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Home My Public Portal AboutDrainage Report (2014-12-12)_201412171410255332 DRAINAGE REPORT Proposed Hotel Development Parcel ID 1238 3 0 80 Elm Street Town of Watertown, Massachusetts Middlesex County Prepared for: Elm Hospitality, LLC 134 Main Street Watertown, MA 02472 Prepared by: BOHLER ENGINEERING 352 Turnpike Road Southborough,MA 01772 (5 Q TEL. avL n No.45496 Ma t' ,P.E. Massachusetts License#45496 BOHLER ENGINE E RING Date: December 12,2014 Bohler Project#M141004 TABLE OF CONTENTS PAGE I. EXECUTIVE SUMMARY 1 II. EXISTING SITE CONDITIONS 2 III. PROPOSED SITE CONDITIONS 3 IV. MASS. DEP STORMWATER MGMT STANDARDS 5 V. METHOD 8 VI. SUMMARY 9 APPENDICES A. USGS MAP B. NRCS SOILS MAP AND SOIL EVALUATION FORMS C. PIPE SIZING CALCULATIONS D. GROUNDWATER RECHARGE AND WATER QUALITY CALCULATIONS E. PRE-DEVELOPMENT AND POST-DEVELOPMENT WATERSHED MAPS F. PRE-DEVELOPMENT AND POST-DEVELOPMENT WATERSHED COMPUTATIONS G. OPERATION AND MAINTENANCE PLAN H. LONG TERM POLLUTION PREVENTION PLAN I. CHECKLIST FOR STORMWATER REPORT I. EXECUTIVE SUMMARY The project involves construction of a proposed 12,128± square foot footprint hotel on a 0.82± acre parcel on the west side of Elm Street. The hydrologic study area is 0.82± acres (encompassing the entire subject parcel) and drains to one point of analysis. This location represents the convergence point of the major watershed boundaries that make up the overall drainage study limits. The point of analysis for the subject study is the Elm Street drainage infrastructure, with the majority of the drainage generated from the subject site conveyed into said infrastructure via the a connection from the Watertown Mall to the south of the subject property. In the existing condition, runoff flows overland from the northeast of the subject site to the southwest of the site onto the Watertown Mall property, and eventually into a catch basin associated with the Watertown Mall which drains towards the Elm Street drainage infrastructure. The proposed project will include hooded, deep sump catch basins, proprietary stormwater quality units, a bioretention area, and stormwater infiltration. Pre-Development and Post- Development Watershed Maps (Appendix E) depict the delineation of watershed areas and the analysis point used in the stormwater designs. The proposed stormwater management system has been designed to meet or exceed the Massachusetts Department of Environmental Protection (MassDEP) and Town of Watertown Department of Public Works (DPW) standards. Appropriate stormwater and erosion controls are proposed for this project to attenuate flows after construction. The project has been designed such that the calculated peak rates of runoff for the 2, 10, 25 and 100-year storm events are less than in the existing condition. Further, the project has been designed in accordance with the Watertown DPW Site Plan Review On-site Drainage Requirements. The project exceeds the requirements for groundwater recharge as described in the MassDEP Stormwater Handbook. Soil erosion and sediment controls are proposed to prevent soil loss during construction. Calculations supporting the project's stormwater i management system design are included within this report's appendices. The Site Development Plans detail the erosion control measures that are proposed during the project's construction phase. A closed collection and conveyance system is proposed to collect and distribute stormwater to the proposed proprietary treatment units and infiltration system. The project has been designed to detain and infiltrate runoff from all captured areas for all storm events analyzed using rainfall data from the "Extreme Precipitation in New York and New England" developed by the Northeast Regional Climate Center (NRCC) at Cornell University and the Natural Resources Conservation Service (MRCS), as required by Watertown DPW standards. Post-development runoff is only from perimeter landscape areas which are not captured and routed through the infiltration system. Post-Development peak discharge rates and volumes have been mitigated to be equal or less than Pre-Development rates and volumes, as indicated in the tables below: Table 1A—Comparison of Peak Runoff Rates (in CFS) Point of 2-Year Stone 10-Year Storm 25-Year Storm 100-Year Storm Analysis Pre I Post A Pre Post A Pre Post A Pre Post A #1 1.26 0.12 -1.14 2.60 0.37 -2.23 3.69 0.60 -3.09 5.98 1.14 -4.84 Table 111—Comparison of Runoff Volumes (in Acre-Feet) Point of 2-Year Storm 10-Year Storm 25-Year Storm 100-Year Storm Analysis Pre Post 1 A Pre Post A Pre Post A Pre Post A #1 0.091 0.011 1 -0.080 0.185 0.028 -0.157 0.263 0.044 -0.219 0.433 0.081 -0.352 II. EXISTING SITE CONDITIONS The 0.82± acre site currently contains a gravel surface over the majority of the site with portions of the site consisting of pavement. The site also contains foundation remains buildings which formerly served the Atlantic Battery Company, but have recently been razed. Formerly,the contained a large building for the Atlantic Battery company and the remainder of the site was entirely paved. The Site is bounded to the east by Elm Street,to the south by the Watertown 2 Mall, to the west by a parking lot attendant to the Watertown Mall, and to the north by a commercial building. The site is moderately sloped from northwest to the southwest. On-site soil evaluation test holes were performed by Bohler Engineering on November 14, 2014. The results of the investigation indicate that the parent material soils are a find to medium sand of hydraulic soil group "A" and are underlying a layer of fill material 5-6 feet deep. Soil evaluation forms for the testing performed are included in Appendix`B". For the purposes of this drainage analysis, the existing Site area drains into one drainage area as shown in the Existing Tributary Drainage map located in Appendix "E". Area E-1 represents the area from the entire subject site which sheet flows from the northeast to the southwest, ultimately to a catch basin on the Watertown Mall property to the southwest of the subject site. The catch basin on the Watertown Mall property ultimately drains to the Elm Street drainage infrastructure, and the Elm Street drainage infrastructure is denoted as Point of Analysis 1 (POA-1). III. PROPOSED SITE CONDITIONS The project involves construction of a proposed 12,128f square foot hotel on a 0.82± acre parcel on the west side of Elm Street. The proposed construction will introduce imperious paved or roofed areas, which will increase post-development runoff rates above pre-development runoff rates without the implementation of appropriate stormwater management controls. The project area was broken into four catchment areas, which drain to one Points of Analysis as exhibited in the proposed watershed map in Appendix "E". The assessment of the anticipated existing and proposed stormwater flows and volumes was performed using HydroCAD°. HydroCAD°input and output data is included in Appendix"F". Area P-1 represents roof runoff from the proposed hotel. Roof runoff is proposed to be directly connected to a proposed subsurface infiltration bed at the north of the site beneath the proposed 3 garage driveway. The proposed infiltration bed contains an extreme event overflow pipe to the Elm Street drainage infrastructure, or Point of Analysis 1 (POA-1), however the infiltration basin has been designed to detain and infiltrate 8.9 inches of precipitation. Area P-2 represents runoff from the subject site which is collected by deep sump hooded catch basins or a trench drain, routed through a proprietary treatment unit, and ultimately discharged into the proposed subsurface infiltration bed at the north of the site beneath the proposed garage driveway. Areas P-3 represents runoff from the subject site which is collected and treated by a proposed bioretention area at the northwest of the subject site, routed through a proprietary separator for additional treatment, and ultimately discharged into the proposed subsurface infiltration bed at the north of the site beneath the proposed garage driveway. Area P-4 represents runoff from remaining landscaped areas at the south and west of the subject site which ultimately sheet flow directly to the Elm Street drainage infrastructure or is collected within the Watertown Mall drainage infrastructure prior to discharge into the Elm Street drainage infrastructure, denoted as Point of Analysis 1 (POA-1). Table 2 provides a comparison of the ground coverage attributes associated with the watersheds in the existing and proposed conditions. The project will result in an increase in impervious surface from the existing condition, however is still considerably less than the original conditions of the recently demolished improvements. The resulting increase in the peak rates of runoff will be mitigated through a combination of the stormwater management practices previously described and as further discussed below. The design of the stormwater system is consistent with the MassDEP Stormwater Management Standards. 4 Table 2—Hydrologic Study Area Land Use Distribution Summary Area Existing(Acres) Proposed (Acres) Roofs/Buildings 0.00 0.29 Pavement,Sidewalks, Hardscapes 0.11 0.22 Gravel Surface 0.71 0.000 Open Space(constructed over 0.000 0.11 subsurface parking). Open Space(woods,grass, 0.000 0.20 landscaped areas) Total 0.82 0.82 Storm Sewer System Catch basins will be deep sump, hooded structues. Storm sewer piping will have a minimum pipe diameter of 6 inches and is generally designed with a minimum slope of 0.005 ft/ft. Pipes have been designed to accommodate the 25-year storm event. Hydraulic grade lines associated with the 100-year storm have been reviewed against the proposed rim elevations of the drainage structures. Drainage structure and pipe sizing information is included in Appendix"C". Infiltration/Detention System The project will include a sub-surface infiltration system infiltrate runoff from the project site for all storm events analyzed per the Watertown DPW requirements. The system will be comprised of a series of concrete StormTrap chambers or approved equivalent sitting on a stone bed. The project will also include two proprietary treatment units to provide water quality treatment for runoff from a portion of the site. The structure is sized using the minimum Water Quality Flow methodology outlined by MassDEP. Sizing calculations are included in Appendix"D". IV. MASSACHUSETTS DEP STORMWATER MANAGEMENT STANDARDS The proposed stormwater management plan for the project has been developed to meet or exceed the requirements of the MassDEP Stormwater Management Policy. Post-development runoff 5 rates will be less than pre-development volumes. The infiltration provided exceeds the required volume. The sub-surface infiltration systems also serve to provide for peak flow attenuation. In terms of stormwater quality,the project's stormwater management plan exceeds the MassDEP requirements for pollutant removal by implementing a combination of Best Management Practices (BMP's). The BMP's have been designed to achieve a TSS removal rate in excess of 80% for the analyzed points of analysis. Proposed stormwater flows will be attenuated through the implementation of a comprehensive stormwater management system designed in accordance with the ten standards associated with the MassDEP Stormwater Management Policy. The Checklist for a Stormwater Report is included in Appendix "I". The following section describes the project's conformance with the MassDEP Stormwater Management Standards, as of January 2, 2008. Standard 41- Untreated Storm Water No point discharges of untreated stormwater to resource areas are proposed. Stormwater quality control for the project includes deep-sump, hooded catch basins, proprietary hydrodynamic stormwater quality structures, bioretention area and sub-surface infiltration basins. All points of discharge are designed to prevent scour and erosion. Standard#2: Post Development Peak Discharge Rates Runoff rates for the pre-development and post-development conditions were calculated for the 2-year, 10-year, 25-year and 100-year 24-hour storm events. Rainfall data for the storm events is from the "Extreme Precipitation in New York and New England" developed by the Northeast Regional Climate Center(NRCC) at Cornell University and the Natural Resources Conservation Service (MRCS), as required by Watertown DPW standards. These calculations are provided in Appendix"F". As summarized in previous sections of this report,there will be no increase in