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SMITH-HS - DRAINAGE REPORT-2013-1010 Stormwater Drainage Report ______________________________________________________________________________________ for Smith College Health Services Building Northampton, MA September 26, 2013 Revised 10/10/13 Prepared by: 4 Allen Place, Northampton, Massachusetts 01060 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 Checklist Project Type: Is the application for new development, redevelopment, or a mix of new and redevelopment? D New development C8l Redevelopment D Mix of New Development and Redevelopment Smith College Wellness Center -Northampton MA Stormwater Report Checklist • Page 2 of 8 Smith College Wellness Center – Northampton MA Stormwater Report Checklist • Page 3 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): 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. Smith College Wellness Center – Northampton MA 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 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 RECHARGE BMP NOT IMPLEMENTED DUE TO SOILS & REDUCTION OF IMPERVIOUS AREA 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 Field1 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. 21E site or a solid waste landfill and a mounding analysis is included. 1 80% TSS removal is required prior to discharge to infiltration BMP if Dynamic Field method is used. Smith College Wellness Center – Northampton MA 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 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. Smith College Wellness Center – Northampton MA 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 4: Water Quality (continued) The BMP is sized (and calculations provided) based on: The ½” or 1” Water Quality Volume or STC450i (see calculations in Appendix D) 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) Not Applicable – Proposed project site is not expected to yield high potential pollutant loads. 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 Not Applicable – Proposed project site is not expected to yield high potential pollutant loads. 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. Smith College Wellness Center – Northampton MA 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 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. Smith College Wellness Center – Northampton MA Stormwater Report Checklist • Page 8 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 for approval by the Northampton DPW construction 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. Health Services Building September 26, 2013 Revised 10/10/13 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Page 1 Table of Contents Introduction 2 Site Terrain and Soils 2 Existing Conditions 2 Proposed Conditions 3 Calculations and Design 3 MADEP Stormwater Standards Compliance 4 Summary 5 Figures Figure 1 Pre- Development Drainage Area Map Figure 2 Post Development Drainage Area Map Figure 3 USDA Soils Map Appendix Appendix A Pre- and Post Development Hydrologic Calculations Appendix B Soil Test Pit Logs Appendix C Water Quality Calculations Appendix D Stormwater Management System Operation & Maintenance Plan P Health Services Building September 26, 2013 Revised 10/10/13 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Page 2 I. Introduction The following report presents an analysis of the stormwater management system for the proposed construction of the Health Services Building located on the north side of Belmont Avenue on the Smith College Campus in Northampton, Massachusetts. The proposed project includes the removal of the existing parking area building and construction a new building & parking lot, stormwater management system, and associated utilities, grading, and landscaping. II. Site Terrain and Soils The project site slopes toward the south and contains pavement and grassed areas (a building and other paved areas were recently removed from the east half of the site). The USDA Soil Survey of Hampshire County, Massachusetts, Central Part report classifies the site soils as (see Figure 3 for Soil Map): • (741A) Amostown-Windsor-Urban Land Complex Hydrologic Group: C III. Existing Conditions The existing site contains 2 drainage areas (E-1 & E-2). The drainage areas and control points are shown on the Pre-Development Drainage Area Plan (see Figure 1). The following is a brief description of each drainage area. E-1 E-1 is approximately 0.78 acres of land and contains existing paved and grass areas. The area flows to existing catch basins which discharge into a 12"RCP drainline into the Belmont Avenue drainage infrastructure which is used as control point 1 (Shown as E-CP1). E-2 E-2 is approximately 0.26 acres of land and while the entire area is currently grass, it also recently contained roof and paved areas that were removed. These impervious areas area included in the runoff calculations to accurately depict existing flow conditions. This area flows to existing catch basins which discharge into the Ahwaga Avenue drainage infrastructure which is used as control point 2 (Shown as E-CP2). Health Services Building September 26, 2013 Revised 10/10/13 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Page 3 IV. Proposed Conditions The stormwater management system in proposed conditions has been designed to treat and reduce runoff on site. The proposed site contains two drainage areas: P- 1 & P-2 (See Figure 2). The site has been designed to include a new stormwater management system designed to replicate and improve the existing flow patterns and provide water quality treatment. P-1 P-1 is approximately 0.64 acres and contains nearly all of the redeveloped site to the north of Belmont Avenue, including most of the large parking area and the entire building. Runoff from this area is directed to deep sump hooded catch basins to collect