat for the hawksbill turtle exists within the pro ject areas. Since the project location lacks suitable nesting habitat, there is a relatively low potential for this project to impact the hawksbill sea turtle. Prepared for: Village of Key Biscayne AECOM 98 K-8 Basin Basis of Design Report (BO OR) Village of Key Biscayne AECOM Project No.: 60690913 Also, sea turtle protection m easures established by NOAA Fisheries would be employed during all in­ w ater construction activities to ensure that no adverse impacts to this species would occur. As a result of these precaution m easures, is not anticipated to adversely affect this species. Therefore, the project may affect, but is not likely to adversely affect the hawksbill sea turtle. Leatherback Sea Turtle (Dermochelys coriacea): Leatherbacks may temporarily forage in the open water areas in the vicinity of the proposed projects; however, no suitable nesting habitat exists within the project areas. Since the pro ject areas lack suitable nesting habitat, there is a relatively low potential for these altern atives to impact the leatherback sea turtle. Also, sea turtle protection measures established by NOAA Fisheries would be employed during all in-water construction activities to ensure that no adverse impacts to this species would occur. Federally designated critical habitat (nearshore reproductive) has been designated within for the loggerhead sea turtle. However, the critical habitat is not located within the project area and the project is anticipated to have no effect on federally designated critical habitat for the loggerhead sea turtle. As a result of these precaution measures, the project may affect, but is not likely to adversely affect this species. Loggerhead Sea Turtle (Caretta caretta): Loggerhead turtle nest sites are typically located on high­ energy, open sandy beaches above the mean high tide and seaward of well-developed dunes; no suitable nesting habitat exists within the project areas. Since the project location lacks the preferred habitat, there is a relatively low potential for the proposed project to impact the loggerhead turtle. Also, sea turtle protection m easures established by NOAA Fisheries would be employed during all in-water construction activities to ensure that no adverse impacts to this species would occur. As a result of these precaution m easures, is not anticipated to adversely affect this species. Therefore, the project may affect but is not likely to adversely affect the loggerhead sea turtle. Gulf Sturgeon (Acipenser oxyrinchus (=oxyrhynchus) desoto1): Gulf sturgeon protection measures have been established by NO AA Fisheries for construction projects. Therefore, the proposed project will have no effect on the Gulf sturgeon. Smalltooth Sawfish (Pristis pectinate): It has been documented that juveniles utilize the red mangrove prop root habitats for protection and foraging. Shallow depths and red mangrove root systems are important in helping the endangered smalltooth sawfi sh avoid predators (Simpfendorfer 2003). As juveniles spend the vast m ajority of their time on shallow mud or sand banks that are less than 1 foot deep, these very shallow areas are inaccessible to their predators (mostly sharks) and increase the sawfi sh's survival. Their compressed body shape helps them in inhabiting these shallow areas, and they can often be observed sw im m ing in only a few inches of water. The use of red mangrove prop root habitat is also likely to aid very small sawfi sh in avoiding predators (Simpfendorfer 2003). The complexity of the red mangrove prop root habitat likely restricts the access of predators and protects the sawf ish. Smalltooth sawfi sh protection m easures have been developed by NOAA Fisheries for in-water construction projects to minimize the potential for adverse impacts to this species. Juvenile smalltooth sawf ish prefer to reside under red mangrove prop roots mainly during incoming high tides, especially when the substrate inundation is greater than one foot in depth. Inundation of mangroves along the accessways/waterw ays is dependent upon the diurnal tidal cycles (two lows and two highs) present in Hurricane Harbor and Biscayne Bay. However, the area may be considered less than optimum habitat for the smalltooth sawfi sh due to the limitations on habitat availability; specifically, the periods of inundation, or lack thereof. Any mangrove impacts will be compensated through the planting of red m angrove trees within the temporarily impacted work zones. As a result of these protection measures, the pro posed project may affect, but is not likely to adversely affect the smalltooth sawfi sh. Prepared for: Village of Key Biscayne AECOM 99 K-8 Ba sin Basis of Design R eport {B O D R ) Village of Key Biscayne AECOM Project No.: 60690913 9.4.3 Birds Audubon's Shearwater (Puffinus lherm inie riv: This is a Bird of Conservation Concern (BCC) throughout its range in the continental USA and Alaska. However, the proposed project