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HomeMy Public PortalAbout2020-01-23 - Watertown Drainage ReportSITE LOCUS: N.T.S. ALLEN & MAJOR ASSOCIATES, INC. #148 WALTHAM STREET SITE REDEVELOPMENT WATERTOWN, MASSACHUSETTS DRAIN -AG REPORT DATE PREPARED: JANUARY 23, 2020 CLIENT: NORDBLOM COMPANY 71 THIRD AVENUE BURLINGTON, MA 01803 PREPARED BY: ALLEN & MAJOR ASSOCIATES, INC. 100 COMMERCE WAY, SUITE 5 WOBURN, MASSACHUSETTS 01801 C) .04 X44 L\V ...,,c5„.„„1-1°„_,,,,,,' c r td, % ;'' WILLIAMS e M "P t , CIVIL G(a,1 >. , ova. x•3119 a. 111:6?6:1";f4-----(21S11--.''frc3.Z;!:1,44'4::4. A&M PROJECT NO. : 2708-01 DRAINAGE REPORT #148 WALTHAM STREET - SITE REDEVELOPMENT PROPONENT: NORDBLOM COMPANY 71 THIRD AVENUE BURLINGTON, MA 01803 PREPARED BY: ALLEN & MAJOR ASSOCIATES, INC. 100 COMMERCE WAY, SUITE 5 WOBURN, MA 01801 ISSUED: JANUARY 23, 2020 A&M PROJECT #2708-01 Table of Contents 1 DRAINAGE REPORT TABLE OF CONTENTS 1-1 INTRODUCTION 1-2 SITE CATEGORIZATION FOR STORMWATER REGULATIONS 1-2 SITE LOCATION AND ACCESS 1-2 WATERSHED 1-3 EXISTING SITE CONDITIONS 1-4 EXISTING SOIL CONDITIONS 1-5 FEMA FLOODPLAIN 1-5 FEMA FLOODWAY 1-5 DRAINAGE ANALYSIS METHODOLOGY 1-6 PEAK RATE OF RUNOFF 1-6 MA DEP STORMWATER PERFORMANCE STANDARDS 1-7 STANDARD #1 1-9 STANDARD #2 1-9 STANDARD #3 1-9 STANDARD #4 1-9 STANDARD #5 1-10 STANDARD #6 1-10 STANDARD #7 1-10 STANDARD #8 1-11 STANDARD #9 1-11 STANDARD #10 1-11 2 OPERATION & MAINTENANCE PLAN TABLE OF CONTENTS 2-1 INTRODUCTION 2-2 NOTIFICATION PROCEDURES FOR CHANGE OF RESPONSIBILITY FOR O&M 2-2 CONTACT INFORMATION 2-2 CONSTRUCTION PERIOD 2-3 LONG TERM POLLUTION PREVENTION PLAN 2-4 HOUSEKEEPING 2-4 STORING OF MATERIALS AND WASTE PRODUCTS 2-4 VEHICLE WASHING 2-4 SPILL PREVENTION AND RESPONSE 2-4 MAINTENANCE OF LAWNS, GARDENS AND OTHER LANDSCAPED AREAS 2-5 STORAGE AND USE OF HERBICIDES AND PESTICIDES 2-6 PET WASTE MANAGEMENT 2-7 OPERATIONS AND MANAGEMENT OF SEPTIC SYSTEMS 2-8 MANAGEMENT OF DEICING CHEMICALS AND SNOW 2-8 LONG TERM MAINTENANCE PLAN - FACILITIES DESCRIPTION 2-8 STORMWATER COLLECTION SYSTEM - ON SITE 2-8 PROPRIETARY SEPARATORS 2-8 STANDARD OPERATION AND MAINTENANCE PROTOCOL 2-9 SUPPLEMENTAL INFORMATION 2-9 OPERATION & MAINTENANCE SCHEDULE & CHECKLIST CDS MAINTENANCE PROCEDURES 3 HYDROCAD WORKSHEETS EXISTING CONDITIONS 4 HYDROCAD WORKSHEETS PROPOSED CONDITIONS 5 APPENDIX USDA SOIL MAPPING STORMTECH ISOLATOR ROW SIZING TABLE CDS TSS REMOVAL EFFICIENCIES 6 WATERSHED PLANS EWS EXISTING WATERSHED PLAN PWS PROPOSED WATERSHED PLAN DRAINAGE REPORT Site Redevelopment #148 Waltham Street, Watertown Section 1.0 Drainage Report TABLE OF CONTENTS 1-1 INTRODUCTION 1-2 SITE CATEGORIZATION FOR STORMWATER REGULATIONS 1-2 SITE LOCATION ANI) ACCESS 1-2 WATERSHED 1-3 EXISTING SITE CONDITIONS 1-4 EXISTING SOIL CONDITIONS 1-5 FEMA FLOODPLAIN 1-5 FEMA FLOODWAY 1-5 DRAINAGE ANALYSIS METHODOLOGY 1-6 PEAK RATE OF RUNOFF 1-6 MA DEP STORMWATER PERFORMANCE STANDARDS 1-7 STANDARD #1 1-9 STANDARD #2 1-9 STANDARD #3. 1-9 STANDARD #4. 1-9 STANDARD #5 1-10 STANDARD #6 1-10 STANDARD #7. 1-10 STANDARD #8. 1-11 STANDARD #9. 1-11 STANDARD # 10 1-11 1-1 DRAINAGE REPORT Site Redevelopment #148 Waltham Street, Watertown INTRODUCTION The purpose of this drainage report is to provide an overview of the proposed stormwater management system for the site redevelopment at #148 Waltham Street, Watertown, MA. The report will show by means of narrative, calculations and exhibits that there is no increase in peak rate of runoff and volume from the site at each of the study points for all design storm events. The project area consists of one parcel located on Waltham Street within Watertown, MA and is approximately 2.6 acres. This parcel is identified as Parcel 803 5B 2. The proposed site improvements include a new 253± -unit residential building with onsite garage and podium parking, along with associated site -work and utilities to service thebuilding. The stormwater management system (SMS) incorporates structural and non-structural BMP's to provide stormwater quality treatment and conveyance. The SMS includes catch basins with deep sumps and hooded outlets, roof drains, drain manholes, trench drains, area drains, proprietary separators (water quality units), subsurface infiltration systems, bioretention areas, and an Operation & Maintenance Plan. All of the stormwater runoff generated from the proposed pavement and roof runoff area will receive water quality treatment prior to discharge to the existing municipal drain in Waltham Street. The primary mechanism to address the peak rate and volume of runoff from the site redevelopment is a reduction in the total impervious area and underground infiltration systems. The proposed redevelopment plan will reduce the impervious area by approximately 0.45 acres. • SITE CATEGORIZATION FOR STORMWATER REGULATIONS The proposed site improvements at 148 Waltham Street are considered a redevelopment under the MA DEP Stormwater Management Standards due to the net reduction in impervious area. A redevelopment project is required to meet the following Stormwater Management Standards only to the maximum extent practicable: Standard 2, Standard 3, and the pretreatment and structural stormwater best management practice requirements of Standards 4, 5, and 6. A redevelopment project shall also comply with all other requirements of the Stormwater Management Standards and improve existing conditions. • SITE LOCATION AND ACCESS The site is located at 148 Waltham Street and is entirely within the City of Watertown, Massachusetts. The site has direct paved access from Waltham Street, which is a 50' wide public right-of-way. 1-2 DRAINAGE REPORT Site Redevelopment — #148 Waltham Street, Watertown • WATERSHED The site is located within the Charles River Watershed but does not directly abut the Charles River. The Charles River Watershed has an area of approximately 308 square miles, encompassing 35 town and cities south and west of Boston Massachusetts. There are 20 dams along the 80 -mile long Charles River, which ultimately flows to Boston Harbor. Exhibit 1 on the following page shows the limits of the Charles River Watershed. EXHIBIT 1: CHARLES RIVER WATERSHED Charles River Watershed foe, d Nicest Image Source: Charles River Watershed Association 1-3 Legend Walershaa Baundary +Pam Charles River Rr1 era, 5tre ams Lakes, Ponds .aquifers IF MATowns Ocean DRAINAGE REPORT Site Redevelopment — #148 Waltham Street, Watertown • EXISTING SITE CONDITIONS The site topography is relatively flat with elevations ranging from 26 to 29. The site is almost entirely developed with buildings and pavement covering the majority of the site. There are few natural features within the lot. The aerial photo below in Exhibit 2 reflects the current site condition. The property boundaries are highlighted in red. EXHIBIT 2: AERIAL PHOTO The surface drainage flows were analyzed at three Study Points. Study Point #1 is a summation of the runoff flowing towards Waltham Street. There is an existing 12" RCP pipe onsite that connects to a drain manhole in Waltham Street. This existing 12" pipe is to remain and be reused under proposed conditions. Study Point #2 is the summation of the runoff flowing towards the existing catch basin in Green River Way at the northern corner of the site. This existing catch basin will be relocated to the edge of the proposed curb line in Green River Way. Study Point #3 is the summation of the runoff flowing towards the existing catch basin in Green River Way at the western corner of the site. This existing catch basin will remain undisturbed. Copies of the Watershed plans providing the boundaries and contributing areas are provided in the back pocket of this report. 1-4 DRAINAGE REPORT Site Redevelopment — #148 Waltham Street, Watertown • EXISTING SOIL CONDITIONS The on -site soils were identified using the USDA Natural Resources Conservation Services (NRCS) Soil Survey for Essex County. The site is entirely soil type 602 — Urban Land. Urban Land consists of areas where the soil has been altered or obscured by buildings, or paved areas. These structures cover 75 percent or more of the surface area. A copy of the soil mapping is included in the Appendix of this report. Surrounding, undeveloped, areas are shown to be soil type 253 — Hinckley Loamy Sand and therefor, for purposes of the analysis, all soils were assumed to be Hydrologic Soil Group «A„ • FEMA FLOODPLAIN The site is located within the FEMA Zone "X" (unshaded), an area outside of the 0.2% annual chance flood, as shown on the Federal Emergency Management Agency (FEMA) Flood Insurance Rate Map (FIRM) for Suffolk County, Massachusetts, Map Number 25017C0552E, Town of Watertown Community Number 250223, Panel Number 0552E, having an effective date of June 4, 2010 as shown on Exhibit 3 below. EXHIBIT 3: FEMA FIRM - 2010 Image Source: FEMA firmette, community panel number 25017C0552E • FEMA FLOODWAY The floodway is the channel of the stream plus any adjacent floodplain areas that must be kept free of encroachment so that the 1% annual chance flood (100 -year storm) can be carried without substantial increases in flood heights. No floodway is shown on the current FIRM beyond the stream channel. 1-5 DRAINAGE REPORT Site Redevelopment — #148 Waltham Street, Watertown • DRAINAGE ANALYSIS METHODOLOGY The peak rate of runoff was determined using techniques and data found in the following: 1. Urban Hydrology for Small Watersheds — Technical Release 55 by the United States Depaituent of Agriculture Soils Conservation Service, June 1986. Runoff curve numbers and 24 -hour precipitation values were obtained from this reference. 2. HydroCAD" Stormwater Modeling System by HydroCAD Software Solutions LLC, version 10.0, 2018. The HydroCAD program was used to generate the runoff hydrographs for the watershed areas, to determine discharge/stage/storage characteristics for the detention basins, to perform drainage routing and to combine the results of the runoff hydrographs. HydroCAD uses the TR-20 methodology of the SCS Unit Hydrograph procedure (SCS-UH). 3. Soil Survey of Middlesex County Massachusetts by United States Department of Agriculture, NRCS. Soil types and boundaries were obtained from this reference. • PEAK RATE OF RUNOFF The storm water runoff analysis of the existing and proposed conditions includes an estimate of the peak rate of runoff from various rainfall events. Peak runoff rates were developed using TR-55 Urban Hydrology for Small Watersheds, developed by the U.S. Department of Commerce, Engineering Division and the HydroCAD 10.0 computer program. Further, the analysis has been prepared in accordance with the Town of Watertown requirements and standard engineering practices. The peak rate and volume of runoff has been estimated for each watershed during the 2, 10, 25 and 100 -year storm events. The rainfall intensities are based on NRCC (The Cornell Study) for the Town of Watertown. The stormwater runoff model shows that the proposed site development reduces the rate and volume of runoff during all storm events at the identified points of analysis. The following tables provide a summary of the estimated peak rate and total runoff volume at each Study Point during each of the design storm events. The HydroCAD worksheets are included in Section 3 and 4 of this report. STUDY POINT #1 (Flow to the Waltham Street) 2 -Year 10 -Year 25 -Year 100 -Year Existing Runoff (CFS) 5.27 7.44 9.88 14.72 Redeveloped Runoff (CFS) 0.70 3.25 4.70 14.49 DECREASE 4.57 4.19 5.18 0.23 Existing Volume (CF) 26,081 41,148 53,143 77,140 Redeveloped Volume (CF) 9,716 23,951 35,378 59,796 DECREASE 16,365 17,197 17,765 17,344 STUDY POINT #2 (Flow to Green River Way) 2 -Year 10 -Year 25 -Year 100 -Year Existing Runoff (CFS) 0.23 0.39 0.51 0.77 Redeveloped Runoff (CFS) 0.00 0.00 0.00 0.00 DECREASE 0.23 0.39 0.51 0.77 Existing Volume (CF) 749 1,322 1,773 2,724 Redeveloped Volume (CF) 0 0 0 0 DECREASE 749 1,322 1,773 2,724 1-6 DRAINAGE REPORT Site Redevelopment — #148 Waltham Street, Watertown STUDY POINT #3 (Flow to Green River Way) 2 -Year 10 -Year 25 -Year 100 -Year Existing Runoff (CFS) 0.10 0.15 0.19 0.27 Redeveloped Runoff (CFS) 0.00 0.00 0.00 0.00 DECREASE 0.10 0.15 0.19 0.27 Existing Volume (CF) 362 569 727 1,056 Redeveloped Volume (CF) 0 0 0 0 DECREASE 362 569 727 1,056 • MA DEP STORMWATER PERFORMANCE STANDARDS The MA DEP Stormwater Management Policy was developed to improve water quality by implementing performance standards for storm water management. The intent is to implement the stormwater management standards through the review of Notice of Intent filings by the issuing authority (Conservation Commission or DEP). The following section outlines how the proposed Stormwater Management System meets the standards set forth by the Policy. BMP's implemented in the design include: Catch Basins with deep sumps and hooded outlets Trench Drains Area Drains Hydro -dynamic (Proprietary) Separators (Contech CDS®) Subsurface Infiltration Bioretention Areas Specific maintenance schedule Stormwater Best Management Practices have been incorporated into the design of the project to mitigate the anticipated pollutant loading. An Operations and Maintenance Plan has been developed for the project, which addresses the long-term maintenance requirements of the proposed system. Temporary erosion and sedimentation controls will be incorporated into the construction phase of the project. These temporary controls may include hay bale and/or silt fence barriers, inlet sediment traps, diversion channels, slope stabilization, and stabilized construction entrances. The Massachusetts Department of Environmental Protection has established ten (10) Stormwater Management Standards. A project that meets or exceeds the standards is presumed to satisfy the regulatory requirements regarding stormwater management. The Standards are as follows: 1. No new stormwater conveyances (e.g. outfalls) may discharge untreated stormwater directly to or cause erosion in wetlands or waters of the Commonwealth. 2. Stormwater management systems shall be designed so that post -development peak discharge rates do not exceed pre -development peak discharge rates. This Standard may be waived for discharges to land subject to coastal storm flowage as defined in 310 CMR 10.04. 3. Loss of annual recharge to groundwater shall be eliminated or minimized through the use of infiltration measures including environmentally sensitive site design, low impact development techniques, stormwater best management practices, and good operation and maintenance. At a minimum, the annual recharge from the post -development site shall approximate the annual recharge from pre -development conditions based on soil type. This Standard is met when the stormwater management system is designed to infiltrate the required recharge volume as determined in accordance with the Massachusetts Stormwater Handbook. 1-7 DRAINAGE REPORT Site Redevelopment — #148 Waltham Street, Watertown 4. Stormwater management systems shall be designed to remove 80% of the average annual post -construction load of Total Suspended Solids (TSS). This Standard is met when: a. Suitable practices for source control and pollution prevention are identified in a long-term pollution prevention plan, and thereafter are implemented and maintained; b. Structural stormwater best management practices are sized to capture the required water quality volume determined in accordance with the Massachusetts Stormwater Handbook; and c. Pretreatment is provided in accordance with the Massachusetts Stormwater Handbook. 5. For land uses with higher potential pollutant loads, source control and pollution prevention shall be implemented in accordance with the Massachusetts Stormwater Handbook to eliminate or reduce the discharge of stormwater runoff from such land uses to the maximum extent practicable. If through source control and/or pollution prevention all land uses with higher potential pollutant loads cannot be completely protected from exposure to rain, snow, snow melt, and stormwater runoff the proponent shall use the specific structural stormwater BMPs determined by the Department to be suitable for such uses as provided in the Massachusetts Stormwater Handbook. Stormwater discharges from land uses with higher potential pollutant loads shall also comply with the requirements of the Massachusetts Clean Waters Act, M.G.L. c. 21, §.'26-53 and the regulations promulgated thereunder at 314 CMR 3.00, 314 CMR 4.00 and 314 CMR 5.00. 6. Stormwater discharges within the Zone II or Interim Wellhead Protection Area of a public water supply, and stormwater discharges near or to any other critical area, require the use of the specific source control and pollution prevention measures and the specific structural stormwater best management practices determined by the Department to be suitable for managing discharges to such areas, as provided in the Massachusetts Stormwater Handbook. A discharge is near a critical area if there is a strong likelihood of a significant impact occurring to said area, taking into account site -specific factors. Stormwater discharges to Outstanding Resource Waters and Special Resource Waters shall be removed and set back from the receiving water or wetland and receive the highest and best practical method of treatment. A "storm water discharge" as defined in 314 CMR 3.04(2)(a)1 or (b) to an Outstanding Resource Water or Special Resource Water shall comply with 314 CMR 3.00 and 314 CMR 4.00. Stormwater discharges to a Zone I or Zone A are prohibited unless essential to the operation of a public water supply. 7. A redevelopment project is required to meet the following Stormwater Management Standards only to the maximum extent practicable: Standard 2, Standard 3, and the pretreatment and structural best management practice requirements of Standards 4, 5, and 6. Existing stormwater discharges shall comply with Standard 1 only to the maximum extent practicable. A redevelopment project shall also comply with all other requirements of the Stormwater Management Standards and improve existing conditions. 8. A plan to control construction -related impacts including erosion, sedimentation and other pollutant sources during construction and land disturbance activities (construction period erosion, sedimentation, and pollution prevention plan) shall be developed and implemented. 