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Drainage Report 10-10-19 DRAINAGE REPORT 303 King Street, Northampton, MA REVISED October 10, 2019 TABLE OF CONTENTS I. Introduction II. Soil Conditions III. Design Requirements IV. Hydraulic Watershed Analysis V. Hydrograph Routing and Hydraulic Modeling with Pre & Post Comparison (Summary Table 1) VI. MA DEP Stormwater Standards Compliance VII. DEP Stormwater Checklist VIII. Pre-Development Drainage Area Map (1”=50’) IX. Post-Development Drainage Area Map (1”=50’) X. Web Soil Survey and Soil Description XI. Rainfall Data (NOAA) XII. HydroCAD Report XIII. Operation & Maintenance Plan Introduction The Colvest Group, LLC proposes to redevelop an existing concrete plant at 303 King Street in Northampton, Massachusetts to construct two multi-tenant retail buildings with associated parking, loading and dumpster areas. The subject parcel contains 3 acres with frontage and a signalized intersection on King Street. Modifications are also proposed to the rear and front of 301 King Street to provide cross parking and access for this adjacent parcel and limit left hand turns. The total area of site disturbance is approximately 3.8 acres. Proposed Building #1 is 6,971 s.f. and includes a single lane drive-thru and outdoor seating area. Building #2 is 24,600 s.f. This development increases the impervious coverage of the overall watershed from 2.410 ac. to 2.604 ac., an 8,452 s.f. increase. A portion of the existing and historic impervious areas were compacted gravel from the previous concrete plant use. Soil Conditions The Web Soil Survey (attached) identifies the on-site soils as Amostown-Windsor silty substratum-Urban land complex. These soils are characterized as Hydraulic Soil Group B. Five test holes were performed on 9/19/18 and observed by Massachusetts Certified Soil Evaluator, Re: Colvest – 303 King Street Northampton, MA 2 Tim Coon, P.E. Our observations of the soil texture confirm the classification of HSG B. Much of the site has been disturbed and filled from the previous concrete plant activities. Test pits 2, 2a and 3 contained fill to 5 or 6 feet deep. Mottling was observed at 48” in test pit 1, limiting infiltration BMP’s to a 24” profile. Test pits 4 & 5 contained buried concrete slabs, also unsuitable for infiltration. Test pits #2A and 3 showed mottling deeper so a deeper profile BMP is feasilbe. However, fill material and concrete slabs in the area of infiltration measures would need to be removed. The permeability rate for HSG B sandy loam soils was assumed to be 1.02 in/hr per recommendation of the Massachusetts Stormwater Handbook Table 2.3.3 (1982 Rawls Rates). The average seasonal high water table elevation in the front of the site is 144.0. The elevation at test pit #3 in the rear of the site is 142.3. Design Requirements The proposed stormwater system is designed to provide zero increase in peak runoff rates for the 1-year, 2-year, 10-year, 25-year, 50-year and 100-year storm events. This peak attenuation is accomplished by providing a storage volume and infiltration area sufficient to attenuate peak flows from the increased runoff. The proposed stormwater system is also designed to comply with MADEP Stormwater Standards including treatment and infiltration of runoff for the entire site. The front system will be treated with subsurface infiltration trenches, rain gardens, deep sump catch basins with hooded outlets and a subsurface detention system for larger storms. The rear system will be treated with deep sump catch basins with hoods and an infiltration basin with forebay. The treatment BMP’s selected are reported to remove 80% of total suspended solids (TSS) as well as other common pollutants from the site discharge. Hydrologic Watershed Analysis The pre-redevelopment watershed is shown on the attached Pre-Redevelopment Drainage Area Map as two watershed areas. The front of 303 King Street drains to the west directly to King Street. The rear of the site drains to the east onto the abutting property which continues to drain to the east toward the rail road tracks and eventually the Connecticut River. The design points for this analysis are 1) the manhole at the site entrance receiving runoff to King Street and Barrett Street and 2) the discharge point of the rear infiltration basin. Since the site is mostly impervious (pavement and compacted gravel) with relatively short flow paths, time of concentration was assumed to be 5 minutes for all watershed analysis. The SCS Unit Hydrograph Method was used to model the hydrologic conditions for each design storm (1, 2, 10, 25, 50 and 100-year Type III 24-hour duration storms). Respective rainfall data for the 24-hour duration was taken from the NOAA website (attached). The post-development watershed was divided into 18 subcatchments for each drainage pipe, roof leader, structure, or basin. The subcatchments and their respective ground cover characteristics are shown on the attached Post-Redevelopment Drainage Area Map. Areas 1S- Re: Colvest – 303 King Street Northampton, MA 3 6S drain to the rear Infiltration Basin. Areas 8S-19S drain to the front subsurface detention system. Hydrograph Routing and Hydraulic Modeling The computer software HydroCAD 10.0 was used to model the pre and post-redevelopment watershed conditions during each design storm. The results demonstrate that the proposed drainage system meets the city’s requirement for zero increase in runoff from each storm event. The 25-year storm results are provided for each subcatchment, drainage structure and treatment BMP. A Node Summary is provided for all the other storm events to avoid redundancy of data. The front drainage system to King Street is designed to avoid flooding of the parking lot up to a 25-year storm. Larger storms will result in some flooding and overflow to King Street, but peak flow rates will not increase. The rear drainage system to the east is designed to retain all runoff up to a 5-year storm. During larger storm events, some discharge will occur. However, peak discharge rates are reduced. The results of this analysis are summarized on the following table 1: Table 1 – Peak Flow Comparison (cfs) STORM FRONT REAR PRE POST PRE POST 1-Year 2.84 1.17 2.53 0.00 2-Year 3.91 1.81 3.40 0.00 5-Year 5.70 2.48 4.85 0.74 10-Year 7.17 3.00 6.03 2.41 25-Year 9.20 4.56 7.65 5.92 50-Year 10.75 8.48 8.89 7.95 100-Year 12.29 12.11 10.12 9.29 These results demonstrate that the proposed redevelopment will significantly reduce peak runoff rates from the site for smaller storms and slightly decrease rates for all storms. In our professional opinion, the proposed development will not adversely impact downstream properties or drainage systems. This drainage analysis assumes a free discharge condition to King Street. While reports are that this system is undersized, this assumptions still demonstrates there will be no increase in peak Re: Colvest – 303 King Street Northampton, MA 4 flow rates. An outlet control condition at King Street would likely increase frequency of flooding, but not above existing conditions. MA DEP Stormwater Standards Compliance: Standard 1: 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 stormwater system collects and treats all the runoff from the site. Standard 2: Stormwater management systems shall be designed so that the post-development peak discharge rates do not exceed pre-development peak discharge rates. The pre and post-redevelopment discharge rates are included in the HydroCAD report and are summarized in Table 1 above. There is no increase in runoff for the 2, 10 or 100-year storms to either design point. 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 best management practices, and good operation and maintenance. At a minimum, the annual recharge from the post- development site shall approximate the annual recharge from pre-development conditions based on soil type. This Standard is met when the stormwater management system is designed to infiltrate the required recharge volume as determined in accordance with the Massachusetts Stormwater Handbook. This site involves the expansion and conversion of an existing industrial site to a commercial use. Parking requirements were set by Colvest based on their experience leasing properties. The amount of parking and impervious area cannot be reduced without negatively impacting the economic viability of the project. Therefore impervious areas cannot be further reduced. Infiltration BMP’s are proposed for all subcatchments areas. The front system discharging to King Street will be treated with subsurface infiltration trenches or rain garden/bioretention. All catch basins include deep sumps and hoods and are configured in an offline layout to avoid resuspension of sediment in the sumps. The rear of the site includes an infiltration basin with forebay. The Massachusetts Stormwater Handbook requires retention of 0.35 inches of runoff for all impervious areas over HSG B soils. The required infiltration volume for each BMP are computed as follows: Re: Colvest – 303 King Street Northampton, MA 5 1. Infiltration Basin (Areas B2, CB1-CB4) = 52,191 s.f. x 0.35”/12 = 1,522 c.f. The infiltration basin has a volume of approximate 9,138 c.f. below the overflow spillway, greatly in excess of the required infiltration volume. 2. Infiltration Trench (CB5&7) = 8,525 s.f. x 0.35”/12 = 249 c.f. The infiltration trench has a static storage capacity of 353 c.f. 3. Infiltration Trench (CB6&8) = 11,302 s.f. x 0.35”/12 = 330 c.f. The infiltration trench has a static storage capacity of 334 c.f. 4. Infiltration Trench (CB10&11) = 14,517 s.f. x 0.35”/12 = 423 c.f. The infiltration trench has a static storage capacity of 490 c.f. 5. Rain Garden #9 (CB9) = 8,657 s.f. x 0.35”/12 = 252 c.f. The rain garden has a static storage volume of 266 c.f. below the overflow CB. 6. Rain Garden #12 (CB12) = 4,807 s.f. x 0.35”/12 = 140 c.f. The rain garden has a static storage volume of 441 c.f. below the overflow CB. 7. Rain Garden #13 (CB13) = 2,541 s.f. x 0.35”/12 = 74 c.f. The rain garden has a static storage volume of 93+ c.f. below the overflow CB. 8. Rain Garden #14 (CB14) = 1,295 s.f. x 0.35”/12 = 38 c.f. The rain garden has a static storage volume of 50+ c.f. below the overflow CB. 9. Rain Garden #15 (CB15) = 1,467 s.f. x 0.35”/12 = 43 c.f. The rain garden has a static storage volume of 88+ c.f. below the overflow CB. The drawdown rate for each infiltration BMP was assumed to be 1.02 in/hr or 0.085 ft/hr per DEP Rawl’s rate for sandy loam. The drawdown time is computed as follows: T = Rv/(K*A) 1. Infiltration Basin with a bottom area of 1,320s.f. = 1,522 c.f./(0.085 ft/hr)(1,320 s.f.) = 14 hours This is less than the maximum allowed 72 hour dray down. It is also conservative since the average surface area during drawdown is larger than the bottom area. 2. Infiltration Trench (5+7) with a bottom area of 652 s.f. = 249 c.f./(0.085 ft/hr)(652) = 5 hours. 3. Infiltration Trench (6+8) with a bottom area of 616 s.f. = 330 c.f./(0.085 ft/hr)(616) = 7 hours. 4. Infiltration Trench (10+11) with a bottom area of 897 s.f. = 423 c.f./(0.085 ft/hr)(897) = 6 hours. 5. Rain Garden #9 with a surface area of 531 s.f. = 252 c.f./(0.085 ft/hr)(531) = 6 hours. Re: Colvest – 303 King Street Northampton, MA 6 6. Rain Garden #12 with a surface area of 1,764 s.f. = 140 c.f./(0.085 ft/hr)(1,764) = 1 hours. 7. Rain Garden #13 with a surface area of 261 s.f. = 74 c.f./(0.085 ft/hr)(261) = 4 hours. 8. Rain Garden #14 with a surface area of 331 s.f. = 38 c.f./(0.085 ft/hr)(331) = 2 hours. 