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HomeMy WebLinkAbout2021-03-16 Drainage Report 10/22/20 I DRAINA GE REPOR T For CROSSPOINT ASSOCIA TES PROPOSED "COMMERCIAL DEVELOPMENT" 419 & 435 Andover Street North Andover, Mrrssrrehusetts Essex County Prepared by; BOHLER ENGINEERING 45 Franklin Street, 5t"Floor Boston, MA 02110 (61 7) 849-8040 TEL. t1 pF. N di E Stephen P. Martorano Massachusetts P.E. Lic. #45942 BOHLER // October 22, 2020 #M201047 BOHLER /l TABLE OF CONTENTS 1. EXISTING SITE CONDITIONS............................................................................................. 5 ExistingSite Description............................................................................................................. 5 On-Site Soil Information............................................................................................................. 5 Existing Collection and Conveyance........................................................................................... 5 Existing Watersheds and Design Point Information.................................................................... 5 II. PROPOSED SITE CONDITIONS........................................................................................... 7 Proposed Development Description............................................................................................7 Proposed Development Collection and Conveyance................................................................... 7 Proposed Watersheds and Design Point Information.................................................................. 8 III. METHODOLOGY................................................................................................................... 8 PeakFlow Calculations............................................................................................................... 8 IV. STORMWATER MANAGEMENT STANDARDS............................................................. 10 Standard#1:No New Untreated Discharges............................................................................. 10 Standard#2,. Peak Rate Attenuation.......................................................................................... 10 Standard#3: Recharge............................................................................................................... 10 Standard#4: Water Quality....................................................................................................... 10 Standard#5: Land Use with Higher Potential Pollutant Loads................................................. I l Standard#6: Critical Areas--.................................................................................................. I I Standard#7: Redevelopment..................................................................................................... I I Standard#8: Construction Period Pollution Prevention and Erosion and Sedimentation Control ................................................................................................................................................... 1 I Standard#9: Operation and Maintenance Plan (O&M Plan).................................................... 12 Standard #10: Prohibition of Illicit Discharges......................................................................... 12 V. SUMMARY........................................................................................................................... 13 M201047-MA Drainage Report.docx EXISTING SITE CONDITIONS- I- 3 BQHLER// LIST OF TABLES Table 1.1: Design Point Peak Runoff Rate Summary.....................................................................4 Table 4.1:North Andover Stormwater Management Regulations Rainfall Intensities.................. 9 Table 5,1: Design Point Peak Runoff Rate Summary................................................................... 13 M201047-MA Drainage Report.doex EXISTING SITE CONDITIONS-2- BOHLER// APPENDICES APPENDIX A; MASSACHUSETTS STORMWATER MANAGEMENT CHECKLIST APPENDIX B: PROJECT LOCATION MAPS ➢ USGS MAP APPENDIX C: SOIL AND WETLAND INFORMATION ➢ NCRS CUSTOM SOIL RESOURCE REPORT APPENDIX D: EXISTING CONDITIONS HYDROLOGIC ANALYSIS ➢ EXISTING CONDITIONS DRAINAGE MAP ➢ EXISTING CONDITIONS HYDROCAD COMPUTATIONS APPENDIX E: PROPOSED CONDITIONS HYDROLOGIC ANALYSIS ➢ PROPOSED CONDITIONS DRAINAGE MAP ➢ PROPOSED CONDITIONS HYDROCAD CALCULATIONS APPENDIX F: STORMWATER CALCULATIONS ➢ MA STANDARD#3 -RECHARGE AND DRAWDOWN TIME ➢ MA STANDARD#4-WATER QUALITY AND TSS REMOVAL APPENDIX G: OPERATION AND MAINTENANCE ➢ STORMWATER OPERATION AND MAINTENANCE PLAN ➢ INSPECTION REPORT ➢ INSPECTION AND MAINTENANCE LOG FORM ➢ LONG-TERM POLLUTION PREVENTION PLAN ➢ SPILL PREVENTION ➢ MANUFACTURER'S INSPECTION AND MAINTENANCE MANUAL M201047-MA Drainage Report.docx EXISTING SITE CONDITIONS-3- 1 B®H LER /I E i EXECUTIVE SUMMARY This report examines the changes in drainage that can be expected as the result of the proposed commercial development located at the corner of Andover Street(Route 125)and Salem Turnpike (Route 114), The site, which contains approximately 2.68 acres of land, contains an existing commercial development.The existing Bertucei's restaurant located closest to the intersection will remain as is while the remainder of the site is proposed to be redeveloped. The proposed project includes the construction of a new urgent care,restaurant drive-through, and bank drive-through along with new paved parking areas, landscaping, storm water management components and associated utilities. This report addresses a comparative analysis of the pre- and post-development site runoff conditions. Additionally, this report provides calculations documenting the design of the proposed stormwater conveyance/management system as illustrated within the accompanying Site Development Plans prepared by Bolder. The project will also provide erosion and sedimentation controls during the demolition and construction periods,as well as long term stabilization of the site. For the purposes of this analysis the pre-and post-development drainage conditions were analyzed at one (1) "design point" where stormwater runoff currently drains to under existing conditions. These design points are described in further detail in Section II below. A summary of the existing and proposed conditions peak runoff rates and volumes for the 2-, 10-, 25-, and 100-year storms can be found in Table 1.1 and Table 1.2 below. In addition, the project has been designed to meet or exceed the Stormwater Management Standards as detailed herein. Table 1.1: Desimn Point Pear Runoff Rate Suminai•y Point of 2 Year Storm lU Year Storm 25 Year 5tprm 400-Year Storm " Analysts Past e Are Post +� Pre.; Post.. "d pre Pos# o DP7 7.39 5.79 -1.60 11.77 9.30 -2.47 15.01 14,11 0.90 21.98 21.61 -0.37 M20I047-MA Drainage Report.doex EXISTING SITE CONDITIONS-4- ROHLER// L EXISTING SITE CONDITIONS Existing Site Description The site consists of approximately 2.68 acres of land located at the corner of Andover Street(Route 125)and Salem Turnpike(Route 114)in the Town of North Andover,Massachusetts.The southern portion of the site contains an existing Bertucci's restaurant to remain.The northern portion of the site contains a building for an Ethan Allen and hair salon and spa, and associated parking lot area, to be demolished and redeveloped as part of the project. On-Site Soil Information The majority of the soils at the site are mapped as Woodbridge fine sandy loam which are classified by the Natural Resource Conservation Service (MRCS) as Hydrologic Soil Group (HSG) "C/D". For the purposes of this report and analysis, the soils have been assumed to fall into the category of HSG C,which will be confirmed by test pits at the time of site demolition.As such, a minimum Rawl's Rate for infiltration of 0.17 inches per hour has been utilized in stormwater calculations. In order to be conservative, the analysis for peak rate of runoff does not model infiltration. Refer to Appendix C for additional information. Existing Collection and Conveyance The existing site slopes severly from east to west,from elevation 220 down to elevation 200 at the western property line,The entire site drains from east to west via overland flow where it discharges to the abutting property at the western property line and into the associated parking lot. There was an existing catch basin observed onsite, located on the west edge of the northern existing building, that was full of water and appears to be a failed drywell. As such, this structure was not incorporated in the modeling. Based on field observations, a portion of the adjacent roadways appear to drain onto the site and ultimately onto the abutting property. In order to be conservative, the existing conditions analysis only models runoff area within the site. Existing Watersheds and Desiun Point Information The site was modeled as one (1) subcatchment (Subcatchment EX01) for the existing conditions to analyze existing and proposed flow rates at the design point. Subcatchment EXO1 in total is 2.678 acres with existing buildings, pavement, and grassed areas. This area flows overland from M201047-MA Dminage Report,docx EXTSTING SITE CONDITIONS-5- 0 BOHLER /l east to west across the site where it discharges overland via sheet flow to the abutting property and parking lot to the west. The stormwater runoff from this subcatchment is not treated or attenuated. The time of concentration for the subcatchment area was calculated as 8.4 minutes, as further I i detailed in the drainage calculations. The pre- and post-development drainage conditions for the site were then analyzed at one (1) "design point"where stormwater runoff currently drains to under existing conditions. Design Point i #1 (DPI) is defined the westwern property line, Under existing conditions, this design point receives stormwater flows from Subcatchment"EXOV as described above. Refer to Table 1.1 and 5.1 for the calculated existing conditions peak rates of runoff. For additional hydrologic information, refer to Appendix D and the Drainage Area Maps in the appendices of this report for a graphical representation of the existing drainage areas. M201047-MA drainage Repors.dou EXISTING SITE CONDITIONS-6- 1 BOHLER / II. PROPOSED SITE CONDITIONS Proposed Development Description The proposed project consists of the construction of a new urgent care, restaurant drive-through, and bank drive-through building including paved parking areas, landscaping, associated utilities, and a new stormwater management system. The existing Bertucei's restaurant building and associated paved parking areas and landscaping located at the southern portion of the site,near the main intersection, is proposed to remain and continue to operate as it does under existing conditions. Runoff from this existing portion of the site will, however, drain into proposed stormwater infrastructure for treatment and infiltration. The overall site, including the proposed parking areas, has been designed to drain to deep-sump, hooded catch basins. The catch basins will capture and convey stormwater runoff, via an underground pipe system, to a proposed infiltration basin. During extreme storm events, the infiltration basin