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Stormwater Report_2016-05-23 - Complete - Stamped - Reduced.pdfilk' 11441 inagEl Proposed Residential Development 87 Bridge Street & 5 Pomeroy Terrace Northampton, Massachusetts Applicant/Owner.. OF U4, Winterberry, LLC , 3 - c/o Matthew Campagnari 128 Federal Street 837( Springfield, Massachusetts 01105 5 ,r I LA Project File: 150620 May 23,2016 1 Proposed Residential Development Stormwater Drainage Report 87 Bridge Street & 5 Pomeroy Terrace Northampton, Massachusetts TABLE OF CONTENTS SECTION PAGE NO. 1. INTRODUCTION...................................................................................................... 1-1 2. SITE DESCRIPTION.................................................................................................... 2-1 2.1 Predevelopment Conditions............................................................................ 2-1 2.2 Resource Areas.............................................................................................. 2-1 2.2.1 Floodplain..................................................................................................... 2-1 2.2.2 Natural Heritage and Endangered Species Program ........................................ 2-2 2.3 Soils...............................................................................................................2-2 2.4 Post Development Conditions......................................................................... 2-2 3. STORMWATER MANAGEMENT SYSTEM...................................................................... 3-1 3.1 Drainage Calculations.................................................................................... 3-1 3.1 .1 Design Points................................................................................................. 3-2 3.1.2 Pre -Development Hydrology........................................................................... 3-2 3.1.3 Post -Development Hydrology.......................................................................... 3-2 3.1.4 Peak Discharge Rates..................................................................................... 3-2 3.2 Hydraulic Analysis.......................................................................................... 3-3 3.3 MassDEP Stormwater Management Standards ................................................. 3-3 3.4 Stormwater Best Management Practices.......................................................... 3-6 3.4.1 Bio -Retention Areas........................................................................................ 3-6 3.4.2 Proprietary Sedimentation Devices.................................................................. 3-6 3.4.3 Subsurface Infiltration Basin............................................................................ 3-7 3.5 Protection of Stormwater Best Management Practices during Construction........ 3-7 3.6 Inspection and Maintenance of Stormwater Best Management Practices ........... 3-7 3.7 Illicit Discharge Compliance Statement........................................................... 3-7 3.8 Low -Impact Development Alternatives Analysis Narrative ................................. 3-8 3.9 Northampton DPW Inspection Schedule Checklist ............................................ 3-8 4. CONCLUSION......................................................................................................... 4-1 List of Tables Table Page No. Table 2.4: Hydrologic Soil Group Classification................................................................... 2-2 Table 3.1: Design Rainfall Data........................................................................................... 3-1 Table 3.1.4 Pre- and Post -Development Peak Discharge Rates ............................................. 3-3 R Levesque Associates, Inc. Page 1 Proposed RESIdEntlal DEVEIOpmEnt 87 Bridge Street & S Pomeroy Terrace Figure Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 List of Figures Site Locus - USGS Map FEMA Flood Map NHESP Map Pre -Development Watershed Plan Post -Development Watershed Plan Appendices Stormwater Drainage Report Northampton, Massachusetts APPENDIX A: CHECKLIST FOR STORMWATER REPORT APPENDIX B: SOILS INFORMATION APPENDIX C: PRE- AND POST- DEVELOPMENT HYDROLOGIC ANALYSIS (2, 10, & 100 YEAR STORM EVENTS) APPENDIX D: MASSDEP CALCULATIONS APPENDIX E: CONSTRUCTION PERIOD EROSION CONTROL PLAN APPENDIX F: LONG-TERM OPERATION AND MAINTENANCE PLAN APPENDIX G: ILLICIT DISCHARGE COMPLIANCE STATEMENT APPENDIX H: LOW IMPACT DEVELOPMENT CONSIDERATIONS APPENDIX I: NORTHAMPTON DPW INSPECTION SCHEDULE R Levesque Associates, Inc. Page ii Proposed Residential Development Stormwater Drainage Report 87 Bridge Street & 5 Pomeroy Terrace I. INTRODUCTION Northampton, Massachusetts The applicant, Winterberry, LLC, is proposing to redevelop two adjacent parcels located at the corner of Bridge Street (Route 9) and Pomeroy Terrace in Northampton, Massachusetts. The parcels have been historically developed and are the locations of a dilapidated motel building with frontage on Bridge Street and two multi -unit apartment buildings with frontage on Pomeroy Terrace. Both parcels have been developed with the existing buildings and associated site improvements including a shared paved parking area, lawn areas, and landscaped areas. As part of the proposed project, the applicant will demolish the existing motel building as well as one of the existing multi -unit buildings. The applicant will renovate the existing multi -unit (6 -unit) building located at the corner of Bridge Street and Pomeroy Terrace. The applicant is proposing to construct three (3) new residential duplex buildings. Additionally, the project will demolish and reconfigure the existing access drives, driveways, and parking areas with associated site improvements. The site is located in close proximity to downtown and due to its urban setting has been mostly developed and cleared of natural vegetation. The existing stormwater best management practices on-site are limited to a single catch basin within the paved parking area. The following is a summary of the proposed site improvements: 1. Construction of three new residential duplex buildings: two buildings with frontage on Bridge Street and one building at approximately the location of the razed building with frontage on Pomeroy Terrace; 2. Associated site improvements including a parking lot, access drives, and common landscaped areas; 3. A stormwater management system to provide water quality treatment and attenuate peak discharge rates from the proposed development; The proposed project will qualify as a redevelopment project due to the overall reduction of impervious area located on the property. Furthermore, the inclusion of Low -Impact -Development Best Management Practices such as bio -retention areas, pervious pavers, and a subsurface infiltration basin will help mitigate the impacts of the proposed development. This report has been prepared to document the compliance of the proposed stormwater management system. The stormwater system has been designed to meet the standards set forth in the City of Northampton Stormwater Management Ordinance as well as the Massachusetts Department of Environmental Protection Stormwater Management Handbook. Due to the eligibility of the project to qualify as a redevelopment, the proposed stormwater management system is subject to the MassDEP Stormwater Handbook "to the maximum extent practicable" R Levesque Associates, Inc. Page 1-1 Proposed RESIdEntial Development StormwatEr DrainagE Report 87 BridgE StrEEt & 5 Pomeroy TErracE Northampton, MassachusEtts 2. SITE DESCRIPTION 2.1 Predevelopment Conditions The properties to be developed are located at 87 Bridge Street and 5 Pomeroy Terrace in an Urban Residence C (URC) zone and are listed as parcels 32A-185-001 and 32A-186-001 in the Northampton Assessor's Office. Figure 1 — USGS Map illustrates the location of the project. The properties are proposed to be combined and for the purposes of this report, the property will be referenced as a single parcel unless otherwise stated. The properties are bounded to the north by Bridge Street, to the south by a residential property, to the east by Pomeroy Terrace, and to the west by residential properties. The combined parcel area is approximately 0.71 acres in size. The properties have been historically developed and are mostly cleared of natural vegetation. There are four existing structures between the two parcels: • A dilapidated motel building with a detached garage accessory building, both to be razed, located at 87 Bridge Street; • Two multi -unit residential buildings, both located at 5 Pomeroy Terrace. The larger of the two buildings, the one with 6 -units located at the corner of Bridge Street and Pomeroy Terrace is to be rehabilitated while the other building is to be razed. There is an existing paved area located behind the buildings that served as a parking lot for both the motel building at 87 Bridge Street and the residential units located at 5 Pomeroy Terrace. The general parcel topography is relatively flat with approximately elevation 139 along the frontages with Bridge Street, Pomeroy Terrace, and along the southern property line. The grade rises slightly to approximately elevation 140 along the western property line. There is an existing catch basin on the property which is located at a low point within the paved parking area. The structure is to be demolished and removed as part of the proposed site improvements. 2.2 Resource Areas A majority of the parcel where the site improvements are proposed has been historically developed and cleared. There were no bordering or isolated vegetation wetland areas delineated on or adjacent to the parcel. 