the stormwater and discharge it to a subsurface detention system designed to mitigate the 2, 10, and 100 year storm events. The detention basin discharges to a stormwater treatment chamber (STC450) which is connected to the existing drainline in Belmont Avenue (shown as P-CP1 on Figure 2). P-2 P-2 is approximately 0.05 acres and a small portion of the new parking lot and grass area to the north of Belmont Avenue. Runoff from this area is directed to the existing drainline in Belmont Avenue (shown as P-CP1 on Figure 2). V. Calculations and Design Drainage calculations were performed on Hydrocad Stormwater Modeling System version 10.0 using Soil Conservation Service (SCS) TR-20 methodology. The SCS method is based on rainfall observations, which were used to develop the Intensity-Duration-Frequency relationship, or IDF curve. The mass curve is a dimensionless distribution of rainfall over time, which indicates the fraction of the rainfall event that occurs at a given time within a 24-hour precipitation event. This synthetic distribution develops peak rates for storms of varying duration and intensities. The SCS distribution provides a cumulative rainfall at any point in time and allows volume dependent routing runoff calculations to occur. These calculations are included in the appendices. The watershed boundaries for calculation purposes are divided according to the proposed site grading and the natural limits of the drainage areas. The curve numbers (CNs) and times of concentration for the existing and proposed subcatchment areas are based on the soil type and the existing and proposed cover conditions at the site. The soil hydrologic group assumed for the site is noted in Health Services Building September 26, 2013 Revised 10/10/13 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Page 4 Figure 3. Watershed subcatchment areas, runoff coefficients and watercourse slopes are based on survey information. Calculations were performed for the 2-, 10-, and 100-year frequency storms under existing and proposed conditions. The results of the calculations are presented in Table 1 below. Appendix A presents the Hydrocad calculations. Table 1. Peak Flow and Peak Volume Summary Table Condition & Point of Analysis 2-Year Storm 3.00” 10-Year Storm 4.50” 100-Year Storm 6.50” Peak Flow Rate(cfs) Volume (acre-ft) Peak Flow Rate(cfs) Volume (acre- ft) Peak Flow Rate(cfs) Volume (acre-ft) Existing (E-CP1)* 1.89 0.140 3.07 0.233 4.62 0.360 Proposed (P-CP1)* 1.79 0.167 2.75 0.288 4.59 0.454 Existing (E-CP2)* 0.56 0.041 0.95 0.071 1.47 0.112 Proposed (P-CP2)* 0.00 0.000 0.00 0.000 0.00 0.000 *Names in parentheses refer to HydroCad model and calculations. VI. MADEP Stormwater Standards Compliance The following section details how the project will meet DEP Stormwater Management Policy’s ten stormwater management standards. Standard 1 - Untreated Stormwater The proposed stormwater system is designed to treat the new direct connection to the Belmont Avenue & Ahwaga Avenue drainage infrastructure. The site currently drains to these systems however no treatment is currently implemented on site. All runoff from the site has been designed to have a minimum of 80% TSS removed prior to discharging (See Appendix C for TSS removal summary. Standard 2 - Post-Development Peak Discharge Rates The stormwater system is designed so that post-development peak discharge rates are less than pre-development peak discharge rates leaving the site. In proposed conditions, there will be a reduction of impervious area of approximately 3,371sf, however, more of the site will be directed to the Ahwaga Avenue drainage infrastructure and in order to control the runoff rates in proposed conditions a new subsurface detention basin has been proposed in the parking lot in order to reduce the runoff leaving the site to be less than or equal to existing conditions. Refer to Health Services Building September 26, 2013 Revised 10/10/13 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Page 5 Table 1 Peak Flow and Volume Summary and Appendix A for HydroCAD calculations. Standard 3 - Recharge to Groundwater The proposed site has designed to have a reduction in total impervious area from existing conditions, therefore the total volume of runoff leaving the site will be reduced. Test pits were conducted where feasible on the existing site (see Appendix B) and showed evidence of fill, poor soils, and moderately high groundwater, which does not provide a conducive setting for an infiltration system. However, the reduction in impervious area on site will adequately address the concern of Standard 3, which is a reduction of volume of runoff. Standard 4 – Water Quality The proposed stormwater management system has been designed to remove the average annual Total Suspended Solids (TSS) load equal to or greater than 80% for the proposed site conditions (see Appendix C for TSS Removal calculations). The stormwater from the developed areas of the site will be directed to deep sump hooded catch basins and a stormwater treatment chamber which discharges into an the existing drainage infrastructure within the roadway. (See TSS removal chart in Appendix C). Standard 5 - Higher Potential Pollutant Loads The proposed project is not expected to yield high potential pollutant loads. Standard 6 - Protection of Critical Areas The project site does not discharge to critical areas as defined in MADEP Stormwater Policy Handbook. Standard 7 - Redevelopment Projects This project is a redevelopment project, and the redevelopment stormwater standards are fully complied with for the proposed design. Standard 8 - Erosion/Sediment Control This project requires a NPDES Construction General Permit and an erosion and sediment control plan will be submitted prior to the start of construction. Standard 9 - Operation/Maintenance Plan An Operation and Maintenance Plan for the