overflows via an outlet control structure to a proposed perforated pipe infiltration trench along the wester property line, which will act as a level spreader to sheet flow excess runoff to the abutting property and parking lot, as it does under existing conditions. Pretreatment of stormwater runoff will be provided by a combination of the deep-sump, hooded catch basins and proprietary treatment units prior to discharge into the proposed infiltration basins. Rooftop runoff has been designed to flow to the basins as well. Proposed Development Collection and Conveyance Deep sump hooded catch basins are proposed to collect and route runoff from the paved parking areas to the stormwater system. The best management practices (BMPs) incorporated into the proposed stormwater management system have been designed to meet the total suspended solid (TSS) removal requirements as set forth in the Massachusetts Department of Environmental Protection Stormwater Handbook standards. Refer to Appendix F for calculations. In addition, a Stormwater Operation and Maintenance (O&M) Plan, attached in Appendix G, has been developed which includes scheduled maintenance and periodic inspections of stormwater management structures [Le catch basins and infiltration basins]. M201047-MA Dfainage Report.doex PROPOSED SITE CONDITIONS-7- E i BOHLER // Proposed Watersheds and Desi$pi Point Information The project has been designed to maintain existing drainage watersheds to the greatest extent possible, with the same design points described in Section II above. Consistent with existing conditions,the site was modeled as one (1)sub catchment for the proposed conditions as described below. Subcatchment PRO] consists of 2.678 acres of entirely area consisting of roof area, pavement and landscaping. This area drains to proposed catch basins and is routed through a Contech CDS unit for pretreatment prior to discharge into a subsurface infiltration basin. During extreme storm events, the infiltration basin overflows via an outlet control structure to a proposed perforated pipe infiltration trench along the wester property line,which will act as a level spreader to sheet flow excess runoff to the abutting property and parking lot, as it does under existing conditions. The time of concentration for the subcatchment was calculated as the minimum of 6 minutes. Refer to Table 1.1 and 5.1 for the calculated proposed conditions peak rates of runoff. For additional hydrologic information, refer to Appendix D and the Drainage Area Maps in the appendices of this report for a graphical representation of the proposed drainage areas. 111. METHODOLOGY Pear Flow Calculations Methodology utilized to design the proposed stormwater management system includes compliance with the guidelines set forth in the latest edition of the Massachusetts DEP Stormwater Handbook. The pre- and post-development runoff rates being discharged from the site were computed using the HydroCAD computer program. The drainage area and outlet information were entered into the program, which routes storm flows based on NRCS TR-20 and TR-55 methods. The other components of the model were determined following standard NRCS procedures for Curve Numbers (CNs) and times of concentrations documented in the appendices of this report. The rainfall data utilized and listed below in table 4.1 below for stormwater calculations is based on the North Andover Stormwater Management Regulations. Refer to Appendix F for more information. M201047-MA Drainage Report.duex METHODOLOGY-8- ROHLERII Table 4.1: North Andover Storinwater Management Regulations Rainfall Intensities �teq»ency 2�re;tr 1b a 25 yeas 100 year 4 Rainfall* (inches) 3.2 4.8 6.0 8.6 *Values derived from North Andover Stornnvater Management Regulations The proposed stormwater management as designed will provide a decrease in peak rates of runoff from the proposed facility for the 2-, 10-,25- and 100-year design storm events. Additionally,the proposed project meets, or exceeds,the MADEP Stormwater Management standards. Compliance with these standards is described further below, M201047-MA Drainage Report.docx METHODOLOGY-9- BOHLERll N. STORMWATER MANAGEMENT STANDARDS Standard #1: No New Untreated Discharges Tile project has been designed so that proposed impervious areas (including the building roof and paved parking/driveway areas)shall be collected and passed through the proposed drainage system i for treatment prior to discharge. i Standard #2: Peak Rate Attenuation As outlined in Table 1.1 and Table 5.1, the development of the site and the proposed stormwater management system, have been designed so that post-development peak rates of runoff are below pre-development conditions for the 2-, 10-,25- and 100-year storm events at all design points. Standard 03: Recharge The stormwater runoff from the project will be collected and diverted to a proposed underground infiltration basin. The project as proposed will involve the creation of 0.134 acres of new impervious area and is required to infiltrate 122 cubic feet of stormwater as defined in Stormwater Standard 3. The proposed infiltration basin will provide 4,062 cubic feet of volume below the lowest outlet for groundwater recharge. Refer to Appendix F of this report for calculations documenting required and provided recharge volumes. The DEP Stormwater Standards require that the infiltration BMP drains completely within 72 hours of the end of the storm event. Calculations showing that the proposed infiltration basin will drain within 71.4 hours,based on a conservative Rawl's Rate of 0.17 inchers per hour,are included in Appendix F of this report. Infiltration is not used as a peak rate mitigator therefore a ground water mounding analysis is not required. Standard #4: Water Quality Water quality treatment is provided via deep sump catch basins, proprietary separators, and an infiltration basin.TSS removal calculations are included in Appendix F of this report. The project as proposed will result in a total of 96,834 impervious area,which is conservative in that it includes the existing impervious on site to remain, and is required to treat 8,069 cubic feet of water quality M201047-MA Drainage Report.doex STORMWATER MANAGEMENT STANDARDS- 10- RQHLERI volume as defined in Stormwater Standard 4. The proposed proprietary separators will be sized for the 1 inch runoff volume for the impervious area at the site,and as such will provide a minimum of 8,069 cubic feet of water quality volume.Additionally,the proposed infiltration basin provides 4,062 cubic feet of water quality volume below the lowest outlet for additional water quality treatment. Refer to Appendix F of this report for calculations documenting required and provided water quality volumes. Standard #5: Land Use with Hii!her Potential Pollutant Loads The proposed project involves "Land Uses with Higher Potential Pollutant Loads". Accordingly, the stormwater management system includes an oil-grit separator (CDS treatment unit) prior to discharge. In addition,the project will provide 44%TSS removal prior to infiltration and treat the 1.0 in water quality depth, as further illustrated in Appendix E of this report. Standard #G: Critical Areas Not Applicable for this project. Standard #7: Redevelopment Not Applicable for this project. Standard #8: Construction Period Pollution Prevention and Erosion and Sedimentation Control The proposed project will provide construction period erosion and sedimentation controls as indicated within the site plan set provided for this project. This includes a proposed construction exit,protection for stormwater inlets,protection around temporary material stock piles and various other techniques as outlined on the erosion and sediment control sheets. Additionally, the project is required to file a Notice of Intent with the US EPA and implement a Stormwater Pollution Prevention Plan (SWPPP) during the construction period. The SWPPP will be prepared prior to the start of construction and will he implemented by the site contractor under the guidance and responsibility of the project's proponent. M201047-MA Drainage Report.doex STORMWATE1t MANAGEMENT STANDARDS-I I- BOHLER //� Standard #9: Operation and Maintenance Plan (O&M Plait An Operation and Maintenance (O&M) Plan for this site has been prepared and is included in Appendix G of this report. The O&M Plan outlines procedures and time tables for the long term operation and ]maintenance of the proposed site stormwater management system, including initial inspections upon completion of construction, and periodic monitoring of the system components, j in accordance with established practices and the manufacturer's recommendations. The O&M Plan includes a list of responsible parties and an estimated budget for inspections and maintenance. Standard #t 0: Prohibition of Illicit Discharges The proposed stormwater system will only convey allowable non-stormwater discharges (firefighting waters, irrigation, air conditioning condensates, etc.) and will not contain any illicit discharges from prohibited sources. An Illicit Discharge Statement is included in Appendix G of this report. M201047-MA Drainage Repomdoex STORMWATER MANAGEMENT STANDARDS-12- BQHLFR //" V. SUMMARY In summary, the proposed stormwater management system illustrated on the drawings prepared by Bohler Engineering results in a reduction in peak rates of runoff from the subject site when compared to pre-development conditions for the 2-, 10-, 25- and 100-year storm frequencies. In addition, the proposed best management practices will result in an effective removal of total suspended solids from the post-development runoff. The pre-development versus post- development stormwater discharge comparisons are contained in Table 5.1 below: Table 5.1: Desian Point Peak Runoff Rate Summa><y Pomtof'. 