2.2.1 Floodplain R. Levesque & Associates, Inc. performed due diligence research on the property in regards to FEMA flood zone mapping. As demonstrated by the most recent FEMA Flood Insurance Rate Maps, the property is not located within any flood hazard areas, see Figure 2 — FEMA FIRM Map. R Levesque AssociatEs, Inc. Page 2-1 Proposed Residential Development Stormwater Drainage Report 87 Bridge Street & 5 Pomeroy Terrace Northampton, Massachusetts 2.2.2 Natural Heritage and Endangered Species Program R. Levesque Associates, Inc. performed due diligence research on the property in regards to Natural Heritage and Endangered Species Program (NHESP) areas. The property is not located within any areas delineated by NHESP as estimated or priority habitats of endangered species, see Figure 3 — NHESP Map. 2.3 Soils R. Levesque & Associates, Inc. researched the soils located on site with information readily available by the United States Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS). Based on a review of the USDA Soil Survey of Hampden County, Massachusetts, Central Part, the site is comprised of the following soil types: Table 2.4: Hydrologic Soil Group Classification Soil Description Map Unit Symbol Hydrologic Soil Group Amostown-Windsor Silty Substratum — Urban Land 741 A B Complex A series of test pits were conducted by Gary Weiner, P.E. SE# 2567 to evaluate the ability of the site to support the proposed stormwater drainage system components. A total of five test holes were dug in that vicinity with none showing evidence of estimate seasonal high groundwater, see Appendix B for additional soils information. In general, the soil evaluations corroborated the NRCS mapping of the area. 2.4 Post Development Conditions The applicant is proposing to demolish the existing dilapidated motel building located at 87 Bridge Street, the duplex apartment building of 5 Pomeroy Terrace, and all accessory buildings and associated site improvements. The applicant is proposing to construct three new residential duplex buildings as well as rehabilitate the existing multi -unit (6 -unit) residential apartment building located at 5 Pomeroy Terrace at the corner with Bridge Street. As part of the project, all of the existing paved areas will be demolished and a new parking and driveway configuration will be constructed. The proposed site improvements include the construction of a new stormwater management system on site which will incorporate low -impact development best management practices such as bio -retention areas, pervious paver parking areas, and a subsurface infiltration system. Water, gas, electric, and sanitary sewer services for the new duplex buildings will be R Levesque Associates, Inc. Page 2-2 Proposed Residential Development Stormwater Drainage Report 87 Bridge Street & 5 Pomeroy Terrace Northampton, Massachusetts brought on site via Pomeroy Terrace and the services for the existing multi -unit building will be maintained. The proposed stormwater management system will collect and convey runoff from the proposed site improvements via an underdrain and overflow system within the bio -retention areas to the proposed subsurface infiltration system. Subsurface manifolds will be installed to capture the roof runoff from the buildings and convey the runoff to the subsurface infiltration system. The subsurface infiltration system will provide groundwater recharge, peak rate attenuation, and water quality treatment for storm events up to and including the 100 -year storm event. There are no proposed stormwater infrastructure connections to the city drainage system. Should the existing catch basin with the parking area be connected to the drainage infrastructure on Pomeroy Terrace, the connection shall be capped and abandoned at the property line. Additionally, the site grading has been designed such that should an extreme storm event occur beyond the 100 - year storm event, water will surcharge into the parking lot and be conveyed off site via the proposed entrance on Pomeroy Terrace. Overall, the proposed site improvements will maintain the general drainage patterns of the site. R Levesque Associates, Inc. Page 2-3 Proposed Residential Development Stormwater Drainage Report 87 Bridge Street & 5 Pomeroy Terrace Northampton, Massachusetts 3. STORMWATER MANAGEMENT SYSTEM R. Levesque & Associates, Inc. has prepared the following drainage system calculations for the proposed project site. These calculations were performed to document compliance with the guidelines set forth by the City of Northampton Stormwater Management Permit requirements and the Massachusetts Department of Environmental Protection Stormwater Management Handbook (MassDEP Handbook). A detailed hydrologic analysis of the system was completed in order to evaluate the performance of the stormwater management system components, see Appendix C — Pre- and Post -Development Hydrologic Analysis. The proposed stormwater management system will collect runoff from on-site impervious areas and utilize stormwater best management practices to provide water quality treatment, groundwater recharge, and peak discharge rate attenuation. 3.1 Drainage Calculations R. Levesque & Associates, Inc. utilized the HydroCAD software program, Version 10.0, developed by HydroCAD Software Solutions LLC, in order to create and analyze the site hydrology. The HydroCAD software is based upon the Soil Conservation Service (SCS) "Technical Release 20 — Urban Hydrology for Small Watersheds" and "Technical Release 55 — Urban Hydrology for small Watersheds" which are generally accepted industry standard methodologies. The analysis was conducted in order to establish the peak discharge rates and estimated run-off volume from the project site. This was accomplished to properly evaluate pre- and post -development conditions during various storm events. Contributing drainage areas were identified and soils, surface cover, watershed slope, and flow paths were evaluated to develop the necessary HydroCAD model input parameters. A minimum Time of Concentration (Tc) of (6) minutes was used in the calculations. Drainage calculations were performed for the Pre and Post -Development conditions for the 24- hour, 2, 10, and 100 -year Type III storm events. The total rainfall for each of the storm events was based upon data provided by the United States Department of Commerce Technical Paper No. 40 — Rainfall Frequency Atlas of the United States. The total rainfall values used in the hydrologic modeling for each event are shown in the following table: Table 3.1: Design Rainfall Data 2 -year, 24-hour storm 10 -year, 24-hour storm 100 -year, 24-hour storm 3.00 inches 4.50 inches 6.40 inches R Levesque Associates, Inc. Page 3-1 Proposed Residential DEVEIOpmEnt 87 Bridge Street & S Pomeroy Terrace 3.1.1 Design Points Stormwater Drainage Report Northampton, Massachusetts In order to compare the difference between pre and post -development peak flows, existing and proposed watersheds were delineated. A single Design Points (DP) was established with flow paths representing the longest time of concentration of run-off in each tributary watershed. For this analysis, the design point was determined as follows: • DP -1 : City Drainage Infrastructure; This design point represents the runoff from the project area which flows offsite towards the city drainage infrastructure; 3.1.2 Pre -Development Hydrology The project area under existing conditions was analyzed as a single (1) sub -catchment discharging to the design points as described above. It has been assumed that the existing catch basin within the parking area behind the building connects to the drainage infrastructure on Pomeroy Terrace. The catch basin had high levels of accumulated sediment which may have been blocking the outlet invert pipe. Furthermore, in support of this assumption, there is a pipe in a drain manhole in Pomeroy Terrace that generally points towards the existing catch basin within the paved area behind the buildings. In any case, whether runoff from the site is conveyed overland by sheet runoff or through underground infrastructure, all runoff makes it to the city drainage infrastructure. The sub -catchment was delineated based on the existing developed areas and the existing topography of the parcel and surrounding areas. The existing watershed areas are shown on the attached Figure 4 entitled "Pre -Development Watershed Plan". Peak discharge rates for the design point are depicted in Table 3.1.4 below. 3.1.3 Post -Development Hydrology The project area under proposed conditions was broken down into five (5) sub -catchments discharging to the same design point as the existing conditions. The proposed stormwater management system will collect most of the runoff produced on site, however, due to challenges with grading areas such as the front yards of the residential buildings, a small portion of the property will still be conveyed to the city drainage infrastructure however the peak discharge rate has been drastically reduced. The proposed watershed areas are shown on the attached Figure 5 entitled "Post -Development Watershed Plan". Peak discharge rates for the design point are depicted in Table 3.1.4 below. 3.1.4 Peak Discharge Rates The table below summarizes the Pre and Post -Development peak discharge rates for each Design Point: R Levesque Associates, Inc. Page 3-2 Proposed Residential Development Stormwater Drainage Report 87 Bridge Street & 5 Pomeroy Terrace Northampton, Massachusetts Table 3.1.4 Pre- and Post -Development Peak Discharge Rates 2 -year storm (cfs) 10 -year storm (cfs) 100 -year storm (cfs) Pre- Post- Pre- Post- Pre- Post - Design Point 1 1.35 0.26 2.48 0.56 3.84 0.95 As depicted in the table, the post -development peak discharge rates do not increase over pre - development peak discharge rates for each of the storm events presented. This is accomplished by provided onsite attenuation through the proposed bio -retention areas and subsurface infiltration basin. 