proposed project is included in Appendix D. It includes general controls for construction and long term maintenance of the stormwater management system. Standard 10 – Prohibition of Illicit Discharges No Illicit Discharge Compliance Statement is included with this report however one will be submitted prior to the discharge of any stormwater to post- construction BMPs. Health Services Building September 26, 2013 Revised 10/10/13 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Page 6 VII. Summary The impervious area from existing to proposed conditions will decrease by approximately 3,371sf and with the addition of new catch basins, stormwater treatment chamber, and a subsurface detention basin, the site has been designed to maintain or reduce the peak flow rates in proposed conditions for the 2-, 10-, and 100-year storm frequencies and promote additional water quality treatment that does not currently. Health Services Building September 26, 2013 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Appendix Figures ) The ::=:::: Berkshire ===== Design !!!!!!!!!!!!!!! Group, Inc. 4 Allen Place Nor1hampton, Massachusetts 01060 (413) 582-7000 • FAX (413) 582-7005 Figure Title: Existing Drainage Areas Health Services Building -Belmont Ave NORTHAMPTON MASSACHUSETTS Revisons: 10/10/13 Date: I Scale: 9126/13 1:60± Figure Number. 1 The ::=:::: Berkshire ===== Design !!!!!!!!!!!!!!! Group, Inc. 4 Allen Place Nor1hampton, Massachusetts 01060 (413) 582-7000 • FAX (413) 582-7005 Figure Title: Proposed Drainage Areas Health Services Building -Belmont Ave NORTHAMPTON MASSACHUSETTS Revisons: 10/10/13 Date: I Scale: 9126/13 1:60± Figure Number. 2 -" ; ----- •••• I ••W"w -" ; Hydrologic Soil Group-Hampshire County, Massachusetts, Central Part MAP LEGEND MAP IN FORMATION Area of lntaraat (AOI) D Area of Interest (AOI} Solla Soll RaOng Polygons D A D AJD .B • BID D c D CID D D D Not rated or not available Soll RaOng LlnA A ~ AJD ~B -°""1 BID c __J ~ CID -°""1 D .. ; Not rated or not available Soll RaOng Points _Qj A ~ AJD •I B •I BID USDA Natural Resources liE Conservation Service _QJ c ~ CID _l:IJ D a Not rated or not available Wat.r Features Streams and Canals Transportation t+i Rails ,,..,_,, Interstate Highways _,,,_ US Route& ,..,._ Major Roads Local Roads Background • Aerial Photography Web Soil Survey National Cooperative Soil Survey The soil surveys that comprise your ADI were mapped at 1 : 15,800. Warning: Soil Map may not be valid at this scale. Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil line placement. The maps do not show the small areas of contrasting soils that could have been shown at a more detailed scale. Please rely on the bar scale on each map sheet for map measurements. Source of Map: Natural Resources Conservation Service Web Soil Survey URL: http://websoilsurvey.nrcs.usda.gov Coordinate System: Web Mercator (EPSG:3857) Maps from the Web Soil Survey are based on the Web Mercator projection, which preserves direction and shape but distorts distance and area. A projection that preserves area, such as the Albers equal-area conic projection, should be used if more accurate 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 7, Sep 22, 2012 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-May 12,2011 The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps. As a result, some minor shifting of map unit boundaries may be evident. 8123/2013 Page 2 of 4 Hydrologic Soil Group--Hampshire County, Massachusetts, Central Part Hydrologic Soil Group Hydrologlc Soll Group-Summary by Map Unit-Hampshire County, Massac:husetts, Central Part (NA609) Map unit symbol Map unit name Rating Acres lnAOI Percent of AOI 741A Amostown-Windsor silty c 3.7 substratum-Urban land complex, 0 to 3 percent slopes Totals for Area of Interest 3.7 Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes (AID, B/D, and C/D). The groups are defined as follows: Group A. Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearty impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (AID, BID, or C/D), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Rating Options Aggregation Method: Dominant Condition 'USDA Natural Resources ~-Conservation Service Web Soil Survey National Cooperative Soil Survey 100.0% 100.0% 812312013 Page3of4 Hydrologic Soil GrouJ>-l-lampshire County, Massachusetts, Central Part Component Percent Cutoff: None Specified Tie-break Rule: Higher Natural Resources Conservation Service Web Soil Survey National Cooperative Soil Survey 8123/2013 Page4 of4 Smith College Wellness Center September 26, 2013 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Appendix Appendix A – HydroCAD Calculations E-1 Existing E-2 Existing P-1 Proposed P-2 Proposed E-CP1 Belmont Ave Drainline E-CP2 Awhaga Drainline P-CP1 Belmont Ave Drainline P-POND Subsurface Detention Pond Routing Diagram for Belmont Street Prepared by {enter your company name here}, Printed 10/23/2013 HydroCAD® 10.00 s/n 00752 © 2013 HydroCAD Software Solutions LLC Subcat Reach Pond Link Belmont Street Printed 10/23/2013Prepared by {enter your company name here} Page 3HydroCAD® 10.00 s/n 00752 © 2013 HydroCAD Software Solutions LLC Area Listing (selected nodes) Area (acres) CNDescription (subcatchment-numbers) 0.67174>75% Grass cover, Good, HSG C (E-1, E-2, P-1, P-2) 1.40198Paved parking, HSG C (E-1, E-2, P-1, P-2) Type III 24-hr 2 YRS Rainfall=3.00"Belmont Street Printed 10/23/2013Prepared by {enter your company name here} Page 4HydroCAD® 10.00 s/n 00752 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment E-1: Existing Runoff=1.89 cfs @ 12.09 hrs, Volume=0.140 af, Depth>2.16" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 YRS Rainfall=3.00" Area (ac)CNDescription 0.57698Paved parking, HSG C 0.20274>75% Grass cover, Good, HSG C 0.77892Weighted Average 0.20225.96% Pervious Area 0.57674.04% Impervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 