2Year:Skvrm 1b-YearSterrn 25-Year Storm 10t1-Year Storm n.Analysis Pre Post d Pre Pvsk b Pre Post A Pre """ ' Post A 7.39 5.79 -1.60 11.77 9.30 -2.47 15.01 14.11 --0.90 21.98 21.61 -0.37 As outlined in the table above, the proposed stormwater management system as designed will provide a decrease in peak rates of runoff from the proposed facility for the 2-, 10-, 25- and 100- year storm events. The proposed project will provide a substantial improvement over existing conditions. Stormwater runoff currently sheet flows across the entire property,untreated,and onto the abutter's property, across the western property line. Under the proposed project, an extensive stormwater system will be installed which will provide treatment, infiltration and peak rate attenuation while also retaining the runoff from most storm events on the site. As further described above, the project meets, or exceeds the MADEP Stormwater Management Standards. M201047-MA Drainage Repori.docx SUMMARY-13- i 3 APPENDIX A: MASSACHUSETTS STORMWATER MANAGEMENT CHECKLIST l i Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report A. Introduction Important:when A Stormwater Report must be submitted with the Notice of Intent permit application to document filing out forms compliance with the Stormwater Management Standards. The following checklist is NOT a substitute for on the computer, the Stormwater Report which should provide more substantive and detailed information but is offered use only the tab p � p } key to move your here as a tool to help the applicant organize their Stormwater Management documentation for their cursor-do not Report and for the reviewer to assess this information in a consistent format.As noted in the Checklist, use the return the Stormwater Report must contain the engineering computations and supporting information set forth in key.. Volume 3 of the Massachusetts Stormwater Handbook. The Stormwater Report must be prepared and certified by a Registered Professional Engineer(RPE) licensed in the Commonwealth. The Stormwater Report must include: • The Stormwater Checklist completed and stamped by a Registered Professional Engineer(see page 2)that certifies that the Stormwater Report contains all required submittals.' This Checklist is to be used as the cover for the completed Stormwater Report. • Applicant/Project Name • Project Address • Name of Firm and Registered Professional Engineer that prepared the Report • Long-Term Pollution Prevention Plan required by Standards 4-6 • Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan required by Standard 82 • Operation and Maintenance Plan required by Standard 9 In addition to all plans and supporting information, the Stormwater Report must include a brief narrative describing stormwater management practices, including environmentally sensitive site design and LID techniques, along with a diagram depicting runoff through the proposed BMP treatment train. Plans are required to show existing and proposed conditions, identify all wetland resource areas, MRCS soil types, critical areas, Land Uses with Higher Potential Pollutant Loads (LUHPPL), and any areas on the site where infiltration rate is greater than 2.4 inches per hour. The Plans shall identify the drainage areas for both existing and proposed conditions at a scale that enables verification of supporting calculations. As noted in the Checklist,the Stormwater Management Report shall document compliance with each of the Stormwater Management Standards as provided in the Massachusetts Stormwater Handbook. The soils evaluation and calculations shall be done using the methodologies set forth in Volume 3 of the Massachusetts Stormwater Handbook. To ensure that the Stormwater Report is complete, applicants are required to fill in the Stormwater Report Checklist by checking the box to indicate that the specified information has been included in the Stormwater Report. If any of the information specified in the checklist has not been submitted, the applicant must provide an explanation. The completed Stormwater Report Checklist and Certification must be submitted with the Stormwater Report, 'The Stormwater Report may also include the Illicit Discharge Compliance Statement required by Standard 10. If not included In the Stormwater Report,the Illicit Discharge Compliance Statement must be submitted prior to the discharge of stormwater runoff to the post-construction best management practices. 2 For some complex projects,It may not be possible to Include the Construction Period Erosion and Sedimentation Control Plan in the Stormwater Report. In that event,the issuing authority has the discretion to issue an Order of Conditions that approves the project and Includes a condition requiring the proponent to submit the Construction Period Erosion and Sedimentation Control Plan before commencing any land disturbance activity on the site. M201 047_MA Stormwater-Checklist.doc•04/01108 Stormwater Report Checklist•Page 1 of 8 i i Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report B. Stormwater Checklist and Certification i The following checklist is intended to serve as a guide for applicants as to the elements that ordinarily need to be addressed in a complete Stormwater Report. The checklist is also intended to provide conservation commissions and other reviewing authorities with a summary of the components necessary j for a comprehensive Stormwater Report that addresses the ten Stormwater Standards. Note:Because stormwater requirements vary from project to project, it is possible that a complete Stormwater Report may not include information on some of the subjects specified in the Checklist. If it is determined that a specific item does not apply to the project under review, please note that the item is not applicable (N.A.) and provide the reasons for that determination. A complete checklist must include the Certification set forth below signed by the Registered Professional Engineer who prepared the Stormwater Report. Registered Professional Engineer's Certification I have reviewed the Stormwater Report, including the soil evaluation, computations, Long-term Pollution Prevention Plan, the Construction Period Erosion and Sedimentation Control Plan (if included), the Long- term Post-Construction Operation and Maintenance Plan, the Illicit Discharge Compliance Statement(if included) and the plans showing the stormwater management system, and have determined that they have been prepared in accordance with the requirements of the Stormwater Management Standards as further elaborated by the Massachusetts Stormwater Handbook. I have also determined that the information presented in the Stormwater Checklist is accurate and that the information presented in the Stormwater Report accurately reflects conditions at the site as of the date of this permit application. Registered Professional Engineer Block and Signature IJA 8 � ct, 2 101221202Q Signature and ate Checklist Project Type: Is the application for new development, redevelopment, or a mix of new and redevelopment? ® New development ❑ Redevelopment ❑ Mix of New Development and Redevelopment M201047_MA_Stormwater-Cheeklist.doe-04/01108 Stormwater Report Checklist•Page 2 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report Checklist (continued) LID Measures: Stormwater Standards require LID measures to be considered. Document what environmentally sensitive design and LID Techniques were considered during the planning and design of the project: ❑ No disturbance to any Wetland Resource Areas ❑ Site Design Practices (e.g. clustered development, reduced frontage setbacks) ❑ Reduced Impervious Area (Redevelopment Only) ❑ Minimizing disturbance to existing trees and shrubs ❑ LID Site Design Credit Requested: ❑ Credit 1 ❑ Credit 2 ❑ Credit 3 ❑ Use of"country drainage"versus curb and gutter conveyance and pipe ❑ Bioretention Cells (includes Rain Gardens) ❑ Constructed Stormwater Wetlands (includes Gravel Wetlands designs) ❑ Treebox Filter ❑ Water Quality Swale ❑ Grass Channel ❑ Green Roof ❑ Other(describe): 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. M201047_MA Stormwater-Checklist.doc•04/01/08 Stormwater Reporl Checklist•Page 3 of 8 ild Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report Checklist (continued) Standard 2: Peak Rate Attenuation ❑ Standard 2 waiver requested because the project is located in land subject to coastal storm flowage and stormwater discharge is to a wetland subject to coastal flooding. ❑ Evaluation provided to determine whether off-site flooding increases during the 100-year 24-hour storm. ® Calculations provided to show that post-development peak discharge rates do not exceed pre- development rates for the 2-year and 10-year 24-hour storms. If evaluation shows that off-site flooding increases during the 100-year 24-hour storm, calculations are also provided to show that post-development peak discharge rates do not exceed pre-development rates for the 100-year 24- hour storm. Standard 3: Recharge ❑ Soil Analysis provided. ® Required Recharge Volume calculation provided. ❑ Required Recharge volume reduced through use of the LID site Design Credits. ® Sizing the infiltration, BMPs is based on the following method: Check the method used. ® Static ❑ Simple Dynamic ❑ Dynamic Field' ® Runoff from all impervious areas at the site discharging to the infiltration BMP. ❑ Runoff from all impervious areas at the site is not discharging to the infiltration BMP and calculations are provided showing that the drainage area contributing runoff to the infiltration BMPs is sufficient to generate the required recharge volume. ® Recharge BMPs have been sized to infiltrate the Required Recharge Volume. ❑ Recharge BMPs have been sized to infiltrate the Required Recharge Volume only to the maximum extent practicable for the following reason: ❑ Site is comprised solely of C and D soils and/or bedrock at the land surface ❑ M.G.L. c. 21 E sites pursuant to 310 CMR 40.0000 ❑ Solid Waste Landfill pursuant to 310 CMR 19.000 ❑ Project is otherwise subject to Stormwater Management Standards only to the maximum extent practicable. ® Calculations showing that the infiltration BMPs will drain in 72 hours are provided. ❑ Property includes a M.G.L, c. 21 E site or a solid waste landfill and a mounding analysis is included. '80%TSS removal Is required prior to discharge to infiltration BMP if Dynamic Field method is used. M201047_MA_Stormwater-Checklist.doc•04101108 Stormwater Report Checklist-Page 4 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report Checklist (continued) Standard 3: Recharge (continued) ❑ The infiltration BMP is used to attenuate peak flows during storms greater than or equal to the 10- year 24-hour storm and separation to seasonal high groundwater is less than 4 feet and a mounding analysis is provided. ❑ Documentation is provided showing that infiltration BMPs do not adversely impact nearby wetland resource areas. Standard 4: Water Quality The Long-Term Pollution Prevention Plan typically includes the following: • Good housekeeping practices; • Provisions for storing materials and waste products inside or under cover; • Vehicle washing controls; • Requirements for routine inspections and maintenance of stormwater BMPs; • Spill prevention and response plans; • Provisions for maintenance of lawns, gardens, and other landscaped areas; • Requirements for storage and use of fertilizers, herbicides, and pesticides; • Pet waste management provisions; • Provisions for operation and management of septic systems; + Provisions for solid waste management; • Snow disposal and plowing plans relative to Wetland Resource Areas; • Winter Road Salt and/or Sand Use and Storage restrictions; • Street sweeping schedules; • Provisions for prevention of illicit discharges to the stormwater management system; • Documentation that Stormwater BMPs are designed to provide for shutdown and containment in the event of a spill or discharges to or near critical areas or from LUHPPL; • Training for staff or personnel involved with implementing Long-Term Pollution Prevention Plan; • List of Emergency contacts for implementing Long-Term Pollution Prevention Plan. ® A Long-Term Pollution Prevention Plan is attached to Stormwater Report and is included as an attachment to the Wetlands Notice of Intent. ❑ Treatment BMPs subject to the 44% TSS removal pretreatment requirement and the one inch rule for calculating the water quality volume are included, and discharge: ❑ is within the Zone II or Interim Wellhead Protection Area ❑ is near or to other critical areas ❑ is within soils with a rapid infiltration rate(greater than 2.4 inches per hour) ❑ involves runoff from land uses with higher potential pollutant loads. ❑ The Required Water Quality Volume is reduced through use of the LID site Design Credits. ® Calculations documenting that the treatment train meets the 80%TSS removal requirement and, if applicable, the 44% TSS removal pretreatment requirement, are provided. M201047_MA_Stormwater-Cheekllst.doc•04101/08 Stormwater Report Checklist•Page 5 of 8 i Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report i Checklist (continued) Standard 4:Water Quality (continued) ® The BMP is sized (and calculations provided) based on: ® The %"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 6: 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. M201047_MA_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 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. M201047µMA—Stormwater-Checklist.doc•04/01/08 Stormwater Report Checklist-Page 7 of 8 i 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 notthe 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. M201047_MA Stormwater-Checklist.doc•04/01/08 Stormwater Report Checklist•Page 8 of B APPENDIX B: PROJECT LOCATION MAPS ➢ GSGS MAP I I i �-! N i''k I. ,. h'�'..