3.2 Hydraulic Analysis As part of the stormwater management system design, a hydraulic analysis was performed on the proposed underground infrastructure and is included in the HydroCAD model. The stormwater management system was analyzed to evaluate the performance of the proposed stormwater piping. The proposed stormwater infrastructure has been sized to convey storm events up to and including the 24-hour, 100 -year storm event. Please refer to Appendix C for the HydroCAD analysis of the proposed stormwater management system. 3.3 MassDEP Stormwater Management Standards R. Levesque & Associates, Inc. has designed the proposed stormwater management system to be in compliance with the MassDEP Stormwater Management Standards. Chapter 1, Volume 3 of the MassDEP Handbook outlines specific calculations, and other information, that must be submitted with each report to document compliance. The following summary highlights elements of the proposed project and how they apply to each standard. • Standard 01 - No new stormwater conveyances (e.g., outfalls) may discharge untreated stormwater directly to or cause erosion in wetlands or waters of the Commonwealth. The proposed project does not introduce any new outfalls and provides best management practices designed to the guidelines of the MassDEP Handbook. Therefore, no new untreated stormwater is discharged. • Standard #2 — Stormwater management systems shall be designed so that post - development peak discharge rates do not exceed pre -development peak discharge rates. This Standard may be waived for discharges to land subject to coastal storm flowage as defined in 310 CMR 10.04. R Levesque Associates, Inc. Page 3-3 Proposed Residential Development Stormwater Drainage Report 87 Bridge Street & 5 Pomeroy Terrace Northampton, Massachusetts The proposed stormwater management system has been designed such that the post - development peak discharge rates are less than the pre -development discharge rates for the 2 -year, 10 -year, and 100 -year 24-hour storms. See Appendix C for the Hydrologic Analysis. • Standard #3 - Loss of annual recharge to groundwater shall be eliminated or minimized through the use of environmentally sensitive site design, low impact development techniques, stormwater BMPs, and good operation and maintenance. At a minimum, the annual recharge from the post -development site shall approximate the annual recharge from pre -development conditions based on soil type. This Standard is met when the stormwater management system is designed to infiltrate the required volume as determined in accordance with the Massachusetts Stormwater Handbook. The proposed subsurface infiltration basin has been designed with the capacity to infiltrate the required recharge volume for the tributary impervious areas. See Appendix D for the Required Recharge Volume Calculations. • Standard 04 - Stormwater management systems shall be designed to remove 80% of the average annual post -construction load of TSS It is presumed that this standard is met when: a. Suitable practices for source control and pollution prevention are identified in a long term pollution prevention plan, and thereafter are implemented and maintained; b. Structural stormwater BMPs practices are sized to capture the required water quality volume determined in accordance with the Massachusetts Stormwater Handbook; and c. Pretreatment is provided in accordance with the Massachusetts Stormwater Handbook The stormwater management system has been designed to provide the required total suspended solids pre-treatment prior to discharge to the subsurface infiltration basin. The following describes the treatment train for the system: • Subsurface Infiltration Basin #1: The treatment train for the subsurface infiltration basin includes filtration through the bio -retention areas and a proprietary sedimentation device to meet the water quality standards. The proposed proprietary treatment device has been sized to treat the water quality flow rate from the respective tributary areas. See Appendix D for the Water Quality Volume Calculations. • Standard #5 - For land uses with higher potential pollutant loads, source control and pollution prevention shall be implemented in accordance with the Massachusetts Stormwater Handbook to eliminate or reduce the discharge of stormwater runoff from such land uses to the maximum extent practicable. if through source control and/or pollution prevention all R Levesque Associates, Inc. Page 3-4 Proposed Residential Development 87 Bridge Street & 5 Pomeroy Terrace Stormwater Drainage Report Northampton, Massachusetts land uses with higher potential pollutant loads cannot be completely protected from exposure to rain, snow, snow melt, and stormwater runoff, the proponent shall use the specific structural stormwater BMPs determined by MassDEP to be suitable for such uses as provided in the Massachusetts Stormwater Handbook. Stormwater discharges from land uses with higher potential pollutant loads shall also comply with the requirements of the Massachusetts Clean Waters Act, M.G. L. c. 21, §§ 26-53 and the regulations promulgated thereunder at 314 CMR 3.00, 314 CMR 4.00 and 314 CMR 5.00. This standard is not applicable. • Standard 06 - Stormwater discharges within the Zone 11 or Interim Wellhead Protection Area of a public water supply, and stormwater discharges near or to any other critical area, require the use of the specific source control and pollution prevention measures and the specific structural stormwater BMPs determined by MassDEP to be suitable for managing discharges to such areas, as provided in the Massachusetts Stormwater Handbook. A discharge is near a critical area if there is a strong likelihood of a significant impact occurring to said area, taking into account site-specific factors. Stormwater discharges to Outstanding Resource Waters and Special Resource Waters shall be removed and set back from the receiving water or wetland and receive the highest and best practical method of treatment. A "storm water discharge" as defined in 314 CMR 3.04(2)(a)1 or (b) to an Outstanding Resource Water or Special Resource Water shall comply with 314 CMR 3.00 and 314 CMR 4.00. Stormwater discharges to a Zone l or Zone A are prohibited unless essential to the operation of a public water supply. This standard is not applicable. • Standard #7 - A redevelopment project is required to meet the following Stormwater Management Standards only to the maximum extent practicable: Standard 2, Standard 3, and the pretreatment and structural BMPs requirements of Standards 4, 5, and 6. Existing stormwater discharges shall comply with Standard 1 only to the maximum extent practicable. A redevelopment project shall also comply with all other requirements of the Stormwater Management Standards and improve existing conditions. The project is considered a redevelopment due to the site being historically developed and the proposed site improvements reducing the overall impervious area. Under existing conditions, runoff is captured via a single catch basin in the paved parking area behind the buildings and is assumed to be conveyed to the city drainage infrastructure in Pomeroy Terrace. The proposed stormwater management system will disconnect from the city drainage infrastructure, provide water quality treatment, groundwater recharge, and peak rate attenuation which currently do not exist. Overall, the proposed stormwater management system will improve the existing conditions. R Levesque Associates, Inc. Page 3-5 Proposed Residential Development Stormwater Drainage Report 87 Bridge Street & 5 Pomeroy Terrace Northampton, Massachusetts • Standard #8 — A plan to control construction -related impacts including erosion, sedimentation and other pollutant sources during construction and land disturbance activities (construction period erosion, sedimentation, and pollution prevention) shall be developed and implemented. A Construction Period Erosion Control Plan has been provided in Appendix E. • Standard #9 — A long-term operation and maintenance plan shall be developed and implemented to ensure that stormwater management systems function as designed. A Long-term Operation & Maintenance Plan has been provided in Appendix F. • Standard #70 -All illicit discharges to the stormwater management system are prohibited An illicit discharge statement will be provided prior to discharge of stormwater to post - construction BMPs. See Appendix G for a copy of the Illicit Discharge Statement. 3.4 Stormwater Best Management Practices The proposed stormwater management system was designed utilizing stormwater best management practices (BMP) as set forth by the MassDEP Handbook. The BMPs utilized as part of the stormwater management system include deep -sump hooded catch basins, underground infrastructure, proprietary sedimentation devices, and subsurface infiltration basins. All of the BMPs were designed to meet the requirements of the MassDEP Handbook and will provide water quality treatment, groundwater recharge, and peak rate attenuation in order to mitigate the impacts of the proposed site improvements. See Appendix D — MassDEP Calculations for the calculations required to document compliance. The following section provides a description of the best management practices (BMPs) being utilized on site. 3.4.1 Bio -Retention Areas Bio -retention areas are a best management practice which is being utilized on site as part of the stormwater management system treatment train process to enhance water runoff quality. Bio - retention areas utilize soils, plants, and microbes to treat stormwater before it is discharged to downstream drainage infrastructure or infiltrated to provide groundwater recharge via an underdrain. The proposed bio -retention areas associated with this project will provide aesthetically pleasing vegetation within the paved parking area. Additionally, the bio -retention areas will provide stormwater pre-treatment prior to discharge to the subsurface infiltration system. 