stormwater runoff rates when compared to the existing condition for the 2, 10, 25 and 100-year storm events. Table I included with the Executive Summary of this report documents compliance with this 6 standard. Additionally, the proposed infiltration basin has been design to detain and infiltrate runoff from all storm events analyzed per Watertown DPW requirements. Standard 43: Rechar-ae to Groundwater The required recharge volume will be obtained through the storage volume available below the lowest outlet to the system. Recharge for this site was calculated using the Static Method as outlined in the Stormwater Management Standards. The guidelines recommend that projects recharge 0.60 inches of runoff from impervious areas for Type A soils. The design exceeds the minimum required recharge volume for the Site, as supported by calculations in Appendix "D". Calculations indicating that the infiltration systems will fully drain over a 72-hour period are also included in Appendix «D„ Standard#4: 80% TSS Removal The proposed Best Management Practices for this site provide for at least 80%TSS removal and consist of a"treatment train"which includes both non-structural and structural techniques. Deep-sump, hooded catch basins, proprietary stormwater quality units, a bioretention area and a subsurface infiltration bed will be used to improve water quality. TSS removal calculations are included in Appendix "D". Standard 95: Land Use with Hijzher Potential Pollutant Loads The project is classified as a use that will generate higher pollutant loads and is subject to the requirements of Standard 5, including pretreatment of stormwater. In accordance with these standards, the project area stormwater management system has been designed to achieve a TSS removal rate greater than 80%, exceeding the rate required under the current MassDEP Stormwater Management Policy. As discussed under Standard 3, groundwater recharge is provided in accordance w/ MassDEP requirements. The portions of the project that are directed to the sub-surface infiltration basins will achieve a TSS removal rate in excess of 44%prior to discharge into the infiltration systems, consistent with MassDEP policy. 7 Standard 46: Protection of Critical Areas The site is not located within a Critical Area. Standard#7: Redevelopment Proiects The site has been designed to meet stormwater standards for new construction. Standard 48: Erosion/Sediment Control During Construction An erosion and sediment control plan has been developed for this project implementing, at a minimum: silt fence, a crushed stone construction exit, catch basin inlet protection, and provisions for stabilizing disturbed areas. A full SWPPP will be prepared in conjunction with filing an EPA NPDES Construction General Permit prior to land disturbance. Standard 99: Operation/Maintenance Plan The stormwater management system will be owned and operated by the owner. The General Contractor (under contract with the owner) will appoint a Project Manager who will be responsible during construction. Costs associated with the operation and maintenance of the stormwater management systems are subject to contracts with licensed maintenance providers and are variable. As a result, costs associated with the Operation and Maintenance Plans are not currently included with this report. The stormwater Drainage Operations and Maintenance Plans are included in Appendix G. Standard#]0: Illicit Discharges To the Engineer's knowledge, there are no known or designed non-stormwater discharges that are or will be connected to the stormwater collection system that would convey pollutants directly to groundwater or surface waters. V. METHOD Methodology utilized to design the stormwater management system associated with this project includes compliance with Massachusetts Department of Environmental Protection (MassDEP) 8 Stormwater Handbook requirements. The proposed stormwater management design will provide a decrease in peak stormwater runoff rates from the proposed facility for the 2, 10, 25 and 100- year design storm events utilizing the SCS TR-55 Urban Hydrology for Small Watersheds method. Rainfall intensities utilized in the analysis are as follows, which are consistent with the web tool "Extreme Precipitation in New York and New England" development by NRCC at Cornell University and NRCS per Watertown DPW requirements: Frequency 2-year 10-year 25-year 100-year Rainfall (Inches) 3.2 4.9 6.2 8.9 The proposed stormwater management design results in net decreases in peak stormwater runoff rates directed towards the points of interest identified in the hydrologic analysis. As previously referenced, the proposed design includes the implementation of several BMP's designed to improve the quality of water runoff and volume of groundwater recharge. The project will also detain and infiltrate all runoff from impervious surface for all storm events analyzed per Watertown DPW requirements. Times of concentration (Tc) utilized in the preparation of this report were generated utilizing the SCS TR-55 Urban Hydrology for Small Watersheds method. Runoff coefficients for the pre- and post-development conditions were calculated using widely accepted, and often utilized runoff coefficients and have been documented within the HydroCAD° contained within Appendix "F" of this report. VI. SUMMARY The anticipated increase in the post-development peak rates of runoff for the analyzed points of analysis will be mitigated through the implementation of a comprehensive stormwater management program. The stormwater controls installed as part of this project will meet or exceed the requirements set forth by the MassDEP Stormwater Management Policy and the Town of Watertown. The stormwater management system has been designed to address both the rate and quality of stormwater runoff generated by the proposed site improvements. 9 APPENDIX A USGS MAP T �� r APPENDIX B NRCS SOILS MAP AND ON-SITE SOIL EVALUATION FORMS Z aZa N N N a a 099Z6917 O19Z697 099Z69b OS9Z69b Ob9Z69b OE9Z6917 OZ9Z69b OT9Z69b 009Z6917 06SZ69b M MAZb oIL `� `� �- MAZb oTL N O N— �� CM a R L9 p N t(p1T� O�fr M 1 P w - � � � a U M Q cc M O _ N O U p �o axi . ! o �- Igi o a + z lA ~ or v __ +t c CL I"�� ,1L ♦ iJ C � o : Um, x 7 I� �1 a o C CL Co — zQ ao _ Z U M.LZ.6 oTL ~~ - , * M,LZb aTL QI 099Z69b OL9Z69b 099Z69b 0.9Z69e OVM6% OE9Z69b OZ9Z69b 0ic?Z69t+ 009Z69d 061Z69b �BI z z N N V v c� CD 0 O OC1 N N O C O) cu 0 T m �_ CD p N L m .� N N N � � O m o 2wa) E m 3c � a fQ 0 0 ai rn 2 cLi o or u) j ^ O D N N y O U N m coi N a� C 0 io - m '� p1 Cl) o m E Sum • 4UOLi m � � a�i r m y � uo� Z CD nm � � 0cm mmur N c) � E 16 YU) 0 E no _m °, `� c nU' ' U m y �+ E m ur Q Q3 c N d ( O ) v ur Z " Z pN 0E o yCD oiw U w- •5QNda o 0, w'm mm o 7 C ,u vm t}o Em Q'n cu 0 CL 'Cc� c°� rn o � ui > �°, > y o o c °u � 3 8 �� .. o m w U � a o m Tam r 3 C o � y m c m ; x w 0 E m Co a> ?Q rZ nmO y an vC 0,C m w) ; aO v° O YN a Na C _ mi mc� w L mrn c nEL n �m cmnu o m mmm ` � -0ErnE R �Sm mv , s 2 Em >1 2w o '? t rnm a) cum y � m o d 0 w > uo,w H m c V) 3 c > rN Nn m InN E c mc c o10 o rn .00 c a) tu � U' EcE N ` i - (n N E O O_ mm om m = -0 O U N = Z = N E E ` o i ' Uo u nv w� waui FL E ) Q cn ) . u .� o a� u, T 0 m m Z m N C/) m O C U > O — m U x a 0 fn N m O y N N N O cc >1 C m L m m m 3 C CL LL U Im O N _ N N m N m m O Z m m rL C p J N 2 .m O O L Q (n O. N E m O a _ T m> O a T) w O 1N, O d ULd CU f0 CN O n r U) n (n 7 J Q Q m m c a Z $ < } Y W m m W 16 N a - o Q O m m c c a� m. m 'p p aCOa)a iD a E a a) o mO o O p ° CO Cl. CL oO � LY _ n a CL a mU) (n o m_n m �' p > o c O ) O c > N U > N O O O 0 m p N 2 N N m C N Ol O m m N C O Q (n fn !n a m m U c) C7 C7 -i a m (n cn N rn rn w IL cmi Lo CL o 7 y C Q N y a7 A y 7 N m O Z U 8 ZI Soil Map—Middlesex County,Massachusetts Map Unit Legend Middlesex County,Massachusetts(MA017) Map Unit Symbol Map Unit Name Acres in AOI Percent of A01 602 Urban land 2.0 100.0% Totals for Area of Interest 2.01 100.0% USDA Natural Resources Web Soil Survey 11/14/2014 Conservation Service National Cooperative Soil Survey Page 3 of 3 Site Location or lot# 80 Elm Street DEEP HOLE#1114-1 Applicant/owner: Cherag Patel DATE: 1 November 14, 2014 WEATHER: Pt. Sunny TEMP: 40° LOCATION: (Refer to sketch attached) (See Attached Sketch) PERFORMED BY: I Matthew Bombaci, P.E. WITNESSED BY: N/A Land Use: Former Industrial Site , Landform: Ground Morraine Vegetation: None _ Slope 0-5% Stone Walls: �Y ® N _ Surface Stones- ❑ Y ® N Distance From: Open Water Bodies: >100 ft. Possible Wet Area: ( >100 ft. Drinking Water Well: I >100 ft. Drainageway: _ >100 ft. l Property Line: 45±ft. Other: DEEP OBSERVATION HOLE LOG Depth Soil Horizon Soil Texture l Soil Color Other: Structures; Stones; Consistency;Boulders; % I _ gravel J 0-8 FILL 1 - { compacted gravel surface 8-65 I FILL Loamy Sand 12.5Y 5/3 I m,firm in place, 20%gravel, 20%cobbles 65-120 { C Sand ` 2.5Y 7/2 fine sand,sg, loose, <5%gravel l 4 1 Parent Material (geologic) , Glacial Outwash Depth to Bedrock: >120" Depth to Groundwater: Standing Water in Hole: Weeping From Pit Face: _I N/A _ l Estimated Seasonal High Groundwater: 120" DETERMINATION FOR SEASONAL HIGH WATER TABLE Method used: i Depth observed standing in obs. hole: Depth to weeping from side of obs.hole: N/A Depth to soil mottles, description: N/A Groundwater adjustment: N/A i Index Well#: i N/A Reading Date: N/A Index llUell I N/A Adj. Factor: N/A 1 Level: Adj. ground water level: N/A Notes: Bohler Engineering—352 Turnpike Road —Southborough, Massachusetts ^^ Site Location or lot#T 80 Elm Street i I DEEP HOLE#1114-2 fApplicantlowner: I Cherag Patel DATE: , November 14,2014 WEATHER. i Pt. Sunny i TEMP: 40° LOCATION: (Refer to sketch attached) (See Attached Sketch) PERFORMED BY: Matthew Bombaci, P.E. WITNESSED BY: N/A Land Use: Former Industrial Site Landform: Ground Morraine IVegetation: None Slope: 0-5% Stone Walls: ❑ Y ® N_ _ Surface Stones: ❑ Y ® N Distance From: Open Water Bodies: _F100 ft. _ Possible Wet Area: _ 1 >100 ft. Drinking Water Well , >100 ft. Drainageway: I >100 ft. Property Line: 125±ft. , Other: T 1 DEEP OBSERVATION HOLE LOG Depth Soil Horizon Soil Textur i Other: Structures; Stones; Boulders; Consistency; Ox P e So I Color i grave! 0-12 FILL - compacted gravel surface 12-55 I FILL Loamy Sand 2.5Y 5/3 m, firm in place, 20%gravel, 20%cobbles 55-100 C1 Loamy Sand 2.5Y 4/3 ` m,firm in place, 10%gravel, 10%cobbles 1 100-120 I C2 Sand 2.5Y 7/2 fine sand,sg, loose,<5%gravel 1 Parent Material (geologic): Glacial Outwash Depth to Bedrock: >120" Depth to Groundwater: ` Standing Water in Hole: Weeping From Pit Face: N/A Estimated Seasonal High Groundwater: 120" DETERMINATION FOR SEASONAL HIGH WATER TABLE Method used: Depth observed standing in obs. hole: _—I-N/A Depth to weeping from side of obs. hole: N/A Depth to soil mottles, description: ` N/A Groundwater adjustment: N/A Index Well TN/A Index Well#: N/A Reading Date: ' N/A N/A Adj. Factor: Level: Adj. ground water level: N/A Notes: Bohler Engineering-352 Turnpike Road-Southborough, Massachusetts Site Location or lot# 80 Elm Street DEEP HOLE# 1114-3 Applicant/owner. Cherag Patel DATE: i November 14, 2014 WEATHER: Pt. Sunny TEMP: 40° LOCATION: (Refer to sketch attached) (See Attached Sketch) lPERFORMED BY Matthew Bombaci, P.E. ` WITNESSED BY: N/A Land Use: Former Industrial Site Landform: Ground Morraine Vegetation: None Slope: 0-5% Stone Walls: ❑Y ® N Surface Stones: ❑ Y ® N Distance From Open Water Bodies: >100 ft. Possible Wet Area: >100 ft. Drinking Water Well: >100 ft. Drainageway: >100 ft. Property Line: 45±ft. Other: DEEP OBSERVATION HOLE LOG Depth Soil Horizon Soil Texture Soil Color Other: Structures; Stones; Boulders; Consistency; % gravel 0-25 FILL - - compacted gravel surface JJJ 25-64 FILL Loamy Sand 2.5Y 5/3 m,firm in place, 20%gravel, 20%cobbles 64-120 C Sand 2.5Y 7/2 fine sand, sg, loose, <5%gravel Parent Material (geologic): Glacial Outwash Depth to Bedrock. >120" Depth to Groundwater: Standing Water in Hole: Weeping From Pit Face: N/A Estimated Seasonal High Groundwater: 120" DETERMINATION FOR SEASONAL HIGH WATER TABLE Method used: Depth observed standing in obs. hole: N/A Depth to weeping from side of obs. hole: N/A Depth to soil mottles, description: N/A Groundwater adjustment: N/A Index Well#: N/A Reading Date: N/A Index Well N/A Adj. Factor: N/A I ` Level: Adj. ground water level: N/A Notes: Bohler Engineering—352 Turnpike Road — Southborough, Massachusetts l Site Location or lot# 80 Elm Street DEEP HOLE# 1114-4 Applicantlowner: Cherag Patel DATE: November 14, 2014 WEATHER: Pt. Sunny TEMP: 40° LOCATION: (Refer to sketch attached) (See Attached Sketch) PERFORMED BY: Matthew Bombaci, P.E. WITNESSED BY: N/A Land Use: Former Industrial Site Landform: Ground Morraine Vegetation: None Slope: 0-5% Stone Walls: ❑ Y ® N Surface Stones: ❑ Y ® N Distance From: Open Water Bodies: >100 ft. Possible Wet Area: >100 ft. Drinking Water Well: >100 ft. Drainageway: >100 ft. Property Line: 30±ft. Other: DEEP OBSERVATION HOLE LOG Depth Soil Horizon Soil Texture Soil Color Other: Structures; Stones; Boulders; Consistency; % gravel 0-11 FILL - - compacted gravel surface 11-62 FILL Loamy Sand 2.5Y 5/3 m, firm in place, 20%gravel, 20%cobbles 62-120 C Sand 2.5Y 7/2 fine sand, sg, loose,<5%gravel Parent Material (geologic): Glacial Outwash Depth to Bedrock: >120" Depth to Groundwater: Standing Water in Hole: Weeping From Pit Face: N/A { Estimated Seasonal High Groundwater: 120" DETERMINATION FOR SEASONAL HIGH WATER TABLE Method used: Depth observed standing in obs. hole: N/A Depth to weeping from side of obs. hole: N/A Depth to soil mottles, description: N/A Groundwater adjustment: N/A [index Well M I N/A Reading Date: N/A Index Well N/A Adj. Factor: N/A _ Level: Adj. groundwater level; N/A Notes: Bohler Engineering —352 Turnpike Road—Southborough, Massachusetts N/F WATERTOWN MALL ASSOCIATES LIMITED PARTNERSHIP 2l%6 7B%0 4w 29A I� ,p�dYY 1S ° 111. S!I° { . MCQu�ax ouv 2°Xs 33u fa• y �._ .