6.0 Direct Entry, Type III 24-hr 2 YRS Rainfall=3.00"Belmont Street Printed 10/23/2013Prepared by {enter your company name here} Page 5HydroCAD® 10.00 s/n 00752 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment E-2: Existing Runoff=0.56 cfs @ 12.09 hrs, Volume=0.041 af, Depth>1.90" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 YRS Rainfall=3.00" Area (sf)CNDescription 7,10198Paved parking, HSG C 4,12274>75% Grass cover, Good, HSG C 11,22389Weighted Average 4,12236.73% Pervious Area 7,10163.27% Impervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 6.0 Direct Entry, Type III 24-hr 2 YRS Rainfall=3.00"Belmont Street Printed 10/23/2013Prepared by {enter your company name here} Page 6HydroCAD® 10.00 s/n 00752 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment P-1: Proposed Runoff=2.23 cfs @ 12.09 hrs, Volume=0.163 af, Depth>1.98" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 YRS Rainfall=3.00" Area (sf)CNDescription 28,18898Paved parking, HSG C 14,73574>75% Grass cover, Good, HSG C 42,92390Weighted Average 14,73534.33% Pervious Area 28,18865.67% Impervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 6.0 Direct Entry, Type III 24-hr 2 YRS Rainfall=3.00"Belmont Street Printed 10/23/2013Prepared by {enter your company name here} Page 7HydroCAD® 10.00 s/n 00752 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment P-2: Proposed Runoff=0.08 cfs @ 12.10 hrs, Volume=0.005 af, Depth>1.31" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 YRS Rainfall=3.00" Area (sf)CNDescription 63098Paved parking, HSG C 1,55474>75% Grass cover, Good, HSG C 2,18481Weighted Average 1,55471.15% Pervious Area 63028.85% Impervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 6.0 Direct Entry, Type III 24-hr 2 YRS Rainfall=3.00"Belmont Street Printed 10/23/2013Prepared by {enter your company name here} Page 8HydroCAD® 10.00 s/n 00752 © 2013 HydroCAD Software Solutions LLC Summary for Reach E-CP1: Belmont Ave Drainline [40] Hint: Not Described (Outflow=Inflow) Inflow Area =0.778 ac,74.04% Impervious, Inflow Depth > 2.16" for 2 YRS event Inflow=1.89 cfs @ 12.09 hrs, Volume=0.140 af Outflow=1.89 cfs @ 12.09 hrs, Volume=0.140 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 YRS Rainfall=3.00"Belmont Street Printed 10/23/2013Prepared by {enter your company name here} Page 9HydroCAD® 10.00 s/n 00752 © 2013 HydroCAD Software Solutions LLC Summary for Reach E-CP2: Awhaga Drainline [40] Hint: Not Described (Outflow=Inflow) Inflow Area =0.258 ac,63.27% Impervious, Inflow Depth > 1.90" for 2 YRS event Inflow=0.56 cfs @ 12.09 hrs, Volume=0.041 af Outflow=0.56 cfs @ 12.09 hrs, Volume=0.041 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 YRS Rainfall=3.00"Belmont Street Printed 10/23/2013Prepared by {enter your company name here} Page 10HydroCAD® 10.00 s/n 00752 © 2013 HydroCAD Software Solutions LLC Summary for Reach P-CP1: Belmont Ave Drainline [40] Hint: Not Described (Outflow=Inflow) Inflow Area =1.036 ac,63.89% Impervious, Inflow Depth > 1.94" for 2 YRS event Inflow=1.79 cfs @ 12.16 hrs, Volume=0.167 af Outflow=1.79 cfs @ 12.16 hrs, Volume=0.167 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2 YRS Rainfall=3.00"Belmont Street Printed 10/23/2013Prepared by {enter your company name here} Page 11HydroCAD® 10.00 s/n 00752 © 2013 HydroCAD Software Solutions LLC Summary for Pond P-POND: Subsurface Detention Pond Inflow Area =0.985 ac,65.67% Impervious, Inflow Depth > 1.98" for 2 YRS event Inflow=2.23 cfs @ 12.09 hrs, Volume=0.163 af Outflow=1.73 cfs @ 12.16 hrs, Volume=0.162 af, Atten= 22%, Lag= 4.2 min Primary=1.73 cfs @ 12.16 hrs, Volume=0.162 af Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Starting Elev= 153.50' Surf.Area= 1,260 sf Storage= 227 cf Peak Elev= 154.53' @ 12.16 hrs Surf.Area= 1,260 sf Storage= 848 cf (621 cf above start) Plug-Flow detention time= 38.4 min calculated for 0.157 af (96% of inflow) Center-of-Mass det. time= 7.9 min ( 816.8 - 808.9 ) VolumeInvertAvail.StorageStorage Description #1153.00'1,569 cf Custom Stage Data (Prismatic) Listed below (Recalc) 4,788 cf Overall - 866 cf Embedded = 3,922 cf x 40.0% Voids #2153.50'487 cf 24.0" Round Pipe Storage Inside #1 L= 155.0' 866 cf Overall - 4.0" Wall Thickness = 487 cf 2,056 cfTotal Available Storage ElevationSurf.AreaInc.StoreCum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 153.001,26000 156.801,2604,7884,788 DeviceRouting InvertOutlet Devices #1Primary153.50'12.0" Round Culvert L= 30.0' CMP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 153.50' / 153.20' S= 0.0100 '/' Cc= 0.900 n= 0.010 PVC, smooth interior, Flow Area= 0.79 sf #2Device 1153.50'9.0" Vert. Orifice/Grate C= 0.600 #3Device 1155.75'6.0" Vert. Orifice/Grate C= 0.600 #4Primary156.75'12.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads Primary OutFlow Max=1.71 cfs @ 12.16 hrs HW=154.52' (Free Discharge) 1=Culvert (Passes 1.71 cfs of 2.16 cfs potential flow) 2=Orifice/Grate (Orifice Controls 1.71 cfs @ 3.87 fps) 3=Orifice/Grate ( Controls 0.00 cfs) 4=Orifice/Grate ( Controls 0.00 cfs) Type III 24-hr 10 YRS Rainfall=4.50"Belmont Street Printed 10/23/2013Prepared by {enter your company name here} Page 12HydroCAD® 10.00 s/n 00752 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment E-1: Existing Runoff=3.07 cfs @ 12.09 hrs, Volume=0.233 af, Depth>3.60" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 YRS Rainfall=4.50" Area (ac)CNDescription 0.57698Paved parking, HSG C 0.20274>75% Grass cover, Good, HSG C 0.77892Weighted Average 0.20225.96% Pervious Area 0.57674.04% Impervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 6.0 Direct Entry, Type III 24-hr 10 YRS Rainfall=4.50"Belmont Street Printed 10/23/2013Prepared by {enter your company name here} Page 13HydroCAD® 10.00 s/n 00752 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment E-2: Existing Runoff=0.95 cfs @ 