9. Rain Garden #15 with a surface area of 300 s.f. = 43 c.f./(0.085 ft/hr)(300) = 2 hours. A maintenance schedule is provided on sheet 8 of the plan set and the city’s documentation form is attached. Standard 4: Stormwater management systems shall be designed to remove 80% of the average annual post-construction load of Total Suspended Solids (TSS). This standard is met when: a) Suitable practices for source control and pollution prevention are identified in a long- term pollution prevention plan, and thereafter are implemented and maintained; b) Structural stormwater best management practices are sized to capture the required water quality volume as determined in accordance with the Massachusetts Stormwater Handbook; and c) Pretreatment is provided in accordance with the Massachusetts Stormwater Handbook. Post-construction maintenance requirements are includes on sheet 8 of the plan set and the O&M Plan attached to this report. The owner hereby agrees to maintain good housekeeping procedures to keep the site clean of litter and debris. Enclosed dumpster pads are provided. The dumpsters will be covered. No other materials will be stored outside. No vehicles will be washed on site. The subsurface infiltration system and deep sump catch basins will be maintained as noted on sheet 8 and the O&M Plan. Spill in the parking areas will be cleaned with absorption materials and disposed in accordance with local state and federal regulations. The maintenance of lawn and pavement areas and the use of pesticides and de-icing material shall be minimized as noted on sheet 8. The infiltration trenches, rain gardens and infiltration basin with forebay are accepted BMP’s for removing 80% TSS. The off-line deep sump catch basin provides pretreatment of 25% TSS. TSS = 1.0 – (1.0 x 0.25) = 0.75 (deep sump pre-treatment) TSS = 0.75 – (0.8 x 0.75) = 0.15 = 85% efficiency The Water Quality Volume for each BMP are computed as follows: 1. Infiltration Basin = 52,191 s.f. impervious x ½”/12 = 2,175 c.f. The infiltration basin has a volume of approximately 9,138 c.f. below the spillway overflow elevation. Re: Colvest – 303 King Street Northampton, MA 7 2. Infiltration Trench (5+7) = 8,525 s.f. impervious x ½”/12 = 355 c.f. The trench contains 353 c.f. of static storage. The total infiltrated volume for a 1-year storm is 0.02 ac-ft or 871 cf. 3. Infiltration Trench (6+8) = 11,302 s.f. impervious x ½”/12 = 471 c.f. The trench contains 334 c.f. of static storage. The total infiltrated volume for a 1-year storm is 0.02 ac-ft or 828 cf. 4. Infiltration Trench (10+11) = 14,517 s.f. impervious x ½”/12 = 605 c.f. The trench contains 490 c.f. of static storage. The total infiltrated volume for a 1-year storm is 0.028 ac-ft or 1,220 cf. 5. Rain Garden #9 = 8,657 s.f. impervious x ½”/12 = 361 c.f. The rain garden has a static storage volume of 266 c.f. below the overflow CB. The total infiltrated volume for a 1-year storm is 0.011 ac-ft or 479 cf. 6. Rain Garden #12 = 4,807 s.f. impervious x ½”/12 = 200 c.f. The rain garden has a static storage volume of 441 c.f. below the overflow CB. The total infiltrated volume for a 1-year storm is 0.014 ac-ft or 610 cf. 7. Rain Garden #13 = 2,541 s.f. impervious x ½”/12 = 106 c.f. The rain garden has a static storage volume of 93+ c.f. below the overflow CB. The total infiltrated volume for a 1-year storm is 0.006 ac-ft or 261 cf. 8. Rain Garden #14 = 1,295 s.f. impervious x ½”/12 = 54 c.f. The rain garden has a static storage volume of 50+ c.f. below the overflow CB. The total infiltrated volume for a 1-year storm is 0.004 ac-ft or 174 cf. 9. Rain Garden #15 = 1,467 s.f. impervious x ½”/12 = 61 c.f. The rain garden has a static storage volume of 88+ c.f. below the overflow CB. The total infiltrated volume for a 1-year storm is 0.004 ac-ft or 174 cf. 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 land uses with higher potential pollutant loads cannot be completely protected from exposure to rain, snow, snow melt and stormwater runoff, the proponent shall use the specific structural stormwater BMPs determined by the Department to be suitable for such uses as provided in the Massachusetts Stormwater Handbook. Stormwater discharges from land uses with higher potential pollutant loads shall also comply with the requirements of the Massachusetts Clean Waters Act, M.G.L.c. 21, §§ 26-53 and the regulations promulgated thereunder at 314 CMR 3.00, 314 CMR 4.00 and 314 CMR 5.00. The proposed use is not considered a higher potential pollutant load. It is a retail site with drive-thru. Therefore this standard does not apply. Standard 6: Stormwater discharges within the Zone II or Interim Wellhead Protection Area of a public water supply and stormwater discharges near or to any other critical area require the use Re: Colvest – 303 King Street Northampton, MA 8 of the specific source control and pollution prevention measures and the specific structural stormwater best management practices determined by the Department to be suitable for managing discharges to such areas, as provided in the Massachusetts Stormwater Handbook. A discharge is near a critical area if there is a strong likelihood of a significant impact occurring to said area, taking into account site-specific factors. Stormwater discharges to Outstanding Resource Waters and Special Resource Waters shall be removed and set back from the receiving water or wetland and receive the highest and best practical method of treatment. A “storm water discharge” as defined in 314 CMR 3.04(2)(a)1. or (b) to an Outstanding Resource Water or Special Resource Water shall comply with 314 CMR 3.00 and 314 CMR 4.00. Stormwater discharges to a Zone I or Zone A are prohibited unless essential to the operation of the public water supply. The subject parcel is not within a critical area. Therefore this standard does not apply. 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 stormwater best management practice requirements of Standards 4, 5, and 6. Existing stormwater discharges shall comply with Standard 1 only to the maximum extent practicable. A redevelopment project shall also comply with all other requirements of the Stormwater Management Standards and improve existing conditions. This project is a redevelopment but increases impervious coverage. As a result it is designed to fully comply with the storm standards. 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 plan) shall be developed and implemented. Sheet 4 of the plan set is the Erosion Control Plan and sheet 8 includes construction-related notes to sequences to prevent erosion and sedimentation during construction. Standard 9: A Long -Term Operation and Maintenance (O&M) Plan shall be developed and implemented to ensure that stormwater management systems function as designed. The post-construction maintenance schedule noted on Sheet 8 of the Plan Set and the attached O&M Plan will be implemented by the property owner who will also maintain logs and records of maintenance efforts. BMP measures are shown on the plans. The estimate annual maintenance budget is $4,000. Standard 10: All illicit discharges to the stormwater management system are prohibited. Re: Colvest – 303 King Street Northampton, MA 9 No illicit (non-stormwater) discharges are proposed or identified at the site. An Illicit Discharge Compliance Statement will be provided by the owner. DEP Stormwater Checklist.doc • 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 A. Introduction Important: When filling out forms on the computer, use only the tab key to move your cursor - do not use the return key. A Stormwater Report must be submitted with the Notice of Intent permit application to document compliance with the Stormwater Management Standards. The following checklist is NOT a substitute for the Stormwater Report (which should provide more substantive and detailed information) but is offered here as a tool to help the applicant organize their Stormwater Management documentation for their Report and for the reviewer to assess this information in a consistent format. As noted in the Checklist, the Stormwater Report must contain the engineering computations and supporting information set forth in 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.1 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. 1 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. DEP Stormwater Checklist.doc • 04/01/08 Stormwater Report Checklist • Page 3 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report Checklist (continued) 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): Infiltration Basin & Infiltration Trenches 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. DEP Stormwater Checklist.doc • 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 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 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. DEP Stormwater Checklist.doc • 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 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. DEP Stormwater Checklist.doc • 04/01/08 Stormwater Report Checklist • Page 6 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report Checklist (continued) Standard 4: Water Quality (continued) The BMP is sized (and calculations provided) based on: The ½” 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. DEP Stormwater Checklist.doc • 04/01/08 Stormwater Report Checklist • Page 7 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report Checklist (continued) Standard 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. DEP Stormwater Checklist.doc • 04/01/08 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. 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. PRE-DEVELOPMENT DRAINAGE AREA MAP 1"=50' REAR 9,064 BRUSH 48,818 GRAVEL FRONT 24,527 GRAVEL 15,601 LAWN 31,633 IMP.S:\Acad\2018 Civil 3D\2018-082 Colvest - Northampton, MA\Russo Drawings\2018-082.dwg, 8/15/2019 1:43:35 PM,1:50 PROPOSED BUILDING#2 24,600 SF PROPOSED BUILDING#1 6,971 SF DRIVE THRU REST. 2,007 SF PATIO350 SF POST-DEVELOPMENT DRAINAGE AREA MAP 1"=50' POND 7,362 LAWN b1 6,971 IMP. cb14 873 LAWN 1,295 IMP. cb15 1,359 LAWN 1,467 IMP. cb13912 LAWN2,541 IMP. cb12 5,150 LAWN 4,807 IMP. cb9 2,574 LAWN 8,657 IMP. b2 25,964 IMP. cb5 413 LAWN 4,682 IMP. cb7387 LAWN 3,843 IMP. cb6 712 LAWN 6,235 IMP. cb8 756 LAWN 5,067 IMP. cb10 580 LAWN 9,055 IMP. cb11 933 LAWN 5,462 IMP. cb1 132 LAWN 8,218 IMP. cb2 328 LAWN 4,168 IMP. cb3150 LAWN6,720 IMP. cb41,527 LAWN7,121 IMP. 1C CB CB1 1D CB DMH1 1P POST REAR 1S A1 2CCB CB2 2D CB DMH2 2P POST FRONT 2S A2 3C CB CB3 3D CB DMH3 3S A3 4CCB CB4 4S A4 5S B2 6S POND 7S PRE REAR 8S A5 9P RG9 9S A6 10S A7 11S A8 12P RG12 12S A9 13P RG13 13S A10 14P RG14 14S A11 15P RG15 15S A12 16P INF-10+11 16S A1317P INF-6+8 17S A14 18P INF-5+7 18S A15 19S B1 20S PRE FRONT Routing Diagram for 2018-082 Colvest Northampton 10-10-19 Prepared by J.R. Russo & Associates, LLC, Printed 10/10/2019 HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Subcat Reach Pond Link Type III 24-hr 25-Year Rainfall=6.06"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 2HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Summary for Pond 1C: CB1 Inflow Area = 0.192 ac, 98.42% Impervious, Inflow Depth > 5.44" for 25-Year event Inflow = 1.17 cfs @ 12.07 hrs, Volume= 0.087 af Outflow = 1.17 cfs @ 12.07 hrs, Volume= 0.087 af, Atten= 0%, Lag= 0.0 min Primary = 1.17 cfs @ 12.07 hrs, Volume= 0.087 af Routing by Stor-Ind method, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Peak Elev= 145.44' @ 12.07 hrs Device Routing Invert Outlet