�- 1� 2f.a ]��, l • 3°x4 --J°x6 Jtw y J`f r J7X9 11. ]A. — 7Q.a Jtxs ` 32Xa J SLa MIrrM� r Slxo imo SIXfi r MI \\ JIX6 N/F k 4 2 10 WHEELER C11m J1 ]]rl \ I ` N/F �• .r. J6Y4 / ;7� y1. Sa.e .[r S• �rd�q.�Ilea WATERTOWN MALL ASSOCIATES LIMITED PARTNERSHIP ETl�_r J JIX9 ` .l1.3 37x1 ' •�j� ]4z5 35z6 31311 \ f L{T / T� • rQ 16•ma� ,74,a A••.55.G�.ys.r e ?w .�-3l111 � ]txo s SaxS 35rA Js� � N R-, ° r1 3If �° r� r 15x2 f %r ° N/F �' elr. A'4 TP 92-94 ELM STREET REALTY TRUST MR, i e„144 R=1 nw 00' `•� WH 112,15' 303 Odwl.]r tYe.K fYa7Y �� Iwo ELM STREET `� ""� Yw _ OOl — iq' niu 7raf (40' — PUBLIC) AamM gl rrN -- r a .»w e R.SS N ..Sf'4 �•7a Ta N 5 1 .5 0 D 1.= 50' SOIL TESTING PREPARED BY EXHIBIT B O H L E R 80 ELM STREET WATERTOWN, MASSACHUSETTS ENGINEERING SCALET'=50' DATE:11/14/2014 APPENDIX C PIPE SIZING CALCULATIONS r > 7 Q to 000 N N qT I- � qt NV r 6 M M (6 -4 V C6 C6 (� 7 f CD� � t ti � -,;r O W `~ m O N N cn (M M O O M_ M cM M co cM M M co O O O O O O O O O O O O O O O O O O a o 0 0 0 0 0 0 0 0 - 000000000 rn p C N N N N N N N N N Q (0 N ti r- O 00 cM T— T— O () V L) 00 O O O N N O O 5 O O O O O O O O L O O O O O O O O O C (O c6 (D CO (O (O (O O O r '- NO Ln Ln O Ln U.) O O O L " O M 't CD co O O IT OD 00 p V o T7 r ry o O o o Q w o 0 0 0 0 0 0 0 0 U) c O O O O O O N N (p O O O O O O O O O L cM cM cM M M C) (M M cM 0 CD O C O O O O O O O O O IL II o L p O O O O O 0) M N N O U O O CM O O Q ~ Q Q O O O O O O O O O U " O O CD O O O O O O 0 L E N O 2 M M CO co O M C) C) ti (� O W V O N O O O O II C w 0 0 0 0 0 0 0 0 0 (� CD U `O ap 0 o rn rn rn rn rn rn rn rn O o 0 0 0 0 0 0 0 0 coo CO d rn 00 r- r- ao 00 m � � E v U N ti M cM r- r- C N Q Q O N O O O O L " O O O O O O O O O C II 2 c}o CN N N LL LL = _ U- Uj p c Z Z U Z O 0 p p p O Fn co co Co (aj Q L cn LL O N = O O p 2 N w w co cn O m m II II U- U U p U) p (n m m LL Q U Z APPENDIX D GROUNDWATER RECHARGE AND WATER QUALITY CALCULATIONS Groundwater Recharge Calculations Recharee Volumes Required: Existing Impervious Area=4,896 sf Proposed Impervious Area=26,477 sf New Impervious Area=21,581 sf Recharge Volume Required=21,581 x 0.60 in/12 in/ft = 1,079 CF See stage-storage volume chart on next page demonstrating adequate recharge volume is provided in the infiltration basin below the lowest outlet. Rv=F * impervious area NRCS Approx. Target Impervious Impervious Infiltration Rv(acre- Rv Hydrologic Soil Depth Area (sq. Area Being Adjustment feet) (cf) Soil Type Texture factor ft.) Infiltrated Factor (inches) (sq.ft.) A Sand 0.60 26,477 22,884 N/A* 0.025 1,079 B Loam 0.35 0.0 J C Silty 0.25 0.0 loam D Clay 0.10 0.0 Total= 22,884 .0025 1,098 * Total impervious area directed to infiltration system exceeds the minimum 65%required in the Stormwater Handbook. Accordingly, no adjustment factor has been applied. Subsurface Volume of Required Infiltration Storage(cf) Storage Basin Volume(cf) INF 6,683 1,079 Basin Drawdown Time: Basin Bottom Area= 1,478 square feet Stored volume below lowest outlet= 0.145 ac-ft (6,683 cf) Infiltration rate= 8.27 inch/hour Depth of water to be infiltrated= 6,683 / 1,478 =4.52 feet= 54.2 inches 54.2 inches/ 8.27 inch per hour=drawdown time of 6.55 hours e 00 N `* r` G) W .0 4 w d L m .-. Q Z4FO � W aci '� Cl* 0 0 E a a E 0 Ui d m m P p4) a `o c W ¢ J E _ o o c M U > y Q h ja CI) .0 ❑ E vi a� O oa U — CO '❑ Lo CD cm CD \ C r w 0 N lO 7 O O O O O O O M CD Q 0 N E N C _ N N @ L cr U_ W L _ i 3 II O � o ti r o CO E r o 0 0 0 CL ca J GC U CO T V/ m U H N O m 0) mF LO m 0 r O C N N N co co O O p E a (> C V o 0 0 0 0 ❑ a`) U) N N a > U U o m N 0 C: Y N Q m o m m o O c O V m m E m N N >° 0 0 C r 0 Q U Y m 0 0 T a (C L t) a N o 0 cps J � m � r � r Q foam 2 Y QU m Qt �' m V 7 o U N m E aV+ m <C ate+ m m V ❑ V M N a fA a ca 5 Z ; N N V L. 7 m 2 E C E N M N U •D `o CO E Z o d m d 3 u) o in - d N H a a DU a p CD C) 4aays)jaoM uoi4einoleo o C� m D E Q IenouaaM SSl = N U- Z 04 CO Z E � e 0 00 U O r L .� vN U o d W C a w Sm Z Q H a o 04 o 0 0 Elo- ,� a a LL r O O O o f0 -p o 0 0 0 o io m m m N 0 ems, CL c � J Ry 0 r O 0 r� m > a g C N p u] .0 O a p 0 o a L) — m c 0) '0 O oo N O O ELp W O C1 O O O O 00 E � O O O O O r E ` Q O N C C C _ N N Cot W L � 3 O CD CD Q O O O O Ew+ N 0 r O O O O CL W 0 4- U U) T V� f6 U L N r O 7 7 }� 2` � 0 m O o M N CD w coo CD 0 0 0 p � d U w � o 0 0 0 0 o U E U) 0 U U r .� N a O o �fl > U o m r Q N ) N O cu > C �+ V �+ U E m m m N >° (D ` N 0 00 m Q C d d L o J a O C Q cLn d m O m ++ U d V c d = O o g U 2 N m r0+ r ` m v O d N O j � cnniZ aWO oCL Via � � o U d � M m jaays)ljoM uoi4sinals� E CD wm Q a = � U) IsnouaaH SSl = y LL Z � cV Cl) i E � Required Water Ouality Flow based on MassDEP Method For Pronrietary Separator#1 WQF=(qu)(A)(WQV) Qu= 795 csm/in based on time of concentration of 5 minutes per attached table A= impervious area in square miles=6,059 sf= 0.00023 sq mi WQV = 1.0 inches WQF=(795 csm/in)x (0.00023 sq. mi). x (1.0 in) WQF= 0.18 cfs For Proprietary Separator#2 WQF = (qu)(A)(WQV) Qu= 795 csm/in based on time of concentration of 5 minutes per attached table A= impervious area in square miles= 3,154 sf=0.00011 sq mi WQV= 1.0 inches WQF =(795 csm/in)x (0.00011 sq. mi). x (1.0 in) WQF= 0.09 cfs Figure 4:for First 1-inch Runoff,Table of qu values for la/P Curve=0.034,listed by tc,for Type III Storm Distribution Tc qu Tc qu Tc qu (Hours) (csm/in) (Hours) (csm/in) (Hours) (csm/in) 0.01 835 2.7 197 7.1 95 0.03 835 2.8 192 7.2 94 0.05 831 2.9 187 7.3 93 0.p67 814 3 183 7.4 92 0.083 795 3.1 179 7.5 91 0.1 774 3.2 175 7.6 90 0.116 755 3.3 171 7.7 89 0.133 736 3.4 168 7.8 88 0.15 717 3.5 164 7.9 87 0.167 700 3.6 161 f 8 86 0.183 685 3.7 158 8.1 85 0.2 669 3.8 155 j 8.2 84 0.217 654 3.9 152 8.3 84 0.233 641 4 149 8.4 83 0.25 628 4.1 146 8.5 82 0.3 593 4.2 144 8.6 81 0.333 572 4.3 141 8.7 80 0.35 563 4.4 139 8.8 79 0.4 536 4.5 137 8.9 79 0.416 528 4.6 134 9 78 0.5 491 4.7 132 9.1 77 0.583 460 4.8 130 C 9.2 76 0.6 454 4.9 128 9.3 76 0.667 433 5 126 9.4 75 0.7 424 5.1 124 9.5 74 0.8 398 ! 5.2 122 9.6 74 0.9 376 5.3 120 9.7 73 f 1 356 I 5.4 119 9.8 72 f 1.1 339 5.5 117 9.9 72 1.2 323 5.6 115 10 71 1.3 309 5.7 114 1.4 296 5.8 112 1.5 285 5.9 111 1.6 274 6 109 1.7 264 6.1 108 1.8 255 6.2 106 1.9 247 6.3 105 2 239 6.4 104 2.1 232 j 6.5 102 2.2 225 6.6 101 2.3 219 6.7 100 2.4 213 6.8 99 2.5 207 6.9 98 2.6 202 7 1 96 MassDEP 4 Rate-Sept. 10,2013-Page 7 -* rye• `x�r �. �� 1 � y �•r L Stormceptore --!STC Stormceptor•is an underground stormwater quality treatment device that is unparalleled in its effectiveness for pollutant capture and retention.With thousands of systems operating worldwide,Stormceptor delivers protection every day in every storm. With patented technology,optimal treatment occurs byallowing free oil to rise and sediment to settle.The Stormceptor design prohibits scour and release of previously captured pollutants,ensuring superior treatment and protection during even the most extreme storm events. Stormceptor is very easy to design and provides flexibility under varying site constraints such as tight right-of-ways,zero lot lines and retrofit projects.Design flexibility allows for a cost-effective approach to stormwater treatment.Stormceptor has proven performance backed by the longest record of lab and field verification in the industry. Tested Performance ■ Fine particle capture ■ Prevents scour or release ■ 95%+Oil removal Massachusetts - Water Quality ( ) Flow Rate DepthStorrnceptor Inside Typical . . .. STC Model Diameter Below -. Pipe Invert Capacity STC 450i 4 68 CO.40 5.5 86 46 STC 900 6 63 0.89 22 251 89 STC 2400 8 104 1.58 22 840 205 STC 4800 10 140 2.47 22 909 543 STC 7200 12 148 3.56 22 1,059 839 STC 11000 2.x10 142 4.94 48 2,792 1,086 STC 16000 2 x 12 148 7.12 48 3,055 1,677 'Depth Below Pipe Inlet Invert to the"tam of Base Slab,and Maximum Sediment Capacity can vary to accommodate specific site designs and pollutant loads. Depths can vary to accommodate specia[designs or site conditions.Contact your local representative for assistance. 'Water Quality Flow Rate(Q)is rased on 80%annual average T5S removal of the OK110 particle sixe distribution. 'Peak Conveyance Flow Rate is based upon ideal velocity of 3 feet per second and outlet pipe diameters of 18-inch,36-inch,and 54-inch diameters. Hydrocarbw&Sediment capacities can be modified to accarnmodate specific site design regulrements,contact your local representative for assistance. M MATERIALS' www.rinkerstormceptor.com Amp W Manufacturing Plant:Westfield,MA Storme Phone:(413)562-3647 www.stormceptor.com 11-22-13-R13-802 MDEP UNIVERSITY OF MASSACHUSETTS Massachusetts Evaluation Evaluation Project AT AMHERST lii PL Water Resources Research Center �413]545-5532 Blaisdell House, UMass 413yy 545-2304 FAX i:.t 310 Hicks Way www.mastep.net r4, Amherst,MA 01003 MASTEP Technology Review Technoloav Name: Stormceptor 450i. Studies Reviewed: Multi-Phase Physical Model Testing of a Stormceptor STC450i Date: March 14, 2009 Reviewers: Jerry Schoen Ratin : 2 Brief rationale for rating: This laboratory study is generally well conducted and documented. No documentation of a quality assurance project,plan but quality control data was reported. Sediment analysis was done by the SSC method,but not the TSS method. Although SSC is considered by many scientists to be the preferred method, it is at odds with Massachusetts stormwater regulations, which are based on TSS treatment. Comparing SSC and TSS results is considered an inexact science. TARP Reauirements Not Met*: • No documentation of a Quality Assurance Project Plan • TSS analysis was not performed. Other Comments • SSC removal efficiency, calculated according to the NJDEP weighted formula,was 59.5—63.6%. • SSC removal evaluated using event mean concentration and modified mass balance method,the latter considered to be a particularly accurate method of evaluating sediment removal in a laboratory setting. • Particle Size Distribution (with d50 of 67 microns)closely matched the 55%sand, 40%silt, 5%clay mix recommended by NJDEP. • A full range of flows (2%- 125%) was tested. • Scour test was performed at 500%of design flow.This is more rigorous than the 125%recommended for scour tests. Effluent concentrations for the scour tests ranged from 5.9—6.1 mg/l, not considered a significant level of scour. *Laboratory testing was based on the NJDEP TARP laboratory testing guidelines. Water Resources Research Center Page 1 University of Massachusetts—Amherst 3/31/2009 APPENDIX E PRE-DEVELOPMENT AND POST-DEVELOPMENT WATERSHED MAPS J PH Wz wz J Q � Q z � � P-i O z Z O0(0 /•• ib� 6 W J Pq P4 W W~ Q:Z) -� Z W Q cp W 1 m it 1 , 1 11 JJ2 , '—j ❑ www � z, z Lu ?iQa W. I 15 15■If, �� /I!` II --�� - -�-= tk -- ---- Ali I lk N II II u u Q �❑ 11 I <Fa II W (WO II $ zOww w¢o- ya S a PH 4 vl!