12.09 hrs, Volume=0.071 af, Depth>3.29" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 YRS Rainfall=4.50" Area (sf)CNDescription 7,10198Paved parking, HSG C 4,12274>75% Grass cover, Good, HSG C 11,22389Weighted Average 4,12236.73% Pervious Area 7,10163.27% Impervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 6.0 Direct Entry, Type III 24-hr 10 YRS Rainfall=4.50"Belmont Street Printed 10/23/2013Prepared by {enter your company name here} Page 14HydroCAD® 10.00 s/n 00752 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment P-1: Proposed Runoff=3.72 cfs @ 12.09 hrs, Volume=0.279 af, Depth>3.39" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 YRS Rainfall=4.50" Area (sf)CNDescription 28,18898Paved parking, HSG C 14,73574>75% Grass cover, Good, HSG C 42,92390Weighted Average 14,73534.33% Pervious Area 28,18865.67% Impervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 6.0 Direct Entry, Type III 24-hr 10 YRS Rainfall=4.50"Belmont Street Printed 10/23/2013Prepared by {enter your company name here} Page 15HydroCAD® 10.00 s/n 00752 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment P-2: Proposed Runoff=0.15 cfs @ 12.09 hrs, Volume=0.011 af, Depth>2.55" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 YRS Rainfall=4.50" Area (sf)CNDescription 63098Paved parking, HSG C 1,55474>75% Grass cover, Good, HSG C 2,18481Weighted Average 1,55471.15% Pervious Area 63028.85% Impervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 6.0 Direct Entry, Type III 24-hr 10 YRS Rainfall=4.50"Belmont Street Printed 10/23/2013Prepared by {enter your company name here} Page 16HydroCAD® 10.00 s/n 00752 © 2013 HydroCAD Software Solutions LLC Summary for Reach E-CP1: Belmont Ave Drainline [40] Hint: Not Described (Outflow=Inflow) Inflow Area =0.778 ac,74.04% Impervious, Inflow Depth > 3.60" for 10 YRS event Inflow=3.07 cfs @ 12.09 hrs, Volume=0.233 af Outflow=3.07 cfs @ 12.09 hrs, Volume=0.233 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 YRS Rainfall=4.50"Belmont Street Printed 10/23/2013Prepared by {enter your company name here} Page 17HydroCAD® 10.00 s/n 00752 © 2013 HydroCAD Software Solutions LLC Summary for Reach E-CP2: Awhaga Drainline [40] Hint: Not Described (Outflow=Inflow) Inflow Area =0.258 ac,63.27% Impervious, Inflow Depth > 3.29" for 10 YRS event Inflow=0.95 cfs @ 12.09 hrs, Volume=0.071 af Outflow=0.95 cfs @ 12.09 hrs, Volume=0.071 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 YRS Rainfall=4.50"Belmont Street Printed 10/23/2013Prepared by {enter your company name here} Page 18HydroCAD® 10.00 s/n 00752 © 2013 HydroCAD Software Solutions LLC Summary for Reach P-CP1: Belmont Ave Drainline [40] Hint: Not Described (Outflow=Inflow) Inflow Area =1.036 ac,63.89% Impervious, Inflow Depth > 3.34" for 10 YRS event Inflow=2.75 cfs @ 12.17 hrs, Volume=0.288 af Outflow=2.75 cfs @ 12.17 hrs, Volume=0.288 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10 YRS Rainfall=4.50"Belmont Street Printed 10/23/2013Prepared by {enter your company name here} Page 19HydroCAD® 10.00 s/n 00752 © 2013 HydroCAD Software Solutions LLC Summary for Pond P-POND: Subsurface Detention Pond Inflow Area =0.985 ac,65.67% Impervious, Inflow Depth > 3.39" for 10 YRS event Inflow=3.72 cfs @ 12.09 hrs, Volume=0.279 af Outflow=2.64 cfs @ 12.17 hrs, Volume=0.277 af, Atten= 29%, Lag= 5.0 min Primary=2.64 cfs @ 12.17 hrs, Volume=0.277 af Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Starting Elev= 153.50' Surf.Area= 1,260 sf Storage= 227 cf Peak Elev= 155.41' @ 12.17 hrs Surf.Area= 1,260 sf Storage= 1,385 cf (1,158 cf above start) Plug-Flow detention time= 28.1 min calculated for 0.272 af (98% of inflow) Center-of-Mass det. time= 7.3 min ( 801.2 - 793.9 ) VolumeInvertAvail.StorageStorage Description #1153.00'1,569 cf Custom Stage Data (Prismatic) Listed below (Recalc) 4,788 cf Overall - 866 cf Embedded = 3,922 cf x 40.0% Voids #2153.50'487 cf 24.0" Round Pipe Storage Inside #1 L= 155.0' 866 cf Overall - 4.0" Wall Thickness = 487 cf 2,056 cfTotal Available Storage ElevationSurf.AreaInc.StoreCum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 153.001,26000 156.801,2604,7884,788 DeviceRouting InvertOutlet Devices #1Primary153.50'12.0" Round Culvert L= 30.0' CMP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 153.50' / 153.20' S= 0.0100 '/' Cc= 0.900 n= 0.010 PVC, smooth interior, Flow Area= 0.79 sf #2Device 1153.50'9.0" Vert. Orifice/Grate C= 0.600 #3Device 1155.75'6.0" Vert. Orifice/Grate C= 0.600 #4Primary156.75'12.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads Primary OutFlow Max=2.61 cfs @ 12.17 hrs HW=155.38' (Free Discharge) 1=Culvert (Passes 2.61 cfs of 3.51 cfs potential flow) 2=Orifice/Grate (Orifice Controls 2.61 cfs @ 5.91 fps) 3=Orifice/Grate ( Controls 0.00 cfs) 4=Orifice/Grate ( Controls 0.00 cfs) Type III 24-hr 100 YRS Rainfall=6.50"Belmont Street Printed 10/23/2013Prepared by {enter your company name here} Page 20HydroCAD® 10.00 s/n 00752 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment E-1: Existing Runoff=4.62 cfs @ 12.09 hrs, Volume=0.360 af, Depth>5.56" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 YRS Rainfall=6.50" Area (ac)CNDescription 0.57698Paved parking, HSG C 0.20274>75% Grass cover, Good, HSG C 0.77892Weighted Average 0.20225.96% Pervious Area 0.57674.04% Impervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 6.0 Direct Entry, Type III 24-hr 100 YRS Rainfall=6.50"Belmont Street Printed 10/23/2013Prepared by {enter your company name here} Page 21HydroCAD® 10.00 s/n 00752 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment E-2: Existing Runoff=1.47 cfs @ 12.09 hrs, Volume=0.112 af, Depth>5.22" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 YRS Rainfall=6.50" Area (sf)CNDescription 7,10198Paved parking, HSG C 4,12274>75% Grass cover, Good, HSG C 11,22389Weighted Average 4,12236.73% Pervious Area 