Devices #1 Primary 144.80'12.0" Round Culvert L= 124.0' CPP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 144.80' / 144.18' S= 0.0050 '/' Cc= 0.900 n= 0.012, Flow Area= 0.79 sf Primary OutFlow Max=1.17 cfs @ 12.07 hrs HW=145.44' (Free Discharge) 1=Culvert (Barrel Controls 1.17 cfs @ 3.18 fps) Summary for Pond 1D: DMH1 Inflow Area = 0.891 ac, 98.81% Impervious, Inflow Depth > 5.49" for 25-Year event Inflow = 5.46 cfs @ 12.07 hrs, Volume= 0.408 af Outflow = 5.46 cfs @ 12.07 hrs, Volume= 0.408 af, Atten= 0%, Lag= 0.0 min Primary = 5.46 cfs @ 12.07 hrs, Volume= 0.408 af Routing by Stor-Ind method, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Peak Elev= 145.36' @ 12.07 hrs Device Routing Invert Outlet Devices #1 Primary 144.00'18.0" Round 18" CPEP L= 58.0' CPP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 144.00' / 143.71' S= 0.0050 '/' Cc= 0.900 n= 0.012, Flow Area= 1.77 sf Primary OutFlow Max=5.46 cfs @ 12.07 hrs HW=145.36' (Free Discharge) 1=18" CPEP (Barrel Controls 5.46 cfs @ 4.27 fps) Summary for Pond 1P: POST REAR Inflow Area = 1.410 ac, 85.00% Impervious, Inflow Depth > 4.96" for 25-Year event Inflow = 7.88 cfs @ 12.07 hrs, Volume= 0.583 af Outflow = 6.05 cfs @ 12.13 hrs, Volume= 0.374 af, Atten= 23%, Lag= 3.8 min Discarded = 0.13 cfs @ 12.13 hrs, Volume= 0.118 af Primary = 5.92 cfs @ 12.13 hrs, Volume= 0.256 af Routing by Stor-Ind method, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Peak Elev= 146.82' @ 12.13 hrs Surf.Area= 4,414 sf Storage= 10,511 cf Plug-Flow detention time= 140.4 min calculated for 0.374 af (64% of inflow) Center-of-Mass det. time= 59.9 min ( 788.6 - 728.7 ) Type III 24-hr 25-Year Rainfall=6.06"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 3HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Volume Invert Avail.Storage Storage Description #1 143.00' 11,310 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 143.00 1,320 0 0 144.00 1,986 1,653 1,653 145.00 2,752 2,369 4,022 146.00 3,619 3,186 7,208 147.00 4,586 4,103 11,310 Device Routing Invert Outlet Devices #1 Discarded 143.00'1.000 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 135.00' #2 Primary 146.50'12.0' long x 16.0' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 Coef. (English) 2.68 2.70 2.70 2.64 2.63 2.64 2.64 2.63 Discarded OutFlow Max=0.13 cfs @ 12.13 hrs HW=146.82' (Free Discharge) 1=Exfiltration ( Controls 0.13 cfs) Primary OutFlow Max=5.91 cfs @ 12.13 hrs HW=146.82' (Free Discharge) 2=Broad-Crested Rectangular Weir (Weir Controls 5.91 cfs @ 1.53 fps) Summary for Subcatchment 1S: A1 Runoff = 1.17 cfs @ 12.07 hrs, Volume= 0.087 af, Depth> 5.44" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Type III 24-hr 25-Year Rainfall=6.06" Area (sf) CN Description 8,218 98 Paved parking, HSG B 132 61 >75% Grass cover, Good, HSG B 8,350 97 Weighted Average 132 1.58% Pervious Area 8,218 98.42% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Pond 2C: CB2 Inflow Area = 0.103 ac, 92.70% Impervious, Inflow Depth > 5.21" for 25-Year event Inflow = 0.62 cfs @ 12.07 hrs, Volume= 0.045 af Outflow = 0.62 cfs @ 12.07 hrs, Volume= 0.045 af, Atten= 0%, Lag= 0.0 min Primary = 0.62 cfs @ 12.07 hrs, Volume= 0.045 af Type III 24-hr 25-Year Rainfall=6.06"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 4HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Routing by Stor-Ind method, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Peak Elev= 145.40' @ 12.07 hrs Device Routing Invert Outlet Devices #1 Primary 145.00'12.0" Round Culvert L= 8.0' CPP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 145.00' / 144.65' S= 0.0437 '/' Cc= 0.900 n= 0.012, Flow Area= 0.79 sf Primary OutFlow Max=0.62 cfs @ 12.07 hrs HW=145.40' (Free Discharge) 1=Culvert (Inlet Controls 0.62 cfs @ 2.14 fps) Summary for Pond 2D: DMH2 Inflow Area = 1.049 ac, 98.66% Impervious, Inflow Depth > 5.48" for 25-Year event Inflow = 6.43 cfs @ 12.07 hrs, Volume= 0.479 af Outflow = 6.43 cfs @ 12.07 hrs, Volume= 0.479 af, Atten= 0%, Lag= 0.0 min Primary = 6.43 cfs @ 12.07 hrs, Volume= 0.479 af Routing by Stor-Ind method, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Peak Elev= 145.17' @ 12.07 hrs Device Routing Invert Outlet Devices #1 Primary 143.63'18.0" Round 18" CPEP L= 50.0' CPP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 143.63' / 143.38' S= 0.0050 '/' Cc= 0.900 n= 0.012, Flow Area= 1.77 sf Primary OutFlow Max=6.43 cfs @ 12.07 hrs HW=145.17' (Free Discharge) 1=18" CPEP (Barrel Controls 6.43 cfs @ 4.41 fps) Summary for Pond 2P: POST FRONT Inflow Area = 1.716 ac, 80.40% Impervious, Inflow Depth > 3.34" for 25-Year event Inflow = 9.21 cfs @ 12.08 hrs, Volume= 0.478 af Outflow = 4.56 cfs @ 12.22 hrs, Volume= 0.476 af, Atten= 51%, Lag= 8.8 min Primary = 4.56 cfs @ 12.22 hrs, Volume= 0.476 af Routing by Stor-Ind method, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Peak Elev= 146.56' @ 12.22 hrs Surf.Area= 113 sf Storage= 5,622 cf Plug-Flow detention time= 22.6 min calculated for 0.476 af (100% of inflow) Center-of-Mass det. time= 21.3 min ( 765.1 - 743.9 ) Type III 24-hr 25-Year Rainfall=6.06"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 5HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Volume Invert Avail.Storage Storage Description #1 143.90' 509 cf 4.00'D x 4.50'H DMH x 9 #2 143.90' 5,321 cf 30.0" Round 30" Flat CPEP L= 1,084.0' #3 148.40' 185 cf Custom Stage Data (Prismatic) Listed below (Recalc) 6,015 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 148.40 370 0 0 148.90 370 185 185 Device Routing Invert Outlet Devices #1 Device 3 143.90'10.0" Vert. 10" Orifice C= 0.600 #2 Device 3 146.40'36.0" W x 4.0" H Vert. 4"x36" Weir/Orifice C= 0.600 #3 Primary 143.90'12.0" Round 12" Culvert L= 16.0' CPP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 143.90' / 143.80' S= 0.0062 '/' Cc= 0.900 n= 0.012, Flow Area= 0.79 sf #4 Primary 148.40'37.0' long x 10.0' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 Coef. (English) 2.49 2.56 2.70 2.69 2.68 2.69 2.67 2.64 Primary OutFlow Max=4.49 cfs @ 12.22 hrs HW=146.55' (Free Discharge) 3=12" Culvert (Passes 4.49 cfs of 5.55 cfs potential flow) 1=10" Orifice (Orifice Controls 3.93 cfs @ 7.20 fps) 2=4"x36" Weir/Orifice (Orifice Controls 0.56 cfs @ 1.25 fps) 4=Broad-Crested Rectangular Weir ( Controls 0.00 cfs) Summary for Subcatchment 2S: A2 Runoff = 0.62 cfs @ 12.07 hrs, Volume= 0.045 af, Depth> 5.21" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Type III 24-hr 25-Year Rainfall=6.06" Area (sf) CN Description 4,168 98 Paved parking, HSG B 328 61 >75% Grass cover, Good, HSG B 4,496 95 Weighted Average 328 7.30% Pervious Area 4,168 92.70% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Type III 24-hr 25-Year Rainfall=6.06"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 6HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Summary for Pond 3C: CB3 Inflow Area = 0.158 ac, 97.82% Impervious, Inflow Depth > 5.44" for 25-Year event Inflow = 0.97 cfs @ 12.07 hrs, Volume= 0.071 af Outflow = 0.97 cfs @ 12.07 hrs, Volume= 0.071 af, Atten= 0%, Lag= 0.0 min Primary = 0.97 cfs @ 12.07 hrs, Volume= 0.071 af Routing by Stor-Ind method, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Peak Elev= 145.36' @ 12.07 hrs Device Routing Invert Outlet Devices #1 Primary 144.80'12.0" Round Culvert L= 13.0' CPP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 144.80' / 144.65' S= 0.0115 '/' Cc= 0.900 n= 0.012, Flow Area= 0.79 sf Primary OutFlow Max=0.97 cfs @ 12.07 hrs HW=145.36' (Free Discharge) 1=Culvert (Barrel Controls 0.97 cfs @ 3.12 fps) Summary for Pond 3D: DMH3 Inflow Area = 1.247 ac, 96.07% Impervious, Inflow Depth > 5.37" for 25-Year event Inflow = 7.57 cfs @ 12.07 hrs, Volume= 0.558 af Outflow = 7.57 cfs @ 12.07 hrs, Volume= 0.558 af, Atten= 0%, Lag= 0.0 min Primary = 7.57 cfs @ 12.07 hrs, Volume= 0.558 af Routing by Stor-Ind method, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Peak Elev= 145.02' @ 12.07 hrs Device Routing Invert Outlet Devices #1 Primary 143.30'18.0" Round Culvert L= 54.0' CPP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 143.30' / 143.00' S= 0.0056 '/' Cc= 0.900 n= 0.012, Flow Area= 1.77 sf Primary OutFlow Max=7.57 cfs @ 12.07 hrs HW=145.02' (Free Discharge) 1=Culvert (Barrel Controls 7.57 cfs @ 4.68 fps) Summary for Subcatchment 3S: A3 Runoff = 0.97 cfs @ 12.07 hrs, Volume= 0.071 af, Depth> 5.44" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Type III 24-hr 25-Year Rainfall=6.06" Type III 24-hr 25-Year Rainfall=6.06"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 7HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Area (sf) CN Description 6,720 98 Paved parking, HSG B 150 61 >75% Grass cover, Good, HSG B 6,870 97 Weighted Average 150 2.18% Pervious Area 6,720 97.82% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Pond 4C: CB4 Inflow Area = 0.199 ac, 82.34% Impervious, Inflow Depth > 4.76" for 25-Year event Inflow = 1.14 cfs @ 12.07 hrs, Volume= 0.079 af Outflow = 1.14 cfs @ 12.07 hrs, Volume= 0.079 af, Atten= 0%, Lag= 0.0 min Primary = 1.14 cfs @ 12.07 hrs, Volume= 0.079 af Routing by Stor-Ind method, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Peak Elev= 145.40' @ 12.07 hrs Device Routing Invert Outlet Devices #1 Primary 144.80'12.0" Round Culvert L= 8.0' CPP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 144.80' / 144.65' S= 0.0188 '/' Cc= 0.900 n= 0.012, Flow Area= 0.79 sf Primary OutFlow Max=1.14 cfs @ 12.07 hrs HW=145.40' (Free Discharge) 1=Culvert (Barrel Controls 1.14 cfs @ 3.34 fps) Summary for Subcatchment 4S: A4 Runoff = 1.14 cfs @ 12.07 hrs, Volume= 0.079 af, Depth> 4.76" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Type III 24-hr 25-Year Rainfall=6.06" Area (sf) CN Description 7,121 98 Paved parking, HSG B 1,527 61 >75% Grass cover, Good, HSG B 8,648 91 Weighted Average 1,527 17.66% Pervious Area 7,121 82.34% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Type III 24-hr 25-Year Rainfall=6.06"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 8HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 5S: B2 Runoff = 3.67 cfs @ 12.07 hrs, Volume= 0.276 af, Depth> 5.55" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Type III 24-hr 25-Year Rainfall=6.06" Area (sf) CN Description 25,964 98 Roofs, HSG B 0 61 >75% Grass cover, Good, HSG B 25,964 98 Weighted Average 25,964 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 6S: POND Runoff = 0.45 cfs @ 12.00 hrs, Volume= 0.025 af, Depth> 1.87" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Type III 24-hr 25-Year Rainfall=6.06" Area (sf) CN Description 7,072 61 >75% Grass cover, Good, HSG B 7,072 100.00% Pervious Area Summary for Subcatchment 7S: PRE REAR Runoff = 7.65 cfs @ 12.07 hrs, Volume= 0.527 af, Depth> 4.76" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Type III 24-hr 25-Year Rainfall=6.06" Area (sf) CN Description 9,064 67 Brush, Poor, HSG B 48,818 96 Gravel surface, HSG B 57,882 91 Weighted Average 57,882 100.00% Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Type III 24-hr 25-Year Rainfall=6.06"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 9HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 8S: A5 Runoff = 0.71 cfs @ 12.07 hrs, Volume= 0.051 af, Depth> 5.21" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Type III 24-hr 25-Year Rainfall=6.06" Area (sf) CN Description 4,682 98 Paved parking, HSG B 413 61 >75% Grass cover, Good, HSG B 5,095 95 Weighted Average 413 8.11% Pervious Area 4,682 91.89% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Pond 9P: RG9 Inflow Area = 0.258 ac, 77.08% Impervious, Inflow Depth > 