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20141118 Stormwater Mgmt Report
I STORMWATER MANAGEMENT REPORT for 85 TERMINAL ROAD NORTH ANDOVER, MASSACHUSETTS �I II Ili Prepared for: Great Circle Central, LLC 54 Logan Lane, Unit C Santa Rosa Beach, Florida 32459 i Prepared by: Meridian Associates, Inc. 500 Cummings Center, Suite 5950 Beverly, Massachusetts 01915 (978) 299-0447 September 19, 2014 Revised: November 6 2014 I MERIDIAN ASSOCIATES I '' TABLE OF CONTENTS ➢ Stormwater Narrative ➢ Appendix • TSS Removal Calculation Worksheet • Checklist for Stormwater Report ➢ Construction Period Pollution Prevention Plan ➢ Operation and Long Term Maintenance Program ➢ Stormwater Analysis and Calculations STORMWATER NARRATIVE Stormwater Manasement Standards Project Narrative: The lease area is located at 85 Terminal Road in North Andover, Massachusetts. The lease area will be accessed from the terminal access road. The topography includes a mixture of brush, woods and grass with mostly gradual slopes. The applicant is proposing to construct an airport hangar. This also includes a driveway, parking area, subsurface infiltration facility, vegetated filter strips,infiltration trenches, utilities and retaining wall. This proposal utilizes several different stormwater management techniques. Incorporated in this design are deep sump catchbasins, vegetated filter strips, infiltration trenches and a subsurface infiltration facility for the treatment and mitigation of the stormwater runoff. The following are the DEP Stormwater Standards as outlined in the Wetlands Regulations: Standard 1: No new Stormwater conveyances may discharge untreated Stormwater directly to or cause erosion in wetlands or waters of the Commonwealth. The stormwater runoff from the proposed building rooftop,parking area and part of the driveway will be directed to the subsurface infiltration facility. The remaining stormwater runoff from the driveway will be directed to the vegetated filter strips and infiltration trenches along the driveway. Standard 2: Peak Rate Attenuation - Stormwater management systems shall be designed so that post-development peak discharge rates do not exceed pre- development peak discharge rates. This standard may be waived for discharges to land subject to coastal storm flowage as defined in 310 CMR 10.04. For the purpose of analyzing pre and post development stormwater peak rates of runoff, two design points have been selected based on existing topographic conditions. The design points in the existing conditions are the same design points in the proposed conditions. Comparison values for pre and post development stormwater peak rates are given for the design points only. The storm events that were used to calculate peak runoff rates for pre and post construction conditions are compiled from the Soil Conservation Service Technical Report No. 55 and the U.S. Department of Commerce Technical Paper No. 40. Full detail of peak rate attenuation along with supplemental stormwater calculations utilizing HydroCAD as well as pre and post development drainage plans can be found in the Stormwater Analysis and Calculations. The details of this report show that the peak rates of runoff for the 2, 10, and 100 year events have been reduced from pre to post conditions. 1 The hydrologic calculations from HydroCAD have been included in the Stormwater Analysis and Calculations section. Proposed Design Points and Subcatchment Areas Design Point#1 is located at the rear of the lease area near the taxiway and is the same for the existing and proposed conditions. The contributing area to Design Point 91 consists of Subcatchment rrI. Design Point#2 is located near the proposed intersection of the driveway and the terminal access road. The contributing area to Design Point#2 consists of Subcatchment#2. The proposed subsurface infiltration facility is located in front of the airport hangar near the taxiway. The proposed vegetated filter strips and infiltration trenches are located on either side of the proposed driveway near the terminal access road. Design Point#1 Storm Event Existing Conditions (Pre) Proposed Conditions (Post) Peak Flow (CFS) Peak Flow (CFS) 2-Year(3.1 in./hr.) 1.34 0.93 10-Year(4.5 in./hr.) 3.02 1.89 100-Year(6.5 in./hr.) 5.79 3.42 Desip-n Point#2 Storm Event Existing Conditions (Pre) Proposed Conditions (Post) Peak Flow(CFS) Peak Flow (CFS) 2-Year(3.1 in./hr.) 1.96 1.47 10-Year(4.5 in./hr.) 4.10 3.48 100-Year(6.5 in./hr.) 7.50 6.35 2 Design Point#1 Storm Event Existing Conditions (Pre) Proposed Conditions (Post) Volume (CF) Volume (CF) 2-Year(3.1 in./hr.) 6,055 3,659 10-Year(4.5 in./hr.) 12,676 7,492 100-Year(6.5 in./hr.) 23,740 22,956 Design Point#2 Storm Event Existing Conditions (Pre) Proposed Conditions (Post) Volume (CF) Volume (CF) 2-Year(3.1 in./hr.) 10,062 7,231 10-Year(4.5 in./hr.) 20,125 15,682 100-Year(6.5 in./hr.) 36,416 29,229 The tables above outline the results of the hydrologic model. As required by Standard #2, the proposed BMP's adequately attenuate for potential increases in peak stormwater flows. As required by the town the proposed BMP's also attenuate potential increases in stormwater runoff volume. Standard 3: Recharge-Loss of annual recharge to groundwater shall be eliminated or minimized...at a minimum, the annual recharge from the post-development site shall approximate the annual recharge from pre-development conditions based on soil type. This standard is met when the stormwater management system is designed to infiltrate the required recharge volume in accordance with the Mass Stormwater Handbook. Loss of