7,10163.27% Impervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 6.0 Direct Entry, Type III 24-hr 100 YRS Rainfall=6.50"Belmont Street Printed 10/23/2013Prepared by {enter your company name here} Page 22HydroCAD® 10.00 s/n 00752 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment P-1: Proposed Runoff=5.71 cfs @ 12.09 hrs, Volume=0.438 af, Depth>5.33" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 YRS Rainfall=6.50" Area (sf)CNDescription 28,18898Paved parking, HSG C 14,73574>75% Grass cover, Good, HSG C 42,92390Weighted Average 14,73534.33% Pervious Area 28,18865.67% Impervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 6.0 Direct Entry, Type III 24-hr 100 YRS Rainfall=6.50"Belmont Street Printed 10/23/2013Prepared by {enter your company name here} Page 23HydroCAD® 10.00 s/n 00752 © 2013 HydroCAD Software Solutions LLC Summary for Subcatchment P-2: Proposed Runoff=0.25 cfs @ 12.09 hrs, Volume=0.018 af, Depth>4.34" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 YRS Rainfall=6.50" Area (sf)CNDescription 63098Paved parking, HSG C 1,55474>75% Grass cover, Good, HSG C 2,18481Weighted Average 1,55471.15% Pervious Area 63028.85% Impervious Area TcLengthSlopeVelocityCapacityDescription (min)(feet)(ft/ft)(ft/sec)(cfs) 6.0 Direct Entry, Type III 24-hr 100 YRS Rainfall=6.50"Belmont Street Printed 10/23/2013Prepared by {enter your company name here} Page 24HydroCAD® 10.00 s/n 00752 © 2013 HydroCAD Software Solutions LLC Summary for Reach E-CP1: Belmont Ave Drainline [40] Hint: Not Described (Outflow=Inflow) Inflow Area =0.778 ac,74.04% Impervious, Inflow Depth > 5.56" for 100 YRS event Inflow=4.62 cfs @ 12.09 hrs, Volume=0.360 af Outflow=4.62 cfs @ 12.09 hrs, Volume=0.360 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 YRS Rainfall=6.50"Belmont Street Printed 10/23/2013Prepared by {enter your company name here} Page 25HydroCAD® 10.00 s/n 00752 © 2013 HydroCAD Software Solutions LLC Summary for Reach E-CP2: Awhaga Drainline [40] Hint: Not Described (Outflow=Inflow) Inflow Area =0.258 ac,63.27% Impervious, Inflow Depth > 5.22" for 100 YRS event Inflow=1.47 cfs @ 12.09 hrs, Volume=0.112 af Outflow=1.47 cfs @ 12.09 hrs, Volume=0.112 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 YRS Rainfall=6.50"Belmont Street Printed 10/23/2013Prepared by {enter your company name here} Page 26HydroCAD® 10.00 s/n 00752 © 2013 HydroCAD Software Solutions LLC Summary for Reach P-CP1: Belmont Ave Drainline [40] Hint: Not Described (Outflow=Inflow) Inflow Area =1.036 ac,63.89% Impervious, Inflow Depth > 5.27" for 100 YRS event Inflow=4.59 cfs @ 12.16 hrs, Volume=0.454 af Outflow=4.59 cfs @ 12.16 hrs, Volume=0.454 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100 YRS Rainfall=6.50"Belmont Street Printed 10/23/2013Prepared by {enter your company name here} Page 27HydroCAD® 10.00 s/n 00752 © 2013 HydroCAD Software Solutions LLC Summary for Pond P-POND: Subsurface Detention Pond Inflow Area =0.985 ac,65.67% Impervious, Inflow Depth > 5.33" for 100 YRS event Inflow=5.71 cfs @ 12.09 hrs, Volume=0.438 af Outflow=4.40 cfs @ 12.16 hrs, Volume=0.436 af, Atten= 23%, Lag= 4.3 min Primary=4.40 cfs @ 12.16 hrs, Volume=0.436 af Routing by Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Starting Elev= 153.50' Surf.Area= 1,260 sf Storage= 227 cf Peak Elev= 156.72' @ 12.16 hrs Surf.Area= 1,260 sf Storage= 2,017 cf (1,790 cf above start) Plug-Flow detention time= 21.7 min calculated for 0.430 af (98% of inflow) Center-of-Mass det. time= 6.9 min ( 788.6 - 781.7 ) VolumeInvertAvail.StorageStorage Description #1153.00'1,569 cf Custom Stage Data (Prismatic) Listed below (Recalc) 4,788 cf Overall - 866 cf Embedded = 3,922 cf x 40.0% Voids #2153.50'487 cf 24.0" Round Pipe Storage Inside #1 L= 155.0' 866 cf Overall - 4.0" Wall Thickness = 487 cf 2,056 cfTotal Available Storage ElevationSurf.AreaInc.StoreCum.Store (feet)(sq-ft)(cubic-feet)(cubic-feet) 153.001,26000 156.801,2604,7884,788 DeviceRouting InvertOutlet Devices #1Primary153.50'12.0" Round Culvert L= 30.0' CMP, projecting, no headwall, Ke= 0.900 Inlet / Outlet Invert= 153.50' / 153.20' S= 0.0100 '/' Cc= 0.900 n= 0.010 PVC, smooth interior, Flow Area= 0.79 sf #2Device 1153.50'9.0" Vert. Orifice/Grate C= 0.600 #3Device 1155.75'6.0" Vert. Orifice/Grate C= 0.600 #4Primary156.75'12.0" Horiz. Orifice/Grate C= 0.600 Limited to weir flow at low heads Primary OutFlow Max=4.35 cfs @ 12.16 hrs HW=156.69' (Free Discharge) 1=Culvert (Passes 4.35 cfs of 4.89 cfs potential flow) 2=Orifice/Grate (Orifice Controls 3.57 cfs @ 8.07 fps) 3=Orifice/Grate (Orifice Controls 0.78 cfs @ 3.99 fps) 4=Orifice/Grate ( Controls 0.00 cfs) Smith College Wellness Center September 26, 2013 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Appendix Appendix B – Test Pit Logs The ::=:::: Berkshire ===== Design !!!!!!!!!!!!!!! Group, Inc. 4 Allen Place Nor1hampton, Massachusetts 01060 (413) 582-7000 • FAX (413) 582-7005 Figure Title: Test Pit Location Map Wellness Center -Belmont Ave NORTHAMPTON MASSACHUSETTS Revisons: Date: I Scale: 9/26/12 1:60± Figure Number. TP Location Address or Lot No. Smith Wellness Center - Northampton, MA Test Pits Performed By B. Darnold, The Berkshire Design Group Witnessed By: Deep Hole Number 1 Date: 9/10/13 Time: 10:00am Weather Cloudy 55 Location (identify on site plan) See Plan Land Use Grass Slope (%) See Plan Surface Stones n/o Vegetation Grassed Landform Urban Position on Landscape (sketch on back) Distances from: See Plan Open Water Body Feet Drainage way Feet Possible Wet Area Feet Property Line Feet Drinking Water Well Feet Other DEEP OBSERVATION HOLE LOG * Depth from Surface(Inches) Soil Horizon Soil Texture (USDA) Soil Color (Munsell) Soil Mottling Other (Structure, Stones, Boulders, Consistency, % Gravel) 0” – 8” A Loam 10YR 3/2 - SABK, friable, roots 8” - 30” FILL Loamy Sand 2.5Y 5/4 - SABK, friable, buried debris evident, some roots 