will have no effect on the Audubon's shearw ater. Black Scoter (Melanitta nigra): This is not a Bird of Conservation Concern (BCC) in this area, but warrants attention because of the Eagle Act or for potential susceptibilities in offshore areas from certain types of development or activities. Therefore, the proposed project will have no effect on the black scooter. Brown Pelican (Pelecanus occidentalis): This is not a Bird of Conservation Concern (BCC) in this area, but warrants attention because of the Eagle Act or for potential susceptibilities in offshore areas from certain types of development or activities. Therefore, the proposed project will have no effect on the brown pelican. Common Eider (Somateria mollissima): This is not a Bird of Conservation Concern (BCC) in this area, but warrants attention because of the Eagle Act or for potential susceptibilities in offshore areas from certain types of development or activities. Therefore, the proposed project will have no effect on the common eider. Common Loon (Gavia immer): This is not a Bird of Conservation Concern (BCC) in this area, but warrants attention because of the Eagle Act or for potential susceptibilities in offshore areas from certain types of development or activities. Therefore, the proposed project will have no effect on the common loon. Great Shearw ater (Puffinus gravis): This is not a Bird of Conservation Concern (BCC) in this area, but warrants attention because of the Eagle Act or for potential susceptibilities in offshore areas from certain types of development or activities. Therefore, the proposed project will have no effect on the great shearwater. Pomarine Jaeger (Stercorarius pomarinus): This is not a Bird of Conservation Concern (BCC) in this area, but warrants attention because of the Eagle Act or for potential susceptibilities in offshore areas from certain types of development or activities. Therefore, the proposed project will have no effect on the pomarine jaeger. Razorbill (Alea torda): This is not a Bird of Conservation Concern (BCC) in this area, but warrants attention because of the Eagle Act or for potential susceptibilities in offshore areas from certain types of development or activities. Therefore, the proposed project will have no effect on the razorbill. Red-breasted Merganser (Mergus serrator): This is not a Bird of Conservation Concern (BCC) in this area, but warrants attention because of the Eagle Act or for potential susceptibilities in offshore areas from certain types of development or activities. Therefore, the proposed project will have no effect on the red­ breasted merganser. Ring-billed Gull (Larus delawarensis): This is not a Bird of Conservation Concern (BCC) in this area, but warrants attention because of the Eagle Act or for potential susceptibilities in offshore areas from certain types of development or activities. Therefore, the proposed project will have no effect on the ring-billed gull. Roseate Tern (Sterna dougallii): This is not a Bird of Conservation Concern (BCC) in this area, but warrants attention because of the Eagle Act or for potential susceptibilities in offshore areas from certain types of development or activities. Therefore, the proposed project will have no effect on the roseate tern. Prepared for: V illage of Key Biscayne AECOM 100 K-8 Ba sin Ba sis of D e sign R eport (B O O R ) Village of Key Biscayne AECOM Project No.: 60690913 Royal Tern ( Thalasseus maximus): This is not a Bird of Conservation Concern (BCC) in this area, but w arrants attention because of the Eagle Act or for potential susceptibilities in offshore areas from certain types of development or activities. Therefore, the proposed project will have no effect on the royal tern. Sooty Tern (Onychoprion fuscatus): This is not a Bird of Conservation Concern (BCC) in this area, but w arrants attention because of the Eagle Act or for potential susceptibilities in offshore areas from certain types of development or activities. Therefore, the pro posed project will have no effect on the sooty tern. White-winged Scoter (Melanitta fusca): This is not a Bird of Conservation Concern (BCC) in this area, but warrants attention because of the Eagle Act or for potential susceptibilities in offshore areas from certain types of development or activities. Therefore, the proposed project will have no effect on the white-winged seater. Wilson's Storm-petrel (Oceanites oceanicus): This is not a Bird of Conservation Concern (BCC) in this area but warrants attention because of the Eagle Act or for potential susceptibilities in offshore areas from certain types of development or activities. Therefore, the proposed project will have no effect on the Wi lson's storm-petrel. 9.4.4 Construction Methods Construction is expected to commence in 2024, and in-water work will require four to six months. Construction would primarily occur from barge-mounted equipment. Equipment staged on landside would augm ent barge and support construction when needed. 