•. a'.� y k'aF `v`^C" 1 5 °^v'""` „7'w'"'.._;:r•:^.xr.PS.r f.� .'.L� a t 1f,1� ■��r per � Aa-1aE'P , 4 Li' f II �I t �' y :r t� .� i {w ems, v .. .� �`-- ° �!' � �J` '--�°ry1• 37 .-�•y,,� 7 r• t+ r�-� it i IAN 1 11 A)"Y % `^.� .E }," ti '�' S� f��� a I d�Y Y� •h' r ����.."»TM^^�.y:��,d �.. 'i�, �•'' I� �Y1 a � '"�f '�",..;��'r�;IY ,1S a f g c'q_ tEt._ra i °5 � + °€'�`'� ,IS��f�a�— d �� � �r+ P � „",•*".�Ylf°, iY fry„ , , � r TStFftil. t y 4 1 �v ua. ��� ti ; t SITE s0Z 3 1 r 1 _ it A � 1 rr��'�' � Y�� 1{ Il.st, �.l;, .'' t1 �d� :f E� ���f-�� ��4�. ^%-•;tr a'm'r I3�Si �_-- �� ��. ��'�y'+ tl 1 USGS MAP ell 419&435 ANDOVER STREET TOWN OF NORTH ANDOVER,MASSACHUSETTS mew } If y I Yt ESSEX COUNTY PREPARED BY BOHLER // � �a i'� - �,ri1° ,�I �Y'(;' I'i Il �. y� �•« "w:.>�'�r . �`� �E. 4 a. SCALER E'W1,000'DATE:10/22/2020 APPENDIX C: SOIL AND WETLAND INFORMATION ➢ NCRS CUSTOM SOIL RESOURCE REPORT Hydrologic Soil Group--Essex County,Massachusetts,Northern Part 3: a � F n n " 0 3295E0 325M 325740 3257a0 325920 325B0 3259M 225940 3258� 42°49317N 42`40'31"N v a o_ a_ v v v P P P Q O 0 o {. in y 1P.I. 'e vAi. at tlii sc.le. 42°40'11 N c 42-40'22"N v2v 32 325700 325740 3257M 3259 D M5940 s � F Map Sccale:1:1,8SO iF printed on A landscape(11"x a S" sheet r Meters N 0 25 50 100 15D A Feet 0 50 100 200 300 Map projection:Web Mercator Comer coordinates-,WGSS4 I;dgetics:ITEM Zone 19N WG584 Natural Resources Web Soil Survey 10/15/2020 ter• Conservation Service National Cooperative Soil Survey Page 1 of 4 Hydrologic Soil Group—Essex County,Massachusetts,Northern Part MAP LEGEND MAP INFORMATION Area of Interest(Aol) ® C The soil surveys that comprise your AOI were mapped at Q Area of Interest(AOq CID 1:15,800. Soils D Warning:Soil Map may not be valid at this scale. Soil Rating Polygons A p Not rated or not available Enlargement of maps beyond the scale of mapping can cause misunderstanding of the detail of mapping and accuracy of soil AID water Features line placement.The maps do not show the small areas of Streams and Canals contrasting soils that could have been shown at a more detailed B Transportation scale. BID 444 Rails Please rely on the bar scale on each map sheet for map C Interstate Highways measurements. 0 CID US Routes Source of Map: Natural Resources Conservation Service Web Soil Survey URL: D Major Roads Coordinate System: Web Mercator(EPSG:3857) 0 Not rated or not available Local Roads Maps from the Web Soil Survey are based on the Web Mercator Soil Rating Lines Background projection,which presences direction and shape but distorts A distance and area.A projection that preserves area,such as the ® Aerial Photography Albers equal-area conic projection,should be used if more �'*• AID accurate calculations of distance or area are required. !* B This product is generated from the USDA-NRCS certified data as BID of the version date(s)listed below. C Soi[Survey Area: Essex County,Massachusetts,Northern Part Survey Area Data: Version 16,Jung,2020 CID Soil map units are labeled(as space allows)for map scales D 1:50,000 or larger. Not rated or not available Date(s)aerial images were photographed: Sep 13,2D19--Oct 5, Soil Rating Points 2D19 ® A The orthophoto or other base-map on which the soil lines were compiled and digitized probably differs from the background ® A/0 imagery displayed on these maps.As a result,some minor g shifting of map unit boundaries may be evident. B/D usDA Natural Resources Web Soil Survey 10/15/2020 iiiii—m Conservation Service National Cooperative Soil Survey Page 2 of 4 Hydrologic Soil Group—Essex County,Massachusetts,Northern Part j Hydrologic Soil Group Map unit symbol Nlap unit Warne Rattng Aares in AOl f?ercetit of AOI 1 Water 0.0 0.0% 72A Whitman fine sandy d 0.0 0.2% loam,0 to 3 percent slopes 310A Woodbridge fine sandy Clta 6.8 45.6% loam,0 to 3 percent slopes 310E Woodbridge fine sandy CID 5.3 35.5% loam,3 to 8 percent slopes 311 B Woodbridge fine sandy CID 0.6 3.8% loam,0 to 8 percent slopes,very stony 405B Charlton fine sandy 8 2.0 13.6% loam,3 to 8 percent slopes 651 Udorthents,smoothed A 0.2 1.1% Totals for Area of Interest 14.9 100.0% us�Da Natural Resources Web Soil Survey 1 0/1 51202 0 Sri Conservation Service National Cooperative Soil Survey Page 3 of 4 Hydrologic Soil Group—Essex County,Massachusetts,Northern Part Description Hydrologic soil groups are based on estimates of runoff potential. Soils are assigned to one of four groups according to the rate of water infiltration when the soils are not protected by vegetation, are thoroughly wet, and receive precipitation from long-duration storms. The soils in the United States are assigned to four groups (A, B, C, and D) and three dual classes(AID, B/D, and CID). The groups are defined as follows: Group A. Soils having a high infiltration rate(low runoff potential)when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of moderately deep or deep, moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture. These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate(high runoff potential)when thoroughly wet. These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group (AID, BID, or CID), the first letter is for drained areas and the second is for undrained areas. Only the soils that in their natural condition are in group D are assigned to dual classes. Rating Options Aggregation Method.Dominant Condition Component Percent Cutoff.*None Specified Tie-break Rule:Higher u Natural Resources Web Soil Surrey 10/1512020 Conservation Service National Cooperative Soil Survey Page 4 of 4 APPENDIX D: EXISTING CONDITIONS HYDROLOGIC ANALYSIS ➢ EXISTING CONDITIONS DRAINAGE MAP ➢ EXISTING CONDITIONS HYDROCAD COMPUTATIONS E i 1 i i E Xv DP T Subcat Reach on Routing Diagram for M201047 Hydro EX Prepared by Bohler Engineering, Printed 1 012 212 0 2 0 HydroCADO 10.00-25 sfn 08955 Q 2019 HydroCAD Software Solutions LLC M201047_Hydro,_EX Prepared by Bohler Engineering Printed 10/22/2020 H droCAD®10.00-25 s/n 08955 ©2019 H droCAD Software Solutions LLC Pacie 2 Area Listing (all nodes) Area CN Description (sq-ft) (subcatchment-numbers) 3,105 86 <50% Grass cover, Poor, HSG C (EX01) 22,586 74 >75% Grass cover, Good, HSG C (EX01) 60,852 98 Paved parking, HSG C (EX01) 30,129 98 Roofs, HSG C (EX01) 116,672 93 TOTAL AREA i M20'1047_Hydro_EX Typo M 24-hr 2-yr Rainfall=3.20" Prepared by Bohler Engineering Printed 10/22/2020 HydroCAD® 10.00-25 s/n 08955 O 2019 HydroCAD Software Solutions LLC Pa-ge3 Summary for Subcatchment EXO'I: Runoff 7.39 cfs @ 12,09 hrs, Volume= 23,779 cf, Depth= 2.45" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 2-yr Rainfall=3.20" Area (so CN Description 30,129 98 Roofs, HSG C 60,852 98 Paved parking, HSG C 3,105 86 <50% Grass cover, Poor, HSG C 22,586 74 >75% Grass cover, Good HSG C 116,672 93 Weighted Average 25,691 22.02% Pervious Area 90,981 77.98% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 3.1 50 0.0840 0.27 Sheet Flow, AB - Grass: Short n= 0,150 P2= 3.26" 2.3 225 0.0524 1.60 Shallow Concentrated Flow, BC Short Grass Pasture Kv= 7.0 fps 0.8 60 0.0300 1.21 Shallow Concentrated Flow, CD Short Grass Pasture Kv= 7.0_fps__ 6.2 335 Total Summary for Link DP1: Inflow Area = 116,672 sf, 77.98% Impervious, Inflow Depth = 2.45" for 2-yr event Inflow - 7.39 cfs @ 12.09 hrs, Volume= 23,779 cf Primary - 7.39 cfs @ 12.09 hrs, Volume= 23,779 cf, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs M201047_Hydro_EX Type 11124-hr 90 yr Rainfall=4.80" Prepared by Bohler Engineering Printed 10/22/2020 H droCAD®10.00-25 s/n 08955 02019 H droCAD Software Solutions LLC Page 4 Summary for Subcatchment EX01: Runoff 11.77 cfs @ 12,09 hrs, Volume= 38,907 cf, Depth= 4.00" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type ill 24-hr 10-yr Rainfall=4.80" Area (sf) CN Description 30,129 98 Roofs, MSG C 60,852 98 Paved parking, HSG C 3,105 86 <50% Grass cover, Poor, HSG C 22,586 74 >75% Grass cover, Good, HSG C 116,672 93 Weighted Average 25,691 22.02% Pervious Area 90,981 77.98% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ftlsec) (cfs) 3.1 50 0.0840 0.27 Sheet Flow, AB Grass: Short n= 0.150 P2= 3.26" 2.3 225 0.0524 1.60 Shallow Concentrated Flow, BC Short Grass Pasture Kv= 7.0 fps 0.8 60 0.0300 1.21 Shallow Concentrated Flow, CD Short Grass Pasture Kv= 7.0 fps 6.2 335 Total Summary for link DPI: inflow Area= 116,672 sf, 77.98% Impervious, Inflow Depth = 4.00" for 10-yr event Inflow - 11.77 cfs @ 12.09 hrs, Volume 38,907 cf Primary = 11.77 cfs @ 12.09 hrs, Volume= 38,907 cf, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs I i M201047_Hydro_EX Type 11124-hr 25-yr Rainfall=6.00" Prepared by Bohler Engineering Printed 10/22/2020 HydroCAD010.00-25 sln 08955 02019 HydroCAD Software Solutions LLC Page 5 Summary for Subcatchment EX01: Runoff - 15.01 cfs @ 12.09 hrs, Volume= 50,389 cf, Depth= 5.18" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 25-yr Rainfall=6.00" Areas CN Description 30,129 98 Roofs, HSG C 60,852 98 Paved parking, HSG C 3,105 86 <50% Grass cover, Poor, HSG C 22,586 74 >75% Grass cover, Good HSG C 116,672 93 Weighted Average 25,691 22.02% Pervious Area 90,981 77.98% Impervious Area Tc Length Slope Velocity Capacity Description min feet ftlft ftlsec cfs 3.1 50 0.0840 0.27 Sheet Flow, AB Grass; Short n= 0.150 P2= 3.26" 2.3 225 0.0524 1.60 Shallow Concentrated Flow, BC Short Grass Pasture Kv= 7.0 fps 0.8 60 0.0300 1.21 Shallow Concentrated Flow, CD Short Grass Pasture Kv= 7.0 fps 6.2 335 Total Summary for Link DP1: Inflow Area = 116,672 sf, 77.98% Impervious, Inflow Depth = 5.18" for 25-yr event Inflow 15.01 cfs @ 12.09 hrs, Volume= 50,389 of Primary _ 15.01 cfs @ 12.09 hrs, Volume= 50,389 cf, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs M201047�Hydro_EX Type li124-hr 100-yr Rainfall=8.60" Prepared by Bohler Engineering Printed 10/22/2020 H droCAD® 10.00-25 s/n 08955 02019 H droCAD Software Solutions LLC Page 6 Summary for Subcatchment EX01: Runoff - 21.98 cfs @ 12.09 hrs, Volume= 75,432 of, Depth= 7.76" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-yr Rainfall=8.60" Areas CN Description 30,129 98 Roofs, HSG C 60,852 98 Paved parking, HSG C 3,105 86 <50% Grass cover, Poor, HSG C 22,586 74 >75% Grass cover, Good HSG C 116,672 93 Weighted Average 25,691 22.02% Pervious Area 90,981 77.98% Impervious Area To Length Slope Velocity Capacity Description min feet ft/ft ft/sec cfs 3.1 50 0.0840 0.27 Sheet Flow, AB Grass: Short n= 0.150 P2= 3.26" 2.3 225 0.0524 1.60 Shallow Concentrated Flow, BC Short Grass Pasture Kv= 7.0 fps 0.8 60 0.0300 1.21 Shallow Concentrated Flow, CD Short Grass Pasture Kv= 7.0 fps 6.2 335 Total Summary for Link DP1: Inflow Area = 116,672 sf, 77.98% Impervious, Inflow Depth = 7.76" for 100-yr event Inflow - 21.98 cfs @ 12.09 hrs, Volume= 75,432 of Primary = 21.98 cfs @ 12.09 hrs, Volume= 75,432 of, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs APPENDIX E: PROPOSED CONDITIONS HYDROLOGIC ANALYSIS I ➢ PROPOSED CONDITIONS DRAINAGE MAP ➢ PROPOSED CONDITIONS HYDROCAD CALCULATIONS I 3 01 E .e. — _ r. � r 0 ti PE SET Rom; 1 ✓ Tc=6.OM€PI,{A11FF.E --__ ��' _ r,_,a— _ /� .