9. A long-term operation and maintenance plan shall be developed and implemented to ensure that stormwater management systems function as designed. 10. All illicit discharges to the stormwater management system are prohibited. 1-8 DRAINAGE REPORT Site Redevelopment — #148 Waltham Street, Watertown The following calculations demonstrate that the proposed stormwater management system is in compliance with the performance standards as outlined in the MA DEP Stormwater Management Handbook. ➢ STANDARD #1: The proposed redevelopment will not introduce any new outfalls with direct discharge to a wetland area or waters of the Commonwealth of Massachusetts. All discharges will be via existing outfall pipes and the rate and volumes will not be increased over existing conditions. ➢ STANDARD #2: The proposed development has been designed so that the post -development peak discharge rates do not exceed the predevelopment peak discharge rates. A summary of the existing and proposed discharge rates is included herein. > STANDARD #3: The proposed site improvements are classified as a "redevelopment" under the MA DEP Stormwater Management Standards. Consequently, compliance with Standard #3 is to the maximum extent practicable. However, the pre -development annual recharge has been approximated in the post -developed condition. This is accomplished by the reduction of the impervious area and underground infiltration. Existing Impervious Area Proposed Impervious Area Reduction in Impervious Area = 109,531 s.f. = 89,771 s.f. =19,760 s.f. Groundwater recharge provided within BMP's: Storage within Underground Infiltration Chambers = 5,124 c.f. (below outlet inv.=23.80) Storage within Bioretention Area #1 = 605 c.f. (below outlet inv.=26.5) Storage within Bioretention Area #2 = 595 c.f. (below outlet inv.=26.5) Drawdown within 72 Hours: Rv System #1, 2, & 3 = 5,124 cf K = 2.41 in/hr (Rawls Rate for "A" Soils) Bottom Area = 8,688 sf Tdrawdown = (5,124) / [(2.41)(8,688)/(12)] = 3 hours Rv Bioretention #1 = 605 cf K = 2.41 in/hr (Rawls Rate for "A" Soils) Bottom Area = 1,088 sf Tdrawdown = (605) / [(2.41)(1,088)/(12)] = 3 hours Rv Bioretention #2 = 595 cf K = 2.41 in/hr (Rawls Rate for "A" Soils) Bottom Area = 937 sf Tdrawdown = (595) / [(2.41)(937)/(12)] = 3 hours ➢ STANDARD #4: The proposed site improvements are classified as a "redevelopment" under the MA DEP Stormwater Management Standards. Consequently, compliance with Standard #4 is to the maximum extent practicable. Standard #4 is met when structural stormwater best management practices are sized to capture and treat the required water quality volume and pretreatment is provided in accordance with the Massachusetts Stormwater Handbook. Standard #4 also requires that suitable source control measures are identified in the Long -Term Pollution Prevention Plan. 1-9 DRAINAGE REPORT Site Redevelopment — #148 Waltham Street, Watertown The water quality volume for the site redevelopment is captured and treated using deep sump catch basins with outlet hoods, underground infiltration chambers (with isolator rows) and Proprietary Separators. Consequently, there is a conversion of water quality volume (WQV) to a peak water quality flow (WQF) rate. The MA DEP has adopted a computational method for this conversion. The proprietary separators have been sized to meet the water quality flow rate for the 1" storm event. The TSS removal efficiencies for the proprietary separators are based on the values assigned under the TARP Tier 1 testing protocol. The Technology Acceptance and Reciprocity Partnership (TARP) is a workgroup of the Environmental Council of States that was originally made of California, Illinois, Maryland, Massachusetts, New Jersey, New York, Pennsylvania and Virginia. TARP is recognized in the MA DEP Stormwater Management Handbook as a valid source for assigning TSS removal efficiencies for proprietary separators. WQV = 1" x Impervious Area = (1/12)(89,771) = 7,481 c.f. Total WQV provided below outlet invert = 6,324 c.f. STUDY POINT #1 (Flow to Waltham Street drainage) BMP TSS Starting Amount Remaining Removal Rate TSS Load Removed Load Catch Basin with deep 0.25 Sump and hooded outlet Infiltration System (with Isolator Row) 0.80 1.00 0.75 0.25 0.75 0.60 0.15 TOTAL TSS REMOVAL 0.85 or 85% ➢ STANDARD #5: The proposed site improvements are classified as a "redevelopment" under the MA DEP Stormwater Management Standards. Consequently, compliance with Standard #5 is to the maximum extent practicable. The site is considered a source of higher potential pollutant loads because it is anticipated that the project will generate greater than 1,000 vehicle trips per day. Pretreatment and source reduction are provided to the maximum extent practicable. > STANDARD #6: The project site does not discharge within a Zone II or Interim Wellhead Protection Area or near a critical area. Critical Areas are Outstanding Resource Waters as designated in 314 CMR 4.00, Special Resource Waters as designated in 314 CMR 4.00, recharge areas for public water supplies as defined in 310 CMR 22.02, bathing beaches as defined in 105 CMR 445.000, cold -water fisheries as defined in 314 CMR 9.02 and 310 CMR 10.04, and shellfish growing areas as defined in 314 CMR 9.02 and 310 CMR 10.04. > STANDARD #7: The proposed project is considered a re -development project under the Stormwater Management Handbook guidelines as there is a decrease in the amount of total impervious area. 1-10 DRAINAGE REPORT Site Redevelopment — #148 Waltham Street, Watertown ➢ STANDARD #8: A plan to control construction -related impacts, including erosion, sedimentation and other pollutant sources during construction and land disturbance activities has been developed. A detailed Erosion and Sedimentation Control Plan is included in the Construction Drawings. A Pollution Prevention Plan is included within this document. The proponent will prepare and submit a Stormwater Pollution Prevention Plan (SWPPP) prior to commencement of construction activities that will result in the disturbance of one acre of land or more. ➢ STANDARD #9: A Long -Term Operation and Maintenance (O&M) Plan has been developed for the proposed stormwater management system and is included within this document. See Section 2.0 of this report. > STANDARD #10: There are no expected illicit discharges to the stormwater management system. The applicant will submit the Illicit Discharge Compliance Statement prior to the discharge of stormwater runoff to the post -construction stormwater best management practices and prior to the issuance of a Certificate of Compliance. DRAINAGE REPORT Site Redevelopment — #148 Waltham Street, Watertown MA Section 2.0 Operation & Maintenance Plan TABLE OF CONTENTS 2-1 INTRODUCTION 2-2 NOTIFICATION PROCEDURES FOR CHANGE OF RESPONSIBILITY FOR O&M 2-2 CONTACT INFORMATION 2-2 CONSTRUCTION PERIOD 2-3 LONG TERM POLLUTION PREVENTION PLAN 2-4 HOUSEKEEPING 2-4 STORING OF MATERIALS AND WASTE PRODUCTS 2-4 VEHICLE WASHING 2-4 SPILL PREVENTION AND RESPONSE 2-4 MAINTENANCE OF LAWNS, GARDENS AND OTHER LANDSCAPED AREAS 2-5 STORAGE AND USE OF HERBICIDES AND PESTICIDES 2-6 PET WASTE MANAGEMENT 2-7 OPERATIONS AND MANAGEMENT OF SEPTIC SYSTEMS 2-8 MANAGEMENT OF DEICING CHEMICALS AND SNOW 2-8 LONG TERM MAINTENANCE PLAN — FACILITIES DESCRIPTION 2-8 STORMWATER COLLECTION SYSTEM — ON SITE 2-8 PROPRIETARY SEPARATORS 2-8 STANDARD OPERATION AND MAINTENANCE PROTOCOL 2-9 SUPPLEMENTAL INFORMATION 2-9 OPERATION & MAINTENANCE SCHEDULE & CHECKLIST CDS MAINTENANCE PROCEDURES DRAINAGE REPORT Site Redevelopment — #148 Waltham Street, Watertown MA INTRODUCTION In accordance with the standards set forth by the Stormwater Management Policy issued by the Department of Environmental Protection (DEP), Allen & Major Associates, Inc. has prepared the following Operation and Maintenance Plan for the redevelopment of #148 Waltham Street, Watertown, MA. The plan is broken down into three major sections. The first section describes construction -related erosion and sedimentation controls (Construction Period). The second section describes the long- term pollution prevention measures (Long Term Pollution Prevention Plan). The third section is a post -construction operation and maintenance plan designed to address the long-term maintenance needs of the stormwater management system (Long Term Maintenance Plan). • NOTIFICATION PROCEDURES FOR CHANGE OF RESPONSIBILITY FOR O&M The Stormwater Management System (SMS) for this project is owned by the Nordblom Company (owner). The owner shall be legally responsible for the long-term operation and maintenance of this SMS as outlined in this Operation and Maintenance (O&M) Plan. Should ownership of the SMS change, the owner will continue to be responsible until the succeeding owner shall notify the Commission that the succeeding owner has assumed such responsibility. In the event the SMS will serve multiple lots/owners, such as the subdivision of the existing parcel or creation of lease areas, the owner(s) shall establish an association on other legally enforceable arrangements under which the association or a single party shall have legal responsibility for the operation and maintenance of the entire SMS. The legal instrument creating such responsibility shall be recorded with the Registry of Deeds and promptly following its recording, a copy thereof shall be furnished to the Conservation Commission. • CONTACT INFORMATION Stormwater Management System Owner: Emergency Contact Information: Nordblom Company 71 Third Avenue Burlington, MA 01803 781.238-4842 o Nordblom Company (owner/operator) o Allen & Major Associates, Inc. (Site Civil Engineer) o Watertown Public Works o Watertown Conservation Commission o Watertown Fire Department (non -emergency line) Phone (781) 238-4842 Phone (781) 935-6889 Phone (617) 972-6420 Phone (617) 972-6426 Phone (617) 972-6512 2-2 DRAINAGE REPORT Site Redevelopment — #148 Waltham Street, Watertown MA • CONSTRUCTION PERIOD 1. Contact the Watertown Engineering Department at least fourteen (14) days prior to start of construction to schedule a pre -construction meeting. 2. Install the haybales, silt fence and construction fencing as shown on the Erosion and Sediment Control Plans. 3. Install the construction entrance at the location shown on the Erosion and Sedimentation Control Plan. 4. Site access shall be achieved only from the designated construction entrance. 5. Stockpiles shall be stabilized with erosion control matting or temporary seeding whenever practicable. 6. Install silt sacks and hay bales around each drain inlet as soon as practicable. 7. Install Erosion control fabric on all vegetated slopes as shown on the Erosion and Sediment Control plans as soon as practicable. 8. All erosion control measures shall be inspected weekly and after every rainfall event. 9. All erosion control measures shall be maintained, repaired or replaced as required or at the direction of the owner's engineer, the Town Engineer, or the Town Conservation Agent. 10. Sediment accumulation up -gradient of the haybales and silt fence greater than 6" in depth shall be removed and disposed of in accordance with all applicable regulations. 11. If it appears that sediment is exiting the site, silt sacks shall be installed in all catch basins adjacent to the site. Sediment accumulation on all adjacent catch basin inlets shall be removed and the silt sack replaced if torn or damaged. 12. The contractor shall comply with the General and Erosion Notes as shown on the Site Development Plans and Specifications. 13. The stabilized construction entrances shall be inspected weekly. The entrances shall be maintained by adding additional clean, angular, durable stone to remove the soil from the construction vehicle's tires when exiting the site. If soil is still leaving the site via the construction vehicle tires, adjacent roadways shall be kept clean by street sweeping. 14. Dust pollution shall be controlled using on -site water trucks and or an approved soil stabilization product. 2-3 DRAINAGE REPORT Site Redevelopment — #148 Waltham Street, Watertown MA • LONG TERM POLLUTION PREVENTION PLAN Standard #4 from the MA DEP Stormwater Management Handbook requires that a Long -Term Pollution Prevention Plan (LTPPP) be prepared and incorporated as part of the Operation and Maintenance of the Stormwater Management System. The purpose of the LTPPP is to identify potential sources of pollution that may affect the quality of stormwater discharges, and to describe the implementation of practices to reduce the pollutants in stormwater discharges. It is prohibited to use herbicides, fertilizers and insecticides beyond the first year of the installation of plant materials, within the Riverfront Area. The following items describe the source control and proper procedures for the LTPPP. o HOUSEKEEPING The proposed site development has been designed to maintain a high level of water quality treatment for all stormwater discharge to the Charles River. An Operation and Maintenance (O&M) plan has been prepared and is included in this section of the report. The owner (or its designee) is responsible for adherence to the O&M plan is a strict and complete manner. o STORING OF MATERIALS AND WASTE PRODUCTS There are no proposed exterior (un-covered) storage areas. The trash and waste program for the site includes interior compactors. There will be a trash contractor used to pick up the waste material in the compactors. The stormwater drainage system has catch basins with hooded outlets and deep sumps designed to capture trash and debris. Each stormwater outfall has a proprietary separator designed to separate any trash and debris that may have entered the stormwater drainage system. o VEHICLE WASHING Outdoor vehicle washing has the potential to result in high loads of nutrients, metals, and hydrocarbons during dry weather conditions, as the detergent -rich water used to wash the grime off the vehicle enters the stormwater drainage system. The proposed project does not include any designated vehicle washing areas, nor is it expected that any vehicle washing will take place on - site. o SPILL PREVENTION AND RESPONSE Sources of potential spill hazards include vehicle fluids, liquid fuels, pesticides, paints, solvents, and liquid cleaning products. The majority of the spill hazards would likely occur within the building and would not enter the stormwater drainage system. However, there are spill hazards from vehicle fluids or liquid fuels located outside of the buildings. These exterior spill hazards have the potential to enter the stormwater drainage system and are to be addressed as follows: 1. Spill Hazards of pesticides, paints, and solvents shall be remediated using the Manufacturers' recommended spill cleanup protocol. 2. Vehicle fluids and liquid fuel spill shall be remediated according to the local and state regulations governing fuel spills. 3. The owner shall have the following equipment and materials on hand to address a spill clean- up: brooms, dust pans, mops, rags, gloves, absorptive material, sand, sawdust, plastic and metal trash containers. 4. All spills shall be cleaned up immediately after discovery 5. Spills of toxic or hazardous material shall be reported, regardless of size, to the Massachusetts Department of Environmental Protection at 888-304-1133. 6. Should a spill occur, the pollution prevention plan will be adjusted to include measures to prevent another spill of a similar nature. A description of the spill, along with the causes and cleanup measures will be included in the updated pollution prevention plan. 2-4 DRAINAGE REPORT Site Redevelopment — #148 Waltham Street, Watertown MA o MAINTENANCE OF LAWNS, GARDENS AND OTHER LANDSCAPED AREAS It should be recognized that this is a general guideline towards achieving high quality and well-groomed landscaped areas. The grounds staff / landscape contractor must recognize the shortcomings of a general maintenance plan such as this, and modify and/or augment it based on weekly, monthly, and yearly observations. In order to assure the highest quality conditions, the staff must also recognize and appreciate the need to be aware of the constantly changing conditions of the landscaping and be able to respond to them on a proactive basis. Questions regarding landscape work in the Riverfront Area and Floodplain should be directed to the civil engineer of record and/or the Watertown Conservation Commission Agent. It is prohibited to fertilizers beyond the first year of the installation of plant materials, within the Riverfront Area. • Fertilizer Maintenance practices should be aimed at reducing environmental, mechanical and pest stresses to promote healthy and vigorous growth. When necessary, pest outbreaks should be treated with the most sensitive control measure available. Synthetic chemical controls should be used only as a last resort to organic and biological control methods. Fertilizer, synthetic chemical controls and pest management applications (when necessary) shall be performed only by licensed applicators in accordance with the manufacturer's label instructions when environmental conditions are conducive to controlled product application. Only slow -release organic fertilizers should be used in the planting and mulch areas to limit the amount of nutrients that could enter downstream resource areas. Fertilization of the planting and mulch areas will be performed within manufacturers labeling instructions and shall not exceed an NPK ration of 1:1:1 (i.e. Triple 10 fertilizer mix), considered a low nitrogen mixture. Fertilizers approved for the use under this O&M Plan are as follows: Type: LESCO® 28-0-12 (Lawn Fertilizer) MERIT® 0.2 Plus Turf Fertilizer MOMENTUMTM Force Weed & Feed A Material Safety Data Sheet for each approved substance is attached to this O&M Plan (See Supplemental Information Section). • Suggested Aeration Program In -season aeration of lawn areas is good cultural practice, and is recommended whenever feasible. It should be accomplished with a solid thin tine aeration method to reduce disruption to the use of the area. The depth of solid tine aeration is similar to core type, but should be performed when the soil is somewhat drier for a greater overall effect. Depending on the intensity of use, it can be expected that all landscaped lawn areas will need aeration to reduce compaction at least once per year. The first operation should occur in late May following the spring season. Methods of reducing compaction will vary based on the nature of the compaction. Compaction on newly established landscaped areas is generally limited to the top 2-3" and can be alleviated using hollow core or thin tine aeration methods. The spring aeration should consist of two passes at opposite directions with 1/4" hollow core tines penetrating 3-5" into the soil profile. Aeration should occur when the soil is 2-5 DRAINAGE REPORT Site Redevelopment — #148 Waltham Street, Watertown MA moist but not saturated. The soil cores should be shattered in place and dragged or swept back into the turf to control thatch. If desired the cores may also be removed and the area top -dressed with sand or sandy loam. If the area drains on average too slowly, the topdressing should contain a higher percentage of sand. If it is draining on average too quickly, the top dressing should contain a higher percentage of soil and organic matter. • Landscape Maintenance Program Practices: • Lawn 1. Mow a minimum of once a week in spring, to a height of 2" to 2 1/2" high. Mowing should be frequent enough so that no more than 1/3 of grass blade is removed at each mowing. The top growth supports the roots; the shorter the grass is cut, the less the roots will grow. Short cutting also dries out the soil and encourages weeds to germinate. 