3.4.2 Proprietary Sedimentation Devices Proprietary sedimentation devices are being utilized on site for the pretreatment of stormwater runoff, in addition to the catch basins, prior to conveyance to the subsurface infiltration basins. R Levesque Associates, Inc. Page 3-6 Proposed Residential Development Stormwater Drainage Report 87 Bridge Street & 5 Pomeroy Terrace Northampton, Massachusetts Due to the stormwater management system utilizing underground infiltration systems, treatment of the stormwater runoff is essential to providing higher water quality than existing conditions. As much sediment should be removed from the stormwater runoff as possible to avoid clogging of the infiltration media. Therefore, maintenance of the proprietary device is crucial to the long- term effectiveness of the subsurface infiltration system. The stormwater management system is utilizing proprietary treatment devices in order to ensure that the amount of sediment reaching the subsurface infiltration basin is minimal. 3.4.3 Subsurface Infiltration Basin Subsurface Infiltration Basins are well suited to provide groundwater recharge an peak rate attenuation from watershed areas such as those associated with this project. The subsurface infiltration basin provides groundwater recharge by collecting and storing of runoff such that the underlying soils can absorb the water. The subsurface infiltration basins consist of underground stormwater chambers embedded in stone. The runoff is conveyed to the subsurface infiltration system via up -gradient underground drainage infrastructure. 3.5 Protection of Stormwater Best Management Practices during Construction Protection of the stormwater best management practices during construction will ensure the proper functioning of the stormwater management system and provide protection to the undisturbed areas until the site has been stabilized. Certain specific erosion and sedimentation controls and good practices to be performed by the site contractor have been documented in a Construction Period Erosion Control Plan. See Appendix E — Construction Period Erosion Control Plan. 3.6 Inspection and Maintenance of Stormwater Best Management Practices Frequent maintenance of the stormwater best management practices is essential to ensuring that the stormwater management system will function properly long-term. The MassDEP provides guidelines for the regular inspection and maintenance of the proposed stormwater best management practices. A Long -Term Stormwater Operation and Maintenance Plan has been prepared which dictates the inspection frequency and maintenance operations for each BMP. See Appendix F — Long -Term Operation and Maintenance Plan. 3.7 Illicit Discharge Compliance Statement RLA has prepared an Illicit Discharge Compliance Statement to document compliance with the Massachusetts Department of Environmental Protection Stormwater Management Handbook, see Appendix G. R Levesque Associates, Inc. Page 3-7 Proposed ResidEntial Development StormwatEr DrainagE Report 87 BridgE StrEEt & 5 Pomeroy TErracE Northampton, MassachusEtts 3.8 Low -Impact Development Alternatives Analysis Narrative RLA has prepared a Low -Impact Development Alternatives Analysis Narrative as part of the Stormwater Drainage Report, see Appendix H. 3.9 Northampton DPW Inspection Schedule Checklist RLA has prepared a checklist for the proposed project identify specific inspection milestones where the Department of Public Works shall make an inspection, see Appendix I. R Levesque Associates, Inc. Page 3-8 Proposed Residential Development Stormwater Drainage Report 87 Bridge Street & 5 Pomeroy Terrace 4. CONCLUSION Northampton, Massachusetts The proposed stormwater management system has been designed to mitigate the impacts of the proposed site improvements by providing a control for runoff water quality and water quantity. Implementation of Low -Impact -Development stormwater best management practices such as bio - retention areas, pervious paving, proprietary sedimentation devices, and a subsurface infiltration basin allows for a stormwater drainage design that is in conformance with the criteria set forth in the City of Northampton Stormwater Management Ordinance requirements and the Massachusetts Department of Environmental Protection Stormwater Management Handbook. As the project is considered a redevelopment, the proposed stormwater management system is subject to the MassDEP Stormwater Standards only to the "maximum extent practicable" however, every effort has been made such that the proposed stormwater management system is in full compliance with the standards. Additionally, the proposed site improvement and stormwater management system provides an improvement over existing conditions. R Levesque Associates, Inc. Page 41 Proposed RESIdEntlal DEVEIOpmEnt 87 Bridge Street & S Pomeroy Terrace Figure 1: Site Locus — USGS Map R Levesque Associates, Inc. Stormwater Drainage Report Northampton, Massachusetts N V,b,i OLD FERR)re RD Bridge - Street 0 Cem ,0� Or SITE{ %rA r� ` 500' 0 500' 1000' PO BAR SCALE 1 " = 500' Matt Cam pagnan JOB NO: 150620 R LEVESQUE ASSOCIATES, INC 128 Federal Street --1: B-1- Aland Planning Services Company SITE LOCUS Springfield, MA 01105 SCALE: AS NOTED USGS MAP Proposed Residential Development 40 School Street - P.O. Box 640 - Westfield, MA 01086 Bridge Street & Pomeroy Terrace ♦ ph: 413.568.0985 fax: 413.568.0986 rlaland.com Northampton, MA Proposed RESIdEntlal DEVEIOpmEnt 87 Bridge Street & S Pomeroy Terrace Figure 2: FEMA Flood Map R Levesque Associates, Inc. Stormwater Drainage Report Northampton, Massachusetts q1, 12 w uj Z 0 N v Y SITE r=r` �z 16> 500' 0 500' 1000' BAR SCALE t 1 " = 500' Matt Campagnari 108 NO: 150620 R LEVESQUE ASSOCIATES, INC 128 Federal Street DATE: 3/18/16 Springfield, MA 01105 SCALE: AS NOTED A Land Planning Services Company FLOOD RATE 40 School Street P.O. Boz 640 - Westfield, MA � ♦ ph: 413.568.0985 fax: 413.568.0986 rlaland.com Bridge Street & Pomeroy Terrace INSURANCE MAP Proposed Residential Development .com Northampton, MA 10 SITE r=r` �z 16> 500' 0 500' 1000' BAR SCALE t 1 " = 500' Matt Campagnari 108 NO: 150620 R LEVESQUE ASSOCIATES, INC 128 Federal Street DATE: 3/18/16 Springfield, MA 01105 SCALE: AS NOTED A Land Planning Services Company FLOOD RATE 40 School Street P.O. Boz 640 - Westfield, MA � ♦ ph: 413.568.0985 fax: 413.568.0986 rlaland.com Bridge Street & Pomeroy Terrace INSURANCE MAP Proposed Residential Development .com Northampton, MA Proposed RESIdEntlal DEVEIOpmEnt 87 Bridge Street & S Pomeroy Terrace Figure 3: NHESP Map R Levesque Associates, Inc. Stormwater Drainage Report Northampton, Massachusetts try , 61 :pltLdt l rr70.9 Rt}.�� u m Ilii f �+ 6 I �x��5�tr�et SITE a �PI`4t1 rl r'77 �Y` A R1gar� AD C III ti r t l I �,�F. 'rn �h,J'r� � f Ed`ika t la rlti E - ng :411�aora tlV,� C 3 YhP ['Do I nMY P•1r Tom ,.�lrademy � 1ln.ti _ .. aster It.] in 51111 e Fd u`_.I%D nn l +y fb c u l la bora l l a - rim p,re JcaElana`1,4� jjt -Ck ,. W. __ j AM W 00 00 000 BAR SCALE 1 " = 500' Matt Cam pa JOB NO 150620 R LEVESQUE ASSOCIATES, INC 128 Federal Street DATE 3/18/16 A land Planning Services Company Natural Heritage and Springfield, MA 01105 SCALE AS NOTED Endangered Species Map Proposed Residential Development 40 School Street - P.O. Box 640 - Westfield, MA 01086 Bridge Sireet & Pomeroy Terrace ig ph: 413.568.0985 fax: 413.568.0986 rlaland.com Northampton, MA Proposed RESIdEntlal DEVEIOpmEnt 87 Bridge Street & S Pomeroy Terrace Figure 4: Pre -Development Watershed Plan R Levesque Associates, Inc. Stormwater Drainage Report Northampton, Massachusetts z 0OD0 m g — \ a O C lD w CD W 1L11 > �Ln �m Ln � o- 01 s o aLn () a W m Amostown-Windsor Silty So -p l!1 �, CD 13s < substratum -Urban Land Complex o ; Q 8 a o/ Q Q Hydrologic Group: B IDS S W �n r a � O�� POMERpYSTERRAGE I � q I Q V So / —1 f I1 4q e q Q TA 4. /0 ^ C q W X39 #$s�R�� ----� E a \ a G W q �R�oGE S — — t 14 \ \ W L \ \w a f0 14 \ \ \ *5TERRACE 0. \ a i- POMERG \ / / 4 / \ \4 q q� ° aq / ES -1 4 q a D \� wu \ O EM \\ tc= 6 min. J w a �� a o \ \ r A OR W C U N O \ \ / m Eo0 41 L o \139_ \ w a E 'W10 \ / 1 / 1 . W .L W a) LL a) 00 0) S L L N C wLnLn r N w 139 0. M 40 LEGEND p •E 0 - TIME OF CONC. TIME GARAGE FLOW PATH JOB NO.: 150620 SUBCATCHMENT NAME DATE: 5/23/16 As noted 1 " = 30'SCALE: 140_/ SUB WATERSHED 15 0 30 — — — — SOIL BOUNDARY Proposed RESIdEntlal DEVEIOpmEnt 87 Bridge Street & S Pomeroy Terrace Figure 5: Post -Development Watershed Plan R Levesque Associates, Inc. Stormwater Drainage Report Northampton, Massachusetts z 0OD0 so W m g - a E W �2 s O w CD W ID U1 �n 01 o- W O C m r •C ' /S0 f0 aLn Amostown-Windsor Silty PS -1 E N cn W o substratum -Urban Land Complex 13 I o W oLn Hydrologic Group: B o i a =° M OE�Jt� I W N0 CL t 0 C C PS -1c E a PS -1 B `13� ' W W 14 PS -1D \ �\ w C_ e \ 139 w -- N M 14 \ 139 1 0 a.1 Efa / ° w �\ \ PS -1A ^�� o L J o \ m o L° *'Oa 139,\� �� , \ wa E �-a-6 �Lb f0 a) LL W 1 W O 00 N C. C W 41 NZ rN 13g 139 o w01 o •F LEGEND 0- TIME TIME OF CONC. FLOW PATH JOB NO.: 150620 SUBCATCHMENT NAME DATE: 5/23/16 1 " = 30'SCALE: As noted 140_/ SUB WATERSHED 15 0 30 *ALL tc= 6 MIN. — — — — SOIL BOUNDARY Proposed RESIdEntlal DEVEIOpmEnt 87 Bridge Street & S Pomeroy Terrace Appendix A: Checklist for Stormwater Report R Levesque Associates, Inc. Stormwater Drainage Report Northampton, Massachusetts Massachusetts 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, (which h h hi Report R t St e Stormwater e wcsouprovide more substantive and detailed information use only the tab thp p ) 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 BMP 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. MassDEP Stormwater Checklist - 2016-05-23 • 04/01/08 Stormwater Report Checklist • Page 1 of 8 Massachusetts 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 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 MassDEP Stormwater Checklist - 2016-05-23 • 04/01/08 Stormwater Report Checklist • Page 2 of 8 Massachusetts 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): Pervious Pavers 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. MassDEP Stormwater Checklist - 2016-05-23 • 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. 