�//f� / P4"Ooosirs r 1 _, - - ♦`® •' ',l. ,,� P1ANbOLI1NEms ASSWATes li ,t :i'.:::.:.:::::::::is is i ii�.` ✓ ' _ .d F % _ LDP1 d„• J �y / j /// PNOpOSED / caxoenoHs WATERGH D MAP !,/ I an W8-PR E PRO 1 .1 P -- -D D P 1 Chamber System Subcat` Rean on . �II1�C Routing Diagram for M201047 Hydro PR Prepared by Bohler Engineering, Printed 10122I2020 HydroGAOO 10.00-25 sin 08955 0 2019 HydroCAD Software Solutions LLG M201047_Hydro_PR Prepared Fy Bohler Engineering Printed 10/22/2020 H droq D810.00-25 sln 08955 ©2019 H droCAD Software Solutions LLC Pacie 2 Area Listing (all nodes) Area CN Description (sq-ft) (subcatchment-numbers) 19,834 79 >75% Grass cover, Goad, HSG C (PR01) 78,681 98 Paved parking, HSG C (PR01) 18,157 98 Roofs, HSG C (PR01) 116,672 94 TOTAL AREA i i i M201047�Hydro_PR Type /1124-hr 2-yr Rainfall=3.20" Prepared by Bohler Engineering Printed 10/22/2020 H droCAD® 10.00-25 sln 08955 OO 2019 H droCAD Software Solutions LLC Page 3 Summary for Subcatchment PR01: Runoff = 7.65 cfs @ 12.08 hrs, Volume= 24,733 cf, Depth= 2.54" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 2-yr Rainfall=3.20" Area (sf) CN Description 18,157 98 Roofs, HSG C 78,681 98 Paved parking, HSG C 19,834 74 >75% Grass cover, Good HSG C 116,672 94 Weighted Average 19,834 17,00% Pervious Area 96,838 83,00% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Direct M201047�Hydro�PR Type 11124-hr 2-yr Rainfall=3.20" Prepared by Bohler Engineering Printed 10/22/2020 HydroCAD010.00-25 s/n 08955 ©2019 HydroCAD Software Solutions LLC Page 4 Summary for Pond 1 P: Chamber System Inflow Area= 116,672 sf, 83.00% Impervious, Inflow Depth = 2.54" for 2-yr event Inflow = 7.65 cfs @ 12.08 hrs, Volume= 24,733 cf Outflow 5,79 cfs @ 12.15 hrs, Volume= 20,674 of, Atten= 24%, Lag= 4.1 min Primary - 5.79 cfs @ 12.15 hrs, Volume= 20,674 of Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0 cf Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs 13 Peak Elev= 202.09' @ 12.15 hrs Surf.Area=4,021 sf Storage= 7,072 of Plug-Flow detention time= 129.7 min calculated for 20,674 of(84% of inflow) Center-of-Mass det. time= 62.3 min ( 849.4 - 787.1 ) Volume Invert Avail.Storage Storage Description #1A 199.50' 3,599 of 49.00'W x 81.941 x 3.50'H Field A 14,052 of Overall -5,053 of Embedded = 8,999 of x 40.0% Voids #2A 200.00' 5,053 of ADS StormTech SC-740+Cap x 110 Inside#1 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.12'L =45.9 of Overall Size= 51.0"W x 30.0"H x 7.561 with 0.44' Overlap 110 Chambers in 10 Rows #3 200.00' 44 of 4.00'D x 7.00'H OCS x 0.5 #4 205.80' 698 of Surface Ponding (WQI-1) (Pyramidal)Listed below (Recalc) #5 206.50' 260 of Surface Pondin CB-10) (Pyramidal)Listed below Recalc 9,655 of Total Available Storage Storage Group A created with Chamber Wizard Elevation Surf.Area Inc.Store Cum.Store Wet.Area feet (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 205.80 4 0 0 4 206.30 400 74 74 401 207.00 1,500 624 698 1,504 Elevation Surf.Area Inc.Store Cum.Store Wet.Area ( q- )_ ( ) cubic-feet) (sq-ft) (feet) s ft cubic-feet 206.50 4 0 0 4 207.00 1,480 260 260 1,481 Device Routing _ Invert Outlet Devices #1 Prima 200.00' 15.0" Round Culvert Primary ulvert L= 25.0' CPP, mitered to conform to fill, Ke= 0.700 Inlet 1 Outlet Invert= 200.00'1198.00' S= 0.0800 '1' Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area 1.23 sf #2 Device 1 202.75' 4.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 #3 Secondary 206.50' 10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 #4 Device 1 201.00' 12.0" Vert. Orifice/Grate X 2.00 C= 0.600 i , M201047 Hydro Type III 24-hr 2- r Rainfall=3.20" _Hyd Yp Y Prepared by Bohler Engineering Printed 10/22/2020 HydroCAD610.00-25 s/n 08955 ©2019 HydroCAD Software Solutions LLC Paces 5 i Primary OutFlow Max=5.78 cfs @ 12.15 hrs HW=202.08' (Free Discharge) t-- =Culvert (Passes 5.78 cfs of 6.30 cfs potential flow) 2=Broad-Crested Rectangular Weir( Controls 0.00 cfs) =OrificelGrate (Orifice Controls 5.78 cfs @ 3.68 fps) te3 Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=199.50' (Free Discharge) =Broad-Crested Rectangular Weir Controls 0.00 cfs g { ) M201047_Hydr'o_PR Type ill 24-hr 2-yr Rainfall=3.20" Prepared by Bohler Engineering Printed 10/22/2020 HydroCAD®1.0.00-25 s/n 08955 ©2019 HydroCAD Software Solutions LLC Page 6 Stage-Area-Storage for Pond 1P; Chamber System Elevation Storage Elevation Storage (feet) (cubic-feet) (feet) (cubic-feet) 199.50 0 204.80 8,683 199.60 161 204.90 8,684 199.70 321 205.00 8,684 199.80 482 205.10 8,685 199.90 642 205.20 8,686 200.00 803 205.30 8,686 200.10 1,139 205.40 8,687 200.20 1,474 205.50 8,687 200.30 1,807 205.60 8,688 200.40 2,137 205.70 8,689 200.50 2,465 205.80 8,689 200.60 2,790 205.90 8,692 200.70 3,113 206.00 8,698 200.80 3,431 206.10 8,711 200.90 3,747 206.20 8,733 201.00 4,058 206.30 8,766 201.10 4,366 206.40 8,813 201.20 4,669 206.50 8,871 201.30 4,967 206.60 8,947 201.40 5,259 206.70 9,051 201.50 5,547 206.80 9,195 201.60 5,828 206.90 9,393 201.70 6,101 207.00 9,666 201.80 6,366 201.90 6,623 202.00 6,870 202.10 7,105 202.20 7,324 202.30 7,521 202.40 7,699 202.50 7,866 202.60 8,027 202.70 8,188 202.80 8,349 202.90 8,511 203.00 8,672 203.10 8,672 203.20 8,673 203.30 8,674 203.40 8,674 203.50 8,675 203.60 8,676 203.70 8,676 203.80 8,677 203.90 8,677 204.00 8,678 204.10 8,679 204.20 8,679 204.30 8,680 204.40 8,681 204.50 8,681 204.60 8,682 204.70 8,682 M201047—Hydro—PR Type 11124-hr 2-yr Rainfall=3.20° Prepared by Bohler Engineering Printed 10/22/2020 j H droCAD®10.00-25 sln 08955 OO 2019 H droCAD Software Solutions LLC Page 7 Summary for Link DP1: i Inflow Area = 116,672 sf, 83.00% Impervious, Inflow Depth = 2.13" for 2-yr event Inflow - 5.79 cfs @ 12.15 hrs, Volume= 20,674 cf Primary 5.79 cfs @ 12.15 hrs, Volume= 20,674 cf, Atten= 0%, Lague 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs M201047_Hydro_PR Type 1/124-hr 90-yr Rainfall=4.80" Prepared by Bohler Engineering Printed 10/22/2020 H droCAD®10.00-25 s/n 08955 ©2019 H droCAD Software Solutions LLC Pa e 8 Summary for Subcatchment PROI: Runoff -- 12.03 cfs @ 12.08 hrs, Volume= 39,968 cf, Depth= 4.11" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 10-yr Rainfall=4.80" Area (sf) CN Description 18,157 98 Roofs, HSG C 78,681 98 Paved parking, HSG C 19,834 74 >75% Grass cover, Good, HSG C 116,672 94 Weighted Average 19,834 17.00% Pervious Area 96,838 83.00% Impervious Area Tc Length Slope Velocity Capacity Description min feet ft/ft) (ft/sec) (cfs 6.0 Direct Entry, Direct i I i M201047_Hydro_PR Type III 24-hr 10-yr Rainfa11=4.80" Prepared by Bohler Engineering Printed 10/22/2020 H droCADO 10.00-25 s/n 08955 ©2019 H droCAD Software Solutions LLC Page 9 Summary for Pond 'I P: Chamber System Inflow Area = 116,672 sf, 83.00% Impervious, Inflow Depth = 4.11" for 10-yr event Inflow - 12.03 cfs @ 12.08 hrs, Volume= 39,968 cf Outflow = 9.30 cfs @ 12.15 hrs, Volume= 35,908 cf, Atten= 23%, Lag= 4.1 min Primary - 9.30 cfs @ 12.15 hrs, Volume= 35,908 cf Secondary = 0.00 cfs @ 0.00 hrs, Volume= 0 cf Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs 13 Peak Elev= 203.80' @ 12.15 hrs Surf.Area= 4,021 sf Storage= 8,677 cf Plug-Flow detention time= 100.2 min calculated for 35,903 cf(90% of inflow) Center-of-Mass det. time= 50.9 min ( 825.5- 774.6 ) Volume Invert Avail.Stora a Storage Description #1A 199.50' 3,599 cf 49.00'W x 81.941 x 3.50'H Field A 14,052 cf Overall -5,053 cf Embedded 8,999 cf x 40.0% Voids #2A 200.00' 5,053 cf ADS_StormTech SC-740 +Cap x 110 Inside#1 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.121 =45.9 cf Overall Size= 51.0"W x 30.0"H x 7.561 with 0.44' Overlap 110 Chambers in 10 Rows #3 200.00' 44 of 4.00'D x 7.00'H OCS x 0.5 #4 205.80' 698 cf Surface Ponding (W0I-1) (Pyramidal)Listed below (Recalc) #5 206.50' 260 cf Surface Pondin CB-10) (Pyramidal)Listed below Recalc 9,655 cf Total Available Storage Storage Group A created with Chamber Wizard Elevation Surf.Area Inc.Store Cum.Store Wet.Area feet s Wft cubic-feet cubic-feet s -ft 205.80 4 0 0 4 206.30 400 74 74 401 207.00 1,500 624 698 1,504 Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet)- (sq-ft) 206.50 4 0 0 4 207.00 1,480 260 260 1,481 Device Routing Invert Outlet Devices #1 Primary 200.00' 15.0" Round Culvert L= 25.0' CPP, mitered to conform to fill, Ke= 0.700 Inlet/Outlet Invert= 200,00' / 198.00' S= 0.0800 T Cc= 0,900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 1.23 sf #2 Device 1 202.75' 4.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 #3 Secondary 206.50' 10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0A0 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 #4 Device 1 201.00' 12.0" Vert. Orifice/Grate X 2.00 C= 0.600 M201047_Hydro_PR Type 11124-hr 10-yr Rainfall=4.80" Prepared by Bohler Engineering Printed 10122/2020 H droCAD® 10.00-25 s/n 08955 ©2019 H droCAD Software Solutions LLC Page 10 Primary OutFlow Max=9.17 cfs @ 12.15 hrs HW=203.72' (Free Discharge) L r Culvert (Inlet Controls 9.17 cfs @ 7.