2. Mow approximately once every two weeks from July 1st to August 15th depending on lawn growth. 3. Mow on a ten-day cycle in fall, when growth is stimulated by cooler nights and increased moisture. 4. Do not remove grass clippings after mowing. 5. Keep mower blades sharp to prevent ragged cuts on grass leaves, which cause a brownish appearance and increase the chance for disease to enter a leaf. • Shrubs 1. Mulch not more than 3" depth with shredded pine or fir bark. 2. Hand prune annually, immediately after blooming, to remove 1/3 of the above -ground biomass (older stems). Stem removals to occur within 6" of the ground to open up shrub and maintain two-year wood (the blooming wood). 3. Fertilize with '/2 lb. slow -release fertilizer (see above section on Fertilizer) every second year. 4. Hand prune evergreen shrubs only as needed to remove dead and damaged wood and to maintain the naturalistic form of the shrub. Never mechanically shear evergreen shrubs. • Trees 1. Provide aftercare for new tree plantings for the first three years. 2. Do not fertilize trees, it artificially stimulates them (unless tree health warrants). 3. Water once a week for the first year; twice a month the second, once a month the third year. 4. Prune trees on a four-year cycle. o STORAGE AND USE OF HERBICIDES AND PESTICIDES Integrated Pest Management is the combination of all methods (of pest control) which may prevent, reduce, suppress, eliminate, or repel an insect population. The main requirements necessary to support any pest population are food, shelter and water, and any upset of the balance of these will assist in controlling a pest population. Scientific pest management is the knowledgeable use of all pest control methods (sanitation, mechanical, chemical) to benefit mankind's health, welfare, comfort, property and food. A Pest Management Professional (PMP) will be retained who is licensed with the Commonwealth of Massachusetts Executive Office of Energy and Environmental Affairs, Department of Agricultural Resources. It is 2-6 DRAINAGE REPORT Site Redevelopment — #148 Waltham Street, Watertown MA prohibited to use herbicides and insecticides beyond the first year of the installation of plant materials, within the Riverfront Area. The site manager will be provided with approved bulletin before entering into or renewing an agreement to apply pesticides for the control of indoor or structural pests. 333 CMR 13.08. Bacillus sphaericus (Bs), or Altosid are larvicide products for stormwater BMPs and should be hand -broadcast. Larviciding must be conducted during or immediately after wet weather, when the wet water quality swale has a standing pool of water. Before beginning each application, the applicator must post a Department approved notice on all of the entrances to the treated room or area. The applicator must leave such notices posted after the application. The notice will be posted at conspicuous point(s) of access to the area treated. The location and number of signs will be determined by the configuration of the area to be treated based on the applicator's best judgment. It is intended to give sufficient notice that no one comes into an area being treated unaware that the applicator is working and pesticides are being applied. However, if the contracting entity does not want the signs posted, he/she may sign a Department approved waiver indicating this. The applicator or employer will provide to any person upon their request the following information on previously conducted applications: 1. Name and phone number of pest control company 2. Date and time of the application; 3. Name and license number of the applicator 4. Target pests 5. Name and EPA Registration Number of pesticide products applied The notification must be made in writing. The intent is so that individuals, who wish to avoid exposure or want to avoid encountering the applicator, can make necessary arrangements. Applicators are required by law to follow all directions on the pesticide label and must take all steps necessary to avoid applications with people present in a room or area to be treated. Individuals occupying a room or area to be treated at the time of application shall be informed of the procedure. Whenever possible, the applicator should not apply pesticides with anyone present. That may mean treating other areas and returning when occupants have left, asking people to leave the area while the work is being done, or treating before or after people occupy the room. If people do not leave, the applicator must make it clear that he is there to apply pesticides. The applicator will be prepared to provide whatever information possible about the pesticides and techniques used. o PET WASTE MANAGEMENT The Town of Watertown has regulations regarding the care of pets within public areas. The Town has a leash law and a pet waste law that requires pet owners to remove pet waste from public areas. The owner's landscape crew (or designee) shall remove any obvious pet waste that has been left behind by pet owners within the project area. The pet waste shall be disposed of in accordance with local and state regulations. 2-7 DRAINAGE REPORT Site Redevelopment — #148 Waltham Street, Watertown MA o OPERATIONS AND MANAGEMENT OF SEPTIC SYSTEMS There are no proposed septic systems within the limits of the project. The sanitary sewer is proposed to connect to the existing MWRA line, which runs through the site. The proposed connection requires a Direct Connection Permit from the MWRA. o MANAGEMENT OF DEICING CHEMICALS AND SNOW Snow will be stockpiled on site within open space areas until the stockpile areas become a hazard to the daily operations of the site. At that point, snow will be disposed of off -site. It will be the responsibility of the snow removal contractor to properly dispose of transported snow according to Massachusetts DEP, Bureau of Resource Protection — Snow Disposal Guideline #BRPG01-01, governing the proper disposal of snow. It will be the responsibility of the snow removal contractor to follow these guidelines and all applicable laws and regulations. The owner's maintenance staff (or its designee) will be responsible for the clearing of the sidewalk and building entrances. The owner may be required to use a de-icing agent such as potassium chloride to maintain a safe walking surface. The de-icing agent for the walkways and building entrances will be kept within the storage rooms located within the building. De-icing agents will not be stored outside. • LONG TERM MAINTENANCE PLAN — FACILITIES DESCRIPTION The following is a description of the stormwater management system for the project site. o STORMWATER COLLECTION SYSTEM — ON SITE The stormwater collection system is a series of catch basins, area drains, and trench drains located at low points within the limits of the paved area and several landscape areas. The catch basin, area drains, and trench drains connect to a proprietary separator prior to discharge. The stormwater runoff from the building rooftops are collected using roof drains. The stormwater is conveyed to the discharge locations using internal building plumbing and external roof leaders. The building rooftop runoff flow to a proprietary separator prior to discharge. o PROPRIETARY SEPARATORS The proposed design includes a CDS1515-3 unit. These devices use a swirl chamber and baffle system to provide TSS removal. The individual maintenance needs of the separators are described further in the sections following. 2-8 DRAINAGE REPORT Site Redevelopment — #148 Waltham Street, Watertown MA STANDARD OPERATION AND MAINTENANCE PROTOCOL This section will present the inspection and maintenance procedures associated with the stormwater collection system. EQUIPMENT Pavement Surface MAINTENANCE ITEM FREQUENCY Perform roadway sweeping following the Semi-annually spring thaw to remove any traction sand applied (Early spring & late fall) during the winter months. Proprietary Inspect grates and hoods Quarterly Separators & Remove sediment using a vacuum truck Yearly Catch Basins Copies of the manufacturer's maintenance procedures are included at the end of this section. Drain Manholes Inspect cover for damage. Inspect pipe inlets and bottom for sign of infiltration/inflow. Perform inspection during dry weather. Quarterly Outfall locations Inspect for sign of erosion or displaced stone. Annually Replace outlet protection stone if needed. Mosquito Control Surveillance is a non chemical inspection method Quarterly that involves classification of mosquito breeding sites, larval presence, and survey. Apply larvicide if larva growth is detected. Snow Storage Debris from melted snow shall be cleared from Yearly the site and properly disposed of at the end of the snow season, but shall be cleared no later than May 15th. Bioretention Inspect twice per year. Mow side slopes Area and bottom as needed (areas with plants shall not be mowed). Remove sediment and debris from inlet locations at least once a year. Re -seed as necessary. Semi-annually Parking Below Vaccuum sweep twice per year. Power scrub Semi-annually the building 1 time annually. Scrubbing would be completed with Tennant 7400 power scrubber or similar. Scrubber shall use a combination of cleaning solution, brushes, and vacuum pick-up to scrub surfaces. Waste water/solution is reclaimed and shall be disposed of by an licensed environmental waste company. SUPPLEMENTAL INFORMATION (See following pages) OPERATION & MAINTENANCE SCHEDULE & CHECKLIST CDS MAINTENANCE PROCEDURES 2-9 OPERATION & MAINTENANCE PLAN SCHEDULE Project: Waltham Street Redevelopment Address: #148 Waltham Street Watertown, MA Date: 1/23/2020 Party Responsible for 0 & M Plan: Nordblom Company (or assignee) Address: 71 Third Avenue Burlington, MA 01803 Annual Budget: $14,500 Structure or Task Maintenance Activity Schedule/Notes Maintenance Cost/Unit Estimated Maintenance Estimated Annual Maintenance Cost Inspection Performed Date: By: Street Sweeping Sweep, power broom or vacuum paved areas. Perform roadway sweeping following the spring thaw to remove any traction sand applied during the winter months. Perform roadway sweeping in the late fall to remove any leaf litter or debris. $1,500/Sweeping Semi-annually (Spring & Fall) $3,000 Maintain information that confirms that all street sweepings have been disposed in accordance with state and local requirements Water Quality Units and CB's vacuum sumps Inspect at least 4x per year using Owner's Manual. Clean when sediment is 6" deep, but never allow sediment to exceed 50% of sump volume. Clean once per year at a minimum. $500/WQ 4 Water Quality Inlets - Cleaned Annually $2,000 Maintain information that confirms that all sediments have been disposed in accordance with state and local requirements Outfall locations Inspect for sign of erosion or displaced stone. Replace outlet protection stone if needed. Inspect flap valves or Tideflex valves at outfall locations for proper operation. Inspect twice a year for the first three years of construction and once per year thereafter $500 allowance Annually $500 allowance Check sediment build-up on a yearly basis and clean as needed using hand methods Mosquito Control CB management targeted larviciding treatment to CB's and all storm drains including proprietary separators to control mosquitoes in their aquatic stages. Surveillance is a non chemical inspection method that involves classification of mosquito breeding sites, larval presence, and survey. Apply larvicide if larva growth is detected. $500 allowance CBs - quarterly $500 allowance Snow Storage Debris from melted snow shall be cleared from the site and properly disposed of at the end of the snow season, but shall be cleared no later than May 15. Avoid dumping snow removal over catch basins. Use areas designated on the approved layout plan for snow storage. Snow shall not be stockpiled within the Wet Water Quality Swale. $500 allowance Annually $500 allowance Bioretention Area Inspect area to make sure the vegetation is adequate and that the side slopes are not eroding. Check for rilling and gullying. Repair eroded areas and revetate. Inspect area twice per year. Mow side slopes and bottom as needed (areas with plants shall not be mowed). Remove sediment and debris from inlet locations at least once a year. Re- seed as necessary. $1,500 allowance Semi-annually (Spring & Fall) $1,500 allowance Parking Below Building Cleaning of the parking below the building using a combination of sweeping and power scubber Vaccuum sweep twice per year. Power scrub 1 time annually. Scrubbing would be completed with Tennant 7400 power scrubber or similar. Scrubber shall use a combination of cleaning solution, brushes, and vacuum pick-up to scrub surfaces. Waste water/solution is reclaimed and shall be disposed of by an licensed environmental waste company. $6,500 Semi-annually (Spring & Fall) $6,500 %►'1e i Irl CONSTRUCTION PRODUCTS INC. CDS® Inspection and Maintenance Guide CDS TECHNOLOGIES Maintenance Cleaning The CDS system should be inspected at regular intervals and maintained when necessary to ensure optimum performance. The rate at which the system collects pollutants will depend more heavily on site activities than the size of the unit. For example, unstable soils or heavy winter sanding will cause the grit chamber to fill more quickly but regular sweeping of paved surfaces will slow accumulation. Inspection Inspection is the key to effective maintenance and is easily performed. Pollutant transport and deposition may vary from year to year and regular inspections will help ensure that the system is cleaned out at the appropriate time. At a minimum, inspections should be performed twice per year (e.g. spring and fall) however more frequent inspections may be necessary in climates where winter sanding operations may lead to rapid accumulations, or in equipment washdown areas. Installations should also be inspected more frequently where excessive amounts of trash are expected. The visual inspection should ascertain that the system components are in working order and that there are no blockages or obstructions in the inlet and separation screen. The inspection should also quantify the accumulation of hydrocarbons, trash, and sediment in the system. Measuring pollutant accumulation can be done with a calibrated dipstick, tape measure or other measuring instrument. If absorbent material is used for enhanced removal of hydrocarbons, the level of discoloration of the sorbent material should also be identified during inspection. It is useful and often required as part of an operating permit to keep a record of each inspection. A simple form for doing so is provided. Access to the CDS unit is typically achieved through two manhole access covers. One opening allows for inspection and cleanout of the separation chamber (cylinder and screen) and isolated sump. The other allows for inspection and cleanout of sediment captured and retained outside the screen. For deep units, a single manhole access point would allows both sump cleanout and access outside the screen. The CDS system should be cleaned when the level of sediment has reached 75% of capacity in the isolated sump or when an appreciable level of hydrocarbons and trash has accumulated. If absorbent material is used, it should be replaced when significant discoloration has occurred. Performance will not be impacted until 100% of the sump capacity is exceeded however it is recommended that the system be cleaned prior to that for easier removal of sediment. The level of sediment is easily determined by measuring from finished grade down to the top of the sediment pile. To avoid underestimating the level of sediment in the chamber, the measuring device must be lowered to the top of the sediment pile carefully. Particles at the top of the pile typically offer less resistance to the end of the rod than consolidated particles toward the bottom of the pile. Once this measurement is recorded, it should be compared to the as -built drawing for the unit to determine weather the height of the sediment pile off the bottom of the sump floor exceeds 75% of the total height of isolated sump. Cleaning of a CDS systems should be done during dry weather conditions when no flow is entering the system. The use of a vacuum truck is generally the most effective and convenient method of removing pollutants from the system. Simply remove the manhole covers and insert the vacuum hose into the sump. The system should be completely drained down and the sump fully evacuated of sediment. The area outside the screen should also be cleaned out if pollutant build-up exists in this area. In installations where