4.65" for 25-Year event Inflow = 1.46 cfs @ 12.07 hrs, Volume= 0.100 af Outflow = 1.46 cfs @ 12.07 hrs, Volume= 0.099 af, Atten= 0%, Lag= 0.1 min Discarded = 0.02 cfs @ 12.07 hrs, Volume= 0.017 af Primary = 1.44 cfs @ 12.07 hrs, Volume= 0.082 af Routing by Stor-Ind method, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Peak Elev= 148.14' @ 12.07 hrs Surf.Area= 838 sf Storage= 36 cf Plug-Flow detention time= 5.0 min calculated for 0.099 af (99% of inflow) Center-of-Mass det. time= 2.3 min ( 756.2 - 753.9 ) Volume Invert Avail.Storage Storage Description #1 147.00' 65 cf Custom Stage Data (Prismatic) Listed below (Recalc) 648 cf Overall x 10.0% Voids Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 147.00 0 0 0 148.00 531 266 266 148.40 1,379 382 648 Device Routing Invert Outlet Devices #1 Device 3 148.00'24.0" x 24.0" Horiz. CB Inlet C= 0.600 Limited to weir flow at low heads #2 Discarded 147.00'1.000 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 144.00' #3 Primary 144.80'12.0" Round Culvert L= 34.0' CPP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 144.80' / 144.30' S= 0.0147 '/' Cc= 0.900 n= 0.012, Flow Area= 0.79 sf Type III 24-hr 25-Year Rainfall=6.06"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 10HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Discarded OutFlow Max=0.02 cfs @ 12.07 hrs HW=148.14' (Free Discharge) 2=Exfiltration ( Controls 0.02 cfs) Primary OutFlow Max=1.44 cfs @ 12.07 hrs HW=148.14' (Free Discharge) 3=Culvert (Passes 1.44 cfs of 6.38 cfs potential flow) 1=CB Inlet (Weir Controls 1.44 cfs @ 1.24 fps) Summary for Subcatchment 9S: A6 Runoff = 0.95 cfs @ 12.07 hrs, Volume= 0.068 af, Depth> 5.09" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Type III 24-hr 25-Year Rainfall=6.06" Area (sf) CN Description 6,235 98 Paved parking, HSG B 712 61 >75% Grass cover, Good, HSG B 6,947 94 Weighted Average 712 10.25% Pervious Area 6,235 89.75% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 10S: A7 Runoff = 0.59 cfs @ 12.07 hrs, Volume= 0.042 af, Depth> 5.21" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Type III 24-hr 25-Year Rainfall=6.06" Area (sf) CN Description 3,843 98 Paved parking, HSG B 387 61 >75% Grass cover, Good, HSG B 4,230 95 Weighted Average 387 9.15% Pervious Area 3,843 90.85% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Type III 24-hr 25-Year Rainfall=6.06"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 11HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 11S: A8 Runoff = 0.79 cfs @ 12.07 hrs, Volume= 0.055 af, Depth> 4.98" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Type III 24-hr 25-Year Rainfall=6.06" Area (sf) CN Description 5,067 98 Paved parking, HSG B 756 61 >75% Grass cover, Good, HSG B 5,823 93 Weighted Average 756 12.98% Pervious Area 5,067 87.02% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Pond 12P: RG12 Inflow Area = 0.229 ac, 48.28% Impervious, Inflow Depth > 3.50" for 25-Year event Inflow = 1.03 cfs @ 12.07 hrs, Volume= 0.067 af Outflow = 0.89 cfs @ 12.12 hrs, Volume= 0.062 af, Atten= 14%, Lag= 2.7 min Discarded = 0.05 cfs @ 12.12 hrs, Volume= 0.032 af Primary = 0.84 cfs @ 12.12 hrs, Volume= 0.030 af Routing by Stor-Ind method, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Peak Elev= 148.10' @ 12.12 hrs Surf.Area= 2,135 sf Storage= 638 cf Plug-Flow detention time= 70.0 min calculated for 0.062 af (93% of inflow) Center-of-Mass det. time= 44.3 min ( 825.8 - 781.5 ) Volume Invert Avail.Storage Storage Description #1 147.50' 1,440 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 147.50 0 0 0 148.00 1,764 441 441 148.40 3,233 999 1,440 Device Routing Invert Outlet Devices #1 Device 3 148.00'24.0" x 24.0" Horiz. CB Inlet C= 0.600 Limited to weir flow at low heads #2 Discarded 147.50'1.000 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 144.00' #3 Primary 144.80'12.0" Round Culvert L= 19.0' CPP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 144.80' / 144.60' S= 0.0105 '/' Cc= 0.900 n= 0.012, Flow Area= 0.79 sf Type III 24-hr 25-Year Rainfall=6.06"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 12HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Discarded OutFlow Max=0.05 cfs @ 12.12 hrs HW=148.10' (Free Discharge) 2=Exfiltration ( Controls 0.05 cfs) Primary OutFlow Max=0.84 cfs @ 12.12 hrs HW=148.10' (Free Discharge) 3=Culvert (Passes 0.84 cfs of 6.33 cfs potential flow) 1=CB Inlet (Weir Controls 0.84 cfs @ 1.04 fps) Summary for Subcatchment 12S: A9 Runoff = 1.46 cfs @ 12.07 hrs, Volume= 0.100 af, Depth> 4.65" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Type III 24-hr 25-Year Rainfall=6.06" Area (sf) CN Description 8,657 98 Paved parking, HSG B 2,574 61 >75% Grass cover, Good, HSG B 11,231 90 Weighted Average 2,574 22.92% Pervious Area 8,657 77.08% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Pond 13P: RG13 Inflow Area = 0.079 ac, 73.59% Impervious, Inflow Depth > 4.43" for 25-Year event Inflow = 0.44 cfs @ 12.07 hrs, Volume= 0.029 af Outflow = 0.43 cfs @ 12.09 hrs, Volume= 0.027 af, Atten= 2%, Lag= 1.0 min Discarded = 0.01 cfs @ 12.09 hrs, Volume= 0.009 af Primary = 0.41 cfs @ 12.09 hrs, Volume= 0.017 af Routing by Stor-Ind method, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Peak Elev= 148.46' @ 12.09 hrs Surf.Area= 566 sf Storage= 160 cf Plug-Flow detention time= 55.9 min calculated for 0.027 af (92% of inflow) Center-of-Mass det. time= 27.7 min ( 787.6 - 759.9 ) Volume Invert Avail.Storage Storage Description #1 147.50' 348 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 147.50 0 0 0 148.00 135 34 34 148.30 261 59 93 148.70 1,011 254 348 Type III 24-hr 25-Year Rainfall=6.06"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 13HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Device Routing Invert Outlet Devices #1 Device 3 148.40'24.0" x 24.0" Horiz. CB Inlet C= 0.600 Limited to weir flow at low heads #2 Discarded 147.50'1.000 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 144.00' #3 Primary 145.20'12.0" Round Culvert L= 10.0' CPP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 145.20' / 145.05' S= 0.0150 '/' Cc= 0.900 n= 0.012, Flow Area= 0.79 sf Discarded OutFlow Max=0.01 cfs @ 12.09 hrs HW=148.46' (Free Discharge) 2=Exfiltration ( Controls 0.01 cfs) Primary OutFlow Max=0.41 cfs @ 12.09 hrs HW=148.46' (Free Discharge) 3=Culvert (Passes 0.41 cfs of 6.29 cfs potential flow) 1=CB Inlet (Weir Controls 0.41 cfs @ 0.82 fps) Summary for Subcatchment 13S: A10 Runoff = 1.35 cfs @ 12.07 hrs, Volume= 0.098 af, Depth> 5.32" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Type III 24-hr 25-Year Rainfall=6.06" Area (sf) CN Description 9,055 98 Paved parking, HSG B 580 61 >75% Grass cover, Good, HSG B 9,635 96 Weighted Average 580 6.02% Pervious Area 9,055 93.98% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Pond 14P: RG14 Inflow Area = 0.050 ac, 59.73% Impervious, Inflow Depth > 3.90" for 25-Year event Inflow = 0.25 cfs @ 12.07 hrs, Volume= 0.016 af Outflow = 0.24 cfs @ 12.09 hrs, Volume= 0.015 af, Atten= 3%, Lag= 1.2 min Discarded = 0.01 cfs @ 12.09 hrs, Volume= 0.009 af Primary = 0.23 cfs @ 12.09 hrs, Volume= 0.007 af Routing by Stor-Ind method, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Peak Elev= 148.44' @ 12.09 hrs Surf.Area= 591 sf Storage= 115 cf Plug-Flow detention time= 56.6 min calculated for 0.015 af (96% of inflow) Center-of-Mass det. time= 40.3 min ( 813.1 - 772.7 ) Type III 24-hr 25-Year Rainfall=6.06"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 14HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Volume Invert Avail.Storage Storage Description #1 148.00' 328 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 148.00 0 0 0 148.30 331 50 50 148.70 1,063 279 328 Device Routing Invert Outlet Devices #1 Device 3 148.40'24.0" x 24.0" Horiz. CB Inlet C= 0.600 Limited to weir flow at low heads #2 Discarded 148.00'1.000 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 144.00' #3 Primary 145.20'12.0" Round Culvert L= 10.0' CPP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 145.20' / 145.05' S= 0.0150 '/' Cc= 0.900 n= 0.012, Flow Area= 0.79 sf Discarded OutFlow Max=0.01 cfs @ 12.09 hrs HW=148.44' (Free Discharge) 2=Exfiltration ( Controls 0.01 cfs) Primary OutFlow Max=0.22 cfs @ 12.09 hrs HW=148.44' (Free Discharge) 3=Culvert (Passes 0.22 cfs of 6.26 cfs potential flow) 1=CB Inlet (Weir Controls 0.22 cfs @ 0.67 fps) Summary for Subcatchment 14S: A11 Runoff = 0.87 cfs @ 12.07 hrs, Volume= 0.061 af, Depth> 4.98" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Type III 24-hr 25-Year Rainfall=6.06" Area (sf) CN Description 5,462 98 Paved parking, HSG B 933 61 >75% Grass cover, Good, HSG B 6,395 93 Weighted Average 933 14.59% Pervious Area 5,462 85.41% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Pond 15P: RG15 Type III 24-hr 25-Year Rainfall=6.06"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 15HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Inflow Area = 0.065 ac, 51.91% Impervious, Inflow Depth > 3.60" for 25-Year event Inflow = 0.30 cfs @ 12.07 hrs, Volume= 0.019 af Outflow = 0.29 cfs @ 12.09 hrs, Volume= 0.017 af, Atten= 2%, Lag= 1.0 min Discarded = 0.01 cfs @ 12.09 hrs, Volume= 0.008 af Primary = 0.28 cfs @ 12.09 hrs, Volume= 0.010 af Routing by Stor-Ind method, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Peak Elev= 148.45' @ 12.09 hrs Surf.Area= 490 sf Storage= 147 cf Plug-Flow detention time= 67.3 min calculated for 0.017 af (90% of inflow) Center-of-Mass det. time= 34.5 min ( 813.9 - 779.4 ) Volume Invert Avail.Storage Storage Description #1 147.80' 311 cf Custom Stage Data (Prismatic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 147.80 0 0 0 148.00 173 17 17 148.30 300 71 88 148.70 812 222 311 Device Routing Invert Outlet Devices #1 Device 3 148.40'24.0" x 24.0" Horiz. CB Inlet C= 0.600 Limited to weir flow at low heads #2 Discarded 147.80'1.000 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 144.00' #3 Primary 145.20'12.0" Round Culvert L= 10.0' CPP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 145.20' / 145.05' S= 0.0150 '/' Cc= 0.900 n= 0.012, Flow Area= 0.79 sf Discarded OutFlow Max=0.01 cfs @ 12.09 hrs HW=148.45' (Free Discharge) 2=Exfiltration ( Controls 0.01 cfs) Primary OutFlow Max=0.28 cfs @ 12.09 hrs HW=148.45' (Free Discharge) 3=Culvert (Passes 0.28 cfs of 6.27 cfs potential flow) 1=CB Inlet (Weir Controls 0.28 cfs @ 0.72 fps) Summary for Subcatchment 15S: A12 Runoff = 1.03 cfs @ 12.07 hrs, Volume= 0.067 af, Depth> 3.50" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Type III 24-hr 25-Year Rainfall=6.06" Type III 24-hr 25-Year Rainfall=6.06"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 16HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Area (sf) CN Description 4,807 98 Paved parking, HSG B 5,150 61 >75% Grass cover, Good, HSG B 9,957 79 Weighted Average 5,150 51.72% Pervious Area 4,807 48.28% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Pond 16P: INF-10+11 Inflow Area = 0.368 ac, 90.56% Impervious, Inflow Depth > 5.19" for 25-Year event Inflow = 2.21 cfs @ 12.07 hrs, Volume= 0.159 af Outflow = 2.21 cfs @ 12.07 hrs, Volume= 0.148 af, Atten= 0%, Lag= 0.0 min Discarded = 0.03 cfs @ 12.07 hrs, Volume= 0.038 af Primary = 2.18 cfs @ 12.07 hrs, Volume= 0.110 af Routing by Stor-Ind method, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Peak Elev= 147.23' @ 12.07 hrs Surf.Area= 909 sf Storage= 493 cf Plug-Flow detention time= 41.2 min calculated for 0.148 af (93% of inflow) Center-of-Mass det. time= 15.0 min ( 749.6 - 734.6 ) Volume Invert Avail.Storage