9.5 Proposed Mitigation Measures Development of construction activities will be designed to minimize and avoid impacts to critical habitat and m anaged species, to the fullest extent possible. State and federal requirements for use of BMPs will be implemented. Those BMPs are as follows: • The lim its of construction will be identified with a turbidity barrier. The turbidity barrier will move with the construction barge. The protection measures will be clearly stated in the construction specifications, and workers will be instructed to avoid conducting activities and disturbing areas beyond construction limits. • BMPs for pile removal and placement will be followed to reduce large sediment disturbance and avoid return ing sediment to waterw ays. o For removal: piling will be removed slowly to minimize turbidity in the water column and sediment disturbance; "wake-up" process will be used (vibrating the piling to break the skin friction bond betw een piling and sediment to avoid pulling out a large block of sediment and possibly breaking off the piling in the process); and work will be confined within a floating turbidity barrier. o For piling placement: hydraulic jetting devices will not be used; nylon cushion blocks will be used to reduce underw ater noise. • The construction contractor will use a soft start for pile driving to give fish and other mobile marine fauna an opportunity to vacate the area before underw ater sound levels reached their peak. • Diver sweeps of each basin will be conducted prior to installing turbidity curtains or construction activities to confirm the basins are cleared of mobile protected species and other fauna. Prep ared fo r: V illage of K ey Biscayne AECOM 101 K-8 Ba sin Ba sis of D e sign R eport (B O O R ) Village of Key Biscayne AECOM Project No.: 60690913 • Tools, equipm ent, barricades, signs, surplus m aterials, demolition debris, and rubbish will be rem oved from the project w ork lim its upon pro ject com pletion. • Equipm ent on the project w ill be m aintained in a clean and well-functioning state to avoid or m inim ize contam ination from autom otive fluids. Equipm ent will be checked daily. • M aterial w ill be stored, used, and disposed of in an appropriate m anner. • A hazardous spill plan w ill be prepared prior to construction. • BM P s for drainage and sedim ent contro l w ill be im plem ented to prevent or reduce nonpoint source pollution and m inim ize soil loss and sedim entation in drainage areas. BM Ps will include all or some of the follow ing actions, depending on site-specific requirements and the Clean Water Act (CWA) Section 401 and 404 and National Pollutant D ischarge Elimination System (NPDES) perm it requirem ents: o R egular site inspections w ill occur during construction to confirm that BMP m easures are pro perly installed and are functioning effectively. o U se tem porary secondary containm ent equipm ent during construction, where practicable, so that accidental releases of hazardous m aterial are prevented or limited in scope. o U se port able catch basins, containm ent berm s, and other similar equipment for refueling equipm ent w here feasible. o Keep spill kits on-site to provide easily accessible cleanup m aterials should a spill occur. o H andle hazardous m aterials/w aste used or generated during proposed activities according to applicable law s and regulations. Personnel involved in project activities w ill receive training on sensitive biological resources that m ay be encountered in the action area. Personnel w ill be rem inded that harassment, handling, or removal of wildlife and/or other sensitive resources from the action area is prohibited by law. Personnel will be instructed that in the event a special status species is identified w ithin an im m ediate work area, work will cease until appro priate personnel are notified and further instructions are provided. 9.6 The Effects of the Action: Summary and Conclusions T he potential fo r adverse im pacts to m arine species designated in the action area is likely to differ fro m species to species, depending upon life history , habitat, and distribution and abundance. However, it is antici pated that short-term im pacts w ill be lim ited to temporary displacement. 10 Manatee Protection Plan (MPP) 10.1 Introduction T he W est India n m anatee (Trichechus m anatus latiro stris) was listed as an endangered species by the U S FW S on June 2, 1970. T his species habitat range is rivers, estuaries, and coastal areas of sub tropical and tropical areas. The W est Indian manatee is an herbivore that migrates to warmer w aters during the colder m o nths. In Florida, m ost m igrate south during the winter and congregate m a inly in estuaries and canals. They prefer brackish over marine environm ents. The present distribution of the W est Indian m anatee incl udes the coasts and rivers of Florida, the Greater Antilles, ea stern M exico and C entral A m erica and northern and eastern South Am erica. A critical habitat