the risk of petroleum spills is small, liquid contaminants may not accumulate as quickly as sediment. However, the system should be cleaned out immediately in the event of an oil or gasoline spill should be cleaned out immediately. Motor oil and other hydrocarbons that accumulate on a more routine basis should be removed when an appreciable layer has been captured. To remove these pollutants, it may be preferable to use absorbent pads since they are usually less expensive to dispose than the oil/water emulsion that may be created by vacuuming the oily layer. Trash and debris can be netted out to separate it from the other pollutants. The screen should be power washed to ensure it is free of trash and debris. Manhole covers should be securely seated following cleaning activities to prevent leakage of runoff into the system from above and also to ensure that proper safety precautions have been followed. Confined space entry procedures need to be followed if physical access is required. Disposal of all material removed from the CDS system should be done in accordance with local regulations. In many jurisdictions, disposal of the sediments may be handled in the same manner as the disposal of sediments removed from catch basins or deep sump manholes. CDS Diameter Distance from Water Surface Sediment Model to Top of Sediment Pile Storage Capacity ft m ft m yd3 m3 CDS2015-4 4 1.2 3.0 0.9 0.5 0.4 3.0 0.9 1.3 1.0 CDS2020 5 1.5 3.5 1.3 1.0 CDS2025 CDS3020 6 1.8 4.0 1.2 2.1 1.6 CDS3035 6 1.8 5.0 1.5 2.1 1.6 CDS4030 4.6 CDS4040 8 2.4 5.7 1.7 5.6 4.3 Table 1: CDS Maintenance Indicators and Sediment Storage Capacities Support • Drawings and specifications are available at www.contechstormwater.com. • Site -specific design support is available from our engineers. ©2010 CONTECH Stormwater Solutions CONTECH Construction Products Inc. provides site solutions for the civil engineering industry. CONTECH's portfolio includes bridges, drainage, sanitary sewer, stormwater and earth stabilization products. For information on other CONTECH division offerings, visit contech- cpi.com or call 800.338.1122 Nothing in this catalog should be construed as an expressed warranty or an implied warranty of merchantability or fitness for any particular purpose. See the CONTECH standard quotation or acknowledgement for applicable warranties and other terms and conditions of sale. The product(s) described may be protected by one or more of the following US patents: 5,322,629; 5,624,576; 5,707,527; 5,759,415; 5,788,848; 5,985,157; 6,027,639; 6,350,374; 6,406,218; 6,641,720; 6,511,595; 6,649,048; 6,991,114; 6,998,038; 7,186,058; 7,296,692; 7,297,266; 7,517,450 related foreign patents or other patents pending. � �i►RTA G �� Fil CONSTRUCTION PRODUCTS INC. 800.925.5240 cdsMaintenance 01/10 contechstormwater.com CDS Inspection & Maintenance Log CDS Model: Location: Date Water depth to sediment' Floatable Layer Thickness' Describe Maintenance Performed Maintenance Personnel Comments 1. The water depth to sediment is determined by taking two measurements with a stadia rod: one measurement from the manhole opening to the top of the sediment pile and the other from the manhole opening to the water surface. If the difference between these measurements is less than eighteen inches the system should be cleaned out. Note: To avoid underestimating the volume of sediment in the chamber, the measuring device must be carefully lowered to the top of the sediment pile. 2. For optimum performance, the system should be cleaned out when the floating hydrocarbon layer accumulates to an appreciable thickness. In the event of an oil spill, the system should be cleaned immediately. 148 Waltham Street - Existing Watershed Type III 24 -hr 2 Year Storm(NRCS) Rainfall=3.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 2 Summary for Subcatchment WS#1: Flow to Waltham Street Runoff = 7.09 cfs @ 12.08 hrs, Volume= 25,805 cf, Depth> 2.86" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 2 Year Storm(NRCS) Rainfall=3.20" Flow to Waltham Street Onsite Pav�ment Area Depr ssion SP1 Study Point #1 Reach Link <WS#2> <ws4 Flow to G een River Flow to G een River ay ay SP2 SP3 Study Point #2 Study Point #3 Routing Diagram for 148 Waltham Street - Existing Watersheds Prepared by Microsoft, Printed 1/22/2020 HydroCAD®10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Area (sf) CN Description 105,047 98 Impervious 3,386 68 <50% Grass cover, Poor, HSG A 108,433 97 Weighted Average 3,386 3.12% Pervious Area 105,047 96.88% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment WS#1: Flow to Waltham Street Hydrograph z 7J 7.09 cfs Type III 24-11r 2 Year Sorrr(NIRC�S) Rainfall=3.20" 6" Runoff Area=108,433 sf Runoff Depth> eF2d.80 cf 1—I 65:./1 R noff Dep hh > Tc=5.0 min T 1 Fl 3 2 1z 4 o 1///////r 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 i6 17 18 19 20 21 22 23 24 Thou (hours) 0 Runo 148 Waltham Street - Existing Watershed Type 11124 -hr 2 Year Storm(NRCS) Rainfall=3.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 3 Summary for Subcatchment WS#2: Flow to Green River Way Runoff = 0.23 cfs @ 12.09 hrs, Volume= 749 cf, Depth> 2.08" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 2 Year Storm(NRCS) Rainfall=3.20" Area (sf) CN Description 3,021 98 Impervious 1,297 68 <50% Grass cover, Poor, HSG A 4,318 89 Weighted Average 1,297 30.04% Pervious Area 3,021 69.96% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment WS#2: Flow to Green River Way Hydrograph 0.25 " 1 0.24 0.23- 0.22 V 21peaIII r-Storni(iSRRCIS)- ainfalhk3 20'� 0.21 _ �Y 0.25 0191 Runoff Area=4,318 sf 0.19 ngQ Ill ,419cif- 0.17 i �� 0.177 n epj h 0 0.15_ j e 5.0-nin 0.14, ; 0.0.1123- ; _197 1 1 1 H 0.11 0.11 00.07.09y- 0.07 o.os= 0.051 1 1 0.04 0.03 12 0.02 0.01' 1 1 1 H 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) CLEM 148 Waltham Street - Existing Watershed Type III 24 -hr 2 Year Storm(NRCS) Rainfall=3.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 4 Summary for Subcatchment WS#3: Flow to Green River Way Runoff = 0.10 cfs @ 12.08 hrs, Volume= 362 cf, Depth> 2.97" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 2 Year Storm(NRCS) Rainfall=3.20" Area (sf) CN Description 1,464 98 Impervious 1,464 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment WS#3: Flow to Green River Way Hydrograph 105J ° ✓ 0.10 cfs o.oss5 T pe41 III 24- r o.oe5 2 e Sto-4i ffiR4)*airtfal 3 20'� 0.085'.--Runoff-Area=1-,-464 sf o.oa�/V-���rrr"���nQJ of m =3 2 0.075 V� 1 0.075Rnff I > 0.oas5 Tc=5.0-min C u 0°.:51/, O.Urot:/ f I I I b 0.031 0.025 002=' f II I I I R 0.0151 0.01 0.005_ 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) Q Runo 148 Waltham Street - Existing Watershed Type 11124 -hr 2 Year Storm(NRCS) Rainfall=3.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 5 Summary for Reach SP1: Study Point #1 Inflow Area = 108,433 sf, 96.88% Impervious, Inflow Depth > 2.89" for 2 Year Storm(NRCS) event Inflow = 5.27 cfs @ 12.20 hrs, Volume= 26,081 cf Outflow = 5.27 cfs @ 12.20 hrs, Volume= 26,081 cf, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Reach SP1: Study Point #1 Hydrograph ■ Inflow • Outflo 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) 148 Waltham Street - Existing Watershed Type III 24 -hr 2 Year Storm(NRCS) Rainfall=3.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 6 Summary for Reach SP2: Study Point #2 Inflow Area = 4,318 sf, 69.96% Impervious, Inflow Depth > 2.08" for 2 Year Storm(NRCS) event Inflow = 0.23 cfs @ 12.09 hrs, Volume= 749 cf Outflow = 0.23 cfs @ 12.09 hrs, Volume= 749 cf, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Reach SP2: Study Point #2 Hydrograph '�� o.za o'"I' ITT 0.23 cfs r— E - 6.23; Infl 3 .. 0.22; 0.21 o. .2; 0.19 � — — ,a� — 1I 1 1 ] 1= 0.04 0.0 0.0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) ■ Inflow • Outflow 148 Waltham Street - Existing Watershed Type 11124 -hr 2 Year Storm(NRCS) Rainfall=3.20" Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 7 Prepared by Microsoft Inflow Area = Inflow = Outflow = Summary for Reach SP3: Study Point #3 1,464 sf,100.00% Impervious, Inflow Depth > 2.97" for 2 Year Storm(NRCS) event 0.10 cfs @ 12.08 hrs, Volume= 362 cf 0.10 cfs @ 12.08 hrs, Volume= 362 cf, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Reach SP3: Study Point #3 Hydrograph 0.105i" - - n 1n rfg 0.09 0.0 0.08 o. 0.07= 0.0657 1. 0.06- ;0.0551y/ 0.055 0 0.05e/ •0.045 / 0.04= 0.035- 0.03 0.025= 0.02 0.015= 0.01 o.00s' o' 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) RI R 1=I I 1 1R 1 1 1 1 1 1� 1- II I I R 1= • Inflow • Ou010 148 Waltham Street - Existing Watershed Type III 24 -hr 2 Year Storm(NRCS) Rainfall=3.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 8 Inflow Area = Inflow = Outflow = Primary = Secondary = Summary for Pond P1: Onsite Pavement Area Depression 108,433 sf, 96.88% Impervious, Inflow Depth > 2.86" for 2 Year Storm(NRCS) event 7.09 cfs @ 12.08 hrs, Volume= 25,805 cf 5.27 cfs @ 12.20 hrs, Volume= 26,081 cf, Atten= 26%, Lag= 6.9 min 5.27 cfs @ 12.20 hrs, Volume= 26,081 cf 0.00 cfs @ 0.00 hrs, Volume= 0 cf Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Peak Elev= 26.56' @ 12.16 hrs Surf.Area= 6,167 sf Storage= 711 cf Plug -Flow detention time= (not calculated: outflow precedes inflow) Center -of -Mass det. time= 0.5 min ( 765.4 - 764.9 ) Volume Invert Avail.Storage Storage Description #1 26.21' 8,472 cf Custom Stage Data (Irregular)Listed below (Recalc) Elevation (feet) 26.21 27.00 Surf.Area Perim. (sq-ft) (feet) 0 0.0 32,171 1,178.0 Inc.Store (cubic -feet) 0 8,472 Device Routing Invert Outlet Devices #1 Primary 24.00' #2 Secondary 26.64' Cum.Store (cubic -feet) 0 8,472 Wet.Area (sq-ft) 0 110,429 12.0" Round Existing 12" RCP L= 72.0' RCP, groove end projecting, Ke= 0.200 Inlet / Outlet Invert= 24.00' / 23.10' S= 0.0125 '/' Cc= 0.900 n= 0.013, Flow Area= 0.79 sf 25.0' long x 5.0' breadth Broad -Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65 2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88 rimary OutFlow Max=5.27 cfs @ 12.20 hrs HW=26.52' TW=0.00' (Dynamic Tailwater) 1=Existing 12" RCP (Barrel Controls 5.27 cfs @ 6.72 fps) Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=26.21' TW=0.00' (Dynamic Tailwater) 2=Broad-Crested Rectangular Weir( Controls 0.00 cfs) 148 Waltham Street - Existing Watershed Type 11124 -hr 2 Year Storm(NRCS) Rainfall=3.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 9 Pond P1: Onsite Pavement Area Depression Hydrograph 5 3 0 11 12 13 14 Time (hours) 24 ■ Inflow ■ Primary ■ Secondary 148 Waltham Street - Existing Watershe Type 111 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD®10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 10 Summary for Subcatchment WS#1: Flow to Waltham Street Runoff = 11.02 cfs @ 12.08 hrs, Volume= 41,080 cf, Depth> 4.55" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Area (sf) CN Description 105,047 98 Impervious 3,386 68 <50% Grass cover, Poor, HSG A 108,433 97 Weighted Average 3,386 3.12% Pervious Area 105,047 96.88% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 11Y Type 1124-h 10� le Yer torn (IitRC) aln�all#4.10" nofiArea=108,433 .f 9. Renotf Vplu a 1 R no D pt 555"" >4 Tc=5.0-min 3 6/ CN=9.H t LL 5/ Direct Entry, Subcatchment WS#1: Flow to Waltham Street Hydrograph 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) 0 R0n0 148 Waltham Street - Existing Watershe Type III 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 11 Summary for Subcatchment WS#2: Flow to Green River Way Runoff = 0.39 cfs @ 12.09 hrs, Volume= 1,322 cf, Depth> 3.68" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Area (sf) CN Description 3,021 98 Impervious 1,297 68 <50% Grass cover, Poor, HSG A 4,318 89 Weighted Average 1,297 30.04% Pervious Area 3,021 69.96% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 0.42 0.4 o.3a=_pe Iii 2tor ) h o.3s� Y ar for S 0.34 _ /—Runoff-Area=4318 sf 0.32y Runo u e -t 3 2 o.28: 0.3 �uno�pti>i68' ent1/„. min o z4.22 /-CDI 89--r- a U 0.2 - LL 0,3 o.1s 0.14- 0.121 0.1 0.06 o.os- 0.04V' 0.02 Direct Entry, Subcatchment WS#2: Flow to Green River Way Hydrograph 0 I I II d R R 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) Runo 148 Waltham Street - Existing Watershe Type III 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 12 Summary for Subcatchment WS#3: Flow to Green River Way Runoff = 0.15 cfs @ 12.08 hrs, Volume= 569 cf, Depth> 4.66" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Area (sf) CN Description 1,464 98 Impervious 1,464 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 0.16 0.15/ T pe III 24-h 0.14/ 1 Y�ar Sto4i11�RCI.S) Rainfall=4.90" 0.13 / Runoff Area=1 dd64 sf 0.12/ R no V lu a-56 cf R0ino f Dieept i>4.661 Tc=5.0 min 0o.oe- .00/ Cr=7H H-1 u. 0.07/ —_ 005 I o.oa 0.03 G 1 I I I a 0.02/ 0.01 Direct Entry, Subcatchment WS#3: Flow to Green River Way Hydrograph 0 1 2 3 4 5 6 7 8 9 10 11 12 13 Time (hours) Q Runo 148 Waltham Street - Existing Watershe Type III 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 13 Summary for Reach SP1: Study Point #1 Inflow Area = 108,433 sf, 96.88% Impervious, Inflow Depth > 4.55" for 10 Year Storm(NRCS) event Inflow = 7.44 cfs @ 12.20 hrs, Volume= 41,148 cf Outflow = 7.44 cfs @ 12.20 hrs, Volume= 41,148 cf, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 2 Reach SP1: Study Point #1 Hydrograph 4 I� ,f} „ ,�►, _, ,l 7.44 cfs 1 1 1 1 1 1 41 I II -kI-H rt Ifi I I rtl�l1 I _LI I I _ I I I _LI_LI 1 ± 0 1 2 3 4 5 6 7 8 9 10 11-.12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) ■ Inflow • Outflow 148 Waltham Street - Existing Watershe Type III 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 14 Summary for Reach SP2: Study Point #2 Inflow Area = 4,318 sf, 69.96% Impervious, Inflow Depth > 3.68" for 10 Year Storm(NRCS) event Inflow = 0.39 cfs @ 12.09 hrs, Volume= 1,322 cf Outflow = 0.39 cfs @ 12.09 hrs, Volume= 1,322 cf, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 0.42 0.38 / 0.0323 / .: / 0.28 / 0.26/ 0.24_ 0.22_ 0 0.2= u. 0.18= 0.0 Reach SP2: Study Point #2 Hydrograph 1— — 4n'4Q, rf In IIerI 1 1 13 0.39cfs I I I I / I 4 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) • Inflow • Outflo 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Time (hours) 20 21 22 23 24 148 Waltham Street - Existing Watershe Type III 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 15 Inflow Area = Inflow = Outflow = Summary for Reach SP3: Study Point #3 1,464 sf,100.00% Impervious, Inflow Depth > 4.66" for 10 Year Storm(NRCS) event 0.15 cfs @ 12.08 hrs, Volume= 569 cf 0.15 cfs @ 12.08 hrs, Volume= 569 cf, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Reach SP3: Study Point #3 Hydrograph 0151cfsf� - 11 1 I 1=1 1 1 1 1=1 - I II _II -I 11 1 1 1 � 1= 11 1 L 1 1 11 L1_ 1 1 1 fi1 I I_ • Inflow • Outflo 148 Waltham Street - Existing Watershe Type III 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 16 Inflow Area = Inflow = Outflow = Primary = Secondary = Summary for Pond P1: Onsite Pavement Area Depression 108,433 sf, 96.88% Impervious, 11.02 cfs @ 12.08 hrs, Volume= 7.44 cfs @ 12.20 hrs, Volume= 5.51 cfs @ 12.20 hrs, Volume= 1.93 cfs @ 12.20 hrs, Volume= Inflow Depth > 4.55" for 10 Year Storm(NRCS) event 41,080 cf 41,148 cf, Atten= 32%, Lag= 7.1 min 39,847 cf 1,301 cf Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Peak Elev= 26.74' @ 12.20 hrs Surf.Area= 14,644 sf Storage= 2,602 cf Plug -Flow detention time= (not calculated: outflow precedes inflow) Center -of -Mass det. time= 1.5 min ( 756.6 - 755.1 ) Volume Invert Avail.Storage Storage Description #1 26.21' 8,472 cf Custom Stage Data (Irregular)Listed below (Recalc) Elevation (feet) 26.21 27.00 Surf.Area Perim. (sq-ft) (feet) 0 0.0 32,171 1,178.0 Device Routing Invert #1 Primary 24.00' #2 Secondary 26.64' Inc.Store (cubic -feet) 0 8,472 Outlet Devices 12.0" Round Existing 12" RCP L= 72.0' RCP, groove end projecting, Ke= 0.200 Inlet / Outlet Invert= 24.00' / 23.10' S= 0.0125 '/' Cc= 0.900 n= 0.013, Flow Area= 0.79 sf 25.0' long x 5.0' breadth Broad -Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65 2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88 Cum.Store (cubic -feet) 0 8,472 Wet.Area (sq-ft) 0 110,429 Primary OutFlow Max=5.51 cfs @ 12.20 hrs HW=26.74' TW=0.00' (Dynamic Tailwater) t1=Existing 12" RCP (Barrel Controls 5.51 cfs @ 7.01 fps) Secondary OutFlow Max=1.91 cfs @ 12.20 hrs HW=26.74' TW=0.00' (Dynamic Tailwater) 2=Broad-Crested Rectangular Weir (Weir Controls 1.91 cfs @ 0.75 fps) 148 Waltham Street - Existing Watershe Type III 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 17 Pond P1: Onsite Pavement Area Depression Hydrograph 11.02 cfs 12/ 11-/=4rff °� �tgr1g7=60$ cf 81/ cfsI7� I --I I 14 5.51 s� LL 5/ 41/ ICI 14 / 3Y I I 2Y 1 1i/ 1.93 cfs 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Time (hours) 5 16 17 8 19 20 21 22 23 24 ■ Inflow ■ Primary ■ Secondary 148 Waltham Street - Existing Watershe Type 11124 -hr 25 Year Storm(NRCS) Rainfall=6.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 18 Summary for Subcatchment WS#1: Flow to Waltham Street Runoff = 14.00 cfs @ 12.08 hrs, Volume= 52,790 cf, Depth> 5.84" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 25 Year Storm(NRCS) Rainfall=6.20" Area (sf) CN Description 105,047 98 Impervious 3,386 68 <50% Grass cover, Poor, HSG A 108,433 97 Weighted Average 3,386 3.12% Pervious Area 105,047 96.88% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment WS#1: Flow to Waltham Street Hydrograph 15V 1a�� lT pe pi 24-hr 11 13J 28 Year Stogn(NRC) rfain1all=6.210" 12/ Runoff Area=108,433 s## 11J/R?noffV 1urpe=52,79 R no t >5.84"I ° 5.0 -mm 9 97 5Y I ± fi 4/ 3� �I I I I 2/ 1a/ 4 14.00 cfs 9 20 21 22 23 24 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Time (hours) H 0 R0n0 148 Waltham Street - Existing Watershe Type III 24 -hr 25 Year Storm(NRCS) Rainfall=6.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 19 Summary for Subcatchment WS#2: Flow to Green River Way Runoff = 0.51 cfs @ 12.09 hrs, Volume= 1,773 cf, Depth> 4.93" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 25 Year Storm(NRCS) Rainfall=6.20" Area (sf) CN Description 3,021 98 Impervious 1,297 68 <50% Grass cover, Poor, HSG A 4,318 89 Weighted Average 1,297 30.04% Pervious Area 3,021 69.96% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment WS#2: Flow to Green River Way Hydrograph 41 0.551 0.5-/ 0.45- 0.41/ 0.351/ ° 0.3 2 0.25 0.21/ 0.15'1 0.1J 0.05-/ 0.51 cfs Type III 24 -hr 25 Year Storn(NRCS) rai, fall=6 O" 1 Runoff Area=4,318 sf Runoff Volume=1,773T Rinoft Dlept lh>4493" Tc=5.0 min L • 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 TIn o (hours) Runo 148 Waltham Street - Existing Watershe Type III 24 -hr 25 Year Storm(NRCS) Rainfall=6.