Storage Description #1 146.00' 271 cf Stone Bedding (Prismatic) Listed below (Recalc) 897 cf Overall - 219 cf Embedded = 678 cf x 40.0% Voids #2 146.08' 219 cf 10.0" Round Pipe Storage Inside #1 L= 402.0' #3 147.00' 2,592 cf Custom Stage Data (Prismatic) Listed below (Recalc) x 2 3,082 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 146.00 897 0 0 147.00 897 897 897 Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 147.00 6 0 0 148.00 6 6 6 148.50 5,154 1,290 1,296 Device Routing Invert Outlet Devices #1 Device 2 147.00'3.0' long Sharp-Crested Rectangular Weir X 2.00 2 End Contraction(s) #2 Primary 144.80'12.0" Round Culvert X 2.00 L= 32.0' CPP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 144.80' / 144.60' S= 0.0063 '/' Cc= 0.900 n= 0.012, Flow Area= 0.79 sf Type III 24-hr 25-Year Rainfall=6.06"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 17HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC #3 Discarded 146.00'1.020 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 144.00' Discarded OutFlow Max=0.03 cfs @ 12.07 hrs HW=147.23' (Free Discharge) 3=Exfiltration ( Controls 0.03 cfs) Primary OutFlow Max=2.18 cfs @ 12.07 hrs HW=147.23' (Free Discharge) 2=Culvert (Passes 2.18 cfs of 10.50 cfs potential flow) 1=Sharp-Crested Rectangular Weir (Weir Controls 2.18 cfs @ 1.58 fps) Summary for Subcatchment 16S: A13 Runoff = 0.44 cfs @ 12.07 hrs, Volume= 0.029 af, Depth> 4.43" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Type III 24-hr 25-Year Rainfall=6.06" Area (sf) CN Description 2,541 98 Paved parking, HSG B 912 61 >75% Grass cover, Good, HSG B 3,453 88 Weighted Average 912 26.41% Pervious Area 2,541 73.59% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Pond 17P: INF-6+8 Inflow Area = 0.293 ac, 88.50% Impervious, Inflow Depth > 5.04" for 25-Year event Inflow = 1.74 cfs @ 12.07 hrs, Volume= 0.123 af Outflow = 1.74 cfs @ 12.07 hrs, Volume= 0.115 af, Atten= 0%, Lag= 0.0 min Discarded = 0.02 cfs @ 12.07 hrs, Volume= 0.026 af Primary = 1.72 cfs @ 12.07 hrs, Volume= 0.090 af Routing by Stor-Ind method, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Peak Elev= 147.20' @ 12.07 hrs Surf.Area= 628 sf Storage= 336 cf Plug-Flow detention time= 37.1 min calculated for 0.115 af (94% of inflow) Center-of-Mass det. time= 13.6 min ( 754.5 - 740.9 ) Volume Invert Avail.Storage Storage Description #1 146.00' 188 cf Stone Bedding (Prismatic) Listed below (Recalc) 616 cf Overall - 146 cf Embedded = 470 cf x 40.0% Voids #2 146.08' 146 cf 10.0" Round Pipe Storage Inside #1 L= 267.0' #3 147.00' 3,371 cf Custom Stage Data (Prismatic) Listed below (Recalc) x 2 3,704 cf Total Available Storage Type III 24-hr 25-Year Rainfall=6.06"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 18HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 146.00 616 0 0 147.00 616 616 616 Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 147.00 6 0 0 148.00 6 6 6 148.50 6,711 1,679 1,685 Device Routing Invert Outlet Devices #1 Device 2 147.00'3.0' long Sharp-Crested Rectangular Weir X 2.00 2 End Contraction(s) #2 Primary 144.80'12.0" Round Culvert X 2.00 L= 31.0' CPP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 144.80' / 144.60' S= 0.0065 '/' Cc= 0.900 n= 0.012, Flow Area= 0.79 sf #3 Discarded 146.00'1.020 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 144.00' Discarded OutFlow Max=0.02 cfs @ 12.07 hrs HW=147.20' (Free Discharge) 3=Exfiltration ( Controls 0.02 cfs) Primary OutFlow Max=1.72 cfs @ 12.07 hrs HW=147.20' (Free Discharge) 2=Culvert (Passes 1.72 cfs of 10.42 cfs potential flow) 1=Sharp-Crested Rectangular Weir (Weir Controls 1.72 cfs @ 1.46 fps) Summary for Subcatchment 17S: A14 Runoff = 0.25 cfs @ 12.07 hrs, Volume= 0.016 af, Depth> 3.90" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Type III 24-hr 25-Year Rainfall=6.06" Area (sf) CN Description 1,295 98 Paved parking, HSG B 873 61 >75% Grass cover, Good, HSG B 2,168 83 Weighted Average 873 40.27% Pervious Area 1,295 59.73% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Type III 24-hr 25-Year Rainfall=6.06"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 19HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Summary for Pond 18P: INF-5+7 Inflow Area = 0.214 ac, 91.42% Impervious, Inflow Depth > 5.21" for 25-Year event Inflow = 1.29 cfs @ 12.07 hrs, Volume= 0.093 af Outflow = 1.29 cfs @ 12.07 hrs, Volume= 0.085 af, Atten= 0%, Lag= 0.0 min Discarded = 0.02 cfs @ 12.07 hrs, Volume= 0.027 af Primary = 1.27 cfs @ 12.07 hrs, Volume= 0.059 af Routing by Stor-Ind method, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Peak Elev= 147.16' @ 12.07 hrs Surf.Area= 664 sf Storage= 355 cf Plug-Flow detention time= 47.4 min calculated for 0.085 af (92% of inflow) Center-of-Mass det. time= 18.3 min ( 752.8 - 734.4 ) Volume Invert Avail.Storage Storage Description #1 146.00' 199 cf Stone Bedding (Prismatic) Listed below (Recalc) 652 cf Overall - 154 cf Embedded = 498 cf x 40.0% Voids #2 146.08' 154 cf 10.0" Round Pipe Storage Inside #1 L= 282.0' #3 147.00' 1,308 cf Custom Stage Data (Prismatic) Listed below (Recalc) x 2 1,661 cf Total Available Storage Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 146.00 652 0 0 147.00 652 652 652 Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 147.00 6 0 0 148.00 6 6 6 148.50 2,585 648 654 Device Routing Invert Outlet Devices #1 Device 2 147.00'3.0' long Sharp-Crested Rectangular Weir X 2.00 2 End Contraction(s) #2 Primary 144.80'12.0" Round Culvert X 2.00 L= 29.0' CPP, square edge headwall, Ke= 0.500 Inlet / Outlet Invert= 144.80' / 144.60' S= 0.0069 '/' Cc= 0.900 n= 0.012, Flow Area= 0.79 sf #3 Discarded 146.00'1.020 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 144.00' Discarded OutFlow Max=0.02 cfs @ 12.07 hrs HW=147.16' (Free Discharge) 3=Exfiltration ( Controls 0.02 cfs) Primary OutFlow Max=1.26 cfs @ 12.07 hrs HW=147.16' (Free Discharge) 2=Culvert (Passes 1.26 cfs of 10.32 cfs potential flow) 1=Sharp-Crested Rectangular Weir (Weir Controls 1.26 cfs @ 1.32 fps) Type III 24-hr 25-Year Rainfall=6.06"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 20HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Summary for Subcatchment 18S: A15 Runoff = 0.30 cfs @ 12.07 hrs, Volume= 0.019 af, Depth> 3.60" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Type III 24-hr 25-Year Rainfall=6.06" Area (sf) CN Description 1,467 98 Paved parking, HSG B 1,359 61 >75% Grass cover, Good, HSG B 2,826 80 Weighted Average 1,359 48.09% Pervious Area 1,467 51.91% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 19S: B1 Runoff = 0.98 cfs @ 12.07 hrs, Volume= 0.074 af, Depth> 5.55" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Type III 24-hr 25-Year Rainfall=6.06" Area (sf) CN Description 6,971 98 Roofs, HSG B 0 61 >75% Grass cover, Good, HSG B 6,971 98 Weighted Average 6,971 100.00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Summary for Subcatchment 20S: PRE FRONT Runoff = 9.20 cfs @ 12.07 hrs, Volume= 0.623 af, Depth> 4.54" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 1.00-20.00 hrs, dt= 0.01 hrs Type III 24-hr 25-Year Rainfall=6.06" Area (sf) CN Description 24,527 96 Gravel surface, HSG B 15,601 61 >75% Grass cover, Good, HSG B 31,633 98 Paved parking, HSG B 71,761 89 Weighted Average 40,128 55.92% Pervious Area 31,633 44.08% Impervious Area Type III 24-hr 25-Year Rainfall=6.06"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 21HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, Type III 24-hr 1-Year Rainfall=2.46"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 22HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Time span=1.00-20.00 hrs, dt=0.01 hrs, 1901 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind method - Pond routing by Stor-Ind method Peak Elev=145.18' Inflow=0.46 cfs 0.032 afPond 1C: CB1 12.0" Round Culvert n=0.012 L=124.0' S=0.0050 '/' Outflow=0.46 cfs 0.032 af Peak Elev=144.77' Inflow=2.15 cfs 0.153 afPond 1D: DMH1 18.0" Round Culvert n=0.012 L=58.0' S=0.0050 '/' Outflow=2.15 cfs 0.153 af Peak Elev=145.66' Storage=6,034 cf Inflow=2.92 cfs 0.206 afPond 1P: POST REAR Discarded=0.09 cfs 0.080 af Primary=0.00 cfs 0.000 af Outflow=0.09 cfs 0.080 af Runoff Area=8,350 sf 98.42% Impervious Runoff Depth>2.02"Subcatchment 1S: A1 Tc=5.0 min CN=97 Runoff=0.46 cfs 0.032 af Peak Elev=145.23' Inflow=0.23 cfs 0.016 afPond 2C: CB2 12.0" Round Culvert n=0.012 L=8.0' S=0.0437 '/' Outflow=0.23 cfs 0.016 af Peak Elev=144.48' Inflow=2.53 cfs 0.180 afPond 2D: DMH2 18.0" Round Culvert n=0.012 L=50.0' S=0.0050 '/' Outflow=2.53 cfs 0.180 af Peak Elev=144.56' Storage=1,208 cf Inflow=3.01 cfs 0.095 afPond 2P: POST FRONT Outflow=1.17 cfs 0.095 af Runoff Area=4,496 sf 92.70% Impervious Runoff Depth>1.82"Subcatchment 2S: A2 Tc=5.0 min CN=95 Runoff=0.23 cfs 0.016 af Peak Elev=145.12' Inflow=0.38 cfs 0.027 afPond 3C: CB3 12.0" Round Culvert n=0.012 L=13.0' S=0.0115 '/' Outflow=0.38 cfs 0.027 af Peak Elev=144.21' Inflow=2.91 cfs 0.204 afPond 3D: DMH3 18.0" Round Culvert n=0.012 L=54.0' S=0.0056 '/' Outflow=2.91 cfs 0.204 af Runoff Area=6,870 sf 97.82% Impervious Runoff Depth>2.02"Subcatchment 3S: A3 Tc=5.0 min CN=97 Runoff=0.38 cfs 0.027 af Peak Elev=145.11' Inflow=0.38 cfs 0.024 afPond 4C: CB4 12.0" Round Culvert n=0.012 L=8.0' S=0.0188 '/' Outflow=0.38 cfs 0.024 af Runoff Area=8,648 sf 82.34% Impervious Runoff Depth>1.48"Subcatchment 4S: A4 Tc=5.0 min CN=91 Runoff=0.38 cfs 0.024 af Runoff Area=25,964 sf 100.00% Impervious Runoff Depth>2.12"Subcatchment 5S: B2 Tc=5.0 min CN=98 Runoff=1.46 cfs 0.105 af Runoff Area=7,072 sf 0.00% Impervious Runoff Depth>0.15"Subcatchment 6S: POND Tc=0.0 min CN=61 Runoff=0.01 cfs 0.002 af Runoff Area=57,882 sf 0.00% Impervious Runoff Depth>1.48"Subcatchment 7S: PRE REAR Tc=5.0 min CN=91 Runoff=2.53 cfs 0.163 af Type III 24-hr 1-Year Rainfall=2.46"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 23HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Runoff Area=5,095 sf 91.89% Impervious Runoff Depth>1.82"Subcatchment 8S: A5 Tc=5.0 min CN=95 Runoff=0.26 cfs 0.018 af Peak Elev=148.07' Storage=31 cf Inflow=0.47 cfs 0.030 afPond 9P: RG9 Discarded=0.02 cfs 0.011 af Primary=0.45 cfs 0.019 af Outflow=0.47 cfs 0.030 af Runoff Area=6,947 sf 89.75% Impervious Runoff Depth>1.73"Subcatchment 9S: A6 Tc=5.0 min CN=94 Runoff=0.35 cfs 0.023 af Runoff Area=4,230 sf 90.85% Impervious Runoff Depth>1.82"Subcatchment 10S: A7 Tc=5.0 min CN=95 Runoff=0.22 cfs 0.015 af Runoff Area=5,823 sf 87.02% Impervious Runoff Depth>1.64"Subcatchment 11S: A8 Tc=5.0 min CN=93 Runoff=0.28 cfs 0.018 af Peak Elev=147.86' Storage=234 cf Inflow=0.21 cfs 0.014 afPond 12P: RG12 Discarded=0.03 cfs 0.014 af Primary=0.00 cfs 0.000 af Outflow=0.03 cfs 0.014 af Runoff Area=11,231 sf 77.08% Impervious Runoff Depth>1.40"Subcatchment 12S: A9 Tc=5.0 min CN=90 Runoff=0.47 cfs 0.030 af Peak Elev=148.41' Storage=135 cf Inflow=0.13 cfs 0.008 afPond 13P: RG13 Discarded=0.01 cfs 0.006 af Primary=0.05 cfs 0.001 af Outflow=0.06 cfs 0.007 af Runoff Area=9,635 sf 93.98% Impervious Runoff Depth>1.92"Subcatchment 13S: A10 Tc=5.0 min CN=96 Runoff=0.51 cfs 0.035 af Peak Elev=148.34' Storage=66 cf Inflow=0.06 cfs 0.004 afPond 14P: RG14 Discarded=0.01 cfs 0.004 af Primary=0.00 cfs 0.000 af Outflow=0.01 cfs 0.004 af Runoff Area=6,395 sf 85.41% Impervious Runoff Depth>1.64"Subcatchment 14S: A11 Tc=5.0 min CN=93 Runoff=0.31 cfs 0.020 af Peak Elev=148.27' Storage=79 cf Inflow=0.07 cfs 0.004 afPond 15P: RG15 Discarded=0.01 cfs 0.004 af Primary=0.00 cfs 0.000 af Outflow=0.01 cfs 0.004 af Runoff Area=9,957 sf 48.28% Impervious Runoff Depth>0.74"Subcatchment 