was established fo r the W est Indian m anatee in 1976. It includes Biscayne Bay, and all adjoining and co nnected lakes, rivers, canals, and w aterw ays from the southern tip of Key Biscayne (U SFW S, 1999). Prep ared fo r: V illage of K ey Biscayne AECOM 102 K-8 Ba sin B a sis of D e sign R eport (B O O R ) Village of Key Biscayne AECOM Project No.: 60690913 The Key Biscayne drainage improvement project has a small portion of workspace located within an area designated as critical habitat for the West Indian manatee, which is listed as an endangered species by both Federal and State regulatory agencies. The issue of incidental take of endangered manatees as a result of watercraft-related activities occurring within peninsular Florida is of continuing concern. Therefore, the contractor shall take measures to protect manatees prior to and during construction activities. These measures are discussed below. 10.2 Manatee Protection Measures 1. All construction personnel associated with the project activities shall be instructed in the appearance, habits, biology, migratory patterns, preservation, and presence of manatees and manatee speed zones in the project area and the need to avoid collisions with, and injury to, manatees. 2. All construction personnel shall be advised that there are civil and criminal penalties for harming, harassing, or killing manatees which are protected under the Marine Mammal Protection Act of 1972, the Endangered Species Act of 1973, and the Florida Manatee Sanctuary Act of 1978. The permittee and contractor will be held jointly responsible for any manatee harmed, harassed, or killed as a result of the construction activities. The Florida M anatee S anctuary A ct states: It shall be unlaw ful for any person at any time, by any m eans, or in any m anner intentionally or negligently to annoy, molest, harass, or disturb any m anatee; capture or collect or attem pt to capture or collect any manatee; pursue, hurt, wound, or kill any m anatee; or possess literally or constructively, any manatee or any part of any manatee. A ny person violating the pro visions of this paragraph shall be guilty of a m isdem eanor of the first deg ree. A d ditional penalties of fines up to $20,000 and one year imprisonm ent, or both, are pro vided for under the F ederal E ndangere d Species Act of 1973, as am ended, and the Marine Mamm al P ro tection A ct of 1972. 3. At least one trained personnel shall be designated as a marine mammal observer for all in-water work and shall be present on-site during all construction or staging activities to maintain a constant surveillance for manatees, assure the cessation of activities that may endanger manatees, and assure that uninhibited passage for the animal is provided. The designated marine mammal observer must have experience in marine mammal observation, be equipped with polarized sunglasses and binoculars during daylight hours, and an immediate means of contacting the mechanical operator(s). Movement of work barges and associated vessels, or any in-water work, shall be minimized to the greatest extent possible after sundown. 4. Prior to commencement of construction, a temporary 3' X 4' placard reading, "Caution: Manatee Zone" will be posted in a location prominently visible to water related construction crews. In addition, each vessel involved in the construction shall display in a prominent location, visible to the operator a temporary 8 ½" X 11" placard reading, "Caution: Manatee Zone/Slow Speed in Construction Area". Awareness signs that have already been approved for this use by the FWC will be used (see MyFWC.com). In the absence of a vessel the placard will be located prominently adjacent to the issued construction permit. Any colli sion w ith and/or injury to a m anatee(s) sh a ll be report ed im m ed iately to the Florida M arine Patrol at 1-800-DIA L-FM P. The Florida Fis h and W ild life C o nserv atio n C om m ission (FW C ) Hotli ne shall also be contacted at 1- 888-4 04-FW C C . T he U .S . Fish and W ildlife Serv ice (U SFW S) should also be contacted in Vero B each (1-561-562-3909) for so uth Florida. 5. Turbidity curtains, if required, shall be made of a material in which manatees cannot become entangled. Turbidity curtains must be properly secured and shall be inspected and monitored to avoid manatee entrapment prior to and after each day's construction activities. Curtains shall not block manatee entry or exit from essential habitat and shall not prevent manatees from traveling north and south in the basin during construction activities. If a manatee becomes entangled in a turbidity curtain the FWC will be notified immediately at 1- 888-404-FWCC. P repa red for: V illage of K ey Biscayne AECOM 103 K-8 B asin Basis of D e sign R eport (B O O R ) Village of Key Biscayne AECOM Pro ject No.: 60690913 6 . A ll vessels associ ated w ith the construction project shall operate at "no wake/idle" speeds at all tim es w hile in the construction area and in any areas while in water where the draft of the vessel pro vide s less tha n a fo ur-foot clearance from the bottom . All vessels will follow routes of deep w ater w he never possible. 