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 20 Summary for Subcatchment WS#3: Flow to Green River Way Runoff = 0.19 cfs @ 12.08 hrs, Volume= 727 cf, Depth> 5.96" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 25 Year Storm(NRCS) Rainfall=6.20" Area (sf) CN Description 1,464 98 Impervious 1,464 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment WS#3: Flow to Green River Way Hydrograph 0.2: / 0.19 pe 1 0.16 0.19 cfs IF o.n, Runoff sf ear�C�S) I�ai��fal 016 0.15✓ Runoff V lume 7 cU o.1a�, Runo�f Deeptt1>3 6 i 0.13= T�=5.0_min o.1z C 9 0.11 r T TI 0.1 0.09 0.08 0.07 0.06 0.04 0.03 0.02 V' 0 0 1 2 3 1=6 0" -H H H 1 H 4I T -HI TI H 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) Q Runo 148 Waltham Street - Existing Watershe Type III 24 -hr 25 Year Storm(NRCS) Rainfall=6.20" Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 21 Prepared by Microsoft Inflow Area = Inflow = Outflow = Summary for Reach SP1: Study Point #1 108,433 sf, 96.88% Impervious, Inflow Depth > 5.88" for 25 Year Storm(NRCS) event 9.88 cfs @ 12.19 hrs, Volume= 53,143 cf 9.88 cfs @ 12.19 hrs, Volume= 53,143 cf, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Reach SP1: Study Point #1 Hydrograph „/- lay 9V 8J/ 7V 6l o u 4V 3J 2- / F Arf!orlura7i-a.70-7 -Ifi 1I) H HH - d 4 2 3 4 5 6 7 8 9 10 11 12 13 14 Time (hours) • 9.88 cfs fi111 �l 1 1 -HI l 1 VI I I 15 16 7 18 19 4 I� 4 �I y 20 21 22 23 24 • Inflow • Outflo 148 Waltham Street - Existing Watershe Type III 24 -hr 25 Year Storm(NRCS) Rainfall=6.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 22 Inflow Area = Inflow = Outflow = Summary for Reach SP2: Study Point #2 4,318 sf, 69.96% Impervious, Inflow Depth > 4.93" for 25 Year Storm(NRCS) event 0.51 cfs @ 12.09 hrs, Volume= 1,773 cf 0.51 cfs @ 12.09 hrs, Volume= 1,773 cf, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 0.55Y 0.5-1 0.45- 0.4y 0.35 - LL 0.25J 0.2Y- / 0.15Y 0.1J Reach SP2: Study Point #2 Hydrograph 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) ■ Inflow • Outflo 148 Waltham Street - Existing Watershe Type III 24 -hr 25 Year Storm(NRCS) Rainfall=6.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 23 Inflow Area = Inflow = Outflow = Summary for Reach SP3: Study Point #3 1,464 sf,100.00% Impervious, Inflow Depth > 5.96" for 25 Year Storm(NRCS) event 0.19 cfs @ 12.08 hrs, Volume= 727 cf 0.19 cfs @ 12.08 hrs, Volume= 727 cf, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Reach SP3: Study Point #3 Hydrograph 021/ 0.2✓/ o.1s✓✓ 0.17: / 0.16-/ 0. 0.1 � o • 0.0 0.0 0.0 0.0 0.04' 0.03= 0.023 0.01 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) In �rO�fl 7 4 12" f' I E P II I I 1 1= • I I ■ Inflow • Ou010 148 Waltham Street - Existing Watershe Type III 24 -hr 25 Year Storm(NRCS) Rainfall=6.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 24 Inflow Area = Inflow = Outflow = Primary = Secondary = Summary for Pond P1: Onsite Pavement Area Depression 108,433 sf, 96.88% Impervious, 14.00 cfs @ 12.08 hrs, Volume= 9.88 cfs @ 12.19 hrs, Volume= 5.58 cfs @ 12.19 hrs, Volume= 4.30 cfs @ 12.19 hrs, Volume= Inflow Depth > 5.84" for 25 Year Storm(NRCS) event 52,790 cf 53,143 cf, Atten= 29%, Lag= 6.4 min 49,120 cf 4,023 cf Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Peak Elev= 26.82' @ 12.19 hrs Surf.Area= 18,896 sf Storage= 3,814 cf Plug -Flow detention time= (not calculated: outflow precedes inflow) Center -of -Mass det. time= 2.7 min ( 753.1 - 750.4 ) Volume Invert Avail.Storage Storage Description #1 26.21' 8,472 cf Custom Stage Data (Irregular)Listed below (Recalc) Elevation (feet) 26.21 27.00 Surf.Area Perim. (sq-ft) (feet) 0 0.0 32,171 1,178.0 Inc.Store (cubic -feet) 0 8,472 Device Routing Invert Outlet Devices #1 Primary 24.00' #2 Secondary 26.64' Cum.Store (cubic -feet) 0 8,472 Wet.Area (sq-ft) 0 110,429 12.0" Round Existing 12" RCP L= 72.0' RCP, groove end projecting, Ke= 0.200 Inlet / Outlet Invert= 24.00' / 23.10' S= 0.0125 '/' Cc= 0.900 n= 0.013, Flow Area= 0.79 sf 25.0' long x 5.0' breadth Broad -Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65 2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88 Primary OutFlow Max=5.58 cfs @ 12.19 hrs HW=26.81' TW=0.00' (Dynamic Tailwater) t1=Existing 12" RCP (Barrel Controls 5.58 cfs @ 7.10 fps) Secondary OutFlow Max=4.18 cfs @ 12.19 hrs HW=26.81' TW=0.00' (Dynamic Tailwater) 2=Broad-Crested Rectangular Weir (Weir Controls 4.18 cfs @ 0.97 fps) 148 Waltham Street - Existing Watershe Type III 24 -hr 25 Year Storm(NRCS) Rainfall=6.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 25 Pond P1: Onsite Pavement Area Depression Hydrograph ■ Inflow ■ Primary ■ Secondary 0 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) 148 Waltham Street - Existing Watersh Type 11124 -hr 100 Year Storm(NRCS) Rainfall=8.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD®10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 26 Summary for Subcatchment WS#1: Flow to Waltham Street Runoff = 20.18 cfs @ 12.08 hrs, Volume= 77,141 cf, Depth> 8.54" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 100 Year Storm(NRCS) Rainfall=8.90" Area (sf) CN Description 105,047 98 Impervious 3,386 68 <50% Grass cover, Poor, HSG A 108,433 97 Weighted Average 3,386 3.12% Pervious Area 105,047 96.88% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, 220 Subcatchment WS#1: Flow to Waltham Street Hydrograph 21, 20.18 cfs :,../, peypll 2{4-h Or a I�.plq 16v unoff ea=101,433 s� 16/Rno Vlu a=77,41 pf 1s2 Ono Atli> -854'1 14 .5.Ommn t'13 f-CN=g7 i V,�t 41+1—H p i 5 4 4 3- 1 0 II I I +1-H1 1- I I 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) 0 R0n0 148 Waltham Street - Existing Watersh Type 111 24 -hr 100 Year Storm(NRCS) Rainfall=8.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 27 Summary for Subcatchment WS#2: Flow to Green River Way Runoff = 0.77 cfs @ 12.09 hrs, Volume= 2,724 cf, Depth> 7.57" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 100 Year Storm(NRCS) Rainfall=8.90" Area (sf) CN Description 3,021 98 Impervious 1,297 68 <50% Grass cover, Poor, HSG A 4,318 89 Weighted Average 1,297 30.04% Pervious Area 3,021 69.96% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment WS#2: Flow to Green River Way Hydrograph 0.85 " F H- 0.8V� / 0.77 cfs 0.75/ T pe III 4-h 0.7V 1q0 Year StalrmvJNR S) Ranfa .901 0.651/ Runo rea=4,318 sf R noffVilu 7 4T o.s� Runoff D pttl>7:57. oss =5.0 min 0.4 5 G r (194 0.4/ 0.35/ 0.3/ 0.25/ 0.2/ 0.15J 0.1/ 0.05V / I 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) Runo 148 Waltham Street - Existing Watersh Type III 24 -hr 100 Year Storm(NRCS) Rainfall=8.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 28 Summary for Subcatchment WS#3: Flow to Green River Way Runoff = 0.27 cfs @ 12.08 hrs, Volume= 1,056 cf, Depth> 8.66" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 100 Year Storm(NRCS) Rainfall=8.90" Area (sf) CN Description 1,464 98 Impervious Tc (min) 5.0 1,464 100.00% Impervious Area Length Slope Velocity Capacity Description (feet) (ft/ft) (ft/sec) (cfs) Direct Entry, Subcatchment WS#3: Flow to Green River Way Hydrograph 1 0.3�� 0.28/ 0.26: 11'0 e'�t0lrm(NRF; 0.24. Runoff Area=11664 sf 0.22/ R no Iu a-1,0 6 f 0.2/ RR0inof f V Dept i>8 66' 0.18 • y=5. n 0.16 11-9 0.14_ u 0.12" 0.08/ 0.06/ 0.04Y 0.02/ 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) F 0.27 cfs 'nfaH9Oti tr -kI II -tIfiItI t fiI I I -L It �I H t fiI IH It -kI-I-I 1 I T I 14 I� Ailli ezczy ilzzi Q Runo 148 Waltham Street - Existing Watersh Type 111 24 -hr 100 Year Storm(NRCS) Rainfall=8.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 29 Summary for Reach SP1: Study Point #1 Inflow Area = 108,433 sf, 96.88% Impervious, Inflow Depth > 8.54" for 100 Year Storm(NRCS) event Inflow = 14.72 cfs @ 12.18 hrs, Volume= 77,140 cf Outflow = 14.72 cfs @ 12.18 hrs, Volume= 77,140 cf, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Reach SP1: Study Point #1 Hydrograph 16J 141/ 121/ 9V//9; ; 7J/ 6l/ 3V: , 0 1 2 Time (hours) 4 f �L14.72 cfs r!.71%771'11' I H -I I I a I I I 71+11- 4 I I II 7 18 19 20 21 22 23 24 ■ Inflow • Outilo 148 Waltham Street - Existing Watersh Type III 24 -hr 100 Year Storm(NRCS) Rainfall=8.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 30 Summary for Reach SP2: Study Point #2 Inflow Area = 4,318 sf, 69.96% Impervious, Inflow Depth > 7.57" for 100 Year Storm(NRCS) event Inflow = 0.77 cfs @ 12.09 hrs, Volume= 2,724 cf Outflow = 0.77 cfs @ 12.09 hrs, Volume= 2,724 cf, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 LL Reach SP2: Study Point #2 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) ■ Inflow • Outflow 148 Waltham Street - Existing Watersh Type 111 24 -hr 100 Year Storm(NRCS) Rainfall=8.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 31 Inflow Area = Inflow = Outflow = Summary for Reach SP3: Study Point #3 1,464 sf,100.00% Impervious, Inflow Depth > 8.66" for 100 Year Storm(NRCS) event 0.27 cfs @ 12.08 hrs, Volume= 1,056 cf 0.27 cfs @ 12.08 hrs, Volume= 1,056 cf, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Reach SP3: Study Point #3 Hydrograph /0.3 0.2 0.24/ 0.2 0.2/ 0.161/ ▪ 0.1E-'1, LL 0.14 0.124, 0.06/ 0.06/ 0.0 0.0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) ■ Inflow • Ou010 148 Waltham Street - Existing Watersh Type 11124 -hr 100 Year Storm(NRCS) Rainfall=8.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 32 Inflow Area = Inflow = Outflow = Primary = Secondary = Summary for Pond P1: Onsite Pavement Area Depression 108,433 sf, 96.88% Impervious, Inflow Depth > 8.54" for 100 Year Storm(NRCS) event 20.18 cfs @ 12.08 hrs, Volume= 77,141 cf 14.72 cfs @ 12.18 hrs, Volume= 77,140 cf, Atten= 27%, Lag= 5.8 min 5.69 cfs @ 12.18 hrs, Volume= 65,693 cf 9.03 cfs @ 12.18 hrs, Volume= 11,447 cf Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Peak Elev= 26.92' @ 12.18 hrs Surf.Area= 26,178 sf Storage= 6,218 cf Plug -Flow detention time= (not calculated: outflow precedes inflow) Center -of -Mass det. time= 2.2 min ( 746.5 - 744.4 ) Volume Invert Avail.Storage Storage Description #1 26.21' 8,472 cf Custom Stage Data (Irregular)Listed below (Recalc) Elevation (feet) 26.21 27.00 Surf.Area Perim. (sq-ft) (feet) 0 0.0 32,171 1,178.0 Device Routing Invert #1 Primary 24.00' #2 Secondary 26.64' Inc.Store (cubic -feet) 0 8,472 Outlet Devices 12.0" Round Existing 12" RCP L= 72.0' RCP, groove end projecting, Ke= 0.200 Inlet / Outlet Invert= 24.00' / 23.10' S= 0.0125 '/' Cc= 0.900 n= 0.013, Flow Area= 0.79 sf 25.0' long x 5.0' breadth Broad -Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65 2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88 Cum.Store (cubic -feet) 0 8,472 Wet.Area (sq-ft) 0 110,429 Primary OutFlow Max=5.69 cfs @ 12.18 hrs HW=26.92' TW=0.00' (Dynamic Tailwater) t1=Existing 12" RCP (Barrel Controls 5.69 cfs @ 7.24 fps) Secondary OutFlow Max=8.74 cfs @ 12.18 hrs HW=26.92' TW=0.00' (Dynamic Tailwater) 2=Broad-Crested Rectangular Weir (Weir Controls 8.74 cfs @ 1.26 fps) 148 Waltham Street - Existing Watersh Type 111 24 -hr 100 Year Storm(NRCS) Rainfall=8.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD®10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 33 148 Waltham Street - Proposed WatersheType 11124 -hr 2 Year Storm(NRCS) Rainfall=3.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 2 Summary for Subcatchment WS#1: Flow to Underground Infiltration Chambers Runoff = 1.56 cfs @ 12.09 hrs, Volume= 5,136 cf, Depth> 1.91" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 2 Year Storm(NRCS) Rainfall=3.20" Area (sf) CN Description 26,270 98 Impervious 5,925 39 >75% Grass cover, Good, HSG A (ws#� Flow to Under4round Infiltration Cham ers Flow to Underground Infiltration Chambers SP1 ;71 K /Study oint #1'. � I � p a�, Q 101 4 (ws#s Undergrou Infiltration Cha bers WQU1 AQ (wsa4) Bioretention #2 Flow to Bioretention Area #2 Bioretention #1 Flow to Bioretention Area #1 32,195 87 Weighted Average 5,925 18.40% Pervious Area 26,270 81.60% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (fUsec) (cfs) 5.0 Direct Entry, Subcatchment WS#1: Flow to Underground Infiltration Chambers Hydrog raph K 9 0 1.56 cfs Type 24 -hr 21Year S or (NR4) Rainfall=3.20" RunoffgArea=32,195 sf Runoff C(epth>1.91I" Tc=5.o mm CN=87 II 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) II 0 Runo Reach Link Routing Diagram for 148 Waltham Street - Proposed Watersheds Prepared by Microsoft, Printed 1/22/2020 HydroCAD®10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC 148 Waltham Street - Proposed WatersheType III 24 -hr 2 Year Storm(NRCS) Rainfall=3.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 3 Summary for Subcatchment WS#2: Flow to Underground Infiltration Chambers Runoff = 1.52 cfs @ 12.09 hrs, Volume= 5,011 cf, Depth> 1.91" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 2 Year Storm(NRCS) Rainfall=3.20" Area (sf) CN Description 25,686 98 Impervious 5,726 39 >75% Grass cover, Good, HSG A Tc (min) 8 5.0 31,412 87 Weighted Average 5,726 18.23% Pervious Area 25,686 81.77% Impervious Area Length Slope Velocity Capacity Description (feet) (ft/ft) (ft/sec) (cfs) Direct Entry, Subcatchment WS#2: Flow to Underground Infiltration Chambers Hydrograph 1.52 cfs 2t1'pea�rlSorr r(NR4) Rainfall=3.I20H Runoff Area=31,412 sf Runoff Rirndff Depth>1.91 cf I -/ Tc=5.0 min CN=a7 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) Runo 148 Waltham Street - Proposed WatersheType 11124 -hr 2 Year Storm(NRCS) Rainfall=3.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 4 Summary for Subcatchment WS#3: Flow to Bioretention Area #1 Runoff = 0.96 cfs @ 12.09 hrs, Volume= 3,169 cf, Depth> 1.47" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 2 Year Storm(NRCS) Rainfall=3.20" Area (sf) CN Description 18,584 98 Impervious 7,317 39 >75% Grass cover, Good, HSG A 25,901 81 Weighted Average 7,317 28.25% Pervious Area 18,584 71.75% Impervious Area Tc (min) 8 5.0 0 0 Length (feet) Slope Velocity Capacity Description (ft/ft) (ft/sec) (cfs) Direct Entry, Subcatchment WS#3: Flow to Bioretention Area #1 Hydrograph 0.96 cfs Type III 24-Itr 2i1'ear S or (NRCO) Rainfall=3.20" Runoff Area=25,901 sf R ungqff Volume=3,169 cf Runoff Depth>1.47" Tc=5.0 min CN=01 II II 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Time (hours) 23 24 ❑ Runo 148 Waltham Street - Proposed WatersheType 111 24 -hr 2 Year Storm(NRCS) Rainfall=3.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 5 Summary for Subcatchment WS#4: Flow to Bioretention Area #2 Runoff = 1.10 cfs @ 12.09 hrs, Volume= 3,617 cf, Depth> 1.76" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 2 Year Storm(NRCS) Rainfall=3.20" Area (sf) CN Description 19,231 98 Impervious 5,476 39 >75% Grass cover, Good, HSG A 24,707 85 Weighted Average 5,476 22.16% Pervious Area 19,231 77.84% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment WS#4: Flow to Bioretention Area #2 Hydrograph 1.10 cfs _/-2-Year S or (NRC) ai fa — . 0' Runoff Area=24,707 sf R}pingqff olulIme 3, 17icf Rilndff eplh> 7 " Tc=5.0 min Cr= 15 I .../.. . ... . .. . 0 1 2 3 4 5 6 7 8 9 10 .4. ...4.. 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) Runo 148 Waltham Street - Proposed WatersheType 11124 -hr 2 Year Storm(NRCS) Rainfall=3.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 6 Summary for Reach SP1: Study Point #1 Inflow Area = 114,215 sf, 78.60% Impervious, Inflow Depth > 1.02" for 2 Year Storm(NRCS) event Inflow = 0.70 cfs @ 12.22 hrs, Volume= 9,716 cf Outflow = 0.70 cfs @ 12.22 hrs, Volume= 9,716 cf, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 0.75 Reach SP1: Study Point #1 Hydrograph I -t tl 1 14 H 1 11 1- 2 3 4 5 6 7 8 9 10 11 12 13-14-1-16-17 18 19 20 21 22 23 24 Time (hours) ■ Inflow ❑ Outflow 148 Waltham Street - Proposed WatersheType III 24 -hr 2 Year Storm(NRCS) Rainfall=3.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 7 Summary for Pond BIO1: Bioretention #1 Inflow Area = 25,901 sf, 71.75% Impervious, Inflow Depth > 1.47" for 2 Year Storm(NRCS) event Inflow = 0.96 cfs @ 12.09 hrs, Volume= 3,169 cf Outflow = 0.70 cfs @ 12.22 hrs, Volume= 2,546 cf, Atten= 28%, Lag= 7.3 min Primary = 0.70 cfs @ 12.22 hrs, Volume= 2,546 cf Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0 cf Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Peak Elev= 26.66' @ 12.22 hrs Surf.Area= 1,884 sf Storage= 879 cf Plug -Flow detention time= 119.9 min calculated for 2,546 cf (80% of inflow) Center -of -Mass det. time= 41.9 min ( 880.3 - 838.3 ) Volume Invert Avail.Storage Storage Description #1 26.00' 4,926 cf Bioretention #1 (Irregular)Listed below (Recalc) #2 23.00' 1 cf 0.67'D x 3.50'H Vertical AD Storage 4,927 cf Total Available Storage Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic -feet) (cubic -feet) (sq-ft) 26.00 854 195.0 0 0 854 27.00 2,580 580.0 1,639 1,639 24,601 28.00 4,047 595.0 3,286 4,926 26,122 Device Routing Invert Outlet Devices #1 Primary 23.69' 12.0" Round Culvert L= 29.0' CPP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 23.69' / 23.40' S= 0.0100 '/' Cc= 0.900 n= 0.012 Corrugated PP, smooth interior, Flow Area= 0.79 sf #2 Device 1 26.50' 4.0' long x 0.5' breadth Weir flow inside OCS Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 #3 Secondary 26.79' 12.0' long x 5.0' breadth Weir Flow at Driveway Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65 2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88 Primary OutFlow Max=0.67 cfs @ 12.22 hrs HW=26.65' TW=23.72' (Dynamic Tailwater) t1=Culvert (Passes 0.67 cfs of 4.69 cfs potential flow) 2=Weir flow inside OCS (Weir Controls 0.67 cfs @ 1.09 fps) Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=23.00' TW=0.00' (Dynamic Tailwater) 3=Weir Flow at Driveway ( Controls 0.00 cfs) 148 Waltham Street - Proposed WatersheType 11124 -hr 2 Year Storm(NRCS) Rainfall=3.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD®10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 8 Pond BIO1: Bioretention #1 Hydrograph Peak Elelvrf �26266° s ,tprage879 cf 0 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) ■ Inflow ■ Primary ■ Secondary 148 Waltham Street - Proposed WatersheType 111 24 -hr 2 Year Storm(NRCS) Rainfall=3.