21E 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. MassDEP Stormwater Checklist - 2016-05-23 • 04/01/08 Stormwater Report Checklist • Page 4 of 8 Massachusetts Department of Environmental Protection 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. MassDEP Stormwater Checklist - 2016-05-23 • 04/01/08 Stormwater Report Checklist • Page 5 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report Checklist (continued) Standard 4: Water Quality (continued) ® The BMP is sized (and calculations provided) based on: ® The 1/2" 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. MassDEP Stormwater Checklist - 2016-05-23 • 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. MassDEP Stormwater Checklist - 2016-05-23 • 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. MassDEP Stormwater Checklist - 2016-05-23 • 04/01/08 Stormwater Report Checklist • Page 8 of 8 Proposed RESIdEntlal DEVEIOpmEnt 87 Bridge Street & S Pomeroy Terrace Appendix 6: Soils Information R Levesque Associates, Inc. Stormwater Drainage Report Northampton, Massachusetts USDA United States A product of the National Custom Soil Resource r Department of Agriculture Cooperative Soil Survey, a joint effort of the United Report for N RCS States Department of Agriculture and other Hampshire County, Federal agencies, State Natural agencies including the Massachusetts, Resources Agricultural Experiment Conservation Stations, and local Central Part Service participants 0 March 2, 2016 Preface Soil surveys contain information that affects land use planning in survey areas. They highlight soil limitations that affect various land uses and provide information about the properties of the soils in the survey areas. Soil surveys are designed for many different users, including farmers, ranchers, foresters, agronomists, urban planners, community officials, engineers, developers, builders, and home buyers. Also, conservationists, teachers, students, and specialists in recreation, waste disposal, and pollution control can use the surveys to help them understand, protect, or enhance the environment. Various land use regulations of Federal, State, and local governments may impose special restrictions on land use or land treatment. Soil surveys identify soil properties that are used in making various land use or land treatment decisions. The information is intended to help the land users identify and reduce the effects of soil limitations on various land uses. The landowner or user is responsible for identifying and complying with existing laws and regulations. Although soil survey information can be used for general farm, local, and wider area planning, onsite investigation is needed to supplement this information in some cases. Examples include soil quality assessments (http://www.nres.usda.gov/wps/portal/ nres/main/soils/health/) and certain conservation and engineering applications. For more detailed information, contact your local USDA Service Center (http:// offices.sc.egov.usda.gov/locator/app?agency=nres) or your NRCS State Soil Scientist (http://www.nres.usda.gov/wps/portal/nres/detail/soils/contactus/? cid=nres142p2_053951). Great differences in soil properties can occur within short distances. Some soils are seasonally wet or subject to flooding. Some are too unstable to be used as a foundation for buildings or roads. Clayey or wet soils are poorly suited to use as septic tank absorption fields. A high water table makes a soil poorly suited to basements or underground installations. The National Cooperative Soil Survey is a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local agencies. The Natural Resources Conservation Service (NRCS) has leadership for the Federal part of the National Cooperative Soil Survey. Information about soils is updated periodically. Updated information is available through the NRCS Web Soil Survey, the site for official soil survey information. The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or a part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means 2 for communication of program information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410 or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer. 3 Contents Preface....................................................................................................................2 How Soil Surveys Are Made..................................................................................5 SoilMap..................................................................................................................7 SoilMap................................................................................................................8 Legend..................................................................................................................9 MapUnit Legend................................................................................................10 MapUnit Descriptions........................................................................................10 Hampshire County, Massachusetts, Central Part...........................................12 741A—Amostown-Windsor silty substratum -Urban land complex, 0 to 3 percent slopes. References ...................... 4 12 14 How Soil Surveys Are Made Soil surveys are made to provide information about the soils and miscellaneous areas in a specific area. They include a description of the soils and miscellaneous areas and their location on the landscape and tables that show soil properties and limitations affecting various uses. Soil scientists observed the steepness, length, and shape of the slopes; the general pattern of drainage; the kinds of crops and native plants; and the kinds of bedrock. They observed and described many soil profiles. A soil profile is the sequence of natural layers, or horizons, in a soil. The profile extends from the surface down into the unconsolidated material in which the soil formed or from the surface down to bedrock. The unconsolidated material is devoid of roots and other living organisms and has not been changed by other biological activity. Currently, soils are mapped according to the boundaries of major land resource areas (MLRAs). MLRAs are geographically associated land resource units that share common characteristics related to physiography, geology, climate, water resources, soils, biological resources, and land uses (USDA, 2006). Soil survey areas typically consist of parts of one or more MLRA. The soils and miscellaneous areas in a survey area occur in an orderly pattern that is related to the geology, landforms, relief, climate, and natural vegetation of the area. Each kind of soil and miscellaneous area is associated with a particular kind of landform or with a segment of the landform. By observing the soils and miscellaneous areas in the survey area and relating their position to specific segments of the landform, a soil scientist develops a concept, or model, of how they were formed. Thus, during mapping, this model enables the soil scientist to predict with a considerable degree of accuracy the kind of soil or miscellaneous area at a specific location on the landscape. Commonly, individual soils on the landscape merge into one another as their characteristics gradually change. To construct an accurate soil map, however, soil scientists must determine the boundaries between the soils. They can observe only a limited number of soil profiles. Nevertheless, these observations, supplemented by an understanding of the soil -vegetation -landscape relationship, are sufficient to verify predictions of the kinds of soil in an area and to determine the boundaries. Soil scientists recorded the characteristics of the soil profiles that they studied. They noted soil color, texture, size and shape of soil aggregates, kind and amount of rock fragments, distribution of plant roots, reaction, and other features that enable them to identify soils. After describing the soils in the survey area and determining their properties, the soil scientists assigned the soils to taxonomic classes (units). Taxonomic classes are concepts. Each taxonomic class has a set of soil characteristics with precisely defined limits. The classes are used as a basis for comparison to classify soils systematically. Soil taxonomy, the system of taxonomic classification used in the United States, is based mainly on the kind and character of soil properties and the arrangement of horizons within the profile. After the soil scientists classified and named the soils in the survey area, they compared the 5 Custom Soil Resource Report individual soils with similar soils in the same taxonomic class in other areas so that they could confirm data and assemble additional data based on experience and research. The objective of soil mapping is not to delineate pure map unit components; the objective is to separate the landscape into landforms or landform segments that have similar use and management requirements. Each map unit is defined by a unique combination of soil components and/or miscellaneous areas in predictable proportions. Some components may be highly contrasting to the other components of the map unit. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The delineation of such landforms and landform segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, onsite investigation is needed to define and locate the soils and miscellaneous areas. Soil scientists make many field observations in the process of producing a soil map. The frequency of observation is dependent upon several factors, including scale of mapping, intensity of mapping, design of map units, complexity of the landscape, and experience of the soil scientist. Observations are made to test and refine the soil - landscape model and predictions and to verify the classification of the soils at specific locations. Once the soil -landscape model is refined, a significantly smaller number of measurements of individual soil properties are made and recorded. These measurements may include field measurements, such as those for color, depth to bedrock, and texture, and laboratory measurements, such as those for content of sand, silt, clay, salt, and other components. Properties of each soil typically vary from one point to another across the landscape. Observations for map unit components are aggregated to develop ranges of characteristics for the components. The aggregated values are presented. Direct measurements do not exist for every property presented for every map unit component. Values for some properties are estimated from combinations of other properties. While a soil survey is in progress, samples of some of the soils in the area generally are collected for laboratory analyses and for engineering tests. Soil scientists interpret the data from these analyses and tests as well as the field -observed characteristics and the soil properties to determine the expected behavior of the soils under different uses. Interpretations for all of the soils are field tested through observation of the soils in different uses and under different levels of management. Some interpretations are modified to fit local conditions, and some new interpretations are developed to meet local needs. Data are assembled from other sources, such as research information, production records, and field experience of specialists. For example, data on crop yields under defined levels of management are assembled from farm records and from field or plot experiments on the same kinds of soil. Predictions about soil behavior are based not only on soil properties but also on such variables as climate and biological activity. Soil conditions are predictable over long periods of time, but they are not predictable from year to year. For example, soil scientists can predict with a fairly high degree of accuracy that a given soil will have a high water table within certain depths in most years, but they cannot predict that a high water table will always be at a specific level in the soil on a specific date. After soil scientists located and identified the significant natural bodies of soil in the survey area, they drew the boundaries of these bodies on aerial photographs and identified each as a specific map unit. Aerial photographs show trees, buildings, fields, roads, and rivers, all of which help in locating boundaries accurately. 0 Soil Map The soil map section includes the soil map for the defined area of interest, a list of soil map units on the map and extent of each map unit, and cartographic symbols displayed on the map. Also presented are various metadata about data used to produce the map, and a description of each soil map unit. 7 Custom Soil Resource Report 3 Soil Map 3 N n - N N 695650 695660 695670 695680 695690 695700 695710 695720 42° 19'22" N fie- 42° 19'22" N 0 IN 14 741 n 0 Z. M O M N p � M .. • oQ f� 7 O I _ O i� O N M pWp� �O N W F y T ppO�� dk OW LAW O O O 0 N O N 42-19-19"N ° "' 42° 19'19" N 695650 695660 695670 695680 695690 695700 695710 695720 695730 3 3 - ro Map Scale: 1:567 if printed on A portrat (8.5" x 11") sheet. F Meters N 0 5 10 20 30 Feet 0 25 SO 100 150 Map projection: Web Mercator Comer coordinates: WGS84 Edge tics: UTM Zone 18N WGS84 8 MAP LEGEND Area of Interest (AOI) Area of Interest (AOI) Soils Spoil Area The soil surveys that comprise your AOI were mapped at 1:15,800. Soil Map Unit Polygons Stony Spot Soil Map Unit Lines 0 Soil Map Unit Points Special Point Features U Blowout Borrow Pit n Clay Spot 0 Closed Depression - Gravel Pit Gravelly Spot C) Landfill Lava Flow Water Features Marsh or swamp Mine or Quarry Please rely on the bar scale on each map sheet for map Miscellaneous Water Perennial Water IV Rock Outcrop f++ Saline Spot Source of Map: Natural Resources Conservation Service Sandy Spot Interstate Highways Severely Eroded Spot Sinkhole Coordinate System: Web Mercator (EPSG:3857) Slide or Slip jV Sodic Spot Custom Soil Resource Report MAP INFORMATION This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Hampshire County, Massachusetts, Central Part Survey Area Data: Version 10, Sep 28, 2015 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Mar 28, 2011—Apr 18, 2011 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background of map unit boundaries may be evident. Spoil Area The soil surveys that comprise your AOI were mapped at 1:15,800. ( Stony Spot Very Stony Spot Warning: Soil Map may not be valid at this scale. Wet Spot Enlargement of maps beyond the scale of mapping can cause n Other misunderstanding of the detail of mapping and accuracy of soil line - placement. The maps do not show the small areas of contrasting .d Special Line Features soils that could have been shown at a more detailed scale. Water Features Streams and Canals Please rely on the bar scale on each map sheet for map measurements. Transportation f++ Rails Source of Map: Natural Resources Conservation Service r ,.r Interstate Highways Web Soil Survey URL: http://websoilsurvey.nres.usda.gov Coordinate System: Web Mercator (EPSG:3857) US Routes Major Roads Maps from the Web Soil Survey are based on the Web Mercator Local Roads projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Background Albers equal-area conic projection, should be used if more accurate ® Aerial Photography calculations of distance or area are required. This product is generated from the USDA-NRCS certified data as of the version date(s) listed below. Soil Survey Area: Hampshire County, Massachusetts, Central Part Survey Area Data: Version 10, Sep 28, 2015 Soil map units are labeled (as space allows) for map scales 1:50,000 or larger. Date(s) aerial images were photographed: Mar 28, 2011—Apr 18, 2011 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background of map unit boundaries may be evident. Custom Soil Resource Report Map Unit Legend Hampshire County, Massachusetts, Central Part (MA609) Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 741A Amostown-Windsor silty substratum -Urban land complex, 0 to 3 percent slopes 0.7 100.0% Totals for Area of Interest 0.7 100.0% Map Unit Descriptions The map units delineated on the detailed soil maps in a soil survey represent the soils or miscellaneous areas in the survey area. The map unit descriptions, along with the maps, can be used to determine the composition and properties of a unit. A map unit delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas. A map unit is identified and named according to the taxonomic classification of the dominant soils. Within a taxonomic class there are precisely defined limits for the properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond the limits defined for a taxonomic class. Areas of soils of a single taxonomic class rarely, if ever, can be mapped without including areas of other taxonomic classes. Consequently, every map unit is made up of the soils or miscellaneous areas for which it is named and some minor components that belong to taxonomic classes other than those of the major soils. Most minor soils have properties similar to those of the dominant soil or soils in the map unit, and thus they do not affect use and management. These are called noncontrasting, or similar, components. They may or may not be mentioned in a particular map unit description. Other minor components, however, have properties and behavioral characteristics divergent enough to affect use or to require different management. These are called contrasting, or dissimilar, components. They generally are in small areas and could not be mapped separately because of the scale used. Some small areas of strongly contrasting soils or miscellaneous areas are identified by a special symbol on the maps. If included in the database for a given area, the contrasting minor components are identified in the map unit descriptions along with some characteristics of each. A few areas of minor components may not have been observed, and consequently they are not mentioned in the descriptions, especially where the pattern was so complex that it was impractical to make enough observations to identify all the soils and miscellaneous areas on the landscape. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The objective of mapping is not to delineate pure taxonomic classes but rather to separate the landscape into landforms or landform segments that have similar use and management requirements. The delineation of such segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, however, onsite investigation is needed to define and locate the soils and miscellaneous areas. 10 Custom Soil Resource Report An identifying symbol precedes the map unit name in the map unit descriptions. Each description includes general facts about the unit and gives important soil properties and qualities. Soils that have profiles that are almost alike make up a soil series. Except for differences in texture of the surface layer, all the soils of a series have major horizons that are similar in composition, thickness, and arrangement. Soils of one series can differ in texture of the surface layer, slope, stoniness, salinity, degree of erosion, and other characteristics that affect their use. On the basis of such differences, a soil series is divided into soil phases. Most of the areas shown on the detailed soil maps are phases of soil series. The name of a soil phase commonly indicates a feature that affects use or management. For example, Alpha silt loam, 0 to 2 percent slopes, is a phase of the Alpha series. Some map units are made up of two or more major soils or miscellaneous areas. These map units are complexes, associations, or undifferentiated groups. A complex consists of two or more soils or miscellaneous areas in such an intricate pattern or in such small areas that they cannot be shown separately on the maps. The pattern and proportion of the soils or miscellaneous areas are somewhat similar in all areas. Alpha -Beta complex, 0 to 6 percent slopes, is an example. An association is made up of two or more geographically associated soils or miscellaneous areas that are shown as one unit on the maps. Because of present or anticipated uses of the map units in the survey area, it was not considered practical or necessary to map the soils or miscellaneous areas separately. The pattern and relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha - Beta association, 0 to 2 percent slopes, is an example. An undifferentiated group is made up of two or more soils or miscellaneous areas that could be mapped individually but are mapped as one unit because similar interpretations can be made for use and management. The pattern and proportion of the soils or miscellaneous areas in a mapped area are not uniform. An area can be made up of only one of the major soils or miscellaneous areas, or it can be made up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example. Some surveys include miscellaneous areas. Such areas have little or no soil material and support little or no vegetation. Rock outcrop is an example. 