7. If m anatee(s) are seen w ithin 100 yards of the active construction operation or vessel m ovement, all appropriate precautions shall be im plem ented to ensure protection of the manatee. These precautions sha ll incl ude the operation of all moving equipm ent no closer than 50 feet of a m anatee. O peration of any equipm ent closer than 50 feet to a m anatee shall necessitate im m ediate shutdow n of that equipm ent. M a natees w ill not be herded aw ay or harassed into leaving. Construction activities will not resum e until the m anatee(s) has departed the project area of its own volition. 8. T he C ontractor shall m aintain a log detailing sightings, collisions, or injuries to manatees should they occur during the contract period. M anatee sighting info rm ation shall include the num ber of m anatees seen per sighting, tim e of day observ ed, indicate if work was stopped due to manatee proxim ity, and w he n in-w ater w ork resum ed once m anatees left the area. Copies of the logs shall be pro vided m o nthly to the FW C. Follow ing project com pletion, a report sum marizing incidents and sightings shall be subm itted to the Florida Fish and W ildlife Conserv ation Comm ission, 620 South M eridia n Street, O E S -B P S , Tallahassee, Florida 32399-1600 or will be subm itted to the FW C , Im periled S pecies M anagem ent (ISM ) Section at: lm periledSpecies@ myfw c.com . 9. C ontractors w ill im plem ent the precautions stipulated in these manatee construction requirem ents. If m anatees are sighted, every effort will be made to protect the anim al, and work w ill cease if necessary . 10 . T he Standard M a natee C onditions for In-W ater W ork (revision 2005) will be fo llowed fo r all in­ w ater activity. 11. A ny collision w ith or injury to a m anatee will be reported im m ediately to the FFW C Hotline at 1-888- 404-FW C C . C ollision and/or injury should also be reported to the FW S in Vero Beach (1-77 2-562- 3909). {rem ainder of this page intentionally blank} P repared fo r: V illage of Key Biscayne AECOM 104 K-8 Ba sin Ba sis of De sign R eport (B O O R ) Village of Key Biscayne AECOM Pro ject No.: 60690913 11 Preliminary Design Plans Appendix A.7 contains the preliminary design plans developed to represent the conceptual design for the storm w ater collection and conveyance system, water quality, and stormwater pumping system im provements put forth in this BO DR at an appro ximate 30% level of completion. The preliminary plans include cover sheet, general notes, abbreviations, stormwater collection and conveyance system plan view sheets, water quality and storm water pump station plan view sheets, and civil details. 12 Preliminary Project Construction Cost Estimate As part of the development of this Basis of Design Report for the K-8 School Basin project, AECOM was tasked with preparing and expected construction budget. The construction cost for this project has been estim ated and organized at a unit price level by major work items. The estimate is an American Association of Cost Engineers, Intern ational (AA CEI) Class 5 estimate and was developed using concept level design documents. Based on the level of design, the Class 5 estimate is the "least" accurate - with an expected accuracy range of -50% to +100% at an 80% confidence level. The estimate carries a 35% design development contingency to account for further design development. Escalation has been applied based on the pro ject starting m id next year and taking 2 years to complete. The contract cost presented is the construction cost without the contingency and escalation. The project cost presented is the construction cost plus the 35% contingency and escalation. The estimated contract cost for the K-8 School Basin project is $25,865,000. The estimated project cost with escalation and contingency is estimated to be $36,235,000. Appendix A.8 contains the contains the full narrative related to the methodology utilized in the development of the cost estimate and a detailed breakdown of the major work items, estimated quantities, and unit costs. {rem ainder of this page intentionally blank} Prep are d fo r: V illa ge of K ey Biscayne AECOM 105 K-8 Basin Basis of Design Report (BO OR) Village of Key Biscayne AECOM Project No.: 60690913 Appendix A Document Summary The fo llow ing documents are appended to this report, and together with this narrative, comprise the entire report. Due to their size, for electronic file transfers, the Appendices will be provided as individual files contained in a single zipped file form at. A.1 ICPR 4 - Existing Conditions Model Input Report with Simulation and Basin Summaries Appendix A.1 contains the ICPR4 Input File and the Simulation and Basin Summaries for the Existing Conditions m odel and consists of 760 pages. A.2 ICPR 4 -Alternative Scenarios