� 0 z w � P4w Q �. QLL �� w z zLLI Oz W /r PH P4 W L6 -" ® � U) LL�� s Z J} P4 W N:Q Oai W � � P m g 7 D r i , f� JW 'zo�z r1 � IIIfP` III � e 4 O a _��7 j m a x d N m m I1 — II II ` II ll !I O J W II a~a 11 = it LL N w W W Z�Q z d Q �Na S a APPENDIX F PRE-DEVELOPMENT AND POST-DEVELOPMENT WATERSHED COMPUTATIONS POA Su�cat IReach ❑n Link Routing Diagram for W141138 Pre ❑ Prepared by Bohler Engineering, Printed 12/12/2014 HydroCAD®10.00 s/n 08311 ©2013 HydroCAD Software Solutions LLC W141138 Pre Type /// 24-hr 2 yr Rainfall=3.20" Prepared by Bohler Engineering Printed 12/12/2014 HydroCAD® 10.00 s/n 08311 ©2013 HydroCAD Software Solutions LLC Page 2 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points x 3 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Subcatchment E-1: Runoff Area=35,610 sf 13.75% Impervious Runoff Depth=1.34" Tc=6.0 min CN=79 Runoff=1.26 cfs 0.091 of Link POA: Inflow=1.26 cfs 0.091 of Primary=1.26 cfs 0.091 of Total Runoff Area = 0.817 ac Runoff Volume= 0.091 of Average Runoff Depth = 1.34" 86.25% Pervious = 0.705 ac 13.75% Impervious = 0.112 ac W141138 Pre Type H/ 24-hr 2 yr Rainfall=3.20" Prepared by Bohler Engineering Printed 12/12/2014 HydroCAD® 10.00 s/n 08311 ©2013 HydroCAD Software Solutions LLC Paoe 3 Summary for Subcatchment E-1: Runoff = 1.26 cfs @ 12.09 hrs, Volume= 0.091 af, Depth= 1.34" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 2 yr Rainfall=3.20" Area (sf) CN Description 4,896 98 Paved parking, HSG A 30,714 76 Gravel surface, HSG A 35,610 79 Weighted Average 30,714 86.25% Pervious Area 4,896 13.75% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Link POA: Inflow Area = 0.817 ac, 13.75% Impervious, Inflow Depth = 1.34" for 2 yr event Inflow = 1.26 cfs @ 12.09 hrs, Volume= 0.091 of Primary = 1.26 cfs @ 12.09 hrs, Volume= 0.091 af, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs W141138 Pre Type /// 24-hr 10 yr Rainfall=4.90" Prepared by Bohler Engineering Printed 12/12/2014 HvdroCADO 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Paae 4 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points x 3 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Subcatchment E-1: Runoff Area=35,610 sf 13.75% Impervious Runoff Depth=2.72" Tc=6.0 min CN=79 Runoff=2.60 cfs 0.185 of Link POA: Inflow=2.60 cfs 0.185 of Primary=2.60 cfs 0.185 of Total Runoff Area = 0.817 ac Runoff Volume= 0.185 of Average Runoff Depth = 2.72" 86.26% Pervious = 0.705 ac 13.75% Impervious = 0.112 ac W141138 Pre Type /// 24-hr 10 yr Rainfall=4.90" Prepared by Bohler Engineering Printed 12/12/2014 HvdroCAD® 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Pacie 5 Summary for Subcatchment E-1: Runoff = 2.60 cfs @ 12.09 hrs, Volume= 0.185 af, Depth= 2.72" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 10 yr Rainfall=4.90" Area (sf) CN Description 4,896 98 Paved parking, HSG A 30.714 76 Gravel surface, HSG A 35,610 79 Weighted Average 30,714 86.25% Pervious Area 4,896 13.75% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Link POA: Inflow Area = 0.817 ac, 13.75% Impervious, Inflow Depth = 2.72" for 10 yr event Inflow = 2.60 cfs @ 12.09 hrs, Volume= 0.185 of Primary = 2.60 cfs @ 12.09 hrs, Volume= 0.185 af, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs W141138 Pre Type /// 24-hr 25 yr Rainfall=6.20" Prepared by Bohler Engineering Printed 12/12/2014 HydroCADO 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Paoe 6 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points x 3 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Subcatchment E-1: Runoff Area=35,610 sf 13.75% Impervious Runoff Depth=3.86" Tc=6.0 min CN=79 Runoff=3.69 cfs 0.263 of Link POA: Inflow=3.69 cfs 0.263 of Primary=3.69 cfs 0.263 of Total Runoff Area = 0.817 ac Runoff Volume= 0.263 of Average Runoff Depth = 3.86" 86.25% Pervious = 0.705 ac 13.75% Impervious = 0.112 ac W141138 Pre Type 111 24-hr 25 yr Rainfall=6.20" Prepared by Bohler Engineering Printed 12/12/2014 HydroCAD® 10.00 s/n 08311 ©2013 HydroCAD Software Solutions LLC Paae 7 Summary for Subcatchment E-1: Runoff = 3.69 cfs @ 12.09 hrs, Volume= 0.263 af, Depth= 3.86" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 25 yr Rainfall=6.20" Area (sf) CN Description 4,896 98 Paved parking, HSG A 30.714 76 Gravel surface. HSG A 35,610 79 Weighted Average 30,714 86.25% Pervious Area 4,896 13.75% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Link POA: Inflow Area = 0.817 ac, 13.75% Impervious, Inflow Depth = 3.86" for 25 yr event Inflow = 3.69 cfs @ 12.09 hrs, Volume= 0.263 of Primary = 3.69 cfs @ 12.09 hrs, Volume= 0.263 af, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs W141138 Pre Type /// 24-hr 100 yr Rainfall=8.90" Prepared by Bohler Engineering Printed 12/12/2014 HydroCADO 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Pape 8 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points x 3 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Subcatchment E-1: Runoff Area=35,610 sf 13.75% Impervious Runoff Depth=6.35" Tc=6.0 min CN=79 Runoff=5.98 cfs 0.433 of Link POA: Inflow=5.98 cfs 0.433 of Primary=5.98 cfs 0.433 of Total Runoff Area= 0.817 ac Runoff Volume= 0.433 of Average Runoff Depth =6.35" 86.25% Pervious =0.705 ac 13.75% Impervious =0.112 ac W141138 Pre Type 111 24-hr 100 yr Rainfall=8.90" Prepared by Bohler Engineering Printed 12/12/2014 HydroCAD® 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Paae 9 Summary for Subcatchment E-1: Runoff = 5.98 cfs @ 12.09 hrs, Volume= 0.433 af, Depth= 6.35" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100 yr Rainfall=8.90" Area (sf) CN Description 4,896 98 Paved parking, HSG A 30,714 76 Gravel surface, HSG A 35,610 79 Weighted Average 30,714 86.25% Pervious Area 4,896 13.75% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Link POA: Inflow Area = 0.817 ac, 13.75% Impervious, Inflow Depth = 6.35" for 100 yr event Inflow = 5.98 cfs @ 12.09 hrs, Volume= 0.433 of Primary = 5.98 cfs @ 12.09 hrs, Volume= 0.433 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs P-3 > B I O P-4 (P-1 ) /INF D POA L, P-2) SufJCat Reach Aon Link Routing Diagram for W141138 Post ❑ Prepared by Bohler Engineering, Printed 12/12/2014 HydroCAD®10.00 s/n 08311 ©2013 HydroCAD Software Solutions LLC W141138 Post Type 11124-hr 2 yr Rainfall=3.20" Prepared by Bohler Engineering Printed 12/12/2014 HydroCADO 10.00 s/n 08311 @ 2013 HydroCA❑Software Solutions LLC Paoe 2 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points x 3 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Subcatchment P-1: Runoff Area=12,507 sf 100.00% Impervious Runoff Depth=2.97" Tc=6.0 min CN=98 Runoff=0.89 cfs 0.071 of Subcatchment P-2: Runoff Area=10,336 sf 83.54% Impervious Runoff Depth=2.00" Tc=6.0 min CN=88 Runoff=0.55 cfs 0.039 of Subcatchment P-3: Runoff Area=3,610 sf 48.25% Impervious Runoff Depth=0.69" Tc=6.0 min CN=67 Runoff=0.06 cfs 0.005 of Subcatchment P-4: Runoff Area=9,146 sf 43.32% Impervious Runoff Depth=0.60" Tc=6.0 min CN=65 Runoff=0.12 cfs 0.011 of Pond BIO: Peak EIev=29.02' Storage=19 cf Inflow=0.06 cfs 0.005 of Discarded=0.03 cfs 0.005 of Primary=0.00 cfs 0.000 of Oufflow=0.03 cfs 0.005 of Pond INF: Peak EIev=24.25' Storage=1,146 cf Inflow=1.45 cfs 0.110 of Discarded=0.28 cfs 0.110 of Primary=0.00 cfs 0.000 of Oufflow=0.28 cfs 0.110 of Link POA: Inflow=0.12 cfs 0.011 of Primary=0.12 cfs 0.011 of Total Runoff Area = 0.817 ac Runoff Volume = 0.126 of Average Runoff Depth = 1.85" 24.59% Pervious = 0.201 ac 75.41% Impervious = 0.616 ac W141138 Post Type /// 24-hr 2 yr Rainfall=3.20" Prepared by Bohler Engineering Printed 12/12/2014 HydroCAD® 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Paae 3 Summary for Subcatchment P-1: Runoff = 0.89 cfs @ 12.08 hrs, Volume= 0.071 af, Depth= 2.97" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 2 yr Rainfall=3.20" Area (sf) CN Description 12,507 98 Roofs, HSG A 12,507 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-2: Runoff = 0.55 cfs @ 12.09 hrs, Volume= 0.039 af, Depth= 2.00" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 2 yr Rainfall=3.20" Area (sf) CN Description 7,389 98 Paved parking, HSG A 1,246 98 Lawn over par, HSG A 1.701 39 >75% Grass cover, Good. HSG A 10,336 88 Weighted Average 1,701 16.46% Pervious Area 8,635 83.54% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-3: Runoff = 0.06 cfs @ 12.10 hrs, Volume= 0.005 af, Depth= 0.69" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 2 yr Rainfall=3.20" Area (sf) CN Description 1,742 98 Paved parking, HSG A 0 98 Lawn over par, HSG A 1,868 39 >75% Grass cover, Good, HSG A 3,610 67 Weighted Average 1,868 51.75% Pervious Area 1,742 48.25% Impervious Area W141138 Post Type 111 24-hr 2 yr Rainfall=3.20" Prepared by Bohler Engineering Printed 12/12/2014 HvdroCAD® 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Paqe 4 Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-4: Runoff = 0.12 cfs @ 12.11 hrs, Volume= 0.011 af, Depth= 0.60" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 2 yr Rainfall=3.20" Area (sf) CN Description 239 98 Paved parking, HSG A 3,723 98 Lawn over par, HSG A 5,184 39 >75% Grass cover. Good. HSG A 9,146 65 Weighted Average 5,184 56.68% Pervious Area 3,962 43.32% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (fUsec) (cfs) 6.0 Direct Entry, Summary for Pond B10: Inflow Area = 0.083 ac, 48.25% Impervious, Inflow Depth = 0.69" for 2 yr event Inflow = 0.06 cfs @ 12.10 hrs, Volume= 0.005 of Outflow = 0.03 cfs @ 12.38 hrs, Volume= 0.005 af, Atten= 51%, Lag= 16.8 min Discarded = 0.03 cfs @ 12.38 hrs, Volume= 0.005 of Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs/ 3 Peak Elev= 29.02' @ 12.38 hrs Surf.Area= 485 sf Storage= 19 cf Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 3.0 min ( 890.1 - 887.0 ) Volume Invert Avail.Storage Storage Description #1 26.25' 442 cf Bioretention Area Extents (Irregular) Listed below (Recalc) 1,411 cf Overall - 969 cf Embedded = 442 cf #2 28.75' 0 cf Mulch (Irregular) Listed below (Recalc) Inside#1 85 cf Overall x 0.0% Voids #3 26.25' 0 cf Soil Media (Irregular) Listed below (Recalc) Inside#1 884 cf Overall x 0.0% Voids 442 cf Total Available Storage W141138 Post Type 11124-hr 2 yr Rainfall=3.20" Prepared by Bohler Engineering Printed 12/12/2014 HvdroCAD® 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Paae 5 Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft) 26.25 355 91.1 0 0 355 28.99 355 91.1 973 973 605 29.00 479 132.9 4 977 1,350 29.75 686 142.3 435 1,411 1,580 Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft) 28.75 355 91.1 0 0 355 28.99 355 91.1 85 85 377 Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft) 26.25 355 91.1 0 0 355 28.74 355 91.1 884 884 582 Device Routinq Invert Outlet Devices #1 Discarded 26.25' 2.410 in/hr Exfiltration over Surface area #2 Primary 25.75' 12.0" Round Outlet Pipe L= 28.0' CPP, projecting, no headwall, Ke= 0.900 Inlet/Outlet Invert= 25.75' /25.44' S= 0.0111 T Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 0.79 sf #3 Device 2 29.50' 12.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads Discarded OutFlow Max=0.03 cfs @ 12.38 hrs HW=29.02' (Free Discharge) L1=Exfiltration (Exfiltration Controls 0.03 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=26.25' TW=22.50' (Dynamic Tailwater) L2=0utlet Pipe (Passes 0.00 cfs of 0.75 cfs potential flow) L3=Orifice/Grate ( Controls 0.00 cfs) Summary for Pond INF: Inflow Area = 0.607 ac, 86.51% Impervious, Inflow Depth = 2.18" for 2 yr event Inflow = 1.45 cfs @ 12.09 hrs, Volume= 0.110 of Outflow = 0.28 cfs, @ 11.85 hrs, Volume= 0.110 af, Atten= 80%, Lag= 0.0 min Discarded = 0.28 cfs @ 11.85 hrs, Volume= 0.110 of Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs/3 Peak Elev= 24.25' @ 12.52 hrs Surf.Area= 1,478 sf Storage= 1,146 cf Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 21.0 min ( 798.3 - 777.4 ) W141138 Post Type 11124-hr 2 yr Rainfall=3.20" Prepared by Bohler Engineering Printed 12/12/2014 HvdroCAD&10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Pape 6. Volume Invert Avail.Storage Storage Description #1 22.50' 0 cf 25.79'W x 57.31'L x 7.67'H Infiltration Bed Extents 11,336 cf Overall - 8,803 cf Embedded = 2,533 cf x 0.0% Voids #2 22.50' 887 cf 25.79'W x 57.31'L x 1.50'H Stone Bed Inside#1 2,217 cf Overall x 40.0% Voids #3 24.00' 5,796 cf 21.79'W x 53.31'L x 5.67'H StormTrap Storage Volume Inside#1 6,586 cf Overall x 88.0% Voids 6,683 cf Total Available Storage Device Routing invert Outlet Devices #1 Discarded 22.50' 8.270 in/hr Exfiltration over Surface area #2 Primary 29.75' 12.0" Round Culvert L= 129.0' CPP, projecting, no headwall, Ke= 0.900 Inlet/ Outlet Invert= 29.75' /27.90' S= 0.0143 '/' Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 0.79 sf Discarded OutFlow Max=0.28 cfs @ 11.85 hrs HW=22.59' (Free Discharge) t-1=Exfiltration (Exfiltration Controls 0.28 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=22.50' TW=0.00' (Dynamic Tailwater) t-2=Culvert ( Controls 0.00 cfs) Summary for Link POA: Inflow Area = 0.817 ac, 75.41% Impervious, Inflow Depth = 0.15" for 2 yr event Inflow = 0.12 cfs @ 12.11 hrs, Volume= 0.011 of Primary = 0.12 cfs @ 12.11 hrs, Volume= 