11 Custom Soil Resource Report Hampshire County, Massachusetts, Central Part 741A—Amostown-Windsor silty substratum -Urban land complex, 0 to 3 percent slopes Map Unit Setting National map unit symbol: 99z2 Mean annual precipitation: 40 to 50 inches Mean annual air temperature: 45 to 52 degrees F Frost -free period: 120 to 240 days Farmland classification: Not prime farmland Map Unit Composition Amostown and similar soils: 35 percent Windsor, silty substratum, and similar soils: 25 percent Urban land: 25 percent Minor components: 15 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Amostown Setting Landform: Deltas, outwash plains, terraces Landform position (two-dimensional): Summit, footslope Landform position (three-dimensional): Tread Down-slope shape: Convex Across -slope shape: Convex Parent material: Friable sandy glaciofluvial deposits over silty glaciolacustrine deposits Typical profile H1 - 0 to 7 inches: fine sandy loam H2 - 7 to 32 inches: fine sandy loam H3 - 32 to 60 inches: stratified very fine sand to silt loam Properties and qualities Slope: 0 to 3 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Moderately well drained Runoff class: Low Capacity of the most limiting layer to transmit water (Ksat): Moderately low to moderately high (0.06 to 0.60 in/hr) Depth to water table: About 18 to 36 inches Frequency of flooding: None Frequency of ponding: None Available water storage in profile: High (about 9.3 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 2w Hydrologic Soil Group: B Description of Windsor, Silty Substratum Setting Landform: Outwash plains 12 Custom Soil Resource Report Landform position (two-dimensional): Footslope Landform position (three-dimensional): Tread Down-slope shape: Convex Across -slope shape: Convex Parent material: Loose sandy glaciofluvial deposits over silty glaciolacustrine deposits Typical profile H1 - 0 to 8 inches: loamy sand H2 - 8 to 21 inches: loamy sand H3 - 21 to 45 inches: sand H4 - 45 to 60 inches: silt loam Properties and qualities Slope: 0 to 3 percent Depth to restrictive feature: More than 80 inches Natural drainage class: Somewhat excessively drained Runoff class: Very low Capacity of the most limiting layer to transmit water (Ksat): Moderately high (0.20 to 0.60 in/hr) Depth to water table: More than 80 inches Frequency of flooding: None Frequency of ponding: None Available water storage in profile: Low (about 5.6 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 3s Hydrologic Soil Group: A Minor Components Enosburg Percent of map unit: 10 percent Landform: Terraces Maybid Percent of map unit: 5 percent Landform: Depressions 13 References American Association of State Highway and Transportation Officials (AASHTO). 2004. Standard specifications for transportation materials and methods of sampling and testing. 24th edition. American Society for Testing and Materials (ASTM). 2005. Standard classification of soils for engineering purposes. ASTM Standard D2487-00. Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of wetlands and deep -water habitats of the United States. U.S. Fish and Wildlife Service FWS/OBS-79/31. Federal Register. July 13, 1994. Changes in hydric soils of the United States. Federal Register. September 18, 2002. Hydric soils of the United States. Hurt, G.W., and L.M. Vasilas, editors. Version 6.0, 2006. Field indicators of hydric soils in the United States. National Research Council. 1995. Wetlands: Characteristics and boundaries. Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service. U.S. Department of Agriculture Handbook 18. http://www.nres.usda.gov/wps/portal/nres/ detail/national/soils/?cid=nres142p2_054262 Soil Survey Staff. 1999. Soil taxonomy: A basic system of soil classification for making and interpreting soil surveys. 2nd edition. Natural Resources Conservation Service, U.S. Department of Agriculture Handbook 436. http://www.nres.usda.gov/wps/portal/ nres/detail/national/soils/?cid=nres142p2_053577 Soil Survey Staff. 2010. Keys to soil taxonomy. 11th edition. U.S. Department of Agriculture, Natural Resources Conservation Service. http://www.nres.usda.gov/wps/ portal/nres/detail/national/soils/?cid=nres142p2_053580 Tiner, R.W., Jr. 1985. Wetlands of Delaware. U.S. Fish and Wildlife Service and Delaware Department of Natural Resources and Environmental Control, Wetlands Section. United States Army Corps of Engineers, Environmental Laboratory. 1987. Corps of Engineers wetlands delineation manual. Waterways Experiment Station Technical Report Y-87-1. United States Department of Agriculture, Natural Resources Conservation Service. National forestry manual. http://www.nres.usda.gov/wps/portal/nres/detail/soils/ home/?cid=nres142p2_053374 United States Department of Agriculture, Natural Resources Conservation Service. National range and pasture handbook. http://www.nres.usda.gov/wps/portal/nres/ detail/national/landuse/rangepasture/?cid=stelprdb1043084 14 Custom Soil Resource Report United States Department of Agriculture, Natural Resources Conservation Service. National soil survey handbook, title 430 -VI. http://www.nres.usda.gov/wps/portal/ nres/detail/soils/scientists/?cid=nres142p2_054242 United States Department of Agriculture, Natural Resources Conservation Service. 2006. Land resource regions and major land resource areas of the United States, the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296. http://www. nres. usda.gov/wps/portal/nres/detail/national/soils/? cid=nres142p2_053624 United States Department of Agriculture, Soil Conservation Service. 1961. Land capability classification. U.S. Department of Agriculture Handbook 210. http:// www.nres.usda.gov/Internet/FSE_DOCUMENTS/nresl42p2_052290.pdf 15 t]G zz � U U) CL 0) r -lo Is �3 J �tt i Vi 00 U) r � �O o0 Q co 40O oc E p E E �. U U LL -4 Ev Li. 1v F- 0 k ti Zi� m -w� � a 0 w - m c Eu Lv m a m,? ori k o 2 LL. > ,uj-, r U u F33 U) ul J t!i Q. CDCD IL. � u x 0 � s CL m If 0 CD 00 qC 3- pL ®o� O N C � z `a Q N �C] t cp M -4 Ev Li. oc u -rn 1.1 r �f C4 U) CL m L7 D c� a� CO) (.0 V• L IJ+ � _ C)le E +Ot cp U) 9 0 0 y wz CO) o c o a a L- 0 [ 0 0 LL. 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U- C? 2 V v 0 W LU u to m 0 s a yo o m _mom o m p � mg m v t� 0 c 4D mO o 0 ca LL m p7i 0 �.1 m W CL ii. 0 0 0 �J m Q tin - �a 7S 3 to o Q C:i CV N CST D �• E2 2 V v 0 W LU u to m 0 s Proposed RESIdEntlal DEVEIOpmEnt Stormwater Drainage Report 87 Bridge Street & 5 Pomeroy Terrace Northampton, Massachusetts Appendix C: Pre- and Post- Development Hydrologic Analysis (2, 10, & 100 Year Storm Events) R Levesque Associates, Inc. DP -1 CES )-1 City Drain Subcat Reach Pon Link Routing Diagram for 150620 - PRE Prepared by R Levesque Associates Inc., Printed 5/23/2016 HydroCAD® 10.00 s/n 02175 © 2013 HydroCAD Software Solutions LLC Bridge St. & Pomeroy Ter. 150620 - PRE Prepared by R Levesque Associates Inc. Printed 5/23/2016 HydroCAD® 10.00 s/n 02175 © 2013 HydroCAD Software Solutions LLC Page 2 Area Listing (all nodes) Area CN Description (sq -ft) (subcatchment-numbers) 10,199 61 >75% Grass cover, Good, HSG B (ES -1) 11,752 98 Paved parking, HSG B (ES -1) 8,794 98 Roofs, HSG B (ES -1) 30,744 86 TOTAL AREA Bridge St. & Pomeroy Ter. 150620 - PRE Type 111 24 -hr 2 -Year Rainfall=3. 00 " Prepared by R Levesque Associates Inc. Printed 5/23/2016 HvdroCAD® 10.00 s/n 02175 © 2013 HvdroCAD Software Solutions LLC Paae 3 Time span=0.00-36.00 hrs, dt=0.05 hrs, 721 points Runoff by SCS TR -20 method, UH=SCS, Weighted -CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment ES -1: City Drain Runoff Area=30,744 sf 66.83% Impervious Runoff Depth=1.66" Tc=6.0 min CN=86 Runoff=1.35 cfs 4,259 cf Link DP -1: Inflow=1.35 cfs 4,259 cf Primary=1.35 cfs 4,259 cf Total Runoff Area = 30,744 sf Runoff Volume = 4,259 cf Average Runoff Depth = 1.66" 33.17% Pervious= 10,199 sf 66.83% Impervious = 20,546 sf Bridge St. & Pomeroy Ter. 150620 - PRE Type 111 24 -hr 2 -Year Rainfall=3. 00 " Prepared by R Levesque Associates Inc. Printed 5/23/2016 HvdroCAD® 10.00 s/n 02175 © 2013 HvdroCAD Software Solutions LLC Paae 4 Summary for Subcatchment ES -1: City Drain Runoff = 1.35 cfs @ 12.09 hrs, Volume= 4,259 cf, Depth= 1.66" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.00-36.00 hrs, dt= 0.05 hrs Type III 24 -hr 2 -Year Rainfall=3.00" Area (sf) CN Description 10,199 61 >75% Grass cover, Good, HSG B 11,752 98 Paved parking, HSG B 8,794 98 Roofs, HSG B 30,744 86 Weighted Average 10,199 61 33.17% Pervious Area 20,546 98 66.83% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment ES -1: City Drain Hydrograph 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 Time (hours) ❑ Runoff Bridge St. & Pomeroy Ter. 150620 - PRE Type 111 24 -hr 2 -Year Rainfall=3. 