�47 fps) 2=Broad-Crested Rectangular Weir(Passes < 12.60 cfs potential flow) 4 OrificelGrate (Passes < 11.26 cfs potential flow) te3 Secondary OutFlow Max=0.00 cfs @ 0.00 hrs HW=199.50' (Free Discharge) =Broad-Crested Rectangular Weir(Controls 0.00 cfs) i M201047�Hydro_PR Type II/ 24-hr 10-yr Rainfall=4.80" Prepared by Bohler Engineering Printed 10/22/2020 HydroCAD® 10.00-25 sln 08955 OO 2019 HydroCAD Software Solutions LLC _Pape 1.1_ Stage-Area-Storage for Pond 1 P: Chamber System Elevation Storage Elevation Storage (feet) (cubic-feet) (feet) (cubic-feet) 199.50 0 204.80 8,683 199.60 161 204.90 8,684 199.70 321 205.00 8,684 199.80 482 205.10 8,685 199.90 642 205.20 8,686 200.00 803 205.30 8,686 200.10 1,139 205.40 8,687 200.20 1,474 205.50 8,687 200.30 1,807 205.60 8,688 200.40 2,137 205.70 8,689 200.50 2,465 205.80 8,689 200.60 2,790 205.90 8,692 200.70 3,113 206.00 8,698 200.80 3,431 206.10 8,711 200.90 3,747 206.20 8,733 201.00 4,058 206.30 8,766 201.10 4,366 206.40 8,813 201.20 4,669 206.50 8,871 201.30 4,967 206.60 8,947 201.40 5,259 206.70 9,051 201.50 5,547 206.80 9,195 201.60 5,828 206.90 9,393 201.70 6,101 207.00 9,665 201.80 6,366 201.90 6,623 202.00 6,870 202.10 7,105 202.20 7,324 202.30 7,521 202.40 7,699 202.50 7,866 202.60 8,027 202.70 8,188 202.80 8,349 202.90 8,511 203.00 8,672 203.10 8,672 203.20 8,673 203.30 8,674 203.40 8,674 203.50 8,675 203.60 8,676 203.70 8,676 203.80 8,677 203.90 8,677 204.00 8,678 204.10 8,679 204.20 8,679 204.30 8,680 204.40 8,681 204.50 8,681 204.60 8,682 204.70 8,682 M201047_Hydro_PR Type III24-hr 10-yrRainfa11=4.80" Prepared by Bohler Engineering Printed 10122/2020 HydroCAD®10.00-25 sln 08955 02019HydroCAD Software Solutions LLC Page 12 Summary for Link DPI: Inflow Area= 116,672 sf, 83.00% Impervious, Inflow Depth = 3.69" for 10-yr event Inflow - 9.30 cfs @ 12.15 hrs, Volume= 35,908 cf Primary = 9.30 cfs @ 12.15 hrs, Volume= 35,908 cf, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs i M201047_Hydro�PR Type 11124-hr 25-yr Rainfall=6.00" Prepared by Bohler Engineering Printed 10/22/2020 H droCAD®10.00-25 sin 08955 02019 H droCAD Software Solutions LLC Pacie 13 Summary for Suhcatchment PR01: Runoff _ 15.28 cfs @ 12.08 hrs, Volume= 51,497 cf, Depth= 5.30" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 25-yr Rainfall=6.00" Area (so CN Description 18,157 98 Roofs, HSG C 78,681 98 Paved parking, HSG C 19,834 74 >75% Grass cover, Good HSG C 116,672 94 Weighted Average 19,834 17.00% Pervious Area 96,838 83,00% Impervious Area Te Length Slope Velocity Capacity Description min feet ftlft ftlsec cfs 6.0 Direct Entry, Direct M201047Hydro_PR Type 11124-hr 25-yr Rainfall=6.00" Prepared [Ty Bohler Engineering Printed 10/22/2020 H droCAD®10.00-25 s/n 08955 ©2019 H droCAD Software Solutions L.LC Pacie 14 Summary for Pond 1 P: Chamber System Inflow Area 116,672 sf, 83.00% Impervious, Inflow Depth = 5.30" for 25-yr event Inflow = 15.28 cfs @ 12.08 hrs, Volume= 51,497 cf Outflow - 14.11 cfs @ 12.12 hrs, Volume= 47,415 of, Atten= 8%, Lag= 2.0 min Primary - 12.78 cfs @ 12.12 hrs, Volume= 47,225 of Secondary = 1.34 cfs @ 12.12 hrs, Volume= 190 of Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs/3 Peak Elev= 206.63' @ 12.12 hrs Surf.Area= 4,988 sf Storage= 8,975 of Plug-Flow detention time= 86.8 min calculated for 47,409 of(92% of inflow) Center-of-Mass det. time= 45.4 min ( 813.9- 768.5 ) Volume Invert Avail.Storage Storage Description #1A 199.50, 3,599 of 49.00'W x 81.94'L.x,, 3.50'H Field A 14,052 of Overall -5,053 of Embedded = 8,999 of x 40.0%Voids #2A 200.00' 5,053 of ADS_StormTeeh SC-740 +Cap x 110 Inside#1 Effective Size= 44.6"W x 30.0"H => 6.45 sf x 7.121 =45.9 cf Overall Size= 51.0"W x 30.0"H x 7.56'L with 0.44' Overlap 110 Chambers in 10 Rows #3 200.00' 44 of 4.00'D x 7.00'H OCS x 0.5 #4 205.80' 698 cf Surface Ponding (WQI-1) (Pyramidal)Listed below (Recalc) #5 206.50' 260 of Surface Pondin CB-10) (Pyramidal)Listed below Recalc 9,655 of Total Available Storage Storage Group A created with Chamber Wizard Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) _ (cubic-feet) 4cu„bic-feet) (sq-ft) 205,80 4 0 0 4 206.30 400 74 74 401 207.00 1,500 624 698 1,504 Elevation Surf.Area Inc.Store Cum.Store Wet.Area _ (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 206.50 4 0 0 4 207.00 1,480 260 260 1,481 Device Routin Invert Outlet Devices #1 Primary 200.00' 15.0" Round Culvert L= 25.0' CPP, mitered to conform to fill, Ke= 0.700 Inlet/Outlet Invert= 200.00'f 198.00' S= 0.0800 T Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 1.23 sf #2 Device 1 202.75' 4.0' long x ON breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 #3 Secondary 206.50' 10.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0A0 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 #4 Device 1 201.00' 12.0" Vert. Orifice/Grate X 2.00 C= 0.600 I M201047 Hydro PR Type ill 24-hr 25-yr Rainfall=6.00" Prepared by Bohler Engineering Printed 10/22/2020 H droCAD®10.00-25 s/n 08955 02019 H droCAD Software Solutions LLC Pa e 15 rimary OutFlow Max=12.78 cfs @ 12.12 hrs HW=206,63' (Free Discharge) -Culvert (Inlet Controls 12.78 cfs @ 10.41 fps) 2=Broad-Crested Rectangular Weir(Passes < 101.46 cfs potential flow) 4 OrificelGrate (Passes < 17.13 cfs potential flow) Secondary OutFlow Max=1.30 cfs @ 12.12 hrs HW=206,63' (Free Discharge) 3=Broad-Crested Rectangular Weir(Weir Controls 1.30 cfs @ 1.01 fps) M201047_Hydro_PR Type 1f124-hr 25 yr Rainfall=6.00" Prepared by BOhler Engineering Printed 10/22/2020 HydroCAD®10.00-25 s/n 08955 02019_HydroCAD Software Solutions LLC Page 16 Stage-Area-Storage for Pond 1 P: Chamber System Elevation Storage Elevation Storage (feet) (cubic-feet) (feet) (cubic-feet) 199.50 0 204.80 8,683 199.60 161 204.90 8,684 199.70 321 205.00 8,684 199.80 482 205.10 8,685 199.90 642 205.20 8,686 200.00 803 205.30 8,686 200.10 1,139 205.40 8,687 200.20 1,474 205.50 8,687 200.30 1,807 205.60 8,688 200.40 2,137 205.70 8,689 200.50 2,465 205.80 8,689 200.60 2,790 205.90 8,692 200.70 3,113 206.00 8,698 200.80 3,431 206.10 8,711 200.90 3,747 206.20 8,733 201.00 4,058 206.30 8,766 201.10 4,366 206.40 8,813 201.20 4,669 206.50 8,871 201.30 4,967 206.60 8,947 201.40 5,259 206.70 9,051 201.50 5,547 206.80 9,195 201.60 5,828 206.90 9,393 201.70 6,101 207.00 9,666 201.80 6,366 201.90 6,623 202.00 6,870 202.10 7,105 202.20 7,324 202.30 7,521 202.40 7,699 202.50 7,866 202.60 8,027 202.70 8,188 202.80 8,349 202.90 8,511 203.00 8,672 203.10 8,672 203.20 8,673 203.30 8,674 203.40 8,674 203.50 8,675 203.60 8,676 203.70 8,676 203.80 8,677 203.90 8,677 204.00 8,678 204.10 8,679 204.20 8,679 204.30 8,680 204.40 8,681 204.50 8,681 204.60 8,682 204.70 8,682 0 i M201047_Hydro_PR Type i1124-hr 25-yr Rainfall=6.00" Prepared by Bohler Engineering Printed 10/22/2020 H droCAD®10.00-25 sln 08955C 2019 H droCAD Software Solutions LLC Page 17 i Summary for Link DPI: ! Inflow Area = 116,672 sf, 83.00% impervious, Inflow Depth = 4.88" for 25-yr event Inflow = 14.11 cfs @ 12.12 hrs, Volume= 47,415 cf Primary - 14.11 cfs @ 12.12 hrs, Volume= 47,415 cf, Atten= 0%, Lag= 0.0 min Primary outflow = Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs M201047_Hydro_PR Type 11i 24-hr I00-yr Rainfall=8.60" Prepared by Bohler Engineering Printed 10/22/2020 H droCAD®10.00-25 s/n 08955 ©2019 H droCAD Software Solutions LLC Pacie 18 Summary for Subcatchment PR01: Runoff = 22.26 cfs @ 12.08 hrs, Volume= 76,603 cf, Depth= 7.88" Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type III 24-hr 100-yr Rainfall=8.60" Areas CN Description 18,157 98 Roofs, HSG C 78,681 98 Paved parking, HSG C 19,834 74 >75% Grass cover, Good HSG C 116,672 94 Weighted Average 19,834 17.00% Pervious Area 96,838 83.00% Impervious Area Tc Length Slope Velocity Capacity Description min feet ft/ft ft/sec cfs 6.0 Direct Entry, Direct E M201047�Hydro_PR Type III 24-hr 100-yr Ralnfail=8.60" Prepared by Bohler Engineering Printed 10/22/2020 HydroCAD®10.00-25 s1n 08955 ©2019 HydroCAD Software Solutions LLC Page 19 i Summary for Pond IP. Chamber System Inflow Area = 116,672 sf, 83.00% Impervious, Inflow Depth = 7.88" for 100-yr event Inflow 22.26 cfs @ 12.08 hrs, Volume= 76,603 cf Outflow = 21.61 cfs @ 1210 hrs, Volume 72,510 cf, Atten= 3%, Lag= 1.2 min Primary = 13.10 cfs @ 12.10 hrs, Volume= 68,930 cf Secondary = 8.52 cfs @ 12.10 hrs, Volume= 3,580 cf i Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs 13 Peak Elev= 206.94' @ 12.10 hrs Surf.Area= 6,536 sf Storage= 9,480 of Plug-Flow detention time= 68.1 min calculated for 72,510 of(95% of inflow) Center-of-Mass det. time= 37.5 min ( 797.2- 759.7 ) Volume Invert Avail.Storage Storage Description #1A 199.50' 3,599 of 49.00'W x 81.941 x 3.50'H Field A 14,052 cf Overall - 5,053 of Embedded = 8,999 cf x 40.0%Voids #2A 200.00' 5,053 cf ADS_StormTech SC-740 +Cap x 110 Inside#1 Effecfive Size= 44.6"W x 30,0"H => 6.45 sf x 7.121 =45.9 of Overall Size= 51.0"W x 30.0"H x 7.561 with 0.44' Overlap 110 Chambers in 10 Rows #3 200,00' 44 cf 4.00'D x 7.00'H OCS x 0.5 #4 20&80' 698 cf Surface Ponding (WQI-1) (Pyramidal)Listed below (Recalc) #5 206.50' 260 cf Surface Ponding (CB-10) (Pyramidal)Listed below (Recalc) 9,655 cf Total Available Storage Storage Group A created with Chamber Wizard Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet)_ (cubic-feet) (sq-ft) 205.80 4 0 0 4 206.30 400 74 74 401 207.00 1,500 624 698 1,504 Elevation Surf.Area Inc.Store Cum.Store Wet.Area feet s -ft cubic-feet cubic-feet s -ft 206.50 4 0 0 4 207.00 1,480 260 260 1,481 Device Routing Invert Outlet Devices #1 Primary 200.00' 15.0" Round Culvert L= 25.0' CPP, mitered to conform to fill, Ke= 0.700 Inlet/Outlet Invert= 200.00'/ 198.00' S= 0.0800 7' Cc= 0.900 n= 0.013 Corrugated PE, smooth interior, Flow Area= 1.23 sf #2 Device 1 202.75' 4.0' long x 0.5' breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 U0 0.80 1.00 Coef. (English) 2,80 2.92 3.08 3.30 3.32 #3 Secondary 206.50' 10.0' long x ON breadth Broad-Crested Rectangular Weir Head (feet) 0.20 0.40 0.60 0.80 1.00 Coef. (English) 2.80 2.92 3.08 3.30 3.32 #4 Device 1 201.00' 12.0" Vert. Orifice/Grate X 2.00 C= 0.600 M201047_Hydro_PR Type 11124-hr 900-yr Rainfall=8.60" Prepared by Bohler Engineering Printed 10/22/2020 H droCAD®90.00-25 sln 08955 O 2019 H droCAD Software Solutions LLC Pacie 20 Primary OutFlow Max=13.10 cfs @ 12.10 hrs HW=206.94' (Free Discharge) 'L =Culvert (Inlet Controls 13.10 cfs @ 10.67 fps) 2=113road-Crested Rectangular Weir(Passes < 113.71 cfs potential flow) 4 Orifice/Grate (Passes < 17.63 cfs potential flow) Secondary Outflow Max=8.47 cfs @ 12.10 hrs HW=206.94' (Free Discharge) 3=Broad-Crested Rectangular Weir(Weir Controls 8.47 cfs @ 1.95 fps) 1 M201047_Hydro_PR Type ifi 24-hr 100-yr Rainfall=8.60" Prepared by Bohler Engineering Printed 10/22/2020 H droCAD®10.00-25 s/n 08955 ©2019 H droCAD Software Solutions LLC Pa e 21 Stage-Area-Storage for Pond 1 P: Chamber System Elevation Storage Elevation Storage (feet) (cubic-feet) (feet) (cubic-feet) 199,50 0 204,80 8,683 1 199.60 161 204.90 8,684 199,70 321 205.00 8,684 199.80 482 205.10 8,685 199.90 642 205.20 8,686 200.00 803 205.30 8,686 200.10 1,139 205.40 8,687 200.20 1,474 205.50 8,687 200.30 1,807 205.60 8,688 200.40 2,137 205.70 8,689 200.50 2,465 205.80 8,689 200.60 2,790 205.90 8,692 200.70 3,113 206.00 8,698 200.80 3,431 206.10 8,711 200,90 3,747 206.20 8,733 201.00 4,058 206.30 8,766 201.10 4,366 206.40 8,813 201.20 4,669 206.50 8,871 201.30 4,967 206.60 8,947 201.40 5,259 206,70 9,051 201.50 5,547 206,80 9,195 201.60 5,828 206.90 9,393 201,70 6,101 207.00 9,665 201.80 6,366 201.90 6,623 202.00 6,870 202.10 7,105 202.20 7,324 202.30 7,521 202.40 7,699 202,50 7,866 202.60 8,027 202.70 8,188 202.80 8,349 202.90 8,511 203.00 8,672 203.10 8,672 203.20 8,673 203.30 8,674 203.40 8,674 203.50 8,675 203.60 8,676 203,70 8,676 203.80 8,677 203.90 8,677 204.00 8,678 204.10 8,679 204.20 8,679 204.30 8,680 204.40 8,681 204.50 8,681 204.60 8,682 204.70 8,682 M201047_Hydro_PR Type Ili 24-hr 100-yr Rainfall=8.60" Prepared by Bohler Engineering Printed 10/22/2020 H droCAD®10.00-25 s/n 08955 ©2019 H dra D Software Solutions LLC Page 22 Summary for Link DPI: Inflow Area= 116,672 sf, 83.00% Impervious, Inflow Depth = 7.46" for 100-yr event Inflow = 21.61 cfs @ 12.10 hrs, Volume= 72,510 of Primary - 21.61 cfs @ 12.10 hrs, Volume= 72,510 cf, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs APPENDIX F: STORMWATER CALCULATIONS MA STANDARD #3-RECHARGE AND DRA WDOWN TIME AM STANDARD#4- WATER WALITYAND TSSREMOVAL Proposed Commercial Development 419&435 Andover Street North Andover, MA Bohler Job Number:M201047 October 22,2020 MA DEP Standard 3: Recharge Volume Calculations ffikx�-ON Existing Site Impervious Area ac 0.000 Proposed Site Impervious Area ac 0.000, .. Proposed Increase in Site Impervious Area ac 0.000 Recharge Volume Required cf 0 Existing Site Impervious Area ac OAOD Proposed Site Impervious Area ac 0.000 Proposed Increase in Site Im ervious Area ac 0.000 Rechar a Volume Required c 0 MOM i l Ex-i'stLing Site Impervious Area ac 2.089 Proposed Site Impervious Area ac 2.223 Proposed Increase in Site Impervious Area ac 0.134 Recharge Volume Required cf 122 Existing Site Impervious Area ac 0.000 Proposed Site Impervious Area ac 0.000 Proposed Increase in Site Impervious Area ac 0.000 Recharge Volume Required c 0 Impervious Are a Directed to Infiltration BMP ac 2.223 %Im ervious Directed to Infiltration BMP 100% Adjustment Factor 1.00 t Chamber System 4,062 .