15S: A12 Tc=5.0 min CN=79 Runoff=0.21 cfs 0.014 af Peak Elev=147.13' Storage=492 cf Inflow=0.82 cfs 0.055 afPond 16P: INF-10+11 Discarded=0.03 cfs 0.028 af Primary=0.93 cfs 0.021 af Outflow=0.96 cfs 0.049 af Runoff Area=3,453 sf 73.59% Impervious Runoff Depth>1.26"Subcatchment 16S: A13 Tc=5.0 min CN=88 Runoff=0.13 cfs 0.008 af Peak Elev=147.10' Storage=335 cf Inflow=0.62 cfs 0.041 afPond 17P: INF-6+8 Discarded=0.02 cfs 0.019 af Primary=0.66 cfs 0.017 af Outflow=0.68 cfs 0.036 af Runoff Area=2,168 sf 59.73% Impervious Runoff Depth>0.95"Subcatchment 17S: A14 Tc=5.0 min CN=83 Runoff=0.06 cfs 0.004 af Type III 24-hr 1-Year Rainfall=2.46"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 24HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Peak Elev=147.10' Storage=354 cf Inflow=0.48 cfs 0.032 afPond 18P: INF-5+7 Discarded=0.02 cfs 0.020 af Primary=0.63 cfs 0.009 af Outflow=0.65 cfs 0.029 af Runoff Area=2,826 sf 51.91% Impervious Runoff Depth>0.79"Subcatchment 18S: A15 Tc=5.0 min CN=80 Runoff=0.07 cfs 0.004 af Runoff Area=6,971 sf 100.00% Impervious Runoff Depth>2.12"Subcatchment 19S: B1 Tc=5.0 min CN=98 Runoff=0.39 cfs 0.028 af Runoff Area=71,761 sf 44.08% Impervious Runoff Depth>1.33"Subcatchment 20S: PRE FRONT Tc=5.0 min CN=89 Runoff=2.84 cfs 0.182 af Type III 24-hr 2-Year Rainfall=3.07"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 25HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Time span=1.00-20.00 hrs, dt=0.01 hrs, 1901 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind method - Pond routing by Stor-Ind method Peak Elev=145.23' Inflow=0.58 cfs 0.041 afPond 1C: CB1 12.0" Round Culvert n=0.012 L=124.0' S=0.0050 '/' Outflow=0.58 cfs 0.041 af Peak Elev=144.88' Inflow=2.72 cfs 0.196 afPond 1D: DMH1 18.0" Round Culvert n=0.012 L=58.0' S=0.0050 '/' Outflow=2.72 cfs 0.196 af Peak Elev=146.24' Storage=8,102 cf Inflow=3.75 cfs 0.268 afPond 1P: POST REAR Discarded=0.11 cfs 0.095 af Primary=0.00 cfs 0.000 af Outflow=0.11 cfs 0.095 af Runoff Area=8,350 sf 98.42% Impervious Runoff Depth>2.59"Subcatchment 1S: A1 Tc=5.0 min CN=97 Runoff=0.58 cfs 0.041 af Peak Elev=145.27' Inflow=0.30 cfs 0.021 afPond 2C: CB2 12.0" Round Culvert n=0.012 L=8.0' S=0.0437 '/' Outflow=0.30 cfs 0.021 af Peak Elev=144.61' Inflow=3.20 cfs 0.230 afPond 2D: DMH2 18.0" Round Culvert n=0.012 L=50.0' S=0.0050 '/' Outflow=3.20 cfs 0.230 af Peak Elev=144.79' Storage=1,808 cf Inflow=3.63 cfs 0.148 afPond 2P: POST FRONT Outflow=1.81 cfs 0.147 af Runoff Area=4,496 sf 92.70% Impervious Runoff Depth>2.39"Subcatchment 2S: A2 Tc=5.0 min CN=95 Runoff=0.30 cfs 0.021 af Peak Elev=145.17' Inflow=0.48 cfs 0.034 afPond 3C: CB3 12.0" Round Culvert n=0.012 L=13.0' S=0.0115 '/' Outflow=0.48 cfs 0.034 af Peak Elev=144.35' Inflow=3.71 cfs 0.264 afPond 3D: DMH3 18.0" Round Culvert n=0.012 L=54.0' S=0.0056 '/' Outflow=3.71 cfs 0.264 af Runoff Area=6,870 sf 97.82% Impervious Runoff Depth>2.59"Subcatchment 3S: A3 Tc=5.0 min CN=97 Runoff=0.48 cfs 0.034 af Peak Elev=145.17' Inflow=0.51 cfs 0.033 afPond 4C: CB4 12.0" Round Culvert n=0.012 L=8.0' S=0.0188 '/' Outflow=0.51 cfs 0.033 af Runoff Area=8,648 sf 82.34% Impervious Runoff Depth>2.01"Subcatchment 4S: A4 Tc=5.0 min CN=91 Runoff=0.51 cfs 0.033 af Runoff Area=25,964 sf 100.00% Impervious Runoff Depth>2.70"Subcatchment 5S: B2 Tc=5.0 min CN=98 Runoff=1.84 cfs 0.134 af Runoff Area=7,072 sf 0.00% Impervious Runoff Depth>0.34"Subcatchment 6S: POND Tc=0.0 min CN=61 Runoff=0.05 cfs 0.005 af Runoff Area=57,882 sf 0.00% Impervious Runoff Depth>2.01"Subcatchment 7S: PRE REAR Tc=5.0 min CN=91 Runoff=3.40 cfs 0.223 af Type III 24-hr 2-Year Rainfall=3.07"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 26HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Runoff Area=5,095 sf 91.89% Impervious Runoff Depth>2.39"Subcatchment 8S: A5 Tc=5.0 min CN=95 Runoff=0.34 cfs 0.023 af Peak Elev=148.08' Storage=32 cf Inflow=0.64 cfs 0.041 afPond 9P: RG9 Discarded=0.02 cfs 0.013 af Primary=0.62 cfs 0.028 af Outflow=0.64 cfs 0.041 af Runoff Area=6,947 sf 89.75% Impervious Runoff Depth>2.29"Subcatchment 9S: A6 Tc=5.0 min CN=94 Runoff=0.45 cfs 0.030 af Runoff Area=4,230 sf 90.85% Impervious Runoff Depth>2.39"Subcatchment 10S: A7 Tc=5.0 min CN=95 Runoff=0.28 cfs 0.019 af Runoff Area=5,823 sf 87.02% Impervious Runoff Depth>2.19"Subcatchment 11S: A8 Tc=5.0 min CN=93 Runoff=0.37 cfs 0.024 af Peak Elev=147.98' Storage=401 cf Inflow=0.34 cfs 0.022 afPond 12P: RG12 Discarded=0.04 cfs 0.021 af Primary=0.00 cfs 0.000 af Outflow=0.04 cfs 0.021 af Runoff Area=11,231 sf 77.08% Impervious Runoff Depth>1.92"Subcatchment 12S: A9 Tc=5.0 min CN=90 Runoff=0.64 cfs 0.041 af Peak Elev=148.43' Storage=144 cf Inflow=0.18 cfs 0.012 afPond 13P: RG13 Discarded=0.01 cfs 0.007 af Primary=0.15 cfs 0.004 af Outflow=0.16 cfs 0.010 af Runoff Area=9,635 sf 93.98% Impervious Runoff Depth>2.49"Subcatchment 13S: A10 Tc=5.0 min CN=96 Runoff=0.66 cfs 0.046 af Peak Elev=148.41' Storage=95 cf Inflow=0.09 cfs 0.006 afPond 14P: RG14 Discarded=0.01 cfs 0.005 af Primary=0.02 cfs 0.000 af Outflow=0.03 cfs 0.006 af Runoff Area=6,395 sf 85.41% Impervious Runoff Depth>2.19"Subcatchment 14S: A11 Tc=5.0 min CN=93 Runoff=0.40 cfs 0.027 af Peak Elev=148.40' Storage=126 cf Inflow=0.10 cfs 0.006 afPond 15P: RG15 Discarded=0.01 cfs 0.006 af Primary=0.00 cfs 0.000 af Outflow=0.01 cfs 0.006 af Runoff Area=9,957 sf 48.28% Impervious Runoff Depth>1.14"Subcatchment 15S: A12 Tc=5.0 min CN=79 Runoff=0.34 cfs 0.022 af Peak Elev=147.14' Storage=492 cf Inflow=1.06 cfs 0.073 afPond 16P: INF-10+11 Discarded=0.03 cfs 0.030 af Primary=1.03 cfs 0.034 af Outflow=1.06 cfs 0.065 af Runoff Area=3,453 sf 73.59% Impervious Runoff Depth>1.76"Subcatchment 16S: A13 Tc=5.0 min CN=88 Runoff=0.18 cfs 0.012 af Peak Elev=147.12' Storage=335 cf Inflow=0.82 cfs 0.055 afPond 17P: INF-6+8 Discarded=0.02 cfs 0.021 af Primary=0.79 cfs 0.028 af Outflow=0.82 cfs 0.049 af Runoff Area=2,168 sf 59.73% Impervious Runoff Depth>1.39"Subcatchment 17S: A14 Tc=5.0 min CN=83 Runoff=0.09 cfs 0.006 af Type III 24-hr 2-Year Rainfall=3.07"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 27HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Peak Elev=147.10' Storage=354 cf Inflow=0.62 cfs 0.043 afPond 18P: INF-5+7 Discarded=0.02 cfs 0.021 af Primary=0.61 cfs 0.017 af Outflow=0.63 cfs 0.038 af Runoff Area=2,826 sf 51.91% Impervious Runoff Depth>1.20"Subcatchment 18S: A15 Tc=5.0 min CN=80 Runoff=0.10 cfs 0.006 af Runoff Area=6,971 sf 100.00% Impervious Runoff Depth>2.70"Subcatchment 19S: B1 Tc=5.0 min CN=98 Runoff=0.49 cfs 0.036 af Runoff Area=71,761 sf 44.08% Impervious Runoff Depth>1.84"Subcatchment 20S: PRE FRONT Tc=5.0 min CN=89 Runoff=3.91 cfs 0.253 af Type III 24-hr 5-Year Rainfall=4.08"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 28HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Time span=1.00-20.00 hrs, dt=0.01 hrs, 1901 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind method - Pond routing by Stor-Ind method Peak Elev=145.30' Inflow=0.78 cfs 0.057 afPond 1C: CB1 12.0" Round Culvert n=0.012 L=124.0' S=0.0050 '/' Outflow=0.78 cfs 0.057 af Peak Elev=145.05' Inflow=3.65 cfs 0.268 afPond 1D: DMH1 18.0" Round Culvert n=0.012 L=58.0' S=0.0050 '/' Outflow=3.65 cfs 0.268 af Peak Elev=146.58' Storage=9,468 cf Inflow=5.14 cfs 0.373 afPond 1P: POST REAR Discarded=0.12 cfs 0.108 af Primary=0.74 cfs 0.063 af Outflow=0.86 cfs 0.171 af Runoff Area=8,350 sf 98.42% Impervious Runoff Depth>3.55"Subcatchment 1S: A1 Tc=5.0 min CN=97 Runoff=0.78 cfs 0.057 af Peak Elev=145.32' Inflow=0.41 cfs 0.029 afPond 2C: CB2 12.0" Round Culvert n=0.012 L=8.0' S=0.0437 '/' Outflow=0.41 cfs 0.029 af Peak Elev=144.80' Inflow=4.29 cfs 0.314 afPond 2D: DMH2 18.0" Round Culvert n=0.012 L=50.0' S=0.0050 '/' Outflow=4.29 cfs 0.314 af Peak Elev=145.21' Storage=2,962 cf Inflow=5.15 cfs 0.251 afPond 2P: POST FRONT Outflow=2.48 cfs 0.250 af Runoff Area=4,496 sf 92.70% Impervious Runoff Depth>3.33"Subcatchment 2S: A2 Tc=5.0 min CN=95 Runoff=0.41 cfs 0.029 af Peak Elev=145.24' Inflow=0.64 cfs 0.047 afPond 3C: CB3 12.0" Round Culvert n=0.012 L=13.0' S=0.0115 '/' Outflow=0.64 cfs 0.047 af Peak Elev=144.57' Inflow=5.02 cfs 0.363 afPond 3D: DMH3 18.0" Round Culvert n=0.012 L=54.0' S=0.0056 '/' Outflow=5.02 cfs 0.363 af Runoff Area=6,870 sf 97.82% Impervious Runoff Depth>3.55"Subcatchment 3S: A3 Tc=5.0 min CN=97 Runoff=0.64 cfs 0.047 af Peak Elev=145.25' Inflow=0.72 cfs 0.048 afPond 4C: CB4 12.0" Round Culvert n=0.012 L=8.0' S=0.0188 '/' Outflow=0.72 cfs 0.048 af Runoff Area=8,648 sf 82.34% Impervious Runoff Depth>2.92"Subcatchment 4S: A4 Tc=5.0 min CN=91 Runoff=0.72 cfs 0.048 af Runoff Area=25,964 sf 100.00% Impervious Runoff Depth>3.67"Subcatchment 5S: B2 Tc=5.0 min CN=98 Runoff=2.46 cfs 0.182 af Runoff Area=7,072 sf 0.00% Impervious Runoff Depth>0.76"Subcatchment 6S: POND Tc=0.0 min CN=61 Runoff=0.16 cfs 0.010 af Runoff Area=57,882 sf 0.00% Impervious Runoff Depth>2.92"Subcatchment 7S: PRE REAR Tc=5.0 min CN=91 Runoff=4.85 cfs 0.324 af Type III 24-hr 5-Year Rainfall=4.08"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 29HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Runoff Area=5,095 sf 91.89% Impervious Runoff Depth>3.33"Subcatchment 8S: A5 Tc=5.0 min CN=95 Runoff=0.46 cfs 0.032 af Peak Elev=148.11' Storage=33 cf Inflow=0.92 cfs 0.061 afPond 9P: RG9 Discarded=0.02 cfs 0.015 af Primary=0.90 cfs 0.045 af Outflow=0.92 cfs 0.060 af Runoff Area=6,947 sf 89.75% Impervious Runoff Depth>3.23"Subcatchment 9S: A6 Tc=5.0 min CN=94 Runoff=0.62 cfs 0.043 af Runoff Area=4,230 sf 90.85% Impervious Runoff Depth>3.33"Subcatchment 10S: A7 Tc=5.0 min CN=95 Runoff=0.39 cfs 0.027 af Runoff Area=5,823 sf 87.02% Impervious Runoff Depth>3.12"Subcatchment 11S: A8 Tc=5.0 min CN=93 Runoff=0.51 cfs 0.035 af Peak Elev=148.04' Storage=513 cf Inflow=0.56 cfs 0.036 afPond 12P: RG12 Discarded=0.05 cfs 0.026 af Primary=0.20 cfs 0.007 af Outflow=0.25 cfs 0.033 af Runoff Area=11,231 sf 77.08% Impervious Runoff Depth>2.83"Subcatchment 12S: A9 Tc=5.0 min CN=90 Runoff=0.92 cfs 0.061 af Peak Elev=148.44' Storage=150 cf Inflow=0.27 cfs 0.017 afPond 13P: RG13 Discarded=0.01 cfs 0.008 af Primary=0.25 cfs 0.008 af Outflow=0.26 cfs 0.015 af Runoff Area=9,635 sf 93.98% Impervious Runoff Depth>3.44"Subcatchment 13S: A10 Tc=5.0 min CN=96 Runoff=0.89 cfs 0.063 af Peak Elev=148.42' Storage=105 cf Inflow=0.14 cfs 0.009 afPond 14P: RG14 Discarded=0.01 cfs 0.007 af Primary=0.10 cfs 0.002 af Outflow=0.11 cfs 0.009 af Runoff Area=6,395 sf 85.41% Impervious Runoff Depth>3.12"Subcatchment 14S: A11 Tc=5.0 min CN=93 Runoff=0.56 cfs 0.038 af Peak Elev=148.42' Storage=136 cf Inflow=0.17 cfs 0.011 afPond 15P: RG15 Discarded=0.01 cfs 0.007 af Primary=0.10 cfs 0.003 af Outflow=0.11 cfs 0.009 af Runoff Area=9,957 sf 48.28% Impervious Runoff Depth>1.88"Subcatchment 15S: A12 Tc=5.0 min CN=79 Runoff=0.56 cfs 0.036 af Peak Elev=147.17' Storage=492 cf Inflow=1.45 cfs 0.102 afPond 16P: INF-10+11 Discarded=0.03 cfs 0.034 af Primary=1.42 cfs 0.059 af Outflow=1.45 cfs 0.092 af Runoff Area=3,453 sf 73.59% Impervious Runoff Depth>2.64"Subcatchment 16S: A13 Tc=5.0 min CN=88 Runoff=0.27 cfs 0.017 af Peak Elev=147.15' Storage=336 cf Inflow=1.13 cfs 0.078 afPond 17P: INF-6+8 Discarded=0.02 cfs 0.023 af Primary=1.11 cfs 0.048 af Outflow=1.13 cfs 0.071 af Runoff Area=2,168 sf 59.73% Impervious Runoff Depth>2.20"Subcatchment 17S: A14 Tc=5.0 min CN=83 Runoff=0.14 cfs 0.009 af Type III 24-hr 5-Year Rainfall=4.08"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 30HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Peak Elev=147.12' Storage=355 cf Inflow=0.85 cfs 0.059 