00 " Prepared by R Levesque Associates Inc. Printed 5/23/2016 HvdroCAD® 10.00 s/n 02175 © 2013 HvdroCAD Software Solutions LLC Paae 5 Summary for Link DP -1: Inflow Area = 30,744 sf, 66.83% Impervious, Inflow Depth = 1.66" for 2 -Year event Inflow = 1.35 cfs @ 12.09 hrs, Volume= 4,259 cf Primary = 1.35 cfs @ 12.09 hrs, Volume= 4,259 cf, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-36.00 hrs, dt= 0.05 hrs v 3 0 LL Link DP -1: Hydrograph 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 Time (hours) o Inflow p Primary Bridge St. & Pomeroy Ter. 150620 - PRE Type 111 24 -hr 10 -Year Rainfall=4.60" Prepared by R Levesque Associates Inc. Printed 5/23/2016 HvdroCAD® 10.00 s/n 02175 © 2013 HvdroCAD Software Solutions LLC Paae 6 Time span=0.00-36.00 hrs, dt=0.05 hrs, 721 points Runoff by SCS TR -20 method, UH=SCS, Weighted -CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment ES -1: City Drain Runoff Area=30,744 sf 66.83% Impervious Runoff Depth=3.10" Tc=6.0 min CN=86 Runoff=2.48 cfs 7,931 cf Link DP -1: Inflow=2.48 cfs 7,931 cf Primary=2.48 cfs 7,931 cf Total Runoff Area = 30,744 sf Runoff Volume = 7,931 cf Average Runoff Depth = 3.10" 33.17% Pervious= 10,199 sf 66.83% Impervious = 20,546 sf Bridge St. & Pomeroy Ter. 150620 - PRE Type 111 24 -hr 10 -Year Rainfall=4.60" Prepared by R Levesque Associates Inc. Printed 5/23/2016 HvdroCAD® 10.00 s/n 02175 © 2013 HvdroCAD Software Solutions LLC Paae 7 Summary for Subcatchment ES -1: City Drain Runoff = 2.48 cfs @ 12.09 hrs, Volume= 7,931 cf, Depth= 3.10" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.00-36.00 hrs, dt= 0.05 hrs Type III 24 -hr 10 -Year Rainfall=4.60" Area (sf) CN Description 10,199 61 >75% Grass cover, Good, HSG B 11,752 98 Paved parking, HSG B 8,794 98 Roofs, HSG B 30,744 86 Weighted Average 10,199 61 33.17% Pervious Area 20,546 98 66.83% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment ES -1: City Drain Hydrograph 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 Time (hours) ❑ Runoff Bridge St. & Pomeroy Ter. 150620 - PRE Type 11124 -hr 10 -Year Rainfall=4.60" Prepared by R Levesque Associates Inc. Printed 5/23/2016 HvdroCAD® 10.00 s/n 02175 © 2013 HvdroCAD Software Solutions LLC Paae 8 Summary for Link DP -1: Inflow Area = 30,744 sf, 66.83% Impervious, Inflow Depth = 3.10" for 10 -Year event Inflow = 2.48 cfs @ 12.09 hrs, Volume= 7,931 cf Primary = 2.48 cfs @ 12.09 hrs, Volume= 7,931 cf, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-36.00 hrs, dt= 0.05 hrs N V 3 0 LL Link DP -1: Hydrograph 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 Time (hours) ❑ Inflow ❑ Primary Bridge St. & Pomeroy Ter. 150620 - PRE Type 111 24 -hr 100 -Year Rainfall=6.50" Prepared by R Levesque Associates Inc. Printed 5/23/2016 HvdroCAD® 10.00 s/n 02175 © 2013 HvdroCAD Software Solutions LLC Paae 9 Time span=0.00-36.00 hrs, dt=0.05 hrs, 721 points Runoff by SCS TR -20 method, UH=SCS, Weighted -CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment ES -1: City Drain Runoff Area=30,744 sf 66.83% Impervious Runoff Depth=4.89" Tc=6.0 min CN=86 Runoff=3.84 cfs 12,518 cf Link DP -1: Inflow=3.84 cfs 12,518 cf Primary=3.84 cfs 12,518 cf Total Runoff Area = 30,744 sf Runoff Volume = 12,518 cf Average Runoff Depth = 4.89" 33.17% Pervious= 10,199 sf 66.83% Impervious = 20,546 sf 150620 - PRE Type 111 24 -hr Prepared by R Levesque Associates Inc. HvdroCAD® 10.00 s/n 02175 © 2013 HvdroCAD Software Solutions LLC Summary for Subcatchment ES -1: City Drain Bridge St. & Pomeroy Ter. 100 -Year Rainfall= 6.50 " Printed 5/23/2016 Paae 10 Runoff = 3.84 cfs @ 12.09 hrs, Volume= 12,518 cf, Depth= 4.89" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.00-36.00 hrs, dt= 0.05 hrs Type III 24 -hr 100 -Year Rainfall=6.50" Area (sf) CN Description 10,199 61 >75% Grass cover, Good, HSG B 11,752 98 Paved parking, HSG B 8,794 98 Roofs, HSG B 30,744 86 Weighted Average 10,199 61 33.17% Pervious Area 20,546 98 66.83% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment ES -1: City Drain Hydrograph 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 Time (hours) ■ Runoff Bridge St. & Pomeroy Ter. 150620 - PRE Type 111 24 -hr 100 -Year Rainfall=6.50" Prepared by R Levesque Associates Inc. Printed 5/23/2016 HvdroCAD® 10.00 s/n 02175 © 2013 HvdroCAD Software Solutions LLC Paae 11 Summary for Link DP -1: Inflow Area = 30,744 sf, 66.83% Impervious, Inflow Depth= 4.89" for 100 -Year event Inflow = 3.84 cfs @ 12.09 hrs, Volume= 12,518 cf Primary = 3.84 cfs @ 12.09 hrs, Volume= 12,518 cf, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-36.00 hrs, dt= 0.05 hrs Link DP -1: Hydrograph 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 Time (hours) ■ Inflow ■ Primary PS -1A � 1 P PS -1 E DP -1 City Drain Z5P Bio -Retention rea #1bsurface Bas' 2P Underdrain #1 Subcat Reach Pon Link 3P 0--P�1B :o -Retention Area #2 4P Underdrain #2 150620 - POST Prepared by R Levesque Associates Inc. HvdroCAD® 10.00 s/n 02175 © 2013 HvdroCAD Software Solutions LLC Area Listing (all nodes) Area CN Description (sq -ft) (subcatchment-numbers) Bridge St. & Pomeroy Ter. Printed 5/23/2016 Paae 2 13,862 61 >75% Grass cover, Good, HSG B (PS -1A, PS -113, PS -1C, PS -1E) 8,630 98 Paved parking, HSG B (PS -1A, PS -1B, PS -1C, PS -1E) 8,252 98 Roofs, HSG B (PS -1A, PS -113, PS -1C, PS -1D, PS -1E) 30,744 81 TOTAL AREA Bridge St. & Pomeroy Ter. 150620 - POST Type 111 24 -hr 2 -Year Rainfall=3. 00 " Prepared by R Levesque Associates Inc. Printed 5/23/2016 HvdroCAD® 10.00 s/n 02175 © 2013 HvdroCAD Software Solutions LLC Paae 3 Time span=0.00-36.00 hrs, dt=0.05 hrs, 721 points Runoff by SCS TR -20 method, UH=SCS, Weighted -CN Reach routing by Stor-Ind method - Pond routing by Stor-Ind method Subcatchment PSAA: Runoff Area=12,635 sf 46.23% Impervious Runoff Depth=1.13" Tc=6.0 min CN=78 Runoff=0.37 cfs 1,189 cf Subcatchment PS -1 B: Runoff Area=4,934 sf 55.05% Impervious Runoff Depth=1.31" Tc=6.0 min CN=81 Runoff=0.17 cfs 540 cf Subcatchment PS -1 C: Runoff Area=2,100 sf 100.00% Impervious Runoff Depth=2.77" Tc=6.0 min CN=98 Runoff=0.14 cfs 484 cf Subcatchment PS -1 D: Runoff Area=2,100 sf 100.00% Impervious Runoff Depth=2.77" Tc=6.0 min CN=98 Runoff=0.14 cfs 484 cf Subcatchment PS -1 E: Runoff Area=8,974 sf 45.97% Impervious Runoff Depth=1.13" Tc=6.0 min CN=78 Runoff=0.26 cfs 844 cf Pond 1P: Bio -Retention Area#1 Peak Elev=138.23' Storage=373 cf Inflow=0.37 cfs 1,189 cf Outflow=0.06 cfs 1,189 cf Pond 2P: Underdrain #1 Peak EIev=134.60' Storage=403 cf Inflow=0.06 cfs 1,189 cf Discarded=0.01 cfs 809 cf Primary=0.04 cfs 380 cf Outflow=0.05 cfs 1,189 cf Pond 3P: Bio -Retention Area #2 Peak EIev=137.86' Storage=133 cf Inflow=0.17 cfs 540 cf Outflow=0.04 cfs 540 cf Pond 4P: Underdrain #2 Peak EIev=134.43' Storage=276 cf Inflow=0.04 cfs 540 cf Discarded=0.01 cfs 540 cf Primary=0.00 cfs 0 cf Outflow=0.01 cfs 540 cf Pond 5P: Subsurface Basin Peak EIev=133.41' Storage=852 cf Inflow=0.27 cfs 1,349 cf Discarded=0.01 cfs 1,147 cf Secondary=0.00 cfs 0 cf Outflow=0.01 cfs 1,147 cf Link DP -1: City Drain Inflow=0.26 cfs 844 cf Primary=0.26 cfs 844 cf Total Runoff Area = 30,744 sf Runoff Volume = 3,542 cf Average Runoff Depth = 1.38" 45.09% Pervious= 13,862 sf 54.91% Impervious = 16,882 sf Bridge St. & Pomeroy Ter. 150620 - POST Type 111 24 -hr 2 -Year Rainfall=3. 00 " Prepared by R Levesque Associates Inc. Printed 5/23/2016 HvdroCAD® 10.00 s/n 02175 © 2013 HvdroCAD Software Solutions LLC Paae 4 Summary for Subcatchment PS -1A: Runoff = 0.37 cfs @ 12.10 hrs, Volume= 1,189 cf, Depth= 1.13" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.00-36.00 hrs, dt= 0.05 hrs Type III 24 -hr 2 -Year Rainfall=3.00" Area (sf) CN Description 6,795 61 >75% Grass cover, Good, HSG B 5,629 98 Paved parking, HSG B 212 98 Roofs, HSG B 12,635 78 Weighted Average 6,795 61 53.77% Pervious Area 5,841 98 46.23% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment PS -1A: Hydrograph 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 Time (hours) ■ Runoff Bridge St. & Pomeroy Ter. 150620 - POST Type 111 24 -hr 2 -Year Rainfall=3. 00 " Prepared by R Levesque Associates Inc. Printed 5/23/2016 HvdroCAD® 10.00 s/n 02175 © 2013 HvdroCAD Software Solutions LLC Paae 5 Summary for Subcatchment PS -1 B: Runoff = 0.17 cfs @ 12.10 hrs, Volume= 540 cf, Depth= 1.31" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.00-36.00 hrs, dt= 0.05 hrs Type III 24 -hr 2 -Year Rainfall=3.00" Area (sf) CN Description 2,218 61 >75% Grass cover, Good, HSG B 793 98 Paved parking, HSG B 1,924 98 Roofs, HSG B 4,934 81 Weighted Average 2,218 61 44.95% Pervious Area 2,716 98 55.05% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment PS -11B: Hydrograph 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 Time (hours) ■ Runoff Bridge St. & Pomeroy Ter. 150620 - POST Type 111 24 -hr 2 -Year Rainfall=3. 00 " Prepared by R Levesque Associates Inc. Printed 5/23/2016 HvdroCAD® 10.00 s/n 02175 © 2013 HvdroCAD Software Solutions LLC Paae 6 Summary for Subcatchment PS -1 C: Runoff = 0.14 cfs @ 12.09 hrs, Volume= 484 cf, Depth= 2.77" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.00-36.00 hrs, dt= 0.05 hrs Type III 24 -hr 2 -Year Rainfall=3.00" Area (sf) CN Description 0 61 >75% Grass cover, Good, HSG B 0 98 Paved parking, HSG B 2,100 98 Roofs, HSG B 2,100 98 Weighted Average 0 61 0.00% Pervious Area 2,100 98 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment PS -1C: Hydrograph 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 Time (hours) ■ Runoff Bridge St. & Pomeroy Ter. 150620 - POST Type 111 24 -hr 2 -Year Rainfall=3. 00 " Prepared by R Levesque Associates Inc. Printed 5/23/2016 HvdroCAD® 10.00 s/n 02175 © 2013 HvdroCAD Software Solutions LLC Paae 7 Summary for Subcatchment PS -1 D: Runoff = 0.14 cfs @ 12.09 hrs, Volume= 484 cf, Depth= 2.77" Runoff by SCS TR -20 method, UH=SCS, Weighted -CN, Time Span= 0.00-36.00 hrs, dt= 0.05 hrs Type III 24 -hr 2 -Year Rainfall=3.00" Area (sf) CN Description 2,100 98 Roofs, HSG B 2,100 98 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment PS -11D: Hydrograph 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 Time (hours) ■ Runoff