- Provided greater than or Equal to Required Volume provided below lowest outlet in cubic feet(co Prepared By: Bohler Engineering 45 Franklin Street, 5th Floor Boston, MA 02127 (617)849-8040 10/22/2020 1 Proposed Commercial Development 419 &435 Andover Street North Andover, MA Bohler Job Number:M201047 October 22, 2020 MA DEP Standard 3: Drawdown Time Calculations Volume below outlet pipe Rv c 4,062 Sail Type : .Sandy Clay Loam .-:C Infiltration rate K * fl.17.. Bottom Areas :4,018 *Infiltration Rates taken from Rawls Table **Drawdown time= Rv 1(K) x(bottom area) Prepared By: Bohler Engineering 45 Franklin Street, 5th Floor Boston, MA 02127 (617) 849-8040 10/22/2020 Proposed Commercial Development 419 &435 Andover Street North Andover, MA Bohler Job Number: M201047 October 22, 2020 MA DBP Standard 4: Water Quality Volume Calculations Water Quality Volume runoff(in.)* 1.0 Total Post Development Impervious Area (so 96,834 *Water Quality volume runoff is equal to 0.5 or 1.0 inches of runoff times the total impervious area of the post development project site. m CDS Treatment Units sized for 1 inch Volume >8,069 0 0 0 0 0 0 0 0 Recharg Met *Volume provided below lowest outlet pipe in cubic feet(cf) *Note-Chamber System also providing 4,062 cf of WQV Prepared By: Bohler Engineering 45 Franklin Street, 5th Floor Boston, MA 02127 (617) 849-8040 10/22/2020 Location: Subcatchrnent 1 A B C D E TSS Removal Starting TSS Amount Remaining BMP1 Rate' Load* Removed (B*C) Load (C-D) Deep'Sump Hooded Catch O Basins 0.25 1.00 0.25. 0.75 `�.., Proprietary Separator v a.+ 0.80 0.75 0.60; 0.15 N Sabsurface Infiltration Basiri 0.80 0.15. 0.12 0.03 O O E 4� CO EL CO _ Total TSS Removal 97% Project: 419&435 Andover street Prepared By: Bohler Engineering *Equals remaining load from previous BMP(E) Date: 1D12212020 which enters the BMP Prepared By: Bohler Engineering 45 Franklin Street,5th Floor Boston, MA 02127 (617)849-8040 10/22/2020 APPENDIX G: OPERATION AND MAINTENANCE ➢ STORMWATER OPERATIONAND MAINTENANCE PLAN ➢ INSPECTION REPORT ➢ INSPECTION AND MAINTENANCE LOG FORM ➢ LONG-TERM POLLUTION PRE VTNTION PLAN ➢ SPILL PREVENTION ➢ MANUFACTURER'S INSPECTIONAND AII41NTENANCE MANUAL i i i STORMWATER OPERATION AND MAINTENANCE PLAN I 419 & 435 Andover Street North Andover,MA RESPONSIBLE PARTY DURING CONSTRUCTION: I Crosspoint Associates 188 Nee(Mant Street,Suite 255 Newton,MA 02464 RESPONSIBLE PARTY POST CONSTRUCTION: Crnsspoint Associates 188 Needham Street,Suite 255 Newton,MA 02464 Construction Phase During the construction phase, all erosion control devices and measures shall be maintained in accordance with the final record plans, local/state approvals and conditions,the EPA Construction General Permit and the Stormwater Pollution Prevention Plan(SWPPP) if applicable, Additionally,the maintenance of all erosion/siltation control measures during construction shall be the responsibility of the general contractor, Contact information of the OWNER and CONTRACTOR shall be listed in the SWPPP for this site. The SWPPP also includes information regarding construction period allowable and illicit discharges, housekeeping and emergency response procedures. Upon proper notice to the property owner,the Town/City or its authorized designee shall be allowed to enter the property at a reasonable time and in a reasonable manner for the purposes of inspection. Post Development Controls Once construction is completed,the post development stormwater controls are to be operated and maintained in compliance with the following permanent procedures(note that the continued implementation of these procedures shall be the responsibility of the Owner or its assignee): 1. Parking lots and on-site driveways; Sweep at least two(2)times per year and on a more frequent basis depending on sanding operations,All resulting sweepings shall be collected and properly disposed of off-site in accordance with MADEP and other applicable requirements. Approximate Maintenance Budget; $1,000/yea►' 2. Catch basins,yard drains, trench drains, manholes and piping: Inspect two (2)times per year and at the end of foliage and snow-removal seasons. These features shall be cleaned once per year or whenever the depth of deposits is greater than or equal to one half the depth from the bottom of the invert of the lowest pipe in the catch basin or underground system.Accumulated sediment and hydrocarbons present must be removed and properly disposed of off-site in accordance with MADEP and other applicable requirements. Approximate Maintenance Budget: $250/year per structure. 3. Water Quality Unit(Proprietary Separator): Follow manufacturer's recommendations (attached), Approximate Maintenance Budget: $500/year per unit. 4. Underground Infiltration Basin: Preventative maintenance after every major storm event during the first three(3)months of operation and at least twice per year thereafter. Inspect structure and pretreatment BMP to ensure proper operation after every major storm event(generally equal or greater to 3.0 inches in 24 hours) for the first three months. The outlet of the basin, if any,shall be inspected for erosion and sedimentation, and rip-rap shall be promptly repaired in the case of erosion. Sediment collecting in the bottom of the basin shall be inspected twice annually,and removal shall commence any time the sediment reaches a depth of six inches anywhere in the basin. Any sediment removed shall be disposed of in accordance with MADEP and other applicable requirements. Approximate Maintenance Budget: Cleaning-$1,000/year, Inspection-$200/year 5. Crushed Stone Level Spreader Infiltration System: Preventative maintenance after every major storm event during the first three(3)months of operation and at least twice per year thereafter. Inspect structure to ensure proper operation after every major storm event (generally equal or greater to 3.0 inches in 24 hours) for the first three months. Sediment collecting in the header pipe shall be inspected twice annually, and removal shall commence any time the sediment reaches a depth of six inches, Any sediment removed shall be disposed of in accordance with MADEP and other applicable requirements. Approximate Maintenance Budget: Cleaning-$500/year, Inspection- $200/year ` I I i STORMWATER MANAGEMENT SYSTEM POST-CONSTRUCTION INSPECTION REPORT i LOCATION: 419& 435 Andover Street North Andover, Massachusetts RESPONSIBLE PARTY: Crosspoint Associates 188 Needham Street, Suite 255 Newton,MA 02464 NAME OF INSPECTOR: INSPECTION DATE: Date. o d tioxz of a Ii ollavv�ng (sedkrrxent depth, deb` standuzg water, damage, etc) Catch Basins: Discharge Points/ Flared End Sections / Rip Rap: Infiltration Basin: i Water Quality Units: Other: Note Recommended Av#vns to be tal en vn the FoltoWing (sedunent and/or ei bris;removal, repairs, eta; Catch Basins: Discharge Points / Flared End Sections / Rip Rap: Infiltration Basin: Water Quality Units: Other: Other: Corn ments STa�MW TER INSI'ECTIQNAN M ;IN TNAN LOGFORM 419& 435 Andover Street--North Andover,MA Stormwater Management Responsible Party Date Maintenance Activity Practice Performed i LONG-TERM POLLUTION PREVENTION PLAN 419& 435 Andover•Street North Andover, MA RESPONSIBLE PARTY DURING CONSTRUCTION: Crosspoint Associates 188 Needham Street, Suite 255 Newton,MA 02464 RESPONSIBLE PARTY POST CONSTRUCTION: Crosspoint Associates 188 Needham Street,Suite 255 Newton, MA 02464 For this site,the Long-Term Pollution Prevention Plan will consist of the following: • The property owner shall be responsible for"good housekeeping" including proper periodic maintenance of building and pavement areas, curbing, landscaping, etc. • Proper storage and removal of solid waste (dumpsters). • Sweeping of driveways a minimum of twice per year with a commercial cleaning unit. Any sediment removed shall be disposed of in accordance with applicable local and state requirements. • Regular inspections and maintenance of Stormwater Management System as noted in the"O&M Plan". • Snow removal shall be the responsibility of the property owner. Snow shall not be plowed, dumped and/or placed in forebays, infiltration basins or similar stormwater controls. i a OPERATON AND MAINTENANCE TRAINING PROGRAM E The Owner will coordinate an annual in-house training session to discuss the Operations and Maintenance Plan, the Long-Term Pollution Prevention Plan, and the Spill Prevention Plan and response procedures. Annual training will include the following; Discuss the Operations and Maintenance Plan • Explain the general operations of the stormwater management system and its p g P g Y BMPs • Identify potential sources of stormwater pollution and measures/methods of reducing or eliminating that pollution • Emphasize good housekeeping measures Discuss the Spill Prevention and Response Procedures • Explain the process in the event of spill • Identify potential sources of spills and procedures for cleanup and/or reporting and notification • Trash and other debris shall be removed from all areas of the site at least twice yearly. • Reseed any bare areas as soon as they occur. Erosion control measures shall be installed in these areas to prevent deposits of sediment from entering the drainage system. • If necessary, stockpiled snow will be removed from the Site and disposed of at an off-site location in accordance with all local, state and federal regulations. • Recycle materials whenever possible. Provide separate containers for recycle materials. Recycling products will be removed by a certified waste hauler. SPILL PREVENTION AND RESPONSE PROCEDURES (POST CONSTRUCTION) In order to prevent or minimize the potential for a spill of Hazardous Substances or Oil or come into contact with stormwater,the following steps will be implemented: I. All Hazardous Substances or Oil(such as pesticides,petroleum products,fertilizers, detergents,acids,paints,paint solvents,cleaning solvents, etc.)will be stored in a secure location,with their lids on,preferably under cover,when not in use. 2. The minimum practical quantity of all such materials will be kept on site. 3. A spill control and containment kit(containing,for example,absorbent materials,acid neutralizing powder, brooms,dust pans,mops, rags,gloves,goggles, plastic and metal trash containers,etc.)will be provided on site. 4. Manufacturer's recommended methods for spill cleanup will be clearly posted and site personnel will be trained regarding these procedures and the location of the information and cleanup supplies. 