0.011 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs W141138 Post Type 111 24-hr 10 yr Rainfall=4.90" Prepared by Bohler Engineering Printed 12/12/2014 HydroCAD® 10.00 s/n 08311 ©2013 HydroCAD Software Solutions LLC Page 7 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points x 3 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Subcatchment P-1: Runoff Area=12,507 sf 100.00% Impervious Runoff Depth=4.66" Tc=6.0 min CN=98 Runoff=1.38 cfs 0.112 of Subcatchment P-2: Runoff Area=10,336 sf 83.54% Impervious Runoff Depth=3.57" Tc=6.0 min CN=88 Runoff=0.97 cfs 0.071 of Subcatchment P-3: Runoff Area=3,610 sf 48.25% Impervious Runoff Depth=1.73" Tc=6.0 min CN=67 Runoff=0.16 cfs 0.012 of Subcatchment P-4: Runoff Area=9,146 sf 43.32% Impervious Runoff Depth=1.59" Tc=6.0 min CN=65 Runoff=0.37 cfs 0.028 of Pond BIO: Peak Elev=29.26' Storage=141 cf Inflow=0.16 cfs 0.012 of Discarded=0.03 cfs 0.012 of Primary=0.00 cfs 0.000 of Outflow=0.03 cfs 0.012 of Pond INF: Peak Elev=25.54' Storage=2,458 cf Inflow=2.35 cfs 0.182 of Discarded=0.28 cfs 0.182 of Primary=0.00 cfs 0.000 of Outflow=0.28 cfs 0.182 of Link POA: Inflow=0.37 cfs 0.028 of Primary=0.37 cfs 0.028 of Total Runoff Area = 0.817 ac Runoff Volume = 0.222 of Average Runoff Depth = 3.26" 24.59% Pervious = 0.201 ac 75.41% Impervious = 0.616 ac W141138 Post Type /// 24-hr 10 yr Rainfall=4.90" Prepared by Bohler Engineering Printed 12/12/2014 HvdroCAD® 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Paoe 8 Summary for Subcatchment P-1: Runoff = 1.38 cfs @ 12.08 hrs, Volume= 0.112 af, Depth= 4.66" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 10 yr Rainfall=4.90" Area (sf) CN Description 12,507 98 Roofs, HSG A 12,507 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-2: Runoff = 0.97 cfs @ 12.09 hrs, Volume= 0.071 af, Depth= 3.57" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 10 yr Rainfall=4.90" Area (sf) CN Description 7,389 98 Paved parking, HSG A 1,246 98 Lawn over par, HSG A 1,701 39 >75% Grass cover. Good. HSG A 10,336 88 Weighted Average 1,701 16.46% Pervious Area 8,635 83.54% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-3: Runoff = 0.16 cfs @ 12.09 hrs, Volume= 0.012 af, Depth= 1.73" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 10 yr Rainfall=4.90" Area (sf) CN Description 1,742 98 Paved parking, HSG A 0 98 Lawn over par, HSG A 1,868 39 >75% Grass cover, Good, HSG A 3,610 67 Weighted Average 1,868 51.75% Pervious Area 1,742 48.25% Impervious Area W141138 Post Type 111 24-hr 10 yr Rainfall=4.90" Prepared by Bohler Engineering Printed 12/12/2014 HydraCA00 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Page 9. Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-4: Runoff = 0.37 cfs @ 12.10 hrs, Volume= 0.028 af, Depth= 1.59" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 10 yr Rainfall=4.90" Area (sf) CN Description 239 98 Paved parking, HSG A * 3,723 98 Lawn over par, HSG A 5,184 39 >75% Grass cover. Good. HSG A 9,146 65 Weighted Average 5,184 56.68% Pervious Area 3,962 43.32% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Pond BIO: Inflow Area = 0.083 ac, 48.25% Impervious, Inflow Depth = 1.73" for 10 yr event Inflow = 0.16 cfs @ 12.09 hrs, Volume= 0.012 of Outflow = 0.03 cfs @ 12.59 hrs, Volume= 0.012 af, Atten= 81%, Lag= 29.6 min Discarded = 0.03 cfs @ 12.59 hrs, Volume= 0.012 of Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs/3 Peak Elev= 29.26' @ 12.59 hrs Surf.Area= 546 sf Storage= 141 cf Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 32.0 min ( 888.7 - 856.7 ) Volume Invert Avail.Storage Storage Description #1 26.25' 442 cf Bioretention Area Extents (Irregular) Listed below (Recalc) 1,411 cf Overall - 969 cf Embedded = 442 cf #2 28.75' 0 cf Mulch (Irregular) Listed below (Recalc) Inside#1 85 cf Overall x 0.0% Voids #3 26.25' 0 cf Soil Media (irregular) Listed below (Recalc) Inside#1 884 cf Overall x 0.0% Voids 442 cf Total Available Storage W141138 Post Type H/24-hr 10 yr Rainfall=4.90" Prepared by Bohler Engineering Printed 12/12/2014 HydroCAD® 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Paae 10 Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (so-ft) 26.25 355 91.1 0 0 355 28.99 355 91.1 973 973 605 29.00 479 132.9 4 977 1.350 29.75 686 142.3 435 1,411 1.580 Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sa-ft) 28.75 355 91.1 0 0 355 28.99 355 91.1 85 85 377 Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft) 26.25 355 91.1 0 0 355 28.74 355 91.1 884 884 582 Device Routinq Invert Outlet Devices #1 Discarded 26.25' 2.410 in/hr Exfiltration over Surface area #2 Primary 25.75' 12.0" Round Outlet Pipe L= 28.0' CPP, projecting, no headwall, Ke= 0.900 Inlet/Outlet Invert= 25.75' /25.44' S= 0.0111 T Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 0.79 sf #3 Device 2 29.50' 12.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads Discarded OutFlow Max=0.03 cfs @ 12.59 hrs HW=29.26' (Free Discharge) t-1=Exfiltration (Exfiltration Controls 0.03 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=26.25' TW=22.50' (Dynamic Tailwater) t-2=Outlet Pipe (Passes 0.00 cfs of 0.75 cfs potential flow) t-3=Orifice/Grate ( Controls 0.00 cfs) Summary for Pond INF: Inflow Area = 0.607 ac, 86.51% Impervious, Inflow Depth = 3.60" for 10 yr event Inflow = 2.35 cfs @ 12.08 hrs, Volume= 0.182 of Outflow = 0.28 cfs @ 11.72 hrs, Volume= 0.182 af, Atten= 88%, Lag= 0.0 min Discarded = 0.28 cfs @ 11.72 hrs, Volume= 0.182 of Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs/ 3 Peak Elev= 25.54' @ 12.67 hrs Surf.Area= 1,478 sf Storage= 2,458 cf Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 55.3 min ( 823.1 - 767.8) W141138 Post Type 111 24-hr 10 yr Rainfall=4.90" Prepared by Bohler Engineering Printed 12/12/2014 HydroCAD® 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Paae 11 Volume Invert Avail.Storage Storage Description #1 22.50' 0 cf 25.79'W x 57.311 x 7.67'H Infiltration Bed Extents 11,336 cf Overall - 8,803 cf Embedded = 2,533 cf x 0.0% Voids #2 22.50' 887 cf 25.79'W x 57.31'L x 1.50'H Stone Bed Inside#1 2,217 cf Overall x 40.0% Voids #3 24.00' 5,796 cf 21.79'W x 53.31'L x 5.67'H StormTrap Storage Volume Inside#1 6,586 cf Overall x 88.0% Voids 6,683 cf Total Available Storage Device Routinq Invert Outlet Devices #1 Discarded 22.50' 8.270 in/hr Exfiltration over Surface area #2 Primary 29.75' 12.0" Round Culvert L= 129.0' CPP, projecting, no headwall, Ke= 0.900 Inlet/ Outlet Invert= 29.75' /27.90' S= 0.0143 T Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 0.79 sf Discarded OutFlow Max=0.28 cfs @ 11.72 hrs HW=22.59' (Free Discharge) t-1=Exfiltration (Exfiltration Controls 0.28 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=22.50' TW=0.00' (Dynamic Tailwater) t-2=Culvert ( Controls 0.00 cfs) Summary for Link POA: Inflow Area = 0.817 ac, 75.41% Impervious, Inflow Depth = 0.41" for 10 yr event Inflow = 0.37 cfs @ 12.10 hrs, Volume= 0.028 of Primary = 0.37 cfs @ 12.10 hrs, Volume= 0.028 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs W141138 Post Type 111 24-hr 25 yr Rainfall=6.20" Prepared by Bohler Engineering Printed 12/12/2014 HydroCADO 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Paoe 12 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points x 3 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Subcatchment P-1: Runoff Area=12,507 sf 100.00% Impervious Runoff Depth=5.96" Tc=6.0 min CN=98 Runoff=1.75 cfs 0.143 of Subcatchment P-2: Runoff Area=10,336 sf 83.54% Impervious Runoff Depth=4.82" Tc=6.0 min CN=88 Runoff=1.29 cfs 0.095 of Subcatchment P-3: Runoff Area=3,610 sf 48.25% Impervious Runoff Depth=2.68" Tc=6.0 min CN=67 Runoff=0.26 cfs 0.019 of Subcatchment P-4: Runoff Area=9,146 sf 43.32% Impervious Runoff Depth=2.50" Tc=6.0 min CN=65 Runoff=0.60 cfs 0.044 of Pond BIO: Peak Elev=29.49' Storage=271 cf Inflow=0.26 cfs 0.019 of Discarded=0.03 cfs 0.019 of Primary=0.00 cfs 0.000 of Outflow=0.03 cfs 0.019 of Pond INF: Peak Elev=26.62' Storage=3,570 cf Inflow=3.04 cfs 0.238 of Discarded=0.28 cfs 0.238 of Primary=0.00 cfs 0.000 of Outflow=0.28 cfs 0.238 of Link POA: Inflow=0.60 cfs 0.044 of Primary=0.60 cfs 0.044 of Total Runoff Area = 0.817 ac Runoff Volume = 0.300 of Average Runoff Depth = 4.41" 24.59% Pervious = 0.201 ac 75.41% Impervious = 0.616 ac W141138 Post Type 111 24-hr 25 yr Rainfall=6.20" Prepared by Bohler Engineering Printed 12/12/2014 HvdroCAD® 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Paae 13 Summary for Subcatchment P-1: Runoff = 1.75 cfs @ 12.08 hrs, Volume= 0.143 af, Depth= 5.96" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 25 yr Rainfall=6.20" Area (sf) CN Description 12,507 98 Roofs, HSG A 12,507 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-2: Runoff = 1.29 cfs @ 12.09 hrs, Volume= 0.095 af, Depth= 4.82" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 25 yr Rainfall=6.20" Area (sf) CN Description 7,389 98 Paved parking, HSG A 1,246 98 Lawn over par, HSG A 1,701 39 >75% Grass cover, Good, HSG A 10,336 88 Weighted Average 1,701 16.46% Pervious Area 8,635 83.54% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (fUsec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-3: Runoff = 0.26 cfs @ 12.09 hrs, Volume= 0.019 af, Depth= 2.68" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 25 yr Rainfall=6.20" Area (sf) CN Description 1,742 98 Paved parking, HSG A 0 98 Lawn over par, HSG A 1.868 39 >75% Grass cover. Good. HSG A 3,610 67 Weighted Average 1,868 51.75% Pervious Area 1,742 48.25% Impervious Area W141138 Post Type /// 24-hr 25 yr Rainfall=6.20" Prepared by Bohler Engineering Printed 12/12/2014 HydroCAD® 10.00 s/n 08311 ©2013 HydroCAD Software Solutions LLC Paqe 14 Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-4: Runoff = 0.60 cfs @ 12.09 hrs, Volume= 0.044 af, Depth= 2.50" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 25 yr Rainfall=6.20" Area (sf) CN Description 239 98 Paved parking, HSG A 3,723 98 Lawn over par, HSG A 5.184 39 >75% Grass cover. Good. HSG A 9,146 65 Weighted Average 5,184 56.68% Pervious Area 3,962 43.32% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Pond B10: Inflow Area = 0.083 ac, 48.25% Impervious, Inflow Depth = 2.68" for 25 yr event Inflow = 0.26 cfs @ 12.09 hrs, Volume= 0.019 of Outflow = 0.03 cfs @ 12.81 hrs, Volume= 0.019 af, Atten= 87%, Lag= 42.8 min Discarded = 0.03 cfs @ 12.81 hrs, Volume= 0.019 of Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs/3 Peak Elev= 29.49' @ 12.81 hrs Surf.Area= 609 sf Storage= 271 cf Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 67.4 min ( 911.0 - 843.6 ) Volume Invert Avail.Storaae Storaqe Description #1 26.25' 442 cf Bioretention Area Extents (Irregular) Listed below (Recalc) 1,411 cf Overall - 969 cf Embedded = 442 cf #2 28.75' 0 cf Mulch (Irregular) Listed below (Recalc) Inside#1 85 cf Overall x 0.0% Voids #3 26.25' 0 cf Soil Media (Irregular) Listed below (Recalc) Inside#1 884 cf Overall x 0.0% Voids 442 cf Total Available Storage W141138 Post Type 11124-hr 25 yr Rainfall=6.20" Prepared by Bohler Engineering Printed 12/12/2014 HydroCADO 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Paoe 15 Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft) 26.25 355 91.1 0 0 355 28.99 355 91.1 973 973 605 29.00 479 132.9 4 977 1,350 29.75 686 142.3 435 1,411 1,580 Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sa-ft) (feet) (cubic-feet) (cubic-feet) (sa-ft) 28.75 355 91.1 0 0 355 28.99 355 91.1 85 85 377 Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft) 26.25 355 91.1 0 0 355 28.74 355 91.1 884 884 582 Device Routinq Invert Outlet Devices #1 Discarded 26.25' 2.410 in/hr Exfiltration over Surface area #2 Primary 25.75' 12.0" Round Outlet Pipe L= 28.0' CPP, projecting, no headwall, Ke= 0.900 Inlet/ Outlet Invert= 25.75' /25.44' S= 0.0111 T Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 0.79 sf #3 Device 2 29.50' 12.