30” – 47” FILL Loamy Sand 2.5Y 6/4 - Pieces of brick & pavement, large rock prohibited further digging at this location * MINIMUM OF 2 HOLES REQUIRED AT EVERY PROPOSED DISPOSAL AREA Parent Material (geologic) Depth to Bedrock: N/O Depth to Groundwater: Standing Water in the Hole: - Weeping from Pit Face: N/A Estimated Seasonal High Ground Water: >47" Percolation Test: Not Performed Depth to Perc: Start Pre-Soak 12”: End Pre-Soak 12”: Time at 12”: Time at 9”: Time at 6”: Time (9”-6”): Rate: Note: This test pit was performed for investigation of general soil conditions and should not be used for purposes related to Title 5 and/or soil suitability assessments for on-site sewage disposal. Location Address or Lot No. Smith Wellness Center - Northampton, MA Test Pits Performed By B. Darnold, The Berkshire Design Group Witnessed By: Deep Hole Number 2 Date: 9/10/13 Time: 11:45am Weather Cloudy 55 Location (identify on site plan) See Plan Land Use Grass Slope (%) See Plan Surface Stones n/o Vegetation Grassed, large tree Landform Urban Position on Landscape (sketch on back) Distances from: See Plan Open Water Body Feet Drainage way Feet Possible Wet Area Feet Property Line Feet Drinking Water Well Feet Other DEEP OBSERVATION HOLE LOG * Depth from Surface(Inches) Soil Horizon Soil Texture (USDA) Soil Color (Munsell) Soil Mottling Other (Structure, Stones, Boulders, Consistency, % Gravel) 0” – 7” A Loam 10YR 3/2 - SABK, friable, roots 7” - 18” FILL Sandy Loam 2.5Y 5/4 - SABK, friable, roots, 5% gravel, 18” – 36” C1 Silty Loam 2.5Y 3/2 5%@30" No gravel/stones, some roots, friable, smearing, heavy silt presence 36” – 72” C2 Silty Loam 5Y 4/2 10-15%@66" Friable, massive, 10% gravel * MINIMUM OF 2 HOLES REQUIRED AT EVERY PROPOSED DISPOSAL AREA Parent Material (geologic) Depth to Bedrock: >72" Depth to Groundwater: Standing Water in the Hole: - Weeping from Pit Face: - Estimated Seasonal High Ground Water: 65" Percolation Test: Not Performed Depth to Perc: Start Pre-Soak 12”: End Pre-Soak 12”: Time at 12”: Time at 9”: Time at 6”: Time (9”-6”): Rate: Note: This test pit was performed for investigation of general soil conditions and should not be used for purposes related to Title 5 and/or soil suitability assessments for on-site sewage disposal. Smith College Wellness Center September 26, 2013 Northampton, Massachusetts Stormwater Drainage Report The Berkshire Design Group, Inc. Appendix Appendix C – Water Quality Calculations V IN S T R U C T I O N S : Ve r s i o n 1 , A u t o m a t e d : M a r . 4 , 2 0 0 8 1. I n B M P C o l u m n , c l i c k o n B l u e C e l l t o A c t i v a t e D r op D o w n M e n u 2. S e l e c t B M P f r o m D r o p D o w n M e n u 3. A f t e r B M P i s s e l e c t e d , T S S R e m o v a l a n d o t h e r C o l um n s a r e a u t o m a t i c a l l y c o m p l e t e d . Lo c a t i o n : B C D E F TS S R e m o v a l S t a r t i n g T S S A m o u n t R e m a i n i n g BM P 1 Ra t e 1 Lo a d * R e m o v e d ( C * D ) L o a d ( D - E ) De e p S u m p a n d H o o d e d Ca t c h B a s i n 0 . 2 5 1. 0 0 0 . 2 5 0 . 7 5 Pr o p r i e t a r y T r e a t m e n t Pr a c t i c e 0 . 8 2 0. 7 5 0 . 6 2 0 . 1 4 0. 0 0 0. 1 4 0 . 0 0 0 . 1 4 0. 0 0 0. 1 4 0 . 0 0 0 . 1 4 0. 0 0 0. 1 4 0 . 0 0 0 . 1 4 To t a l T S S R e m o v a l = 87 % Separate Form Needs to be Completed for Each Outlet or BMP Train Pr o j e c t : Sm i t h W e l l n e s s C e n t e r , N o r t h a m p t o n MA Pr e p a r e d B y : BC D *E q u a l s r e m a i n i n g l o a d f r o m p r e v i o u s B M P ( E ) Da t e : 9/ 2 6 / 2 0 1 3 wh i c h e n t e r s t h e B M P TSS Removal Calculation Worksheet Ca t c h B a s i n > S T C 4 5 0 ( F o r L a r g e P a r k i n g L o t ) No n - a u t o m a t e d T S S C a l c u l a t i o n S h e e t mu s t b e u s e d i f P r o p r i e t a r y B M P P r o p o s e d 1. F r o m M a s s D E P S t o r m w a t e r H a n d b o o k V o l . 1 Ma s s . D e p t . o f E n v i r o n m e n t a l P r o t e c t i o n Stormceptor Design Summary -1/2 Stormceptor Design Summary PCSWMM for Stormceptor Project Information Date 9/24/2013 Project Name Smith Wellness Center Project Number N/A Location Northampton MA Designer Information Company Berkshire Design Contact Brian Darnold Rainfall Name BIRCH HILL DAM State MA ID 666 Years of Records 1948 to 2005 Latitude 42°38'0"N Longitude 72°7'0"W Notes N/A Water Quality Objective TSS Removal (%)80 Drainage Area Total Area (ac)0.99 Imperviousness (%)66 The Stormceptor System model STC 450i achieves the water quality objective removing 82% TSS for a Fine (organics, silts and sand) particle size distribution. Upstream Storage Storage Discharge (ac-ft)(cfs) 0 0 Stormceptor Sizing Summary Stormceptor Model TSS Removal % STC 450i 82 STC 900 89 STC 1200 89 STC 1800 89 STC 2400 91 STC 3600 92 STC 4800 94 STC 6000 94 STC 7200 95 STC 11000 96 STC 13000 97 STC 16000 97 Stormceptor Design Summary -2/2 Particle Size Distribution Removing silt particles from runoff ensures that the majority of the pollutants, such as hydrocarbons and heavy metals that adhere to fine particles, are not discharged into our natural water courses. The table below lists the particle size distribution used to define the annual TSS removal. Fine (organics, silts and sand) Particle Size Distribution Specific Gravity Settling Velocity Particle Size Distribution Specific Gravity Settling Velocity µm %ft/s µm %ft/s 20 20 1.3 0.0013 60 20 1.8 0.0051 150 20 2.2 0.0354 400 20 2.65 0.2123 2000 20 2.65 0.9417 Stormceptor Design Notes ·Stormceptor performance estimates are based on simulations using PCSWMM for Stormceptor. ·Design estimates listed are only representative of specific project requirements based on total suspended solids (TSS) removal. ·Only the STC 450i is adaptable to function with a catch basin inlet and/or inline pipes. ·Only the Stormceptor models STC 450i to STC 7200 may accommodate multiple