afPond 18P: INF-5+7 Discarded=0.02 cfs 0.023 af Primary=0.83 cfs 0.030 af Outflow=0.85 cfs 0.054 af Runoff Area=2,826 sf 51.91% Impervious Runoff Depth>1.96"Subcatchment 18S: A15 Tc=5.0 min CN=80 Runoff=0.17 cfs 0.011 af Runoff Area=6,971 sf 100.00% Impervious Runoff Depth>3.67"Subcatchment 19S: B1 Tc=5.0 min CN=98 Runoff=0.66 cfs 0.049 af Runoff Area=71,761 sf 44.08% Impervious Runoff Depth>2.73"Subcatchment 20S: PRE FRONT Tc=5.0 min CN=89 Runoff=5.70 cfs 0.375 af Type III 24-hr 10-Year Rainfall=4.91"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 31HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Time span=1.00-20.00 hrs, dt=0.01 hrs, 1901 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind method - Pond routing by Stor-Ind method Peak Elev=145.36' Inflow=0.95 cfs 0.069 afPond 1C: CB1 12.0" Round Culvert n=0.012 L=124.0' S=0.0050 '/' Outflow=0.95 cfs 0.069 af Peak Elev=145.18' Inflow=4.41 cfs 0.326 afPond 1D: DMH1 18.0" Round Culvert n=0.012 L=58.0' S=0.0050 '/' Outflow=4.41 cfs 0.326 af Peak Elev=146.68' Storage=9,882 cf Inflow=6.28 cfs 0.460 afPond 1P: POST REAR Discarded=0.13 cfs 0.113 af Primary=2.41 cfs 0.142 af Outflow=2.54 cfs 0.254 af Runoff Area=8,350 sf 98.42% Impervious Runoff Depth>4.34"Subcatchment 1S: A1 Tc=5.0 min CN=97 Runoff=0.95 cfs 0.069 af Peak Elev=145.35' Inflow=0.50 cfs 0.035 afPond 2C: CB2 12.0" Round Culvert n=0.012 L=8.0' S=0.0437 '/' Outflow=0.50 cfs 0.035 af Peak Elev=144.95' Inflow=5.19 cfs 0.383 afPond 2D: DMH2 18.0" Round Culvert n=0.012 L=50.0' S=0.0050 '/' Outflow=5.19 cfs 0.383 af Peak Elev=145.62' Storage=4,110 cf Inflow=6.88 cfs 0.344 afPond 2P: POST FRONT Outflow=3.00 cfs 0.343 af Runoff Area=4,496 sf 92.70% Impervious Runoff Depth>4.12"Subcatchment 2S: A2 Tc=5.0 min CN=95 Runoff=0.50 cfs 0.035 af Peak Elev=145.29' Inflow=0.78 cfs 0.057 afPond 3C: CB3 12.0" Round Culvert n=0.012 L=13.0' S=0.0115 '/' Outflow=0.78 cfs 0.057 af Peak Elev=144.75' Inflow=6.09 cfs 0.444 afPond 3D: DMH3 18.0" Round Culvert n=0.012 L=54.0' S=0.0056 '/' Outflow=6.09 cfs 0.444 af Runoff Area=6,870 sf 97.82% Impervious Runoff Depth>4.34"Subcatchment 3S: A3 Tc=5.0 min CN=97 Runoff=0.78 cfs 0.057 af Peak Elev=145.32' Inflow=0.90 cfs 0.061 afPond 4C: CB4 12.0" Round Culvert n=0.012 L=8.0' S=0.0188 '/' Outflow=0.90 cfs 0.061 af Runoff Area=8,648 sf 82.34% Impervious Runoff Depth>3.69"Subcatchment 4S: A4 Tc=5.0 min CN=91 Runoff=0.90 cfs 0.061 af Runoff Area=25,964 sf 100.00% Impervious Runoff Depth>4.46"Subcatchment 5S: B2 Tc=5.0 min CN=98 Runoff=2.97 cfs 0.221 af Runoff Area=7,072 sf 0.00% Impervious Runoff Depth>1.19"Subcatchment 6S: POND Tc=0.0 min CN=61 Runoff=0.28 cfs 0.016 af Runoff Area=57,882 sf 0.00% Impervious Runoff Depth>3.69"Subcatchment 7S: PRE REAR Tc=5.0 min CN=91 Runoff=6.03 cfs 0.408 af Type III 24-hr 10-Year Rainfall=4.91"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 32HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Runoff Area=5,095 sf 91.89% Impervious Runoff Depth>4.12"Subcatchment 8S: A5 Tc=5.0 min CN=95 Runoff=0.57 cfs 0.040 af Peak Elev=148.12' Storage=35 cf Inflow=1.15 cfs 0.077 afPond 9P: RG9 Discarded=0.02 cfs 0.016 af Primary=1.13 cfs 0.061 af Outflow=1.15 cfs 0.076 af Runoff Area=6,947 sf 89.75% Impervious Runoff Depth>4.01"Subcatchment 9S: A6 Tc=5.0 min CN=94 Runoff=0.76 cfs 0.053 af Runoff Area=4,230 sf 90.85% Impervious Runoff Depth>4.12"Subcatchment 10S: A7 Tc=5.0 min CN=95 Runoff=0.47 cfs 0.033 af Runoff Area=5,823 sf 87.02% Impervious Runoff Depth>3.90"Subcatchment 11S: A8 Tc=5.0 min CN=93 Runoff=0.63 cfs 0.043 af Peak Elev=148.07' Storage=572 cf Inflow=0.76 cfs 0.048 afPond 12P: RG12 Discarded=0.05 cfs 0.029 af Primary=0.48 cfs 0.016 af Outflow=0.53 cfs 0.045 af Runoff Area=11,231 sf 77.08% Impervious Runoff Depth>3.58"Subcatchment 12S: A9 Tc=5.0 min CN=90 Runoff=1.15 cfs 0.077 af Peak Elev=148.45' Storage=155 cf Inflow=0.34 cfs 0.022 afPond 13P: RG13 Discarded=0.01 cfs 0.008 af Primary=0.32 cfs 0.012 af Outflow=0.33 cfs 0.020 af Runoff Area=9,635 sf 93.98% Impervious Runoff Depth>4.23"Subcatchment 13S: A10 Tc=5.0 min CN=96 Runoff=1.08 cfs 0.078 af Peak Elev=148.43' Storage=110 cf Inflow=0.19 cfs 0.012 afPond 14P: RG14 Discarded=0.01 cfs 0.007 af Primary=0.16 cfs 0.004 af Outflow=0.18 cfs 0.012 af Runoff Area=6,395 sf 85.41% Impervious Runoff Depth>3.90"Subcatchment 14S: A11 Tc=5.0 min CN=93 Runoff=0.69 cfs 0.048 af Peak Elev=148.44' Storage=142 cf Inflow=0.22 cfs 0.014 afPond 15P: RG15 Discarded=0.01 cfs 0.007 af Primary=0.20 cfs 0.005 af Outflow=0.21 cfs 0.013 af Runoff Area=9,957 sf 48.28% Impervious Runoff Depth>2.54"Subcatchment 15S: A12 Tc=5.0 min CN=79 Runoff=0.76 cfs 0.048 af Peak Elev=147.20' Storage=493 cf Inflow=1.77 cfs 0.126 afPond 16P: INF-10+11 Discarded=0.03 cfs 0.036 af Primary=1.74 cfs 0.080 af Outflow=1.77 cfs 0.115 af Runoff Area=3,453 sf 73.59% Impervious Runoff Depth>3.38"Subcatchment 16S: A13 Tc=5.0 min CN=88 Runoff=0.34 cfs 0.022 af Peak Elev=147.17' Storage=336 cf Inflow=1.39 cfs 0.097 afPond 17P: INF-6+8 Discarded=0.02 cfs 0.024 af Primary=1.37 cfs 0.065 af Outflow=1.39 cfs 0.089 af Runoff Area=2,168 sf 59.73% Impervious Runoff Depth>2.90"Subcatchment 17S: A14 Tc=5.0 min CN=83 Runoff=0.19 cfs 0.012 af Type III 24-hr 10-Year Rainfall=4.91"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 33HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Peak Elev=147.14' Storage=355 cf Inflow=1.04 cfs 0.073 afPond 18P: INF-5+7 Discarded=0.02 cfs 0.025 af Primary=1.01 cfs 0.042 af Outflow=1.03 cfs 0.067 af Runoff Area=2,826 sf 51.91% Impervious Runoff Depth>2.63"Subcatchment 18S: A15 Tc=5.0 min CN=80 Runoff=0.22 cfs 0.014 af Runoff Area=6,971 sf 100.00% Impervious Runoff Depth>4.46"Subcatchment 19S: B1 Tc=5.0 min CN=98 Runoff=0.80 cfs 0.059 af Runoff Area=71,761 sf 44.08% Impervious Runoff Depth>3.48"Subcatchment 20S: PRE FRONT Tc=5.0 min CN=89 Runoff=7.17 cfs 0.478 af Type III 24-hr 50-Year Rainfall=6.94"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 34HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Time span=1.00-20.00 hrs, dt=0.01 hrs, 1901 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind method - Pond routing by Stor-Ind method Peak Elev=145.49' Inflow=1.35 cfs 0.100 afPond 1C: CB1 12.0" Round Culvert n=0.012 L=124.0' S=0.0050 '/' Outflow=1.35 cfs 0.100 af Peak Elev=145.50' Inflow=6.27 cfs 0.470 afPond 1D: DMH1 18.0" Round Culvert n=0.012 L=58.0' S=0.0050 '/' Outflow=6.27 cfs 0.470 af Peak Elev=146.89' Storage=10,820 cf Inflow=9.10 cfs 0.678 afPond 1P: POST REAR Discarded=0.13 cfs 0.122 af Primary=7.95 cfs 0.346 af Outflow=8.09 cfs 0.468 af Runoff Area=8,350 sf 98.42% Impervious Runoff Depth>6.28"Subcatchment 1S: A1 Tc=5.0 min CN=97 Runoff=1.35 cfs 0.100 af Peak Elev=145.43' Inflow=0.72 cfs 0.052 afPond 2C: CB2 12.0" Round Culvert n=0.012 L=8.0' S=0.0437 '/' Outflow=0.72 cfs 0.052 af Peak Elev=145.35' Inflow=7.38 cfs 0.552 afPond 2D: DMH2 18.0" Round Culvert n=0.012 L=50.0' S=0.0050 '/' Outflow=7.38 cfs 0.552 af Peak Elev=148.44' Storage=5,847 cf Inflow=10.80 cfs 0.584 afPond 2P: POST FRONT Outflow=8.48 cfs 0.582 af Runoff Area=4,496 sf 92.70% Impervious Runoff Depth>6.04"Subcatchment 2S: A2 Tc=5.0 min CN=95 Runoff=0.72 cfs 0.052 af Peak Elev=145.40' Inflow=1.11 cfs 0.083 afPond 3C: CB3 12.0" Round Culvert n=0.012 L=13.0' S=0.0115 '/' Outflow=1.11 cfs 0.083 af Peak Elev=145.38' Inflow=8.70 cfs 0.645 afPond 3D: DMH3 18.0" Round Culvert n=0.012 L=54.0' S=0.0056 '/' Outflow=8.70 cfs 0.645 af Runoff Area=6,870 sf 97.82% Impervious Runoff Depth>6.28"Subcatchment 3S: A3 Tc=5.0 min CN=97 Runoff=1.11 cfs 0.083 af Peak Elev=145.46' Inflow=1.33 cfs 0.092 afPond 4C: CB4 12.0" Round Culvert n=0.012 L=8.0' S=0.0188 '/' Outflow=1.33 cfs 0.092 af Runoff Area=8,648 sf 82.34% Impervious Runoff Depth>5.58"Subcatchment 4S: A4 Tc=5.0 min CN=91 Runoff=1.33 cfs 0.092 af Runoff Area=25,964 sf 100.00% Impervious Runoff Depth>6.39"Subcatchment 5S: B2 Tc=5.0 min CN=98 Runoff=4.20 cfs 0.318 af Runoff Area=7,072 sf 0.00% Impervious Runoff Depth>2.45"Subcatchment 6S: POND Tc=0.0 min CN=61 Runoff=0.60 cfs 0.033 af Runoff Area=57,882 sf 0.00% Impervious Runoff Depth>5.58"Subcatchment 7S: PRE REAR Tc=5.0 min CN=91 Runoff=8.89 cfs 0.618 af Type III 24-hr 50-Year Rainfall=6.94"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 35HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Runoff Area=5,095 sf 91.89% Impervious Runoff Depth>6.04"Subcatchment 8S: A5 Tc=5.0 min CN=95 Runoff=0.81 cfs 0.059 af Peak Elev=148.16' Storage=38 cf Inflow=1.70 cfs 0.117 afPond 9P: RG9 Discarded=0.02 cfs 0.018 af Primary=1.68 cfs 0.099 af Outflow=1.70 cfs 0.117 af Runoff Area=6,947 sf 89.75% Impervious Runoff Depth>5.93"Subcatchment 9S: A6 Tc=5.0 min CN=94 Runoff=1.10 cfs 0.079 af Runoff Area=4,230 sf 90.85% Impervious Runoff Depth>6.04"Subcatchment 10S: A7 Tc=5.0 min CN=95 Runoff=0.67 cfs 0.049 af Runoff Area=5,823 sf 87.02% Impervious Runoff Depth>5.81"Subcatchment 11S: A8 Tc=5.0 min CN=93 Runoff=0.91 cfs 0.065 af Peak Elev=148.12' Storage=674 cf Inflow=1.25 cfs 0.081 afPond 12P: RG12 Discarded=0.05 cfs 0.034 af Primary=1.06 cfs 0.041 af Outflow=1.11 cfs 0.075 af Runoff Area=11,231 sf 77.08% Impervious Runoff Depth>5.47"Subcatchment 12S: A9 Tc=5.0 min CN=90 Runoff=1.70 cfs 0.117 af Peak Elev=148.47' Storage=165 cf Inflow=0.51 cfs 0.035 afPond 13P: RG13 Discarded=0.01 cfs 0.010 af Primary=0.49 cfs 0.022 af Outflow=0.50 cfs 0.032 af Runoff Area=9,635 sf 93.98% Impervious Runoff Depth>6.16"Subcatchment 13S: A10 Tc=5.0 min CN=96 Runoff=1.55 cfs 0.114 af Peak Elev=148.45' Storage=118 cf Inflow=0.29 cfs 0.019 afPond 14P: RG14 Discarded=0.01 cfs 0.009 af Primary=0.27 cfs 0.009 af Outflow=0.29 cfs 0.019 af Runoff Area=6,395 sf 85.41% Impervious Runoff Depth>5.81"Subcatchment 14S: A11 Tc=5.0 min CN=93 Runoff=1.00 cfs 0.071 af Peak Elev=148.46' Storage=150 cf Inflow=0.36 cfs 0.024 afPond 15P: RG15 Discarded=0.01 cfs 0.008 af Primary=0.34 cfs 0.013 af Outflow=0.36 cfs 0.021 af Runoff Area=9,957 sf 48.28% Impervious Runoff Depth>4.25"Subcatchment 15S: A12 Tc=5.0 min CN=79 Runoff=1.25 cfs 0.081 af Peak Elev=147.26' Storage=493 cf Inflow=2.55 cfs 0.185 afPond 16P: INF-10+11 Discarded=0.03 cfs 0.040 af Primary=2.51 cfs 0.134 af Outflow=2.55 cfs 0.173 af Runoff Area=3,453 sf 73.59% Impervious Runoff Depth>5.24"Subcatchment 16S: A13 Tc=5.0 min CN=88 Runoff=0.51 cfs 0.035 af Peak Elev=147.22' Storage=336 cf Inflow=2.01 cfs 0.143 afPond 17P: INF-6+8 Discarded=0.02 cfs 0.027 af Primary=1.99 cfs 0.109 af Outflow=2.01 cfs 0.136 af Runoff Area=2,168 sf 59.73% Impervious Runoff Depth>4.68"Subcatchment 17S: A14 Tc=5.0 min CN=83 Runoff=0.29 cfs 0.019 af Type III 24-hr 50-Year Rainfall=6.94"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 36HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Peak Elev=147.18' Storage=355 cf Inflow=1.49 cfs 0.108 afPond 18P: INF-5+7 Discarded=0.02 cfs 0.028 af Primary=1.46 cfs 0.072 af Outflow=1.49 cfs 0.100 af Runoff Area=2,826 sf 51.91% Impervious Runoff Depth>4.36"Subcatchment 18S: A15 Tc=5.0 min CN=80 Runoff=0.36 cfs 0.024 af Runoff Area=6,971 sf 100.00% Impervious Runoff Depth>6.39"Subcatchment 19S: B1 Tc=5.0 min CN=98 Runoff=1.13 cfs 0.085 af Runoff Area=71,761 sf 44.08% Impervious Runoff Depth>5.35"Subcatchment 20S: PRE FRONT Tc=5.0 min CN=89 Runoff=10.75 cfs 0.735 af Type III 24-hr 100-Year Rainfall=7.82"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 37HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Time span=1.00-20.00 hrs, dt=0.01 hrs, 1901 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind method - Pond routing by Stor-Ind method Peak Elev=145.54' Inflow=1.52 cfs 