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 9 Summary for Pond B102: Bioretention #2 Inflow Area = 24,707 sf, 77.84% Impervious, Inflow Depth > 1.76" for 2 Year Storm(NRCS) event Inflow = 1.10 cfs @ 12.09 hrs, Volume= 3,617 cf Outflow = 1.00 cfs @ 12.10 hrs, Volume= 3,018 cf, Atten= 10%, Lag= 0.2 min Primary = 1.00 cfs @ 12.10 hrs, Volume= 3,018 cf Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Peak Elev= 26.55' @ 12.10 hrs Surf.Area= 1,349 sf Storage= 667 cf Plug -Flow detention time= 100.5 min calculated for 3,018 cf (83% of inflow) Center -of -Mass det. time= 31.8 min ( 856.7 - 824.9 ) Volume Invert Avail.Storage Storage Description #1 26.00' 3,486 cf Bioretention #2 (Irregular)Listed below (Recalc) #2 23.35' 40 cf 4.00'D x 3.15'H Vertical OCS Storage 3,525 cf Total Available Storage Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic -feet) (cubic -feet) (sq-ft) 26.00 937 241.0 0 0 937 27.00 1,709 306.0 1,304 1,304 3,780 28.00 2,692 383.0 2,182 3,486 8,015 Device Routing Invert Outlet Devices #1 Primary #2 Device 1 23.44' 12.0" Round Culvert L= 14.0' CPP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 23.44' / 23.30' S= 0.0100 '/' Cc= 0.900 n= 0.012 Corrugated PP, smooth interior, Flow Area= 0.79 sf 26.50' 2.0" x 2.0" Horiz. Orifice/Grate X 6.00 columns X 6 rows C= 0.600 Limited to weir flow at low heads T-rimary OutFlow Max=0.99 cfs @ 12.10 hrs HW=26.55' TW=23.62' (Dynamic Tailwater) 1=Culvert (Passes 0.99 cfs of 4.83 cfs potential flow) 2=Orifice/Grate (Weir Controls 0.99 cfs @ 0.76 fps) 148 Waltham Street - Proposed WatersheType 11124 -hr 2 Year Storm(NRCS) Rainfall=3.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD®10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 10 0 Pond B102: Bioretention #2 Hydrograph 1.10 cfs Inflow lAre j� ,7 7 sir I Peak EIeV=26.55'11.00 cfs J Storagle16571 cf 12 13 14 Time (hours) 20 21 22 23 24 • Inflow • Primary 148 Waltham Street - Proposed WatersheType III 24 -hr 2 Year Storm(NRCS) Rainfall=3.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 11 Inflow Area = Inflow = Outflow = Primary = Secondary = Summary for Pond UIS: Underground Infiltration Chambers 88,314 sf, 80.61% Impervious, Inflow Depth > 1.79" for 2 Year Storm(NRCS) event 4.07 cfs @ 12.09 hrs, Volume= 13,165 cf 0.39 cfs @ 13.14 hrs, Volume= 7,170 cf, Atten= 90%, Lag= 63.0 min 0.39 cfs @ 13.14 hrs, Volume= 7,170 cf 0.00 cfs @ 0.00 hrs, Volume= 0 cf Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Peak Elev= 24.15' @ 13.14 hrs Surf.Area= 8,626 sf Storage= 7,345 cf Plug -Flow detention time= 264.6 min calculated for 7,170 cf (54% of inflow) Center -of -Mass det. time= 151.6 min ( 978.2 - 826.6 ) Volume Invert Avail.Storage Storage Description #1A 22.80' 2,604 cf #2A 23.30' 2,123 cf #3 23.30' 46 cf #4 26.50' 2,451 cf #5B 22.80' 2,321 cf #6B 23.30' 3,032 cf #7C 22.80' 2,243 cf #8C 23.30' 2,756 cf 28.17W x 131.36'L x 2.33'H Field A 8,633 cf Overall - 2,123 cf Embedded = 6,510 cf x 40.0% Voids ADS_StormTech SC -310 +Cap x 144 Inside #1 Effective Size= 28.9"W x 16.0"H => 2.07 sf x 7.12'L = 14.7 cf Overall Size= 34.0"W x 16.0"H x 7.56'L with 0.44' Overlap 144 Chambers in 8 Rows 4.00'D x 3.70'H Vertical Manhole Storage Parking Lot (Irregular)Listed below (Recalc) 15.75W x 160.26'L x 3.50'H Field B 8,834 cf Overall - 3,032 cf Embedded = 5,802 cf x 40.0% Voids ADS_StormTech SC -740 +Cap x 66 Inside #5 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L = 45.9 cf Overall Size= 51.0"W x 30.0"H x 7.56'L with 0.44' Overlap 66 Chambers in 3 Rows 11.00W x 217.22'L x 3.50'H Field C 8,363 cf Overall - 2,756 cf Embedded = 5,606 cf x 40.0% Voids ADS_StormTech SC -740 +Cap x 60 Inside #7 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L = 45.9 cf Overall Size= 51.0"W x 30.0"H x 7.56'L with 0.44' Overlap 60 Chambers in 2 Rows Total Available Storage 17,576 cf Storage Group A created with Chamber Wizard Storage Group B created with Chamber Wizard Storage Group C created with Chamber Wizard Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic -feet) (cubic -feet) (sq-ft) 26.50 0 0.0 0 0 0 27.00 3,485 320.0 581 581 8,149 27.50 4,000 330.0 1,870 2,451 8,691 Device Routing Invert #1 Primary Outlet Devices 23.80' 12.0" Round Proposed 12" HDPE L= 64.0' CPP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 23.80' / 23.40' S= 0.0063 '/' Cc= 0.900 n= 0.012 Corrugated PP, smooth interior, Flow Area= 0.79 sf 148 Waltham Street - Proposed WatersheType 11124 -hr 2 Year Storm(NRCS) Rainfall=3.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 12 #2 Secondary 26.80' 24.0' long x 5.0' breadth Weir Flow at Driveway Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65 2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88 Primary OutFlow Max=0.39 cfs @ 13.14 hrs HW=24.15' TW=23.65' (Dynamic Tailwater) t1=Proposed 12" HDPE (Inlet Controls 0.39 cfs @ 1.59 fps) Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=22.80' TW=0.00' (Dynamic Tailwater) '-2=Weir Flow at Driveway ( Controls 0.00 cfs) Pond UIS: Underground Infiltration Chambers Hydrograph 4 3 0.00 cfs 4. cfs .07 121::aZ 51 1 4 '-t?r,gefi P15Fc! 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Thne (hours) ❑ Inflow I ❑ Primary ❑ Secondary 148 Waltham Street - Proposed WatersheType III 24 -hr 2 Year Storm(NRCS) Rainfall=3.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 13 Inflow Area = Inflow = Outflow = Primary = Summary for Pond WQU1: WQU1 114,215 sf, 78.60% Impervious, Inflow Depth > 1.02" for 2 Year Storm(NRCS) event 0.70 cfs @ 12.22 hrs, Volume= 9,716 cf 0.70 cfs @ 12.22 hrs, Volume= 9,716 cf, Atten= 0%, Lag= 0.0 min 0.70 cfs @ 12.22 hrs, Volume= 9,716 cf Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Peak Elev= 23.73' @ 12.23 hrs Device Routing Invert Outlet Devices #1 Primary 23.30' 12.0" Round Existing 12" RCP L= 15.0' RCP, groove end projecting, Ke= 0.200 Inlet / Outlet Invert= 23.30' / 23.10' S= 0.0133 '/' Cc= 0.900 n= 0.013 Concrete pipe, straight & clean, Flow Area= 0.79 sf Primary OutFlow Max=0.67 cfs @ 12.22 hrs HW=23.72' TW=0.00' (Dynamic Tailwater) L1=Existing 12" RCP (Barrel Controls 0.67 cfs @ 3.18 fps) Pond WQU1: WQU1 Hydrograph I n 711 rf 0.75. 0.70 cfs 0.657 / e R G e r3. 2 0 0.5 0. 0.457 0.4: 2 0.357/ 0.257/ 0.21/ 0.157 oL 6 er 1=m17 � I�Ifi H 6:00���/���! : %.., ,..� 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14.-15' -16-11;...1g. 19 20 21 22 23 24 Time (hours) ■ Inflow 0 Primary' 148 Waltham Street - Proposed WatershType III 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Paoe 14 Summary for Subcatchment WS#1: Flow to Underground Infiltration Chambers Runoff = 2.77 cfs @ 12.09 hrs, Volume= 9,315 cf, Depth> 3.47" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Area (sf) CN Description 26,270 98 Impervious 5,925 39 >75% Grass cover, Good, HSG A 32,195 87 Weighted Average 5,925 18.40% Pervious Area 26,270 81.60% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (fUsec) (cfs) 5.0 3 2 3 Direct Entry, Subcatchment WS#1: Flow to Underground Infiltration Chambers Hydrograph 2.77 cfs T pe II24-h 1( Ye r 4to4n(If RC ) I air�fall 4.�0" Runoff Area=32,195 sf Ri pnojf Vp e9,35 Gf R no pt >34/" Tc=5.0 min CN=8 I ` II 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) 0 Rnn0 148 Waltham Street - Proposed WatershType III 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 15 Summary for Subcatchment WS#2: Flow to Underground Infiltration Chambers Runoff = 2.70 cfs @ 12.09 hrs, Volume= 9,089 cf, Depth> 3.47" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Area (sf) CN Description 25,686 98 Impervious 5,726 39 >75% Grass cover, Good, HSG A 31,412 87 Weighted Average 5,726 18.23% Pervious Area 25,686 81.77% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 3/ Direct Entry, Subcatchment WS#2: Flow to Underground Infiltration Chambers Hydrograph 17 2.70 cfs T e 4-h 1gYer24tor�n(I,RC) I,airlfall4.90" Runoff Area=31,412 sf Rino Vplurhe471 of R no D pt >3 47" Tc=5.0 min CN=8,7 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) 148 Waltham Street - Proposed WatershType III 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD®10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 16 Summary for Subcatchment WS#3: Flow to Bioretention Area #1 Runoff = 1.90 cfs @ 12.09 hrs, Volume= 6,251 cf, Depth> 2.90" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Area (sf) CN Description 18,584 98 Impervious 7,317 39 >75% Grass cover, Good, HSG A 25,901 81 Weighted Average 7,317 28.25% Pervious Area 18,584 71.75% Impervious Area Tc (min) 5.0 2 Length Slope Velocity Capacity Description (feet) (ft/ft) (fUsec) (cfs) Direct Entry, Subcatchment WS#3: Flow to Bioretention Area #1 Hydrograph 1.90 cfs T pe 111 24-h 1(( Yer 4to1n(IIRC) F airtfall 4.0" RunoffArea=25,901 sf Runoff Volu a-6,2 1 cf ROnoff Deptli>290' Tc=5.0 min CN=81 I- ] -I 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Time (hours) 9 20 2 0 RUno 148 Waltham Street - Proposed WatershType III 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 17 Summary for Subcatchment WS#4: Flow to Bioretention Area #2 Runoff = 2.02 cfs @ 12.09 hrs, Volume= 6,742 cf, Depth> 3.27" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Area (sf) CN Description 19,231 98 Impervious 5,476 39 >75% Grass cover, Good, HSG A 24,707 85 Weighted Average 5,476 22.16% Pervious Area 19,231 77.84% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment WS#4: Flow to Bioretention Area #2 Hydrograph 2Y 3 j 1 o II 2.02 cfs 1TgYe er24-h4tor�n(I.RC ) I air�faII 4.�0" Runoff Area=24,707 sf Runoff Volu a-6,7 2 of ino R Depth>347"1 Tc=5.0 min CII=8 0.. . �.. 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) I 0323 148 Waltham Street - Proposed WatershType III 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 18 Summary for Reach SP1: Study Point #1 Inflow Area = 114,215 sf, 78.60% Impervious, Inflow Depth > 2.52" for 10 Year Storm(NRCS) event Inflow = 3.25 cfs @ 12.24 hrs, Volume= 23,951 cf Outflow = 3.25 cfs @ 12.24 hrs, Volume= 23,951 cf, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 LL / 3 - 0 f/� 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) II Reach SP1: Study Point #1 • Inflow • outflo 148 Waltham Street - Proposed WatershType III 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 19 Summary for Pond BIO1: Bioretention #1 Inflow Area = 25,901 sf, 71.75% Impervious, Inflow Depth > 2.90" for 10 Year Storm(NRCS) event Inflow = 1.90 cfs @ 12.09 hrs, Volume= 6,251 cf Outflow = 1.59 cfs @ 12.15 hrs, Volume= 5,620 cf, Atten= 16%, Lag= 3.4 min Primary = 1.59 cfs @ 12.15 hrs, Volume= 5,620 cf Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0 cf Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Peak Elev= 26.77' @ 12.15 hrs Surf.Area= 2,102 sf Storage= 1,105 cf Plug -Flow detention time= 75.1 min calculated for 5,620 cf (90% of inflow) Center -of -Mass det. time= 26.7 min ( 845.4 - 818.8 ) Volume Invert Avail.Storage Storage Description #1 26.00' 4,926 cf Bioretention #1 (Irregular)Listed below (Recalc) #2 23.00' 1 cf 0.67'D x 3.50'H Vertical AD Storage 4,927 cf Total Available Storage Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic -feet) (cubic -feet) (sq-ft) 26.00 854 195.0 0 0 854 27.00 2,580 580.0 1,639 1,639 24,601 28.00 4,047 595.0 3,286 4,926 26,122 Device Routing Invert Outlet Devices #1 Primary 23.69' 12.0" Round Culvert L= 29.0' CPP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 23.69' / 23.40' S= 0.0100 '/' Cc= 0.900 n= 0.012 Corrugated PP, smooth interior, Flow Area= 0.79 sf #2 Device 1 26.50' 4.0' long x 0.5' breadth Weir flow inside OCS Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 #3 Secondary 26.79' 12.0' long x 5.0' breadth Weir Flow at Driveway Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65 2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88 Primary OutFlow Max=1.52 cfs @ 12.15 hrs HW=26.76' TW=24.29' (Dynamic Tailwater) t1=Culvert (Passes 1.52 cfs of 4.69 cfs potential flow) 2=Weir flow inside OCS (Weir Controls 1.52 cfs @ 1.45 fps) Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=23.00' TW=0.00' (Dynamic Tailwater) 3=Weir Flow at Driveway ( Controls 0.00 cfs) 148 Waltham Street - Proposed WatershType III 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 20 Pond BIO1: Bioretention #1 Hydrograph 0 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) ■ Inflow ■ Primary ■ Secondary 148 Waltham Street - Proposed WatershType III 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 21 Summary for Pond B102: Bioretention #2 Inflow Area = 24,707 sf, 77.84% Impervious, Inflow Depth > 3.27" for 10 Year Storm(NRCS) event Inflow = 2.02 cfs @ 12.09 hrs, Volume= 6,742 cf Outflow = 1.77 cfs @ 12.13 hrs, Volume= 6,142 cf, Atten= 13%, Lag= 2.2 min Primary = 1.77 cfs @ 12.13 hrs, Volume= 6,142 cf Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Peak Elev= 26.63' @ 12.12 hrs Surf.Area= 1,412 sf Storage= 775 cf Plug -Flow detention time= 66.4 min calculated for 6,142 cf (91% of inflow) Center -of -Mass det. time= 22.5 min ( 829.6 - 807.2 ) Volume Invert Avail.Storage Storage Description #1 26.00' 3,486 cf Bioretention #2 (Irregular)Listed below (Recalc) #2 23.35' 40 cf 4.00'D x 3.15'H Vertical OCS Storage 3,525 cf Total Available Storage Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic -feet) (cubic -feet) (sq-ft) 26.00 937 241.0 0 0 937 27.00 1,709 306.0 1,304 1,304 3,780 28.00 2,692 383.0 2,182 3,486 8,015 Device Routing Invert Outlet Devices #1 Primary #2 Device 1 23.44' 12.0" Round Culvert L= 14.0' CPP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 23.44' / 23.30' S= 0.0100 '/' Cc= 0.900 n= 0.012 Corrugated PP, smooth interior, Flow Area= 0.79 sf 26.50' 2.0" x 2.0" Horiz. Orifice/Grate X 6.00 columns X 6 rows C= 0.600 Limited to weir flow at low heads T-rimary OutFlow Max=1.71 cfs @ 12.13 hrs HW=26.63' TW=24.47' (Dynamic Tailwater) 1=Culvert (Passes 1.71 cfs of 4.38 cfs potential flow) 2=Orifice/Grate (Orifice Controls 1.71 cfs @ 1.71 fps) 148 Waltham Street - Proposed WatershType III 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 22 Pond B102: Bioretention #2 Hydrograph Time (hours) 3 14 15 16 17 18 19 20 21 22 23 24 • Inflow • Primary 148 Waltham Street - Proposed WatershType III 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 23 Inflow Area = Inflow = Outflow = Primary = Secondary = Summary for Pond UIS: Underground Infiltration Chambers 88,314 sf, 80.61% Impervious, Inflow Depth > 3.34" for 10 Year Storm(NRCS) event 7.20 cfs @ 12.09 hrs, Volume= 24,545 cf 2.26 cfs @ 12.52 hrs, Volume= 18,331 cf, Atten= 69%, Lag= 25.8 min 2.26 cfs @ 12.52 hrs, Volume= 18,331 cf 0.00 cfs @ 0.00 hrs, Volume= 0 cf Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Peak Elev= 24.94' @ 12.43 hrs Surf.Area= 8,626 sf Storage= 11,513 cf Plug -Flow detention time= 171.7 min calculated for 18,254 cf (74% of inflow) Center -of -Mass det. time= 88.2 min ( 896.3 - 808.0 ) Volume Invert Avail.Storage Storage Description #1A 22.80' 2,604 cf #2A 23.30' 2,123 cf #3 23.30' 46 cf #4 26.50' 2,451 cf #5B 22.80' 2,321 cf #6B 23.30' 3,032 cf #7C 22.80' 2,243 cf #8C 23.30' 2,756 cf 28.17W x 131.36'L x 2.33'H Field A 8,633 cf Overall - 2,123 cf Embedded = 6,510 cf x 40.0% Voids ADS_StormTech SC -310 +Cap x 144 Inside #1 Effective Size= 28.9"W x 16.0"H => 2.07 sf x 7.12'L = 14.7 cf Overall Size= 34.0"W x 16.0"H x 7.56'L with 0.44' Overlap 144 Chambers in 8 Rows 4.00'D x 3.70'H Vertical Manhole Storage Parking Lot (Irregular)Listed below (Recalc) 15.75W x 160.26'L x 3.50'H Field B 8,834 cf Overall - 3,032 cf Embedded = 5,802 cf x 40.0% Voids ADS_StormTech SC -740 +Cap x 66 Inside #5 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L = 45.9 cf Overall Size= 51.0"W x 30.0"H x 7.56'L with 0.44' Overlap 66 Chambers in 3 Rows 11.00W x 217.22'L x 3.50'H Field C 8,363 cf Overall - 2,756 cf Embedded = 5,606 cf x 40.0% Voids ADS_StormTech SC -740 +Cap x 60 Inside #7 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L = 45.9 cf Overall Size= 51.0"W x 30.0"H x 7.56'L with 0.44' Overlap 60 Chambers in 2 Rows Total Available Storage 17,576 cf Storage Group A created with Chamber Wizard Storage Group B created with Chamber Wizard Storage Group C created with Chamber Wizard Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic -feet) (cubic -feet) (sq-ft) 26.50 0 0.0 0 0 0 27.00 3,485 320.0 581 581 8,149 27.50 4,000 330.0 1,870 2,451 8,691 Device Routing Invert #1 Primary Outlet Devices 23.80' 12.0" Round Proposed 12" HDPE L= 64.0' CPP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 23.80' / 23.40' S= 0.0063 '/' Cc= 0.900 n= 0.012 Corrugated PP, smooth interior, Flow Area= 0.79 sf 148 Waltham Street - Proposed WatershType III 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 24 #2 Secondary 26.80' 24.0' long x 5.0' breadth Weir Flow at Driveway Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65 2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88 Primary OutFlow Max=2.28 cfs @ 12.52 hrs HW=24.91' TW=24.33' (Dynamic Tailwater) t1=Proposed 12" HDPE (Inlet Controls 2.28 cfs @ 2.90 fps) Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=22.80' TW=0.00' (Dynamic Tailwater) L2=Weir Flow at Driveway ( Controls 0.00 cfs) Pond UIS: Underground Infiltration Chambers Hydrograph LL 3 0.00 cfs 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Time (hours) 5 16 17 18 19 20 21 22 23 24 7.20 cfs 2.26 cfs 71 H ICI 1 LW t H 1 I -HI H W H ❑ Inflow I ❑ Primary ❑ Secondary 148 Waltham Street - Proposed WatershType III 24 -hr 10 Year Storm(NRCS) Rainfall=4.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 25 Inflow Area = Inflow = Outflow = Primary = Summary for Pond WQU1: WQU1 114,215 sf, 78.60% Impervious, Inflow Depth > 2.52" for 10 Year Storm(NRCS) event 3.25 cfs @ 12.24 hrs, Volume= 23,951 cf 3.25 cfs @ 12.24 hrs, Volume= 23,951 cf, Atten= 0%, Lag= 0.0 min 3.25 cfs @ 12.24 hrs, Volume= 23,951 cf Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Peak Elev= 24.45' @ 12.24 hrs Device Routing Invert Outlet Devices #1 Primary 23.30' 12.0" Round Existing 12" RCP L= 15.0' RCP, groove end projecting, Ke= 0.200 Inlet / Outlet Invert= 23.30' / 23.10' S= 0.0133 '/' Cc= 0.900 n= 0.013 Concrete pipe, straight & clean, Flow Area= 0.79 sf Primary OutFlow Max=3.13 cfs @ 12.24 hrs HW=24.42' TW=0.00' (Dynamic Tailwater) L1=Existing 12" RCP (Barrel Controls 3.13 cfs @ 4.45 fps) 2 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) Pond WQU1: WQU1 Hydrograph etck Elev=24'.45'V r oundCulvert 0h=0-0113 I I I L=15.0' =1 {i3H/' • Inflow II • Primary 148 Waltham Street - Proposed WatershType III 24 -hr 25 Year Storm(NRCS) Rainfall=6.