5. It is the OWNER's responsibility to ensure that all Hazardous Waste on site is disposed of property by a licensed hazardous material disposal company. The OWNER is responsible for not exceeding Hazardous Waste storage requirements mandated by the EPA or state and local authorities. In the event of a spill of Hazardous Substances or Oil,the following procedures should be followed; 1. All measures should be taken to contain and abate the spill and to prevent the discharge of the Hazardous Substance or Oil to stormwater or oft-site. (The spill area should be Dept well ventilated and personnel should wear appropriate protective clothing to prevent injury from contact with the Hazardous Substances.) 2. For spills of less than five(5)gallons of material, proceed with source control and containment,clean-up with absorbent materials or other applicable means unless an imminent hazard or other circumstances dictate that the spill should be treated by a professional emergency response contractor. 3. For spills greater than five(5)gallons of material immediately contact the MADEP at the toll-free 24-hour statewide emergency number: 1-888-304-1133,the local fire department(9- 1-1)and an approved emergency response contractor. Provide information on the type of material spilled,the location of the spill,the quantity spilled,and the time of the spill to the emergency response contractor or coordinator, and proceed with prevention,containment and/or clean-up if so desired. (Use the form provided,or similar). 4, If there is a Reportable Quantity(RQ)release,then the National Response Center should be notified immediately at(800)424-8802; within 14 days a report should be submitted to the EPA regional office describing tine release, the date and circumstances of the release and the steps taken to prevent another release. This Pollution Prevention Plan should be updated to reflect any such steps or actions taken and measures to prevent the same from reoccurring. i E I I. SPILL PREVENTION CONTROL AND COUNTERMEASURE FORM 419 & 435 Amlover Street North Andover,MA Where a release containing a hazardous substance occurs,the following steps shall be taken by the facility manager and/or supervisor: I. Immediately notify The North Andover fire Department(at 9-1-1) 2. All measures must be taken to contain and abate the spill and to prevent the discharge of the pollutant(s)to off-site locations,receiving waters,wetlands and/or resource areas. 3. Notify the North Andover Health Department at(978)688-9540 and the North Andover Conservation Commission at(978)688-9530. 4. Provide documentation from licensed contractor showing disposal and cleanup procedures were completed as well as details on chemicals that were spilled to the Town of North Andover Health Department and Conservation Commission. Date of spill: Tithe: Reported By: Weather Conditions: Material Spilled Location of Approximate Agency(s)Notified Date of Spill Quantity of Spill Notification ingallons) a Cause of Spill: Measures Taken to Clean up Spill: Type of equipment: Make: Size: License or SIN: Location and Method of Disposal Procedures,method,and precautions instituted to prevent a similar occurrence from recurring: Additional Contact Numbers: • DEPARTMENT OF ENVIRONMENTAL PROTECTION (DEP) EMERGENCY PHONE: 1-888-304-1133 • NATIONAL RESPONSE CENTER PHONE: (800) 424-8802 • U.S. ENVIRONMENTAL PROTECTION AGENCYPHONE: (888) 372-7341 CV40NTECHO ENGINEERED SOLUTIONS i 1 CDS° Inspection and Maintenance Guide e.. P: ^� 5 �' 5 t ;s i 4 1�ftll�lylll'1,1 TEOUJOlO(3tE5 Maintenance Cleaning The CDS system should be inspected at regular intervals and Cleaning of a CDS systems should be done during dry weather maintained when necessary to ensure optimum performance. conditions when no flow is entering the system.The use of a The rate at which the system collects pollutants will depend more vacuum truck is generally the most effective and convenient heavily on site activities than the size of the unit. For example, method of removing pollutants from the system. Simply remove unstable soils or heavy winter sanding will cause the grit chamber the manhole covers and insert the vacuum hose into the sump. to fill more quickly but regular sweeping of paved surfaces will The system should be completely drained down and the sump slow accumulation. fully evacuated of sediment.The area outside the screen should also be cleaned out if pollutant build-up exists in this area. Inspection In installations where the risk of petroleum spills is small,liquid Inspection is the key to effective maintenance and is easily contaminants may not accumulate as quickly as sediment, performed. Pollutant transport and deposition may vary from However, the system should be cleaned out immediately in year to year and regular inspections will help ensure that the the event of an oil or gasoline spill should be cleaned out system is cleaned out at the appropriate time. At a minimum, immediately. Motor oil and other hydrocarbons that accumulate inspections should be performed twice per year(e.g.spring on a more routine basis should be removed when an appreciable and fall)however more frequent inspections may be necessary layer has been captured.To remove these pollutants, it may in climates where winter sanding operations may lead to rapid be preferable to use absorbent pads since they are usually less accumulations,or in equipment washdown areas. Installations expensive to dispose than the oil/water emulsion that may be should also be inspected more frequently where excessive created by vacuuming the oily layer.Trash and debris can be amounts of trash are expected. netted out to separate it from the other pollutants. The screen The visual inspection should ascertain that the system should be power washed to ensure it is free of trash and debris. components are in working order and that there are no Manhole covers should be securely seated following cleaning blockages or obstructions in the inlet and separation screen. activities to prevent leakage of runoff into the system from above The inspection should also quantify the accumulation of and also to ensure that proper safety precautions have been hydrocarbons, trash,and sediment in the system. Measuring followed. Confined space entry procedures need to be followed pollutant accumulation can be done with a calibrated dipstick, if physical access is required. Disposal of all material removed tape measure or other measuring instrument. If absorbent from the CDS system should be done in accordance with local material is used for enhanced removal of hydrocarbons,the level regulations. In many jurisdictions,disposal of the sediments may of discoloration of the sorbent material should also be identified be handled in the same manner as the disposal of sediments during inspection. It is useful and often required as part of an removed from catch basins or deep sump manholes. operating permit to keep a record of each inspection. A simple form for doing so is provided. Access to the CDS unit is typically achieved through two manhole access covers. One opening allows for inspection and cleanout of the separation chamber(cylinder and screen)and isolated sump. The other allows for inspection and cleanout of sediment captured and retained outside the screen. For deep units,a single manhole access point would allows both sump cleanout and access outside the screen. The CDS system should be cleaned when the level of sediment has reached 75%of capacity in the isolated sump or when an appreciable level of hydrocarbons and trash has accumulated. If absorbent material is used, it should be replaced when significant discoloration has occurred. Performance will not be impacted until 100%of the sump capacity is exceeded however it is recommended that the system be cleaned prior to that for easier removal of sediment. The level of sediment is easily determined by measuring from finished grade down to the top of the sediment pile. To avoid underestimating the level of x sediment in the chamber,the measuring device must be lowered to the top of the sediment pile carefully. Particles at the top of the pile typically offer less resistance to the end of the rod than consolidated particles toward the bottom of the pile. Once this measurement is recorded, it should be compared to the as-built drawing for the unit to determine weather the height of the sediment pile off the bottom of the sump floor exceeds 75%of the total height of isolated sump. _ j s, Diameter Distance from Water Surface Sediment Storage Capacity to Top of Sediment Pile CDS Model ft m ft m y3 m3 r 1 • 1 I • 1 1 � r • qqg gg pk B g II 1 • g 1 I�iii� 'u ► E / �I���YEI .Ill, itY.', Ali��!,., '6 �� Il' $�iR��,�E��y B�tl�P�I 11 1 1 / �i k �� � I q 1 1 •' � 1 I I T'4 '!' a III II,I Ir�!'i,� 4�IIl�Illl a 1 1 • 1 R E, t v$�ii r'i i$�I p$'kl�� ' !'. III II Plyi III Ii'lu ICI { IIIII r,lil,,� j'.i• II!, II � •/ � i I 11 •, `$Il�lll{ V1^, h. �• r i•: / 4 r `"a`��lZll\ ��1� 1� ,t 1 t e.�-`�li +s',$$�tt•1 1 j'IS• -'n , L j 'J Taq �E � 7 f i f �s � 7C ' } 1 f�!♦. r t-._f}, 1 � . - 4 :!•fir � { �L .',� li���, _ _ __--_— 1 i pior Support • Drawings and specificallons are available at www.contechstormwater.com. • Site-specific design support is available from our engineers. D2017 Contech Engineered Solutions LLC,a QUIKRETE Company Contech Engineered Solutions LLC provides site solutions for the civil engineeriny industry.Contecb's portfolio includes bridges,drainage,sanitary sewer, stormwater,earth stahilization and wastewater treament products,For information,visit www,ContechES.com or call 800.338.1122 NOTHING IN THIS CATALOG SHOULD BE CONSTRUED AS AN EXPRESSED WARRANTY OR AN IMPLIED WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE.SEE THE CONTECH STANDARD CONDITION OF SALES(VIEWABLE AT WWW.CONTECHES.COM/COS)FOR MORE INFORMATION. The product(s)described nray he protected by one or more of the following US patents; 5,322,629;5,624,576;5,707,527;5,759,415;5,788,848; S,g85,157;6,027,639;6,350,374;6.406,218;6,641,720;6,511,595;6,649,048:6,991,114;6,598,038;7,186.058;7,296,692;7,297,266;7,517.450 related foreign patents or other patents pending. :rr .r InspectionCDS iMaintenance ! t CD5 Model: Location: Water Floatable Describe Date depth to Layer Maintenance Maintenance Comments sediment' Thicknessz Performed Personnel f. The water depth to sediment is determined bytaking two measurements with a stadia rod:one measurement from the manhole opening to the top of the sediment pile and the other from the manhole opening to the water surface If the difference between these measurements is less than the values listed in table 1 the system should be cleaned out. Note:to avoid underestimating the volume of sediment in the chamber, the measuring device must be carefully lowered to the top of the sediment pile. Z. For optimum performance,the system should be cleaned out when the floating hydrocarbon layer accumulates to an appreciable thickness.In the event of an oil spill,the system should be cleaned immediately. CAS Maintenance Guide-7118(PDF)