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads Discarded OutFlow Max=0.03 cfs @ 12.81 hrs HW=29.49' (Free Discharge) L1=Exfiltration (Exfiltration Controls 0.03 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=26.25' TW=22.50' (Dynamic Tailwater) L2=Outlet Pipe (Passes 0.00 cfs of 0.75 cfs potential flow) L3=Orifice/Grate ( Controls 0.00 cfs) Summary for Pond INF: Inflow Area = 0.607 ac, 86.51% Impervious, Inflow Depth = 4.70" for 25 yr event Inflow = 3.04 cfs @ 12.08 hrs, Volume= 0.238 of Outflow = 0.28 cfs @ 11.63 hrs, Volume= 0.238 af, Atten= 91%, Lag= 0.0 min Discarded = 0.28 cfs @ 11.63 hrs, Volume= 0.238 of Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs/ 3 Peak Elev= 26.62' @ 12.92 hrs Surf.Area= 1,478 sf Storage= 3,570 cf Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 87.7 min ( 850.6 - 763.0 ) W141138 Post Type 111 24-hr 25 yr Rainfall=6.20" Prepared by Bohler Engineering Printed 12/12/2014 HydroCAM 10.00 s/n 08311 a 2013 HvdroCAD Software Solutions LLC Paae 16 Volume Invert Avail.Storaae Storage Description #1 22.50' 0 cf 25.79'W x 57.31'L x 7.67'H Infiltration Bed Extents 11,336 cf Overall - 8,803 cf Embedded = 2,533 cf x 0.0% Voids #2 22.50' 887 cf 25.79'W x 57.31'L x 1.50'H Stone Bed Inside#1 2,217 cf Overall x 40.0% Voids #3 24.00' 5,796 cf 21.79'W x 53.31'L x 5.67'H StormTrap Storage Volume Inside#1 6.586 cf Overall x 88.0% Voids 6,683 cf Total Available Storage Device Routinq Invert Outlet Devices #1 Discarded 22.50' 8.270 in/hr Exfiltration over Surface area #2 Primary 29.75' 12.0" Round Culvert L= 129.0' CPP, projecting, no headwall, Ke= 0.900 Inlet/ Outlet Invert= 29.75' /27.90' S= 0.0143 7' Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 0.79 sf Discarded OutFlow Max=0.28 cfs @ 11.63 hrs HW=22.59' (Free Discharge) L1=Exfiltration (Exfiltration Controls 0.28 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=22.50' TW=0.00' (Dynamic Tailwater) t-2=Culvert ( Controls 0.00 cfs) Summary for Link POA: Inflow Area = 0.817 ac, 75.41% Impervious, Inflow Depth = 0.64" for 25 yr event Inflow = 0.60 cfs @ 12.09 hrs, Volume= 0.044 of Primary = 0.60 cfs @ 12.09 hrs, Volume= 0.044 af, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs W141138 Post Type 111 24-hr 100 yr Rainfall=8.90" Prepared by Bohler Engineering Printed 12/12/2014 HvdroCADO 10.00 s/n 08311 ©2013 HydroCAD Software Solutions LLC Pa4e 17 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points x 3 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Subcatchment P-1: Runoff Area=12,507 sf 100.00% Impervious Runoff Depth=8.66" Tc=6.0 min CN=98 Runoff=2.51 cfs 0.207 of Subcatchment P-2: Runoff Area=10,336 sf 83.54% Impervious Runoff Depth=7.45" Tc=6.0 min CN=88 Runoff=1.95 cfs 0.147 of Subcatchment P-3: Runoff Area=3,610 sf 48.25% Impervious Runoff Depth=4.88" Tc=6.0 min CN=67 Runoff=0.47 cfs 0.034 of Subcatchment P-4: Runoff Area=9,146 sf 43.32% Impervious Runoff Depth=4.63" Tc=6.0 min CN=65 Runoff=1.14 cfs 0.081 of Pond BIO: Peak Elev=29.59' Storage=335 cf Inflow=0.47 cfs 0.034 of Discarded=0.04 cfs 0.026 of Primary=0.27 cfs 0.008 of Outflow=0.31 cfs 0.034 of Pond INF: Peak Elev=29.54' Storage=6,553 cf Inflow=4.46 cfs 0.362 of Discarded=0.28 cfs 0.363 of Primary=0.00 cfs 0.000 of Outflow=0.28 cfs 0.363 of Link POA: Inflow=1.14 cfs 0.081 of Primary=1.14 cfs 0.081 of Total Runoff Area = 0.817 ac Runoff Volume= 0.469 of Average Runoff Depth = 6.89" 24.59% Pervious = 0.201 ac 75.41% Impervious = 0.616 ac W141138 Post Type 111 24-hr 100 yr Rainfall=8.90" Prepared by Bohler Engineering Printed 12/12/2014 HydroCAD® 10.00 s/n 08311 ©2013 HvdroCAD Software Solutions LLC Page 18 Summary for Subcatchment P-1: Runoff = 2.51 cfs @ 12.08 hrs, Volume= 0.207 af, Depth= 8.66" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100 yr Rainfall=8.90" Area (sf) CN Description 12,507 98 Roofs. HSG A 12,507 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-2: Runoff = 1.95 cfs @ 12.08 hrs, Volume= 0.147 af, Depth= 7.45" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100 yr Rainfall=8.90" Area (sf) CN Description 7,389 98 Paved parking, HSG A 1,246 98 Lawn over par, HSG A 1.701 39 >75% Grass cover. Good. HSG A 10,336 88 Weighted Average 1,701 16.46% Pervious Area 8,635 83.54% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-3: Runoff = 0.47 cfs @ 12.09 hrs, Volume= 0.034 af, Depth= 4.88" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100 yr Rainfall=8.90" Area (sf) CN Description 1,742 98 Paved parking, HSG A 0 98 Lawn over par, HSG A 1,868 39 >75% Grass cover. Good. HSG A 3,610 67 Weighted Average 1,868 51.75% Pervious Area 1,742 48.25% Impervious Area W141138 Post Type 111 24-hr 100 yr Rainfall=8.90" Prepared by Bohler Engineering Printed 12/12/2014 HydroCAD® 10.00 s/n 08311 ©2013 HydroCAD Software Solutions LLC Paqe 19 Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Subcatchment P-4: Runoff = 1.14 cfs @ 12.09 hrs, Volume= 0.081 af, Depth= 4.63" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100 yr Rainfall=8.90" Area (sf) CN Description 239 98 Paved parking, HSG A 3,723 98 Lawn over par, HSG A 5,184 39 >75% Grass cover, Good, HSG A 9,146 65 Weighted Average 5,184 56.68% Pervious Area 3,962 43.32% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Summary for Pond B10: Inflow Area = 0.083 ac, 48.25% Impervious, Inflow Depth = 4.88" for 100 yr event Inflow = 0.47 cfs @ 12.09 hrs, Volume= 0.034 of Outflow = 0.31 cfs @ 12.18 hrs, Volume= 0.034 af, Atten= 36%, Lag= 5.8 min Discarded = 0.04 cfs @ 12.18 hrs, Volume= 0.026 of Primary = 0.27 cfs @ 12.18 hrs, Volume= 0.008 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs/3 Peak Elev= 29.59' @ 12.18 hrs Surf.Area= 638 sf Storage= 335 cf Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 60.5 min ( 886.8- 826.3 ) Volume Invert Avail.Storage Storaqe Description #1 26.25' 442 cf Bioretention Area Extents (Irregular) Listed below (Recalc) 1,411 cf Overall - 969 cf Embedded = 442 cf #2 28.75' 0 cf Mulch (Irregular) Listed below (Recalc) Inside#1 85 cf Overall x 0.0% Voids #3 26.25' 0 cf Soil Media (irregular) Listed below (Recalc) Inside#1 884 cf Overall x 0.0% Voids 442 cf Total Available Storage W141138 Post Type 111 24-hr 100 yr Rainfall=8.90" Prepared by Bohler Engineering Printed 12/12/2014 HydroCADO 10.00 s/n 08311 0 2013 HvdroCAD Software Solutions LLC Paqe 20 Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft) 26.25 355 91.1 0 0 355 28.99 355 91.1 973 973 605 29.00 479 132.9 4 977 1,350 29.75 686 142.3 435 1,411 1,580 Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft) 28.75 355 91.1 0 0 355 28.99 355 91.1 85 85 377 Elevation Surf.Area Perim. Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (feet) (cubic-feet) (cubic-feet) (sq-ft) 26.25 355 91.1 0 0 355 28.74 355 91.1 884 884 582 Device Routinq Invert Outlet Devices #1 Discarded 26.25' 2.410 in/hr Exfiltration over Surface area #2 Primary 25.75' 12.0" Round Outlet Pipe L= 28.0' CPP, projecting, no headwall, Ke= 0.900 Inlet/ Outlet Invert= 25.75' / 25.44' S= 0.0111 T Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 0.79 sf #3 Device 2 29.50' 12.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads Discarded OutFlow Max=0.04 cfs @ 12.18 hrs HW=29.59' (Free Discharge) t1=Exfiltration (Exfiltration Controls 0.04 cfs) Primary OutFlow Max=0.27 cfs @ 12.18 hrs HW=29.59' TW=27.27' (Dynamic Tailwater) t--2=Outlet Pipe (Passes 0.27 cfs of 4.55 cfs potential flow) L3=Orifice/Grate (Weir Controls 0.27 cfs @ 0.97 fps) Summary for Pond INF: Inflow Area = 0.607 ac, 86.51% Impervious, Inflow Depth = 7.16" for 100 yr event Inflow = 4.46 cfs @ 12.08 hrs, Volume= 0.362 of Outflow = 0.28 cfs @ 11.23 hrs, Volume= 0.363 af, Atten= 94%, Lag= 0.0 min Discarded = 0.28 cfs @ 11.23 hrs, Volume= 0.363 of Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs/ 3 Peak Elev= 29.54' @ 13.60 hrs Surf.Area= 1,478 sf Storage= 6,553 cf Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= 181.1 min ( 937.0 - 755.8) W141138 Post Type /// 24-hr 100 yr Rainfall=8.90" Prepared by Bohler Engineering Printed 12/12/2014 HydroCAD® 10.00 s/n 08311 ©2013 HydroCAD Software Solutions LLC Paae 21 Volume Invert Avail.Storage Storage Description #1 22.50' 0 cf 25.79'W x 57.31'L x 7.67'H Infiltration Bed Extents 11,336 cf Overall - 8,803 cf Embedded = 2,533 cf x 0.0% Voids #2 22.50' 887 cf 25.79'W x 57.31'L x 1.50'H Stone Bed Inside#1 2,217 cf Overall x 40.0% Voids #3 24.00' 5,796 cf 21.79'W x 53.31'L x 5.67'H StormTrap Storage Volume Inside#1 6,586 cf Overall x 88.0% Voids 6,683 cf Total Available Storage Device Routinq Invert Outlet Devices #1 Discarded 22.50' 8.270 in/hr Exfiltration over Surface area #2 Primary 29.75' 12.0" Round Culvert L= 129.0' CPP, projecting, no headwall, Ke= 0.900 Inlet/Outlet Invert= 29.75' /27.90' S= 0.01437' Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 0.79 sf Discarded OutFlow Max=0.28 cfs @ 11.23 hrs HW=22.58' (Free Discharge) L1=Exfiltration (Exfiltration Controls 0.28 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=22.50' TW=0.00' (Dynamic Tailwater) t-2=Culvert ( Controls 0.00 cfs) Summary for Link POA: Inflow Area = 0.817 ac, 75.41% Impervious, Inflow Depth = 1.19" for 100 yr event Inflow = 1.14 cfs @ 12.09 hrs, Volume= 0.081 of Primary = 1.14 cfs @ 12.09 hrs, Volume= 0.081 af, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs APPENDIX G OPERATION AND MAINTENANCE PLAN LONG TERM STORMWATER SYSTEM OPERA TION AND MAINTENANCE PLAN Owner: Elm Hospitality, LLC General Contractor: TBD COMPONENT: Parking Lot Sweeping RESPONSIBILITY: During Construction: General Contractor Post Construction: Owner ACTION: Street Sweeping with a High Efficiency Vacuum Sweeper FREQUENCY: During Construction: As needed Post Construction: Semi-annually,with sweeping scheduled in Spring&Fall DESCRIPTION: Driveway and parking areas shall be swept twice per year(with sweeping scheduled in the Spring and Fall)to remove sediments prior to introduction into the stormwater management system. The Owner/Lessee will monitor all areas and remove sediments as necessary, considering both annual necessity and the need for more frequent cleaning during construction. Sweeping shall be performed with a high efficiency vacuum sweeper to remove sediments prior to introduction into the stormwater collection system. Washing and water jetting shall be discouraged. BUDGET: $500/year based on semi-annual sweepings post construction. COMPONENT: Catch basins RESPONSIBILITY: During Construction: General Contractor Post Construction: Owner ACTION: Cleaning(Sediment removal/sump cleaning)and Inspection FREQUENCY: 1. Inspection—Two times per year 2. Cleaning—Once per year or whenever the depth of deposits is greater than or equal to one half the depth from the bottom invert of the lowest pipe in the basin. DESCRIPTION: Basins are to be cleaned on an annual basis or when the depth of deposits is greater than or equal to one half the depth from the bottom of the sump to the invert of the lowest pipe in the basin. The Owner will inspect sumps post construction a minimum of twice per year. Precautions shall take place to maintain the integrity of the oil trapping hoods during cleaning. The hoods shall be inspected and repaired as necessary. Accumulated hydrocarbons shall be collected separately from accumulated sediment. All material shall be disposed of in accordance with DEP regulations. Inspections: o Frame and Grate o Inlet and Outlet condition o Cracks and settlement o Joint failure o Leaking o Sediment Accumulation o Oil/Gas Sheen in water o Condition of trap hood o General inspection of structure BUDGET: Inspection/cleaning- $1,000/yr per catch basin for semi-annual inspections and annual cleaning. COMPONENT: Stormwater Ouality Unit RESPONSIBILITY: During Construction: General Contractor Post Construction: Owner ACTION: Inspection/cleaning FREQUENCY: Per Manufacturer's Maintenance Guidelines or once per six months whichever is more restrictive. DESCRIPTION: See Manufacturer's Maintenance Guidelines. All accumulated materials shall be disposed of in accordance with DEP regulations. COMPONENT: Underground Infiltration Basin RESPONSIBILITY: During Construction: General Contractor Post Construction: Owner ACTION: Preventative Maintenance,Inspection,Cleaning FREQUENCY: During Construction Cleaning—As needed during construction or whenever the sediment depth exceeds a depth of six(6)inches. Inspection—As needed during construction but once at month at a minimum. Post Construction Preventative Maintenance-Two times per year Inspection to ensure proper functioning—After every major storm during the first 3 months of operation and twice a year thereafter and when there are discharges through the high outlet orifice. Inspect and clean pretreatment devices-Every other month is recommended and at least twice a year and after every major storm event. DESCRIPTION: The infiltration basins shall be inspected a minimum of twice a year to ensure they are operating as intended and that all components are stable and in working order. Inspections shall be by qualified personnel assigned by the property owner. The outlet of the basin, if any, shall be inspected for erosion and sedimentation, and rip-rap shall be promptly repaired in the case of erosion. Sediment collecting in the bottom of the basin shall be inspected twice annually, and removal shall commence any time the sediment reaches a depth of six inches anywhere in the pond. Any pond sediments removed shall be disposed of in accordance with the latest DEP guidelines for stormwater sediment disposal. Inspections: o Inlet and Outlet condition o Sediment Accumulation o Oil/Gas Sheen in water o Condition of outlet structure o General Inspection of basin COMPONENT: Bioretention Area RESPONSIBILITY: During Construction: General Contractor Post Construction: Owner ACTION: Preventative Maintenance, Inspection&Mowing FREQUENCY: During Construction 1. Cleaning—As needed during construction or whenever the sediment depth is 6"deep. 2. Inspection—As needed during construction but once a month at a minimum. Post Construction I. Preventative Maintenance-Two times per year 2. Inspection to ensure proper functioning—After every major storm during the first 3 months of operation and twice a year thereafter. 