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 26 Summary for Subcatchment WS#1: Flow to Underground Infiltration Chambers Runoff = 3.70 cfs @ 12.09 hrs, Volume= 12,629 cf, Depth> 4.71" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 25 Year Storm(NRCS) Rainfall=6.20" Area (sf) CN Description 26,270 98 Impervious 5,925 39 >75% Grass cover, Good, HSG A 32,195 87 Weighted Average 5,925 18.40% Pervious Area 26,270 81.60% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (fUsec) (cfs) 5.0 4 Direct Entry, Subcatchment WS#1: Flow to Underground Infiltration Chambers Hydrograph 3y 1-Z 3.70 cfs Type pi 24-1-i 25 Year gtor�n(Ir RC) Flair�fall '6.�0" Runoff Area=32,195 sf— R no Volu a-12, 29 cf R ino Dept >471" Tc=5.0 min II 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) 0 Rnn0 148 Waltham Street - Proposed WatershType III 24 -hr 25 Year Storm(NRCS) Rainfall=6.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 27 Summary for Subcatchment WS#2: Flow to Underground Infiltration Chambers Runoff = 3.61 cfs @ 12.09 hrs, Volume= 12,322 cf, Depth> 4.71" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 25 Year Storm(NRCS) Rainfall=6.20" Area (sf) CN Description 25,686 98 Impervious 5,726 39 >75% Grass cover, Good, HSG A 31,412 87 Weighted Average 5,726 18.23% Pervious Area 25,686 81.77% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment WS#2: Flow to Underground Infiltration Chambers Hydrograph 4/ 17 i 3.61 cfs Type pi 25' 2 Year Itairfall 6.0" y-Runoff-Area=39-,412 sf- 3 R no Volu a-12, 22 cf Runof f Depth>471' Tc=5.0 min CN=8 1y 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) 148 Waltham Street - Proposed WatershType III 24 -hr 25 Year Storm(NRCS) Rainfall=6.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 28 Summary for Subcatchment WS#3: Flow to Bioretention Area #1 Runoff = 2.64 cfs @ 12.09 hrs, Volume= 8,774 cf, Depth> 4.06" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 25 Year Storm(NRCS) Rainfall=6.20" Area (sf) CN Description 18,584 98 Impervious 7,317 39 >75% Grass cover, Good, HSG A 25,901 81 Weighted Average 7,317 28.25% Pervious Area 18,584 71.75% Impervious Area Tc Length (min) (feet) 5.0 2 Slope Velocity Capacity Description (ft/ft) (ft/sec) (cfs) Direct Entry, Subcatchment WS#3: Flow to Bioretention Area #1 Hydrograph I I 2.64 cfs T e 4-h 2 Ye�r24to4n(NRC ) I airifaII 6.70" Runoff Area=25,901 sf tinor,Dept >4O6i R noff Dept >4 O6" Tc=5.0 min CN=81 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Time (hours) 9 20 21 22 23 24 0 RUno 148 Waltham Street - Proposed WatershType III 24 -hr 25 Year Storm(NRCS) Rainfall=6.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 29 Summary for Subcatchment WS#4: Flow to Bioretention Area #2 Runoff = 2.74 cfs @ 12.09 hrs, Volume= 9,244 cf, Depth> 4.49" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 25 Year Storm(NRCS) Rainfall=6.20" Area (sf) CN Description 19,231 98 Impervious 5,476 39 >75% Grass cover, Good, HSG A 24,707 85 Weighted Average 5,476 22.16% Pervious Area 19,231 77.84% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment WS#4: Flow to Bioretention Area #2 Hydrograph 3� I Irt 2 2.74 cfs Te 4-h 2 rer24tor�n(t,RC) I airfaII e6.0" Runoff Area=24,707 sf Runof D pth>40blutine i of R no D pt >4 49" Tc=5.0 min CN=85 Irt -hl 0 �� 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) Runo 148 Waltham Street - Proposed WatershType III 24 -hr 25 Year Storm(NRCS) Rainfall=6.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 30 Summary for Reach SP1: Study Point #1 Inflow Area = 114,215 sf, 78.60% Impervious, Inflow Depth > 3.72" for 25 Year Storm(NRCS) event Inflow = 4.70 cfs @ 12.10 hrs, Volume= 35,378 cf Outflow = 4.70 cfs @ 12.10 hrs, Volume= 35,378 cf, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Reach SP1: Study Point #1 Hydrograph I a7nrr 5_ 'rf! rya=1r 47 4/ II 0 1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 19 20 22 23 14 15 16 17 18 21 23 24 Time • Inflow • Outflow 148 Waltham Street - Proposed WatershType III 24 -hr 25 Year Storm(NRCS) Rainfall=6.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 31 Summary for Pond BIO1: Bioretention #1 Inflow Area = 25,901 sf, 71.75% Impervious, Inflow Depth > 4.06" for 25 Year Storm(NRCS) event Inflow = 2.64 cfs @ 12.09 hrs, Volume= 8,774 cf Outflow = 2.32 cfs @ 12.13 hrs, Volume= 8,138 cf, Atten= 12%, Lag= 2.5 min Primary = 2.16 cfs @ 12.14 hrs, Volume= 8,050 cf Secondary = 0.17 cfs @ 12.12 hrs, Volume= 88 cf Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Peak Elev= 26.83' @ 12.14 hrs Surf.Area= 2,218 sf Storage= 1,229 cf Plug -Flow detention time= 59.5 min calculated for 8,104 cf (92% of inflow) Center -of -Mass det. time= 23.1 min ( 832.2 - 809.1 ) Volume Invert Avail.Storage Storage Description #1 26.00' 4,926 cf Bioretention #1 (Irregular)Listed below (Recalc) #2 23.00' 1 cf 0.67'D x 3.50'H Vertical AD Storage 4,927 cf Total Available Storage Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic -feet) (cubic -feet) (sq-ft) 26.00 854 195.0 0 0 854 27.00 2,580 580.0 1,639 1,639 24,601 28.00 4,047 595.0 3,286 4,926 26,122 Device Routing Invert Outlet Devices #1 Primary 23.69' 12.0" Round Culvert L= 29.0' CPP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 23.69' / 23.40' S= 0.0100 '/' Cc= 0.900 n= 0.012 Corrugated PP, smooth interior, Flow Area= 0.79 sf #2 Device 1 26.50' 4.0' long x 0.5' breadth Weir flow inside OCS Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 #3 Secondary 26.79' 12.0' long x 5.0' breadth Weir Flow at Driveway Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65 2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88 Primary OutFlow Max=2.06 cfs @ 12.14 hrs HW=26.82' TW=24.96' (Dynamic Tailwater) t1=Culvert (Passes 2.06 cfs of 4.07 cfs potential flow) 2=Weir flow inside OCS (Weir Controls 2.06 cfs @ 1.62 fps) Secondary OutFlow Max=0.15 cfs @ 12.12 hrs HW=26.82' TW=0.00' (Dynamic Tailwater) 3=Weir Flow at Driveway (Weir Controls 0.15 cfs @ 0.41 fps) 148 Waltham Street - Proposed WatershType III 24 -hr 25 Year Storm(NRCS) Rainfall=6.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 32 LL Pond BIO1: Bioretention #1 Hydrograph lzfiz l�ev!2�2 71 �! 2.16 cfs �tpr�ge�1 2 I cf 11 11 0 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) ■ Inflow ■ Primary ■ Secondary 148 Waltham Street - Proposed WatershType III 24 -hr 25 Year Storm(NRCS) Rainfall=6.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 33 Summary for Pond B102: Bioretention #2 Inflow Area = 24,707 sf, 77.84% Impervious, Inflow Depth > 4.49" for 25 Year Storm(NRCS) event Inflow = 2.74 cfs @ 12.09 hrs, Volume= 9,244 cf Outflow = 2.32 cfs @ 12.14 hrs, Volume= 8,643 cf, Atten= 15%, Lag= 3.0 min Primary = 2.32 cfs @ 12.14 hrs, Volume= 8,643 cf Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Peak Elev= 26.73' @ 12.14 hrs Surf.Area= 1,491 sf Storage= 914 cf Plug -Flow detention time= 53.8 min calculated for 8,643 cf (93% of inflow) Center -of -Mass det. time= 19.6 min ( 817.9 - 798.3 ) Volume Invert Avail.Storage Storage Description #1 26.00' 3,486 cf Bioretention #2 (Irregular)Listed below (Recalc) #2 23.35' 40 cf 4.00'D x 3.15'H Vertical OCS Storage 3,525 cf Total Available Storage Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic -feet) (cubic -feet) (sq-ft) 26.00 937 241.0 0 0 937 27.00 1,709 306.0 1,304 1,304 3,780 28.00 2,692 383.0 2,182 3,486 8,015 Device Routing Invert Outlet Devices #1 Primary #2 Device 1 23.44' 12.0" Round Culvert L= 14.0' CPP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 23.44' / 23.30' S= 0.0100 '/' Cc= 0.900 n= 0.012 Corrugated PP, smooth interior, Flow Area= 0.79 sf 26.50' 2.0" x 2.0" Horiz. Orifice/Grate X 6.00 columns X 6 rows C= 0.600 Limited to weir flow at low heads T-rimary OutFlow Max=2.24 cfs @ 12.14 hrs HW=26.72' TW=25.27' (Dynamic Tailwater) 1=Culvert (Passes 2.24 cfs of 3.59 cfs potential flow) 2=Orifice/Grate (Orifice Controls 2.24 cfs @ 2.24 fps) 148 Waltham Street - Proposed WatershType III 24 -hr 25 Year Storm(NRCS) Rainfall=6.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 34 2 Pond B102: Bioretention #2 Hydrograph !Inflow rea= ,7p7 sf Peak lev=2 . 3' toragle 1914 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) • Inflow • Primary 148 Waltham Street - Proposed WatershType III 24 -hr 25 Year Storm(NRCS) Rainfall=6.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 35 Inflow Area = Inflow = Outflow = Primary = Secondary = Summary for Pond UIS: Underground Infiltration Chambers 88,314 sf, 80.61% Impervious, Inflow Depth > 4.56" for 25 Year Storm(NRCS) event 9.54 cfs @ 12.09 hrs, Volume= 33,594 cf 3.41 cfs @ 12.43 hrs, Volume= 27,240 cf, Atten= 64%, Lag= 20.5 min 3.41 cfs @ 12.43 hrs, Volume= 27,240 cf 0.00 cfs @ 0.00 hrs, Volume= 0 cf Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Peak Elev= 26.25' @ 12.39 hrs Surf.Area= 8,626 sf Storage= 15,010 cf Plug -Flow detention time= 148.0 min calculated for 27,127 cf (81% of inflow) Center -of -Mass det. time= 77.5 min ( 876.5 - 798.9 ) Volume Invert Avail.Storage Storage Description #1A 22.80' 2,604 cf #2A 23.30' 2,123 cf #3 23.30' 46 cf #4 26.50' 2,451 cf #5B 22.80' 2,321 cf #6B 23.30' 3,032 cf #7C 22.80' 2,243 cf #8C 23.30' 2,756 cf 28.17W x 131.36'L x 2.33'H Field A 8,633 cf Overall - 2,123 cf Embedded = 6,510 cf x 40.0% Voids ADS_StormTech SC -310 +Cap x 144 Inside #1 Effective Size= 28.9"W x 16.0"H => 2.07 sf x 7.12'L = 14.7 cf Overall Size= 34.0"W x 16.0"H x 7.56'L with 0.44' Overlap 144 Chambers in 8 Rows 4.00'D x 3.70'H Vertical Manhole Storage Parking Lot (Irregular)Listed below (Recalc) 15.75W x 160.26'L x 3.50'H Field B 8,834 cf Overall - 3,032 cf Embedded = 5,802 cf x 40.0% Voids ADS_StormTech SC -740 +Cap x 66 Inside #5 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L = 45.9 cf Overall Size= 51.0"W x 30.0"H x 7.56'L with 0.44' Overlap 66 Chambers in 3 Rows 11.00W x 217.22'L x 3.50'H Field C 8,363 cf Overall - 2,756 cf Embedded = 5,606 cf x 40.0% Voids ADS_StormTech SC -740 +Cap x 60 Inside #7 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L = 45.9 cf Overall Size= 51.0"W x 30.0"H x 7.56'L with 0.44' Overlap 60 Chambers in 2 Rows Total Available Storage 17,576 cf Storage Group A created with Chamber Wizard Storage Group B created with Chamber Wizard Storage Group C created with Chamber Wizard Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic -feet) (cubic -feet) (sq-ft) 26.50 0 0.0 0 0 0 27.00 3,485 320.0 581 581 8,149 27.50 4,000 330.0 1,870 2,451 8,691 Device Routing Invert #1 Primary Outlet Devices 23.80' 12.0" Round Proposed 12" HDPE L= 64.0' CPP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 23.80' / 23.40' S= 0.0063 '/' Cc= 0.900 n= 0.012 Corrugated PP, smooth interior, Flow Area= 0.79 sf 148 Waltham Street - Proposed WatershType III 24 -hr 25 Year Storm(NRCS) Rainfall=6.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 36 #2 Secondary 26.80' 24.0' long x 5.0' breadth Weir Flow at Driveway Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65 2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88 Primary OutFlow Max=3.41 cfs @ 12.43 hrs HW=26.20' TW=24.90' (Dynamic Tailwater) t1=Proposed 12" HDPE (Inlet Controls 3.41 cfs @ 4.34 fps) Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=22.80' TW=0.00' (Dynamic Tailwater) L2=Weir Flow at Driveway ( Controls 0.00 cfs) Pond UIS: Underground Infiltration Chambers Hydrograph 10 8 7 5 6 3 2 0.00 cfs 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Time (hours) 5 16 17 18 19 20 21 22 23 24 3.41 cfs ❑ Inflow I ❑ Primary ❑ Secondary 148 Waltham Street - Proposed WatershType III 24 -hr 25 Year Storm(NRCS) Rainfall=6.20" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 37 Summary for Pond WQU1: WQU1 Inflow Area = 114,215 sf, 78.60% Impervious, Inflow Depth > 3.71" for 25 Year Storm(NRCS) event Inflow = 4.61 cfs @ 12.29 hrs, Volume= 35,289 cf Outflow = 4.61 cfs @ 12.29 hrs, Volume= 35,289 cf, Atten= 0%, Lag= 0.0 min Primary = 4.61 cfs @ 12.29 hrs, Volume= 35,289 cf Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Peak Elev= 24.99' @ 12.29 hrs Device Routing Invert Outlet Devices #1 Primary 23.30' 12.0" Round Existing 12" RCP L= 15.0' RCP, groove end projecting, Ke= 0.200 Inlet / Outlet Invert= 23.30' / 23.10' S= 0.0133 '/' Cc= 0.900 n= 0.013 Concrete pipe, straight & clean, Flow Area= 0.79 sf Primary OutFlow Max=4.59 cfs @ 12.29 hrs HW=24.99' TW=0.00' (Dynamic Tailwater) L1=Existing 12" RCP (Barrel Controls 4.59 cfs @ 5.85 fps) Pond WQU1: WQU1 Hydrograph 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) ■ Inflow • Primary I 3Y 148 Waltham Street - Proposed Waters Type III 24 -hr 100 Year Storm(NRCS) Rainfall=8.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD®10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 38 Summary for Subcatchment WS#1: Flow to Underground Infiltration Chambers Runoff = 5.61 cfs @ 12.09 hrs, Volume= 19,655 cf, Depth> 7.33" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 100 Year Storm(NRCS) Rainfall=8.90" Area (sf) CN Description 26,270 98 Impervious 5,925 39 >75% Grass cover, Good, HSG A 32,195 87 Weighted Average 5,925 18.40% Pervious Area 26,270 81.60% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (fUsec) (cfs) 5.0 Direct Entry, Subcatchment WS#1: Flow to Underground Infiltration Chambers Hydrograph 6-A 4I 5.61 cfs l T� pe11124-h '—'+R IHf+8190 z_ R noff Area 32,195 sf Renojf VpluI >= 'J cf , R no t x7.3333" Tc=5.0 min �r=87H H f -I H 4 +I H 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 -20-21 22 23 24 Time (hours) 0 Rnn0 148 Waltham Street - Proposed Waters Type III 24 -hr 100 Year Storm(NRCS) Rainfall=8.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 39 Summary for Subcatchment WS#2: Flow to Underground Infiltration Chambers Runoff = 5.47 cfs @ 12.09 hrs, Volume= 19,177 cf, Depth> 7.33" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 100 Year Storm(NRCS) Rainfall=8.90" Area (sf) CN Description 25,686 98 Impervious 5,726 39 >75% Grass cover, Good, HSG A 31,412 5,726 25,686 87 Weighted Average 18.23% Pervious Area 81.77% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment WS#2: Flow to Underground Infiltration Chambers 6� I Irt Type ?Il 13 h 10 i' 1 0 ar Sto ( R S) Rai fa 81 90' Runoff Area=31,412 sf Rnot p 9,77,cf Ri no D D pt >7 33" Tc=5.0 min C =8( t t 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) 148 Waltham Street - Proposed Waters Type III 24 -hr 100 Year Storm(NRCS) Rainfall=8.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD®10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 40 Summary for Subcatchment WS#3: Flow to Bioretention Area #1 Runoff = 4.19 cfs @ 12.09 hrs, Volume= 14,232 cf, Depth> 6.59" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 100 Year Storm(NRCS) Rainfall=8.90" Area (sf) CN Description 18,584 98 Impervious 7,317 39 >75% Grass cover, Good, HSG A 25,901 81 Weighted Average 7,317 28.25% Pervious Area 18,584 71.75% Impervious Area Tc Length (min) (feet) 5.0 Slope Velocity Capacity Description (ft/ft) (ft/sec) (cfs) Direct Entry, Subcatchment WS#3: Flow to Bioretention Area #1 Hydrog raph 4f 3Y 2_/ 4.19 cfs 1010 year IStorm(NRCS) Rainfall=8]90' Runoff Area=25,901 sf R no Volume=14,232 cf Rtino uspttll>6i59" 1/ Tc=5.0 min CN=8 II I I 2...r 0 1 2 3 4 5 6 7 8 9 10 12 13 14 15 16 17 18 Time (hours) 9 20 21 22 23 24 0 RUno 148 Waltham Street - Proposed Waters Type 11124 -hr 100 Year Storm(NRCS) Rainfall=8.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 41 Summary for Subcatchment WS#4: Flow to Bioretention Area #2 Runoff = 4.21 cfs @ 12.09 hrs, Volume= 14,582 cf, Depth> 7.08" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs Type III 24 -hr 100 Year Storm(NRCS) Rainfall=8.90" Area (sf) CN Description 19,231 98 Impervious 5,476 39 >75% Grass cover, Good, HSG A 24,707 85 Weighted Average 5,476 22.16% Pervious Area 19,231 77.84% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Subcatchment WS#4: Flow to Bioretention Area #2 Hydrograph 4 OOe4a ISt;Tn01R S) RaMfallI=8190 Runoff Area=24,707 sf Runo Ry,no Tc=5.0 min CN=85 II Volu a=14, 82 cf ©eptl i>7:08' 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) Runo 148 Waltham Street - Proposed Waters Type III 24 -hr 100 Year Storm(NRCS) Rainfall=8.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 42 Summary for Reach SP1: Study Point #1 Inflow Area = 114,215 sf, 78.60% Impervious, Inflow Depth > 6.28" for 100 Year Storm(NRCS) event Inflow = 14.49 cfs @ 12.15 hrs, Volume= 59,796 cf Outflow = 14.49 cfs @ 12.15 hrs, Volume= 59,796 cf, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Reach SP1: Study Point #1 Hydrograph 0 1 2 3 4 5 6 7 8 9 10 12 13 14 15 16 17 18 8 19 20 21 22 23 24 Time (hours) • Inflow • Outflow 148 Waltham Street - Proposed Waters Type III 24 -hr 100 Year Storm(NRCS) Rainfall=8.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 43 Summary for Pond BIO1: Bioretention #1 Inflow Area = 25,901 sf, 71.75% Impervious, Inflow Depth > 6.59" for 100 Year Storm(NRCS) event Inflow = 4.19 cfs @ 12.09 hrs, Volume= 14,232 cf Outflow = 3.99 cfs @ 12.11 hrs, Volume= 13,586 cf, Atten= 5%, Lag= 1.5 min Primary = 2.96 cfs @ 12.11 hrs, Volume= 12,921 cf Secondary = 1.03 cfs @ 12.11 hrs, Volume= 665 cf Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Peak Elev= 26.90' @ 12.11 hrs Surf.Area= 2,368 sf Storage= 1,396 cf Plug -Flow detention time= 44.1 min calculated for 13,586 cf (95% of inflow) Center -of -Mass det. time= 18.9 min ( 814.4 - 795.5 ) Volume Invert Avail.Storage Storage Description #1 26.00' 4,926 cf Bioretention #1 (Irregular)Listed below (Recalc) #2 23.00' 1 cf 0.67'D x 3.50'H Vertical AD Storage 4,927 cf Total Available Storage Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic -feet) (cubic -feet) (sq-ft) 26.00 854 195.0 0 0 854 27.00 2,580 580.0 1,639 1,639 24,601 28.00 4,047 595.0 3,286 4,926 26,122 Device Routing Invert Outlet Devices #1 Primary 23.69' 12.0" Round Culvert L= 29.0' CPP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 23.69' / 23.40' S= 0.0100 '/' Cc= 0.900 n= 0.012 Corrugated PP, smooth interior, Flow Area= 0.79 sf #2 Device 1 26.50' 4.0' long x 0.5' breadth Weir flow inside OCS Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 #3 Secondary 26.79' 12.0' long x 5.0' breadth Weir Flow at Driveway Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65 2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88 Primary OutFlow Max=2.73 cfs @ 12.11 hrs HW=26.89' TW=26.06' (Dynamic Tailwater) Culvert (Inlet Controls 2.73 cfs @ 3.48 fps) 2=Weir flow inside OCS (Passes 2.73 cfs of 2.89 cfs potential flow) Secondary OutFlow Max=0.96 cfs @ 12.11 hrs HW=26.90' TW=0.00' (Dynamic Tailwater) 3=Weir Flow at Driveway (Weir Controls 0.96 cfs @ 0.76 fps) 148 Waltham Street - Proposed Waters Type III 24 -hr 100 Year Storm(NRCS) Rainfall=8.