Baseline Model Input Report with Simulation Summaries Appendix A.2 contains the ICPR4 Input File and the Simulation and Basin Summaries for the Baseline Altern ative Scenarios m odel and consists of 358 pages. A.3 ICPR 4 - Nodal Diagrams Appendix A.3 contains the larger scale versions of the ICPR 4 Nodal Diagrams for both the Existing Conditions m odel (1 page) and the Baseline Altern ative Scenarios model (1 page) and consisting of 2 total pages. A.4 ICPR 4 - Nodal Min/Max Stage Reports AppendixA.4 contains the ICPR 4 Nodal Minimum/Maximum Stage Reports for both the Existing Conditions (4 pages) and Baseline Altern ative Scenario (3 pages) models and consists of 7 total pages. A.5 ICPR 4 - Link Maximum Flow Reports Appendix A.5 contains the ICPR 4 Link Maximum Flow Reports for both the Existing Conditions (6 pages) and Baseline Altern ative Scenario (4 pages) models and consisting of 10 total pages. A.6 Standard Manatee Conditions for In-Water Work Appendix A.6 contains the Standard M anatee Conditions for In-Water W ork and consists of 2 pages. A. 7 Preliminary Plans Appendix A.7 contains the preliminary plans developed for this BOOR (approximate 30% level of completion) and consists of 22 sheets - including cover sheet, general notes, abbreviations, stormwater collection and conveyance system plan view sheets, water quality and stormwater pump station plan view sheets, and civil details. A.8 AACEI Class 5 Preliminary Project Cost Estimate Appendix A.8 contains the planning level construction cost estimate for this Project and consists of 28 pages. The estimate is an American Association of Cost Engineers, International (AA CEI) Class 5 estimate and was developed using concept level design documents. Prepared for: Village of Key Biscayne AECOM 106 K-8 Basin Basis of Design Report (BO DR) Village of Key Biscayne AECOM Project No.: 60690913 DISCLAIMER FOR TRANSFER OF DIGITAL MODEL FILES The DIGITAL MODEL FILES were developed by AECOM Technical Services, Inc (AECOM) for the Village of Key Biscayne's (Village) Stormwater Planning Program. The VILLAGE understands and acknowledges that the DIGITAL MODEL FILES were not created or intended for use directly as design or construction documentation by third parties and after the DIGITAL MODEL FILES are provided they can become digitally corrupted without detection, can be modified without AECOM's knowledge, may not be readable by the VILLAGE or by third parties due to file format incompatibilities, and the original DIGITAL MODEL FILES may be modified by AECOM after the DIGITAL MODEL FILES are transferred pursuant to the protocol described in this statement, any of which circumstance could cause damage or loss to the VILLAGE; and whereas, the VILLAGE understands and acknowledges that these risks are inherent with any use of the DIGITAL MODEL FILES and that use of the DIGITAL MODEL FILES will save the VILLAGE considerable time and expense in the coordination and management of the Project, which represents good and valuable consideration for the following indemnification and release; Therefore, in consideration of AECOM transferring the DIGITAL MODEL FILES to the VILLAGE exclusively for the Reference Uses provided herein, the VILLAGE understands and acknowledges that the DIGITAL MODEL FILES will continue to be modified and refined by the VILLAGE during the design process and the transferred DIGITAL MODEL FILES only represent a transitory state in that evolution. The VILLAGE understands and acknowledges that the DIGITAL MODEL FILES developed by AECOM have been created for the purposes of developing the preliminary design intent of the project. Therefore, AECOM makes no warrantee, express or implied, that the DIGITAL MODEL FILES contain all elements that may have an impact on the Referenced Uses. The DIGITAL MODEL FILES have been prepared in accordance with the standard of care in the industry for similar projects under similar circumstances. While the DIGITAL MODEL FILES can be used to detect potential conflicts between elements, they may not accurately reflect all quantities, surface areas, and volumes, and may not accurately or completely describe all architectural elements that may have an impact on the Referenced Uses in the actual construction of the project. It is understood that the DIGITAL MODEL FILES are provided for the Reference Uses provided herein. Any use, misuse, reuse, alteration, or modification of the DIGITAL MODEL FILES for purposes other than provided herein shall be at the VILLAGE's sole risk, with no liability to AECOM whatsoever. VILLAGE does not have the right to sub-license for VILLAGE's use any software required to access the DIGITAL MODEL FILES, and no such license is granted hereby. VILLAGE acknowledges its responsibility to obtain all hardware and software needed to access the electronic files. Note: The model takes precedence over any inconsistencies within the report, figures, and exhibits. fi'aecom.com Prepared for: Village of Key Biscayne AECOM 107