3. Mow the buffer area and side slopes.Remove all grass clippings and accumulated organic matter-Twice yearly during the growing season. 4. Inspect and clean pretreatment devices-After every major storm during the first 3 months of operation and twice a year thereafter. DESCRIPTION: The Infiltration&Bioretention ponds shall be inspected a minimum of two times per year to ensure that they are operating as intended and that all components are stable and in working order.Inspections shall be by qualified personnel. During the growing season,the ponds shall be mowed at least twice,with additional cuttings performed as needed. All tree saplings of any species will be removed from embankments and the pond bottom. The inlet to the pond shall be inspected for erosion and sedimentation, and rip-rap shall be promptly repaired as needed. Sediment collecting in the pond bottom shall be inspected four times annually, and removal shall commence any time the sediment reaches a depth of six inches anywhere in the pond. Any pond sediments removed shall be disposed of in accordance with the latest DEP guidelines for stormwater sediment disposal. Inspections: o Inlet and Outlet condition o Sediment Accumulation o Oil/Gas Sheen in water o General Inspection of basin BUDGET: Inspection& Cleanings- $2500/yr based on semi-annual inspections&cleanings CONSTR UCTIONACTIVITY FORM NOTE: The contractor is responsible for maintaining an accurate and complete log of construction activities, including,but not limited to,commencement of stabilization,major grading activities, timeframes when construction ceases on a portion of site(temporary or permanent)until the Notice of Termination(NOT)is filed. MAJOR STABILIZA TION AND GRADING ACTIVITIES _Construction Activity Contractor Name _Start Date End Date Location f { J I i J j 4 APPENDIX H LONG TERM POLLUTION PREVENTION PLAN Long-Term Pollution Prevention Plan Proposed Hotel Development 80 Elm Street Watertown, Massachusetts 1. Good Housekeeping Practices The Owner/Operator shall use good housekeeping practices by following the Operation and Maintenance plans as provided within this report. 2. Provisions for storing materials and waste products inside or under cover Hazardous materials or wastes associated with typical retail sales or retail building use may be stored at the proposed project. Any such materials or wastes will be stored and handled in accordance with all applicable local, state, and federal regulations. In the event of a significant spill of any hazardous material or waste, emergency contact numbers are listed below. 3. Vehicle washing controls Vehicle washing is not anticipated to occur at this site. In the event vehicles are washed at the site, they shall be washed in an area that will collect the runoff in the storm sewer system and discharge it to a water treatment unit. Direct discharge of wash water to wetlands shall be prohibited. 4. Requirements for routine inspections and maintenance of stormwater BMPs The Owner/Operator shall maintain the BMP's by following the Operation and Maintenance Plan. 5. Spill prevention and response plan There is very limited risk of significant spills at this site. Any spill requiring action would most likely be associated with motor vehicles. In the event of a large spill contact the following: Mass DEP 24 hour Spill Emergency Response Notification line: 888-304-1133. Regulatory Contacts Contact information for reporting oil and hazardous materials releases to the EPA, DEP, and local agencies are provided below. Agency Telephone Fire Department 911 /(617)972-6567 Massachusetts Department Of Environmental Protection 888-304-1133 United States Environmental Protection Agency (617)918-1279 6. Provisions for maintenance of lawns,gardens,and other landscaped areas The use of chemical fertilizers shall be minimized or avoided where possible. 7. Requirements for storage and use of fertilizers,herbicides,and pesticides Fertilizers, herbicides, and pesticides are not likely to be stored at the site, but if they are, such materials will be in closed containers under cover. All necessary precautions will be taken to minimize the potential for these materials to mix with storm runoff. 8. Provisions for solid waste management All solid waste management systems shall be inspected and maintained in accordance with all local, state and federal requirements. APPENDIX I CHECKLIST FOR STORMWATER REPORT LlMassachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report A. Introduction Important:When A Stormwater Report must be submitted with the Notice of Intent permit application to document filling out forms compliance with the Stormwater Management Standards. The following checklist is NOT a substitute for on the computer, 9 use only the tab the Stormwater Report(which should provide more substantive and detailed information) but is offered key to move your here as a tool to help the applicant organize their Stormwater Management documentation for their cursor-do not Report and for the reviewer to assess this information in a consistent format. As noted in the Checklist, use the return the Stormwater Report must contain the engineering computations and supporting information set forth in key. Volume 3 of the Massachusetts Stormwater Handbook. The Stormwater Report must be prepared and certified by a Registered Professional Engineer(RPE) licensed in the Commonwealth The Stormwater Report must include: • The Stormwater Checklist completed and stamped by a Registered Professional Engineer(see page 2) that certifies that the Stormwater Report contains all required submittals.' This Checklist is to be used as the cover for the completed Stormwater Report. • Applicant/Project Name • Project Address • Name of Firm and Registered Professional Engineer that prepared the Report • Long-Term Pollution Prevention Plan required by Standards 4-6 • Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan required by Standard 82 • Operation and Maintenance Plan required by Standard 9 In addition to all plans and supporting information, the Stormwater Report must include a brief narrative describing stormwater management practices, including environmentally sensitive site design and LID techniques, along with a diagram depicting runoff through the proposed 6MP treatment train. Plans are required to show existing and proposed conditions, identify all wetland resource areas, NRCS soil types, critical areas, Land Uses with Higher Potential Pollutant Loads(LUHPPL), and any areas on the site where infiltration rate is greater than 2.4 inches per hour. The Plans shall identify the drainage areas for both existing and proposed conditions at a scale that enables verification of supporting calculations. As noted in the Checklist, the Stormwater Management Report shall document compliance with each of the Stormwater Management Standards as provided in the Massachusetts Stormwater Handbook. The soils evaluation and calculations shall be done using the methodologies set forth in Volume 3 of the Massachusetts Stormwater Handbook. To ensure that the Stormwater Report is complete, applicants are required to fill in the Stormwater Report Checklist by checking the box to indicate that the specified information has been included in the Stormwater Report. If any of the information specified in the checklist has not been submitted, the applicant must provide an explanation. The completed Stormwater Report Checklist and Certification must be submitted with the Stormwater Report. 'The Stormwater Report may also include the Illicit Discharge Compliance Statement required by Standard 10. If not included in the Stormwater Report,the Illicit Discharge Compliance Statement must be submitted prior to the discharge of stormwater runoff to the post-construction best management practices. 2 For some complex projects,it may not be possible to include the Construction Period Erosion and Sedimentation Control Plan in the Stormwater Report. In that event,the issuing authority has the discretion to issue an Order of Conditions that approves the project and includes a condition requiring the proponent to submit the Construction Period Erosion and Sedimentation Control Plan before commencing any land disturbance activity on the site. Stormwater Report Checklist.doc•04/01/08 Stormwater Report Checklist•Page 1 of 8 LlMassachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report B. Stormwater Checklist and Certification The following checklist is intended to serve as a guide for applicants as to the elements that ordinarily need to be addressed in a complete Stormwater Report. The checklist is also intended to provide conservation commissions and other reviewing authorities with a summary of the components necessary for a comprehensive Stormwater Report that addresses the ten Stormwater Standards. Note: Because stormwater requirements vary from project to project, it is possible that a complete Stormwater Report may not include information on some of the subjects specified in the Checklist. If it is determined that a specific item does not apply to the project under review, please note that the item is not applicable (N.A.) and provide the reasons for that determination. A complete checklist must include the Certification set forth below signed by the Registered Professional Engineer who prepared the Stormwater Report. Registered Professional Engineer's Certification I have reviewed the Stormwater Report, including the soil evaluation, computations, Long-term Pollution Prevention Plan, the Construction Period Erosion and Sedimentation Control Plan (if included), the Long- term Post-Construction Operation and Maintenance Plan, the Illicit Discharge Compliance Statement(if included) and the plans showing the stormwater management system, and have determined that they have been prepared in accordance with the requirements of the Stormwater Management Standards as further elaborated by the Massachusetts Stormwater Handbook. I have also determined that the information presented in the Stormwater Checklist is accurate and that the information presented in the Stormwater Report accurately reflects conditions at the site as of the date of this permit application. Registered Professional Engineer Block and Signature -,K OF V.ATTH V D. smi l U avl�. No.45496 ,4 ONAL Signature and Date Checklist Project Type: Is the application for new development, redevelopment, or a mix of new and redevelopment? ® New development ❑ Redevelopment ❑ Mix of New Development and Redevelopment Stormwater Report Checklist.doc•04/01/08 Stormwater Report Checklist•Page 2 of 8 LlMassachusetts Department of Environmental Protection Bureau of Resource Protection -Wetlands Program Checklist for Stormwater Report Checklist (continued) LID Measures: Stormwater Standards require LID measures to be considered. Document what environmentally sensitive design and LID Techniques were considered during the planning and design of the project: ® No disturbance to any Wetland Resource Areas ❑ Site Design Practices (e.g. clustered development, reduced frontage setbacks) ❑ Reduced Impervious Area (Redevelopment Only) ❑ Minimizing disturbance to existing trees and shrubs ❑ LID Site Design Credit Requested: ❑ Credit 1 ❑ Credit 2 ❑ Credit 3 ❑ Use of"country drainage" versus curb and gutter conveyance and pipe ® Bioretention Cells (includes Rain Gardens) ❑ Constructed Stormwater Wetlands (includes Gravel Wetlands designs) ❑ Treebox Filter ❑ Water Quality Swale ❑ Grass Channel ❑ Green Roof ® Other(describe): Stormwater Infiltration Standard 1: No New Untreated Discharges ® No new untreated discharges ❑ Outlets have been designed so there is no erosion or scour to wetlands and waters of the Commonwealth ❑ Supporting