inlet pipes. ·Inlet and outlet invert elevation differences are as follows: Inlet and Outlet Pipe Invert Elevations Differences Inlet Pipe Configuration STC 450i STC 900 to STC 7200 STC 11000 to STC 16000 Single inlet pipe 3 in. 1 in. 3 in. Multiple inlet pipes 3 in. 3 in.Only one inlet pipe. ·Design estimates are based on stable site conditions only, after construction is completed. ·Design estimates assume that the storm drain is not submerged during zero flows. For submerged applications, please contact your local Stormceptor representative. ·Design estimates may be modified for specific spills controls. Please contact your local Stormceptor representative for further assistance. ·For pricing inquiries or assistance, please contact Rinker Materials 1 (800) 909-7763 www.rinkerstormceptor.com Smith Wellness Center September 26, 2013 Northampton, Massachusetts 1 Proposed Stormwater Management Plan System Operation & Maintenance During Construction The Contractor shall be responsible for inspection and maintenance during construction. At all times, siltation fabric fencing, stakes and hay bales sufficient to construct a sedimentation control barrier a minimum of 50 feet long will be stockpiled on the site in order to repair established barriers which may have been damaged or breached. An inspection of all erosion control and stormwater management systems shall be conducted by the Contractor at least once a week and during all rain storms until the completion of construction. In case of any noted breach or failure, the Contractor shall immediately make appropriate repairs to any erosion control system and notify the engineer of any problems involving stormwater management systems. A rain storm shall be defined as all or one of the following: • Any storm in which rain is predicted to last for twelve consecutive hours or more. • Any storm for which a flash flood watch or warning is issued. • Any single storm predicted to have a cumulative rainfall of greater than one-half inch. • Any storm not meeting the previous three thresholds but which would mark a third consecutive day of measurable rainfall. The Contractor shall also inspect the erosion control and stormwater management systems at times of significant increase in surface water runoff due to rapid thawing when the risk of failure of erosion control measures is significant. In such instances as remedial action is necessary, the Contractor shall repair any and all significant deficiencies in erosion control systems within two days. The Northampton Department of Public Works shall be notified of any significant failure of stormwater management systems and erosion and sediment control measures and shall be notified of any release of pollutants to a water body (stream, brook, pond, etc.). The Contractor shall remove the sediment from behind the fence of the sedimentation control barrier when the accumulated sediment has reached one-half of the original installed height of the barrier. Smith Wellness Center September 26, 2013 Northampton, Massachusetts 2 Post-Construction Stormwater Management System Owner: Smith College 7 College Lane Northampton, MA 01063 Party Responsible for Operation & Maintenance: Smith College 7 College Lane Northampton, MA 01063 Inspection & Maintenance Schedule: 1) Street Sweeping Street and parking area sweeping shall take place a minimum of 2 times per year. 2) Hooded Catch Basin and/or Drain Manhole with Sump Oil and water separators should be inspected at least four times per year and cleaned annually or more often if required. Oil and sediments should be removed and disposed of in accordance with local, state and federal guidelines and regulations. In the case of an oil or bulk pollutant release, the system must be cleaned immediately following the spill and the proper authorities notified. 3) Stormwater Treatment Chambers The Stormwater Treatment Chamber, of which there is 1 StormCeptor (Model # STC450) water quality structure or equal treatment chamber, shall be inspected and maintained according the manufacturer’s specifications. Rinker, the manufacturer of Stormceptor recommends that maintenance be completed on the structures at least once per year, but advises that the units be checked once every three months during the first year to determine the rate of sediment and oil accumulation and to establish an appropriate maintenance schedule. The rate at which the system collects pollutants will depend on site activities. Maintenance or cleaning shall be performed when the stored volume reaches 15% (6 inch sediment depth) of the Stormceptor capacity, when oil (hydrocarbon) has accumulated to 1 inch or greater depth, or immediately in the event of a fuel or oil spill according the manufacturer’s specifications. All material removed from the Stormceptor shall be disposed in accordance with applicable local, state, and federal guidelines and regulations. For more detail of how the StormCeptor should be maintained see the StormCeptor's Owner Manual. Smith Wellness Center September 26, 2013 Northampton, Massachusetts 3 4) Subsurface Detention Basin & Outlet Control Structure The subsurface detention basin requires regular removal of accumulated sediment to maintain volume capacity. Pretreatment BMPs (Deep Sump Hooded Catch Basin) should be routinely inspected and cleaned at least twice a year to prevent sediment from entering the infiltration system. Proper maintenance of roof gutters and pretreatment systems will help to protect the integrity of the subsurface detention basin. The outlet control structure should be inspected after large storms to ensure no debris is prohibiting flow through the outlet orifices in the riser pipe. All materials removed from the detention basin and outlet control structure should be removed and disposed of in accordance with local, state and federal guidelines and regulations.