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 44 Pond BIO1: Bioretention #1 Hydrograph 10 11 12 13 Time (hours) 4 15 16 17 18 19 20 21 22 23 ■ Inflow ■ Primary ■ Secondary 148 Waltham Street - Proposed Waters Type 11124 -hr 100 Year Storm(NRCS) Rainfall=8.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 45 Summary for Pond B102: Bioretention #2 Inflow Area = 24,707 sf, 77.84% Impervious, Inflow Depth > 7.08" for 100 Year Storm(NRCS) event Inflow = 4.21 cfs @ 12.09 hrs, Volume= 14,582 cf Outflow = 2.36 cfs @ 11.99 hrs, Volume= 13,978 cf, Atten= 44%, Lag= 0.0 min Primary = 2.36 cfs @ 11.99 hrs, Volume= 13,978 cf Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Peak Elev= 27.52' @ 12.25 hrs Surf.Area= 2,204 sf Storage= 2,352 cf Plug -Flow detention time= 41.6 min calculated for 13,920 cf (95% of inflow) Center -of -Mass det. time= 18.9 min ( 804.7 - 785.8 ) Volume Invert Avail.Storage Storage Description #1 26.00' 3,486 cf Bioretention #2 (Irregular)Listed below (Recalc) #2 23.35' 40 cf 4.00'D x 3.15'H Vertical OCS Storage 3,525 cf Total Available Storage Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic -feet) (cubic -feet) (sq-ft) 26.00 937 241.0 0 0 937 27.00 1,709 306.0 1,304 1,304 3,780 28.00 2,692 383.0 2,182 3,486 8,015 Device Routing Invert Outlet Devices #1 Primary #2 Device 1 23.44' 12.0" Round Culvert L= 14.0' CPP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 23.44' / 23.30' S= 0.0100 '/' Cc= 0.900 n= 0.012 Corrugated PP, smooth interior, Flow Area= 0.79 sf 26.50' 2.0" x 2.0" Horiz. Orifice/Grate X 6.00 columns X 6 rows C= 0.600 Limited to weir flow at low heads T-rimary OutFlow Max=2.26 cfs @ 11.99 hrs HW=26.72' TW=25.57' (Dynamic Tailwater) 1=Culvert (Passes 2.26 cfs of 3.20 cfs potential flow) 2=Orifice/Grate (Orifice Controls 2.26 cfs @ 2.26 fps) 148 Waltham Street - Proposed Waters Type III 24 -hr 100 Year Storm(NRCS) Rainfall=8.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 46 Pond B102: Bioretention #2 Hydrograph eIa �7' SP le :� -2 2' tl let2,3 c11- 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) • Inflow ` E Primary) 148 Waltham Street - Proposed Waters Type III 24 -hr 100 Year Storm(NRCS) Rainfall=8.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 47 Inflow Area = Inflow = Outflow = Primary = Secondary = Summary for Pond UIS: Underground Infiltration Chambers 88,314 sf, 80.61% Impervious, Inflow Depth > 7.18" for 100 Year Storm(NRCS) event 12.22 cfs @ 12.08 hrs, Volume= 52,809 cf 10.43 cfs @ 12.17 hrs, Volume= 46,209 cf, Atten= 15%, Lag= 5.4 min 4.04 cfs @ 12.11 hrs, Volume= 39,616 cf 7.07 cfs @ 12.18 hrs, Volume= 6,593 cf Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Peak Elev= 27.05' @ 12.17 hrs Surf.Area= 12,160 sf Storage= 15,880 cf Plug -Flow detention time= 116.9 min calculated for 46,018 cf (87% of inflow) Center -of -Mass det. time= 62.8 min ( 849.7 - 786.9 ) Volume Invert Avail.Storage Storage Description #1A 22.80' 2,604 cf #2A 23.30' 2,123 cf #3 23.30' 46 cf #4 26.50' 2,451 cf #5B 22.80' 2,321 cf #6B 23.30' 3,032 cf #7C 22.80' 2,243 cf #8C 23.30' 2,756 cf 28.17W x 131.36'L x 2.33'H Field A 8,633 cf Overall - 2,123 cf Embedded = 6,510 cf x 40.0% Voids ADS_StormTech SC -310 +Cap x 144 Inside #1 Effective Size= 28.9"W x 16.0"H => 2.07 sf x 7.12'L = 14.7 cf Overall Size= 34.0"W x 16.0"H x 7.56'L with 0.44' Overlap 144 Chambers in 8 Rows 4.00'D x 3.70'H Vertical Manhole Storage Parking Lot (Irregular)Listed below (Recalc) 15.75W x 160.26'L x 3.50'H Field B 8,834 cf Overall - 3,032 cf Embedded = 5,802 cf x 40.0% Voids ADS_StormTech SC -740 +Cap x 66 Inside #5 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L = 45.9 cf Overall Size= 51.0"W x 30.0"H x 7.56'L with 0.44' Overlap 66 Chambers in 3 Rows 11.00W x 217.22'L x 3.50'H Field C 8,363 cf Overall - 2,756 cf Embedded = 5,606 cf x 40.0% Voids ADS_StormTech SC -740 +Cap x 60 Inside #7 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L = 45.9 cf Overall Size= 51.0"W x 30.0"H x 7.56'L with 0.44' Overlap 60 Chambers in 2 Rows 17,576 cf Total Available Storage Storage Group A created with Chamber Wizard Storage Group B created with Chamber Wizard Storage Group C created with Chamber Wizard Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic -feet) (cubic -feet) (sq-ft) 26.50 0 0.0 0 0 0 27.00 3,485 320.0 581 581 8,149 27.50 4,000 330.0 1,870 2,451 8,691 Device Routing Invert Outlet Devices #1 Primary 23.80' 12.0" Round Proposed 12" HDPE L= 64.0' CPP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 23.80' / 23.40' S= 0.0063 '/' Cc= 0.900 n= 0.012 Corrugated PP, smooth interior, Flow Area= 0.79 sf 148 Waltham Street - Proposed Waters Type III 24 -hr 100 Year Storm(NRCS) Rainfall=8.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 48 #2 Secondary 26.80' 24.0' long x 5.0' breadth Weir Flow at Driveway Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 Coef. (English) 2.34 2.50 2.70 2.68 2.68 2.66 2.65 2.65 2.65 2.65 2.67 2.66 2.68 2.70 2.74 2.79 2.88 Primary OutFlow Max=2.94 cfs @ 12.11 hrs HW=27.02' TW=26.05' (Dynamic Tailwater) t1=Proposed 12" HDPE (Inlet Controls 2.94 cfs @ 3.74 fps) Secondary OutFlow Max=6.58 cfs @ 12.18 hrs HW=27.04' TW=0.00' (Dynamic Tailwater) L2=Weir Flow at Driveway (Weir Controls 6.58 cfs @ 1.16 fps) Pond UIS: Underground Infiltration Chambers Hydrograph 4 12.22 cfs ,3 f 8,14 A -E ! ,2!, e I 2�5� ifi tI 1 � Irt 12 9 7 -stQ �efi� �' T r -W I IL 8L/ 7.07* fiI 1 II 51 L I 4 I 3 2 1- I I 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) ❑ Inflow I ❑ Primary ❑ Secondary 148 Waltham Street - Proposed Waters Type 11124 -hr 100 Year Storm(NRCS) Rainfall=8.90" Prepared by Microsoft Printed 1/22/2020 HydroCAD® 10.00-24 s/n 02881 © 2018 HydroCAD Software Solutions LLC Page 49 Summary for Pond WQU1: WQU1 Inflow Area = 114,215 sf, 78.60% Impervious, Inflow Depth > 5.52" for 100 Year Storm(NRCS) event Inflow = 7.01 cfs @ 12.11 hrs, Volume= 52,537 cf Outflow = 7.01 cfs @ 12.11 hrs, Volume= 52,537 cf, Atten= 0%, Lag= 0.0 min Primary = 7.01 cfs @ 12.11 hrs, Volume= 52,537 cf Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.10 hrs / 3 Peak Elev= 26.16' @ 12.11 hrs Device Routing Invert Outlet Devices #1 Primary 23.30' 12.0" Round Existing 12" RCP L= 15.0' RCP, groove end projecting, Ke= 0.200 Inlet / Outlet Invert= 23.30' / 23.10' S= 0.0133 '/' Cc= 0.900 n= 0.013 Concrete pipe, straight & clean, Flow Area= 0.79 sf Primary OutFlow Max=6.81 cfs @ 12.11 hrs HW=26.05' TW=0.00' (Dynamic Tailwater) L1=Existing 12" RCP (Barrel Controls 6.81 cfs @ 8.67 fps) 7Y 6J 5/ 4Y 3y 2f 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Time (hours) let°17EtZ:: oundlCulvert L=150' Pond WQU1: WQU1 Hydrograph • Inflow • Primary Section 5.0 Appendix USDA SOIL MAPPING STORMTECH ISOLATOR ROW SIZING TABLE CDS TSS REMOVAL EFFICIENCIES f ,fir} ..� . � • � �. did sto rAi r �f a �'. -'253B `.i`' ` All, jx I z 655 r . ' a •` 626B #y ; J-653 • ` �-� yea ,'+ ' - 1�''-_a "' �'' 11119�1 y ' ~ / m easant - 1 ri I •� 1 _ 602 16B- 1 655 655t` 1 0 655 ,z �` x 4 r + ✓ le M o maw n6 bQ d o MQ RM2 h MAP LEGEND Area of Interest (AOI) 0 Area of Interest (AOI) Soils 0 Soil Map Unit Polygons rwr Soil Map Unit Lines 0 Soil Map Unit Points Special Point Features Vo Blowout Borrow Pit Clay Spot Closed Depression Gravel Pit .14 Gravelly Spot 0 Landfill Lava Flow Marsh or swamp + Mine or Quarry Miscellaneous Water Perennial Water Rock Outcrop Saline Spot 4 Sandy Spot Severely Eroded Spot Sinkhole Slide or Slip oa Sodic Spot Soil Map —Middlesex County, Massachusetts MAP INFORMATION Spoil Area The soil surveys that comprise your AOI were mapped at 1:25,000. Stony Spot Very Stony Spot Warning: Soil Map may not be valid at this scale. Wet Spot Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil Other line placement. The maps do not show the small areas of .- Special Line Features contrasting soils that could have been shown at a more detailed scale. Water Features Streams and Canals Please rely on the bar scale on each map sheet for map measurements. Transportation Rails Source of Map: Natural Resources Conservation Service Web Soil Survey URL: rwr Interstate Highways Coordinate System: Web Mercator (EPSG:3857) US Routes Maps from the Web Soil Survey are based on the Web Mercator L Major Roads projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Local Roads Albers equal-area conic projection, should be used if more accurate calculations of distance or area are required. Background . Aerial Photography This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Middlesex County, Massachusetts Survey Area Data: Version 19, Sep 12, 2019 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Sep 11, 2019—Oct 5, 2019 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. USDA Natural Resources Web Soil Survey 12/24/2019 Conservation Service National Cooperative Soil Survey Page 2 of 3 Soil Map —Middlesex County, Massachusetts Map Unit Legend Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 1 253B Water 4.0 10.7 2.6% 7.1 % Hinckley loamy sand, 3 to 8 percent slopes 602 Urban land 83.8 55.8% 626E Merrimac -Urban land complex, 0 to 8 percent slopes 34.6 23.0% 629C Canton -Charlton -Urban land complex, 3 to 15 percent slopes 0.7 0.5% 653 Udorthents, sandy 2.4 1.6% 655 Udorthents, wet substratum 14.2 9.4% Totals for Area of Interest 150.3 100.0% UT Natural Resources Web Soil Survey 12/24/2019 Conservation Service National Cooperative Soil Survey Page 3 of 3 Defen.0-on i Refen9-on - Wa W r 0tfafity 1>iu.r.si.on D . STORMTECH ISOLATOR ROW SIZING CHART SC-310 SC-740 DC-780 MC-3500 MC-4500 Chamber Area (Sq.Ft.) 20 27.8 27.8 43.2 30.1 Treated Flow Rate per chamber (CFS) 0.11 0.15 0.15 0.24 0.17 NOTE: Testing of the Isolator Row completed by Tennesse Tech has been verified by NJCAT and it has shown to have a TSS removal efficiency of 84% for SIL-CO-SIL 250 NJCAT verified Treated Flow Rate (GPM / Sq.Ft.) 2.5 A%'**v4 T E C H N ENC-ANEERED SOLUTIONS CDS Area Weighted C t' CDS Model CDS ESTIMATED NET ANNUAL SOLIDS LOAD REDUCTION BASED ON THE RATIONAL RAINFALL METHOD 148 WALTHAM STREET WATERTOWN, MA 2.06 ac Unit Site Designation WQU 0.9 Rainfall Station # 69 6 min 1515-3 CDS Treatment Capacity 1.0 cfs Rainfall Intensity' in/hr Percent Rainfall Cumulative Rainfall Volume Total Flowrate cfs Treated Flowrate Incremental Removal (%1 Volume' cfs 0.02 10.2% 10.2% 0.04 0.04 10.1 0.04 9.6% 19.8% 0.07 0.07 9.4 0.06 9.4% 29.3% 0.11 0.11 9.1 0.08 7.7% 37.0% 0.15 0.15 7.3 0.10 8.6% 45.6% 0.19 0.19 7.9 0.12 6.3% 51.9% 0.22 0.22 5.7 0.14 4.7% 56.5% 0.26 0.26 4.1 0.16 4.6% 61.2% 0.30 0.30 4.1 0.18 3.5% 64.7% 0.33 0.33 3.0 0.20 4.3% 69.1 % 0.37 0.37 3.6 0.25 8.0% 77.1 % 0.46 0.46 6.3 0.30 5.6% 82.7% 0.56 0.56 4.2 0.35 4.4% 87.0% 0.65 0.65 3.1 0.40 2.5% 89.5% 0.70 0.70 1.7 0.45 2.5% 92.1 % 0.70 0.70 1.7 0.50 1.4% 93.5% 0.70 0.70 0.9 0.75 5.0% 98.5% 0.70 0.70 3.4 1.00 1.0% 99.5% 0.70 0.70 0.7 1.50 0.0% 99.5% 0.70 0.70 0.0 2.00 0.0% 99.5% 0.70 0.70 0.0 3.00 0.5% 100.0% 0.70 0.70 0.3 Removal Efficiency Adjustmentz = Predicted % Annual Rainfall Treated = Predicted Net Annual Load Removal Efficiency = 86.9 6.5% 93.5% 80.5% 1 - Based on 10 years of hourly precipitation data from NCDC Station 770, Boston WSFO AP, Suffolk County, MA 2 - Reduction due to use of 60-minute data for a site that has a time of concentration less than 30-minutes. STUDY POINT 1 ONSITE FLOW TO WALTHAM STREET AREA=108,433 S.F. 2YR STORM 5.27 CFS 26,081 CF 10YR STORM 7.44 CFS 41,148 CF 50YR STORM 9.88 CFS 53,143 CF 100YR STORM 14.72 CFS 77,140 CF /=21.3 AI A l TLJ A -23(PUBLIC Sr-' WIDE) rRLcT - 17 STUDY POINT ONSITE FLOW TO AREA=4,318 S.F. 2 GREEN RIVER WAY 2YR STORM 0.23 CFS 749 CF 10YR STORM 0.39 CFS 1,322 CF 50YR STORM 0.51 CFS 1,773 CF 100YR STORM 0.77 CFS 2,724 CF STUDY POINT ONSITE FLOW TO AREA=1,464 S.F. 3 GREEN RIVER WAY 2YR STORM 0.10 CFS 362 CF 10YR STORM 0.15 CFS 569 CF 50YR STORM 0.19 CFS 727 CF 100YR STORM 0.27 CFS 1.056 CF DIG SAFE BEFORE YOU DIG CALL 811 OR 1-888-DIG-SAFE 1-888-344-7233 k=� 26 I �q U 26.7 001 II I N I J VS / 027.42 27.16 2 I 26.99 28.41 28.4E 28.21 � N o N 1=24.5 R=28.69 S �7�-27.01 27.29 BFA= \1�1,171)f SQ. N 27. 5 z W 2 .05 ?Y 7.31 ,JT 1 27.27S`TE��t' i D RAI NAG E AREA #2 26.88 \ V /g7.pp 04 27d1 - - _ 2Z.00 as 29.43 N N ■ N T U I x METAL BH=29.55 BFA= 10, 923f SQ. FT. 2Z51 BIT. CONC. 27.55\> 28.01 1 27.94 rCONC/ 27.92 v �a R- �- / D 27 09 Z- -� D -� R= m w 18" 3 N a C - �-- I a --- � sunnnnARY of AREAS DRAINAGE AREA AREA (SF) CN 1 108,433 97 2 4,318 1 89 3 1,464 98 �Y SITE TOTAL 114,215 95 �I DRAINAGE AREA #1 / 26.37 27.05 27.12 ` \ 27.26 27.24 ENT. I1 26.66 \ 1 I I � 1 STORY I METAL \ I 2727 BH=31 nR I 26.81 BFA= COLUMN 12, 085f SQ. FT (Ty 4' I x 0.\ I (TYP.) \ �.89 \ 2749 I II \ II \ I \ II � \ N 2619C U� I 27.29 26.W2 I1- I � I II II I I I I I BIT. CONC, D RAI NAG E AREA #3 2b ENT. 27.54 28.17 I s" s T 01 4 2` �� X 28.32 � 4 27.80 ` 28.8 X _ 6" e" 6 1 12" 28.s2101/ERHAN6 i rCON- X� / I -GONG. WALL x 28.5012" T x i27.1 27.6I / -X-CLF' 12 12/ ur. CONC. J 12" 28.20 CLF X 0 27.88 mom m .2 �R=27.40 2&W 40- j 1-1� 27.85 27.87 27.95 �4 28.40---�- ?83 I� O i U -99 I I 26.76 II / II / WALL 27 37 BIT. CONC. 27.871 2789 COLUMN 0.5' x 0.5' (TYP.) 12782 127.79 I2787 12783 I 1 2Z73 I 27.10 27.46 GRAPHIC SCALE 30 0 15 30 60 120 ( IIy FEET) 1 inch = 30 ft. PROFESSIONAL ENGINEER FOR ALLEN & MAJOR ASSOCIATES, INC. REV DATE DESCRIPTION APPLICANT: NORDBLOM COMPANY 71 TH I RD AVE BURLINGTON, MA 01803 PROJECT: 148 WALTHAM STREET WATERTOWN, MA 02472 PROJECT NO. 2708-01 DATE: 01-23-2020 SCALE: 1" = 30' DWG. NAME: C2708-01 DESIGNED BY: NCD CHECKED BY: TJW PREPARED BY: ALLLN & MNIOR ASSOCIATLS, INC. civil & structural cnginccring ♦ land surveying cnvironmcntal consulting* landscape architecturc w w w a l l e n m a i o r. c o m 100 COMMERCE WAY, SUITE 5 WOBURN MA 01801 TEL: (781) 935-6889 FAX: (781) 935-2896 WOBTTRN, MA ♦ LAKEVILLE, MA ♦ MANCIIESTER, NII THIS DRAWING HAS BEEN PREPARED IN ELECTRONIC FORMAT. CLIENT/CLIENTS REPRESENTATIVE OR CONSULTANT MAY BE PROVIDED COPIES OF DRAWINGS AND SPECIFICATIONS ON MAGNETIC MEDIA FOR HIS/HER INFORMATION AND USE FOR SPECIFIC APPLICATION TO THIS PROJECT. DUE TO THE POTENTIAL THAT THE MAGNETIC INFORMATION MAY BE MODIFIED UNINTENTIONALLY OR OTHERWISE, ALLEN & MAJOR ASSOCIATES, INC. MAY REMOVE ALL INDICATION OF THE DOCUMENT'S AUTHORSHIP ON THE MAGNETIC MEDIA. PRINTED REPRESENTATIONS OF THE DRAWINGS AND SPECIFICATIONS ISSUED SHALL BE THE ONLY RECORD COPIES OF ALLEN & MAJOR ASSOCIATES, INC.'S WORK PRODUCT. DRAWING TITLE: SHEET No. EXISTING WATERSHED PLAN EW-1 Copyrieht©2019AIlen & Major Associates, Inc. All Rights Reserved STUDY POINT 1 ONSITE FLOW TO WALTHAM STREET AREA=114,215 S.F. 2YR STORM 0.70 CFS 9,716 CF 10YR STORM 3.25 CFS 23,951 CF 50YR STORM 4.70 CFS 35,378 CF 100YR STORM 14.49 CFS 59,796 CF 26.91 27.04 2 �CONC26.80/J 2� 6.72 26.37 2� 26.40 1=21.3 1 R=26.61 S 2* n / N I A//1 / TL/4 M (PUBLIC - 50' WIDE) S T���� 1=23. f _ _ _s° 2s (1963 COUNTY RELOCATION) _ D DIG SAFE BEFORE YOU DIG CALL 811 OR 1-888-DIG-SAFE 1-888-344-7233 z STUDY POINT ONSITE FLOW TO AREA=4,318 S.F. 2 GREEN RIVER WAY 2YR STORM 0.00 CFS 0 CF 10YR STORM 0.00 CFS 0 CF 50YR STORM 0.00 CFS 0 CF 100YR STORM 0.00 CFS 0 CF STUDY POINT ONSITE FLOW TO AREA=1,464 S.F. 3 GREEN RIVER WAY 2YR STORM 0.00 CFS 0 CF 10YR STORM 0.00 CFS 0 CF 50YR STORM 0.00 CFS 0 CF 100YR STORM 0.00 CFS 0 CF 11 r . nlnln ^ ° 28. 28.3 N - ^ °p N � II N 1=24.5 R=28.69 S 27.51 O cr p0 29.5¢t B1T. CONC. �G 28 29• 528. rC 28.�� 28 2 � � / 8. cam• 21.94 /GONG. 28.50 r2 ONCI "'?.55 �S° 1"61-1 p1 p 26,99 28.49 rn 'rn �6.88 2 R w 26.96 D i SYl S° 3 Ro s6o f� s 27.74 r r A R� � / D �rN` 1 • 1 50' 1i1�l ) R=27.33 • 11 11 YY v (pUBUC - 27 '� � � � • i i UD �UD / • -, � - _ -uD _ 26 D - 27 27.2 AMENITY N' J I MULTI -FAMILY RESIDENTIALIDWELLING 253-UIITS 1 IIIIIIi IIIIIIIII�. 11� 1 1 1 1 1 D RAI NAG E 1 AREA #3 D RAI NAG E 1 AREA # 1 1 1 _ Ims wo mom mm OWN - wo mm r D RAI NAG E AREA #2 D RAI NAG E AREA #4 I I POOL 1 1 _ 1 ABOVE ' - - (0 1 �, I� L----- ICJ 1 �7.95 L_ - - -m- 2671- - - - C -2B:96 27.2 1.85 27.87 SUMRAARY OF AREAS DRAINAGE AREA AREA (SF) CN 1 32,195 87 2 31,412 87 3 25,901 81 4 24,707 85 SITE TOTAL 1 114,215 85 GRAPHIC SCALE 30 0 15 30 60 120 ( I1y FEET ) 1 inch = 30 ft. PROFESSIONAL ENGINEER FOR ALLEN & MAJOR ASSOCIATES, INC. REV DATE DESCRIPTION APPLICANT: NORDBLOM COMPANY 71 TH I RD AVE BURLINGTON, MA 01803 PROJECT: 148 WALTHAM STREET WATERTOWN, MA 02472 PROJECT NO. 2708-01 DATE: 01-23-2020 SCALE: 1" = 30' DWG. NAME: C2708-01 DESIGNED BY: NCD CHECKED BY: TJW PREPARED BY: jk*lwk ALLLN & MNIOR ASSOCIATLS, INC. civil & structural cnginccring ♦ land surveying cnvironmcntal consulting* landscape architecturc w w w. a l l e n m a i o r. c o m 100 COMMERCE WAY, SUITE 5 WOBURN MA 01801 TEL: (781) 935-6889 FAX: (781) 935-2896 BTTRN, MA ♦LAKEVILLE, MA ♦ MANCIIESTER, NH S DRAWING HAS BEEN PREPARED IN ELECTRONIC FORMAT. ENT/CLIENTS REPRESENTATIVE OR CONSULTANT MAY BE r VIDED COPIES OF DRAWINGS AND SPECIFICATIONS ON MAGNETIC DIA FOR HIS/HER INFORMATION AND USE FOR SPECIFIC APPLICATION TO THIS PROJECT. DUE TO THE POTENTIAL THAT THE MAGNETIC INFORMATION MAY BE MODIFIED UNINTENTIONALLY OR OTHERWISE, ALLEN & MAJOR ASSOCIATES, INC. MAY REMOVE ALL INDICATION OF THE DOCUMENT'S AUTHORSHIP ON THE MAGNETIC MEDIA. PRINTED REPRESENTATIONS OF THE DRAWINGS AND SPECIFICATIONS ISSUED SHALL BE THE ONLY RECORD COPIES OF ALLEN & MAJOR ASSOCIATES, INC.'S WORK PRODUCT. DRAWING TITLE: SHEET No. PROPOSED WATERSHED PLAN PW_1 Copyrieht02019AIlen & Major Associates, Inc. All Rights Reserved