0.114 afPond 1C: CB1 12.0" Round Culvert n=0.012 L=124.0' S=0.0050 '/' Outflow=1.52 cfs 0.114 af Peak Elev=145.65' Inflow=7.07 cfs 0.532 afPond 1D: DMH1 18.0" Round Culvert n=0.012 L=58.0' S=0.0050 '/' Outflow=7.07 cfs 0.532 af Peak Elev=146.93' Storage=11,013 cf Inflow=10.33 cfs 0.773 afPond 1P: POST REAR Discarded=0.13 cfs 0.126 af Primary=9.29 cfs 0.437 af Outflow=9.43 cfs 0.563 af Runoff Area=8,350 sf 98.42% Impervious Runoff Depth>7.12"Subcatchment 1S: A1 Tc=5.0 min CN=97 Runoff=1.52 cfs 0.114 af Peak Elev=145.46' Inflow=0.81 cfs 0.059 afPond 2C: CB2 12.0" Round Culvert n=0.012 L=8.0' S=0.0437 '/' Outflow=0.81 cfs 0.059 af Peak Elev=145.66' Inflow=8.32 cfs 0.626 afPond 2D: DMH2 18.0" Round Culvert n=0.012 L=50.0' S=0.0050 '/' Outflow=8.32 cfs 0.626 af Peak Elev=148.53' Storage=5,878 cf Inflow=12.35 cfs 0.693 afPond 2P: POST FRONT Outflow=12.11 cfs 0.690 af Runoff Area=4,496 sf 92.70% Impervious Runoff Depth>6.88"Subcatchment 2S: A2 Tc=5.0 min CN=95 Runoff=0.81 cfs 0.059 af Peak Elev=145.45' Inflow=1.25 cfs 0.094 afPond 3C: CB3 12.0" Round Culvert n=0.012 L=13.0' S=0.0115 '/' Outflow=1.25 cfs 0.094 af Peak Elev=145.63' Inflow=9.83 cfs 0.732 afPond 3D: DMH3 18.0" Round Culvert n=0.012 L=54.0' S=0.0056 '/' Outflow=9.83 cfs 0.732 af Runoff Area=6,870 sf 97.82% Impervious Runoff Depth>7.12"Subcatchment 3S: A3 Tc=5.0 min CN=97 Runoff=1.25 cfs 0.094 af Peak Elev=145.51' Inflow=1.51 cfs 0.106 afPond 4C: CB4 12.0" Round Culvert n=0.012 L=8.0' S=0.0188 '/' Outflow=1.51 cfs 0.106 af Runoff Area=8,648 sf 82.34% Impervious Runoff Depth>6.41"Subcatchment 4S: A4 Tc=5.0 min CN=91 Runoff=1.51 cfs 0.106 af Runoff Area=25,964 sf 100.00% Impervious Runoff Depth>7.23"Subcatchment 5S: B2 Tc=5.0 min CN=98 Runoff=4.74 cfs 0.359 af Runoff Area=7,072 sf 0.00% Impervious Runoff Depth>3.06"Subcatchment 6S: POND Tc=0.0 min CN=61 Runoff=0.76 cfs 0.041 af Runoff Area=57,882 sf 0.00% Impervious Runoff Depth>6.41"Subcatchment 7S: PRE REAR Tc=5.0 min CN=91 Runoff=10.12 cfs 0.710 af Type III 24-hr 100-Year Rainfall=7.82"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 38HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Runoff Area=5,095 sf 91.89% Impervious Runoff Depth>6.88"Subcatchment 8S: A5 Tc=5.0 min CN=95 Runoff=0.92 cfs 0.067 af Peak Elev=148.18' Storage=39 cf Inflow=1.94 cfs 0.135 afPond 9P: RG9 Discarded=0.02 cfs 0.019 af Primary=1.92 cfs 0.116 af Outflow=1.94 cfs 0.135 af Runoff Area=6,947 sf 89.75% Impervious Runoff Depth>6.76"Subcatchment 9S: A6 Tc=5.0 min CN=94 Runoff=1.24 cfs 0.090 af Runoff Area=4,230 sf 90.85% Impervious Runoff Depth>6.88"Subcatchment 10S: A7 Tc=5.0 min CN=95 Runoff=0.76 cfs 0.056 af Runoff Area=5,823 sf 87.02% Impervious Runoff Depth>6.64"Subcatchment 11S: A8 Tc=5.0 min CN=93 Runoff=1.04 cfs 0.074 af Peak Elev=148.13' Storage=706 cf Inflow=1.47 cfs 0.096 afPond 12P: RG12 Discarded=0.06 cfs 0.036 af Primary=1.26 cfs 0.053 af Outflow=1.31 cfs 0.089 af Runoff Area=11,231 sf 77.08% Impervious Runoff Depth>6.29"Subcatchment 12S: A9 Tc=5.0 min CN=90 Runoff=1.94 cfs 0.135 af Peak Elev=148.48' Storage=169 cf Inflow=0.58 cfs 0.040 afPond 13P: RG13 Discarded=0.01 cfs 0.011 af Primary=0.56 cfs 0.027 af Outflow=0.57 cfs 0.037 af Runoff Area=9,635 sf 93.98% Impervious Runoff Depth>7.00"Subcatchment 13S: A10 Tc=5.0 min CN=96 Runoff=1.75 cfs 0.129 af Peak Elev=148.45' Storage=122 cf Inflow=0.34 cfs 0.023 afPond 14P: RG14 Discarded=0.01 cfs 0.010 af Primary=0.32 cfs 0.012 af Outflow=0.33 cfs 0.022 af Runoff Area=6,395 sf 85.41% Impervious Runoff Depth>6.64"Subcatchment 14S: A11 Tc=5.0 min CN=93 Runoff=1.14 cfs 0.081 af Peak Elev=148.46' Storage=154 cf Inflow=0.42 cfs 0.028 afPond 15P: RG15 Discarded=0.01 cfs 0.009 af Primary=0.40 cfs 0.017 af Outflow=0.42 cfs 0.025 af Runoff Area=9,957 sf 48.28% Impervious Runoff Depth>5.02"Subcatchment 15S: A12 Tc=5.0 min CN=79 Runoff=1.47 cfs 0.096 af Peak Elev=147.28' Storage=494 cf Inflow=2.88 cfs 0.210 afPond 16P: INF-10+11 Discarded=0.04 cfs 0.041 af Primary=2.85 cfs 0.158 af Outflow=2.88 cfs 0.199 af Runoff Area=3,453 sf 73.59% Impervious Runoff Depth>6.06"Subcatchment 16S: A13 Tc=5.0 min CN=88 Runoff=0.58 cfs 0.040 af Peak Elev=147.24' Storage=337 cf Inflow=2.28 cfs 0.164 afPond 17P: INF-6+8 Discarded=0.02 cfs 0.028 af Primary=2.26 cfs 0.128 af Outflow=2.28 cfs 0.156 af Runoff Area=2,168 sf 59.73% Impervious Runoff Depth>5.48"Subcatchment 17S: A14 Tc=5.0 min CN=83 Runoff=0.34 cfs 0.023 af Type III 24-hr 100-Year Rainfall=7.82"2018-082 Colvest Northampton 10-10-19 Printed 10/10/2019Prepared by J.R. Russo & Associates, LLC Page 39HydroCAD® 10.00-21 s/n 05524 © 2018 HydroCAD Software Solutions LLC Peak Elev=147.19' Storage=355 cf Inflow=1.68 cfs 0.123 afPond 18P: INF-5+7 Discarded=0.02 cfs 0.029 af Primary=1.66 cfs 0.086 af Outflow=1.68 cfs 0.115 af Runoff Area=2,826 sf 51.91% Impervious Runoff Depth>5.14"Subcatchment 18S: A15 Tc=5.0 min CN=80 Runoff=0.42 cfs 0.028 af Runoff Area=6,971 sf 100.00% Impervious Runoff Depth>7.23"Subcatchment 19S: B1 Tc=5.0 min CN=98 Runoff=1.27 cfs 0.096 af Runoff Area=71,761 sf 44.08% Impervious Runoff Depth>6.17"Subcatchment 20S: PRE FRONT Tc=5.0 min CN=89 Runoff=12.29 cfs 0.848 af Attachment A: Stormwater Facility Maintenance Schedule Page 1 of 3 ATTACHMENT A Stormwater Facility Maintenance Schedule Name of Project: Colvest/Northampton, LLC Project Location: 303 King Street Assessor’s Map, Parcel(s): 24B 070 001 Owner of the Stormwater System: Colvest/Northampton, LLC 1259 East Columbus Ave Springfield, MA 01105 Responsible Party for Operation & Maintenance of Stormwater System: Colvest/Northampton, LLC 1259 East Columbus Ave Springfield, MA 01105 Financial Responsibility for Operation & Maintenance of Stormwater System: Colvest/Northampton, LLC 1259 East Columbus Ave Springfield, MA 01105 Maintenance Schedule Parking Lot Sweeping: All Paved areas will be swept in accordance with the following minimum schedule: a) For litter: No less than once per week b) For sand: annually – in the spring of each year c) For leaves and organic debris: annually – in the fall of each year Catch Basins: All catch basins within the premises will be inspected annually for accumulation of sediment, debris, indications of oil product, condition and overall function. All storm system structures will be cleaned at least once per year and more often if sediment accumulates to within 24” of the outlet pipe. The Subsurface Detention System will be inspected annually. Oil products and sediments will be removed and disposed of in accordance with state and federal guidelines and applicable regulations. In the case of an oil or other bulk pollutant release, the onsite storm system must be cleaned immediately following the spill and the proper authorities notified. Attachment A: Stormwater Facility Maintenance Schedule Page 2 of 3 Pervious Pavement: There are 6 pervious pavement encompassing the 5 parking spaces closest to each drainage structure between Building #1 and Building #2. This pavement is designed to infiltrate surface runoff before it reaches the catch basin. During larger storm events (>3”), expect the pervious pavement to overflow into the catch basin. The following maintenance practices shall be followed: 1. Do not use sand for winter deicing as this will clog the pervious pavement. 2. Inspect pavement during a storm event: monthly for the first 3 months and annually thereafter. 3. If water is immediately overflowing to the catch basin, power wash the surface and check during the next rain event. 4. If surface is still not receiving any runoff, contract a vendor to vacuum the surface. If this does not correct the problem, the pavement shall be removed down to the layer which is receiving water and the removed materials shall be replaced. Check to confirm the underdrain is not clogged. Rain Garden/Bioretention: There are 5 rain garden bioretention areas on the site, three in the front yard between King Street and Building #1, and the fourth and fifth are on the right side of the entrance drive (south side). The rain gardens are designed to collect surface runoff from paved surfaces and infiltrate this runoff through a soil media. During rainfall events, expect standing water. Water should dissipate within 24 hours. If water remains longer than 72 hours, the systems will require evaluation by the Site Engineer or other qualified professional. During larger storms, the rain gardens are designed to overflow to the subsurface detention system through an elevated drainage structure in the middle of the rain garden. Regular maintenance will help insure the long term function of the rain gardens. The following maintenance practices shall be followed: 1. Inspect after every major storm event (>3”) to confirm water is draining from basin. 2. Remove trash from basins once a week. 3. Remove leaves and organic debris annually in the fall of each year. 4. Fertilize, prune vegetation, remove dead growth and replace bark mulch annually. 5. If water does not drain within 72 hours, remove top layers of soil media until soils drain. Check to confirm underdrain is not clogged. Replace underdrain and soil media as required. Infiltration Basin: There is one infiltration basin at the southeast corner of the site. The following maintenance practices shall be flowed: 1. Inspect to ensure proper functioning: After every major storm (>3”). 2. Mow the buffer area, side slopes, and basin bottom; remove trash and debris; remove grass clippings and accumulated organic matter Attachment A: Stormwater Facility Maintenance Schedule Page 3 of 3 3. Inspect and clean forebay, at least twice a year and after every major storm event. Accumulated sediment is to be removed when within 24” of the top of the stone filter berm. Repair rip rap as needed. 4. Landscape plantings in the basin will be maintained and replace as needed. 5. When basin fails to drain or drains slowly, remove accumulated sediments, deeply till the remaining soil, cap with sandy loam and revegetate Subsurface Detention System: The front building, access drive and parking area between Building #1 and #2 contains a subsurface detention system that receives overflow and filtered underdrain flows from the pervious pavement and rain gardens. This system is designed to temporarily store and slow down the rate of runoff leaving the site for larger storm events. The following maintenance practices shall be followed on a semi-annual basis: 1. Inspect manholes (15 total) by removing covers and looking for evidence of standing water, accumulated sediment or debris. If any of these are present, clean pipes with a jet vac system designed to power wash the pipes and pump out the water into a tanker truck for disposal off site. 2. Check outlet structure near King Street entrance (double manhole covers) to confirm 10” orifice and outlet pipe are unobstructed. Record Keeping and Annual Reports: Records shall be maintained by Colvest/Northampton, LLC at their offices as described above and shall document all routine and emergency maintenance work to the stormwater management system and shall bear the signature of the individual supervising the work. Annual reports documenting the inspection, maintenance, and proper functioning of the stormwater management system in accordance with the approved design shall be submitted to the Northampton Department of Public Works and the Northampton Office of Planning and Development no later than October 1st of each year. The annual report shall document any deficiencies in function or maintenance of the stormwater management system and include a plan to correct the deficiencies.