calculations specified in Volume 3 of the Massachusetts Stormwater Handbook included. Stormwater Report Checklist.doc•04/01/08 Stormwater Report Checklist•Page 3 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report Checklist (continued) Standard 2: Peak Rate Attenuation ❑ Standard 2 waiver requested because the project is located in land subject to coastal storm flowage and stormwater discharge is to a wetland subject to coastal flooding. ❑ Evaluation provided to determine whether off-site flooding increases during the 100-year 24-hour storm. ® Calculations provided to show that post-development peak discharge rates do not exceed pre- development rates for the 2-year and 10-year 24-hour storms. If evaluation shows that off-site flooding increases during the 100-year 24-hour storm, calculations are also provided to show that post-development peak discharge rates do not exceed pre-development rates for the 100-year 24- hour storm. Standard 3: Recharge ® Soil Analysis provided. ® Required Recharge Volume calculation provided. ❑ Required Recharge volume reduced through use of the LID site Design Credits. ® Sizing the infiltration, BMPs is based on the following method: Check the method used. ® Static ❑ Simple Dynamic ❑ Dynamic Field' ❑ Runoff from all impervious areas at the site discharging to the infiltration BMP. ® Runoff from all impervious areas at the site is not discharging to the infiltration BMP and calculations are provided showing that the drainage area contributing runoff to the infiltration BMPs is sufficient to generate the required recharge volume. ® Recharge BMPs have been sized to infiltrate the Required Recharge Volume. ❑ Recharge BMPs have been sized to infiltrate the Required Recharge Volume only to the maximum extent practicable for the following reason: ❑ Site is comprised solely of C and D soils and/or bedrock at the land surface ❑ M.G.L. c. 21 E sites pursuant to 310 CMR 40.0000 ❑ Solid Waste Landfill pursuant to 310 CMR 19.000 ❑ Project is otherwise subject to Stormwater Management Standards only to the maximum extent practicable. ® Calculations showing that the infiltration BMPs will drain in 72 hours are provided. ❑ Property includes a M.G.L. c. 21 E site or a solid waste landfill and a mounding analysis is included. 80%TSS removal is required prior to discharge to infiltration BMP if Dynamic Field method is used. Stormwater Report Checklist.doc•04/01/08 Stormwater Report Checklist•Page 4 of 8 Massachusetts Department of Environmental Protection f' Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report Checklist (continued) Standard 3: Recharge (continued) ❑ The infiltration BMP is used to attenuate peak flows during storms greater than or equal to the 10- year 24-hour storm and separation to seasonal high groundwater is less than 4 feet and a mounding analysis is provided. ❑ Documentation is provided showing that infiltration BMPs do not adversely impact nearby wetland resource areas. Standard 4: Water Quality The Long-Term Pollution Prevention Plan typically includes the following: • Good housekeeping practices; • Provisions for storing materials and waste products inside or under cover; • Vehicle washing controls; • Requirements for routine inspections and maintenance of stormwater BMPs; • Spill prevention and response plans; • Provisions for maintenance of lawns, gardens, and other landscaped areas; • Requirements for storage and use of fertilizers, herbicides, and pesticides; • Pet waste management provisions; • Provisions for operation and management of septic systems; • Provisions for solid waste management; • Snow disposal and plowing plans relative to Wetland Resource Areas; • Winter Road Salt and/or Sand Use and Storage restrictions; • Street sweeping schedules; • Provisions for prevention of illicit discharges to the stormwater management system; • Documentation that Stormwater BMPs are designed to provide for shutdown and containment in the event of a spill or discharges to or near critical areas or from LUHPPL; • Training for staff or personnel involved with implementing Long-Term Pollution Prevention Plan; • List of Emergency contacts for implementing Long-Term Pollution Prevention Plan. ® A Long-Term Pollution Prevention Plan is attached to Stormwater Report and is included as an attachment to the Wetlands Notice of Intent. ® Treatment BMPs subject to the 44% TSS removal pretreatment requirement and the one inch rule for calculating the water quality volume are included, and discharge: ❑ is within the Zone II or Interim Wellhead Protection Area ❑ is near or to other critical areas ® is within soils with a rapid infiltration rate (greater than 2.4 inches per hour) ❑ involves runoff from land uses with higher potential pollutant loads. ❑ The Required Water Quality Volume is reduced through use of the LID site Design Credits. ® Calculations documenting that the treatment train meets the 80% TSS removal requirement and, if applicable, the 44% TSS removal pretreatment requirement, are provided. Stormwater Report Checklist.doc•04/01/08 Stormwater Report Checklist•Page 5 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program t Checklist for Stormwater Report Checklist (continued) Standard 4: Water Quality (continued) ® The BMP is sized (and calculations provided) based on: ® The '/z' or 1"Water Quality Volume or ® The equivalent flow rate associated with the Water Quality Volume and documentation is provided showing that the BMP treats the required water quality volume. ® The applicant proposes to use proprietary BMPs, and documentation supporting use of proprietary BMP and proposed TSS removal rate is provided. This documentation may be in the form of the propriety BMP checklist found in Volume 2, Chapter 4 of the Massachusetts Stormwater Handbook and submitting copies of the TARP Report, STEP Report, and/or other third party studies verifying performance of the proprietary BMPs. ❑ A TMDL exists that indicates a need to reduce pollutants other than TSS and documentation showing that the BMPs selected are consistent with the TMDL is provided. Standard 5: Land Uses With Higher Potential Pollutant Loads (LUHPPLs) ❑ The NPDES Multi-Sector General Permit covers the land use and the Stormwater Pollution Prevention Plan (SWPPP) has been included with the Stormwater Report. ❑ The NPDES Multi-Sector General Permit covers the land use and the SWPPP will be submitted prior to the discharge of stormwater to the post-construction stormwater BMPs. ® The NPDES Multi-Sector General Permit does not cover the land use. ❑ LUHPPLs are located at the site and industry specific source control and pollution prevention measures have been proposed to reduce or eliminate the exposure of LUHPPLs to rain, snow, snow melt and runoff, and been included in the long term Pollution Prevention Plan. ❑ All exposure has been eliminated. ❑ All exposure has not been eliminated and all BMPs selected are on MassDEP LUHPPL list. ❑ The LUHPPL has the potential to generate runoff with moderate to higher concentrations of oil and grease (e.g. all parking lots with >1000 vehicle trips per day) and the treatment train includes an oil grit separator, a filtering bioretention area, a sand filter or equivalent. Standard 6: Critical Areas ❑ The discharge is near or to a critical area and the treatment train includes only BMPs that MassDEP has approved for stormwater discharges to or near that particular class of critical area. ❑ Critical areas and BMPs are identified in the Stormwater Report. Stormwater Report Checklist.doc•04/01/08 Stormwater Report Checklist•Page 6 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report Checklist (continued) Standard 7: Redevelopments and Other Projects Subject to the Standards only to the maximum extent practicable ❑ The project is subject to the Stormwater Management Standards only to the maximum Extent Practicable as a: ❑ Limited Project ❑ Small Residential Projects: 5-9 single family houses or 5-9 units in a multi-family development provided there is no discharge that may potentially affect a critical area. ❑ Small Residential Projects: 2-4 single family houses or 2-4 units in a multi-family development with a discharge to a critical area ❑ Marina and/or boatyard provided the hull painting, service and maintenance areas are protected from exposure to rain, snow, snow melt and runoff ❑ Bike Path and/or Foot Path ❑ Redevelopment Project ❑ Redevelopment portion of mix of new and redevelopment. ❑ Certain standards are not fully met(Standard No. 1, 8, 9, and 10 must always be fully met) and an explanation of why these standards are not met is contained in the Stormwater Report. ❑ The project involves redevelopment and a description of all measures that have been taken to improve existing conditions is provided in the Stormwater Report. The redevelopment checklist found in Volume 2 Chapter 3 of the Massachusetts Stormwater Handbook may be used to document that the proposed stormwater management system (a) complies with Standards 2, 3 and the pretreatment and structural BMP requirements of Standards 4-6 to the maximum extent practicable and (b) improves existing conditions. Standard 8: Construction Period Pollution Prevention and Erosion and Sedimentation Control A Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan must include the following information: • Narrative; • Construction Period Operation and Maintenance Plan; • Names of Persons or Entity Responsible for Plan Compliance; • Construction Period Pollution Prevention Measures; • Erosion and Sedimentation Control Plan Drawings; • Detail drawings and specifications for erosion control BMPs, including sizing calculations; • Vegetation Planning; • Site Development Plan; • Construction Sequencing Plan; • Sequencing of Erosion and Sedimentation Controls; • Operation and Maintenance of Erosion and Sedimentation Controls; • Inspection Schedule; • Maintenance Schedule; • Inspection and Maintenance Log Form. ❑ A Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan containing the information set forth above has been included in the Stormwater Report. Stormwater Report Checklist.doc•04/01/08 Stormwater Report Checklist•Page 7 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection -Wetlands Program Checklist for Stormwater Report Checklist (continued) Standard 8: Construction Period Pollution Prevention and Erosion and Sedimentation Control (continued) ❑ The project is highly complex and information is included in the Stormwater Report that explains why it is not possible to submit the Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan with the application. A Construction Period Pollution Prevention and Erosion and Sedimentation Control has not been included in the Stormwater Report but will be submitted before land disturbance begins. ® The project is not covered by a NPDES Construction General Permit. ❑ The project is covered by a NPDES Construction General Permit and a copy of the SWPPP is in the Stormwater Report. ❑ The project is covered by a NPDES Construction General Permit but no SWPPP been submitted. The SWPPP will be submitted BEFORE land disturbance begins. Standard 9: Operation and Maintenance Plan ® The Post Construction Operation and Maintenance Plan is included in the Stormwater Report and includes the following information: ® Name of the stormwater management system owners; ® Party responsible for operation and maintenance; ® Schedule for implementation of routine and non-routine maintenance tasks; ❑ Plan showing the location of all stormwater BMPs maintenance access areas; ❑ Description and delineation of public safety features; ® Estimated operation and maintenance budget; and ® Operation and Maintenance Log Form. ❑ The responsible party is not the owner of the parcel where the BMP is located and the Stormwater Report includes the following submissions: ❑ A copy of the legal instrument(deed, homeowner's association, utility trust or other legal entity) that establishes the terms of and legal responsibility for the operation and maintenance of the project site stormwater BMPs; ❑ A plan and easement deed that allows site access for the legal entity to operate and maintain BMP functions. Standard 10: Prohibition of Illicit Discharges ® The Long-Term Pollution Prevention Plan includes measures to prevent illicit discharges; ❑ An Illicit Discharge Compliance Statement is attached; ❑ NO Illicit Discharge Compliance Statement is attached but will be submitted prior to the discharge of any stormwater to post-construction BMPs. Stormwater Report Checklist.doc•04/01/08 Stormwater Report Checklist•Page 8 of 8