annual recharge to groundwater has been minimized through the use of stormwater Best Management Practices (BMP's), deep sump catchbasins, a subsurface infiltration facility, vegetated filter strips, infiltration trenches and a proposed operation and maintenance program are proposed for this project. Based on soil maps provided by the U.S. Department of Agriculture Soil Conservation Service the property has a hydrologic soil group rating of C. Utilizing the current regulations, the proposed project will meet this standard as per the following calculation: Rv=Fx Rv=Required Recharge Volume F =Target Depth Factor associated with hydrologic soil groups located in table 2.3.2 in Volume 3 of the Stormwater Management Handbook x=Total impervious area proposed 3 Impervious area draining to the subsurface infiltration facility: 34,010 square feet(sf). Required recharge volume depth factor for C type soils: 0.25 inches Therefore Rv= (34,010 sf)(0.2 5 inches/I 2inches per foot) Rv=709 cubic feet (cf) The proposed subsurface infiltration facility provides a total recharge storage volume under the outlet pipe invert of 12,981 cf of stormwater. Impervious area draining to infiltration trench#1: 2,438 square feet(sf). Required recharge volume depth factor for C type soils: 0.25 inches Therefore Rv=(2,438 sf)(0.25inches/12inches per foot) Rv= 51 cubic feet(cf) The proposed infiltration trench#1 provides a total recharge storage volume of 1,133 cf of stormwater. Impervious area draining to infiltration trench#2: 2,400 square feet(sf). Required recharge volume depth factor for C type soils: 0.25 inches Therefore Rv=(2,400 sf)(0.25inches/12inches per foot) Rv=50 cubic feet(cf) The proposed infiltration trench#2 provides a total recharge storage volume of 958 cf of stonnwater. The Stormwater Handbook also requires recharge facilities be installed in soils capable of absorbing the recharge volume with the ability to drain within 72 hours. The formula for drawdown is as follows: General Formula: TDR= requiredstoragevolume (RawlsRaOABottomSurfaceAreaofSystem) (*Required storage volume is equal to the larger of the calculated required recharge or treatment volumes In this case, treatment volume is greater as indicated in Standard 4). 4 Subsurface Infiltration Facility: Volume to Treat= 1,418 cf TDR_ 1,418cf = 8.5hrs 0.27in/hr (7,452sf 1.2in l ft 8.5hrs <72hrs Infiltration Trench#I: Volume to Treat= 102 cf TDR= 102cf =6.3hrs 0.27in 1 hr (724.f 12in l ft 6.3hrs <72hrs Infiltration Trench#2: Volume to Treat= 100 cf TDR_ 100cf =7.lhrs 0.27in/hr (628sf 12in l ft 7.1 hrs < 72hrs A portion of the total onsite impervious area is not directed into one of the proposed infiltration facilities. In accordance with the Stormwater Handbook, a capture area adjustment calculation is required when runoff from only a portion of the impervious area on a site is directed to one or more infiltration BMPs. The following are steps of the capture area adjustment calculation to demonstrate the required minimum 65% of the impervious area onsite is being directed to an infiltration BMP. The calculation also determines the increase in storage capacity of the infiltration BMPs to ensure they are able to capture sufficient runoff from the impervious surfaces within the contributing drainage area to infiltrate the required recharge volume. 1. Calculate Rv for the project: From above Rv= 816 cf 5 2. Calculate the impervious area draining to recharge facilities: Area= 38,848 sf 3. Divide total site impervious by the impervious area draining to recharge facilities: Total site impervious area=40,631 sf 40,631 sf/38,848 sf= 1.05 4. P��ultiply quotient from step 3 by the original Rv to determine the adjusted minimum storage volume needed to meet the recharge requirement: 1.05x810= 851 cf Infiltration facilities provide 15,072 cf of storage 5. Insure minimum of 65% of the site impervious area is being directed to the infiltration facilities: 38,848 sf/40,631 sf=95.6% In surnmary,the infiltration facilities onsite provide a total recharge storage volume of 15,072 cf which is greater than the adjusted minimum storage volume calculated by the capture area adjustment. The project also directs a minimum 65%of the impervious area into the recharge facility which will provide sufficient runoff to infiltrate the required recharge volume. This insures the post development annual recharge rate will approximate the annual rate from pre development conditions. Standard 4: Water Quality—Stormwater management systems shall be designed to remove 80% of the average annual post-construction load of Total Suspended Solids (TSS). The standard is met with pollution prevention plans, stormwater BMP's sized to capture required water quality volume, and pretreatment measures. As discussed above,there are no untreated stormwater discharges from the proposed project. The stormwater management system has been designed to remove a minimum of 80%of the average annual post-construction load of Total Suspended Solids (TSS). TSS Removal Calculation Worksheets are included in the Stonnwater Analysis and Calculations Report noted herein. These percentages have been achieved by the use of deep sump catchbasins, vegetated filter strips, infiltration trenches and a subsurface infiltration system. The Stormwater Management Handbook assigns TSS removal percentages to each treatment BMP. Each treatment BMP is sized to capture the required water quality volume as calculated in accordance with the Handbook in order to achieve the assigned TSS removal rates. 6 General Equation from Stormwater Management Handbook Vwq = (Dwq)(A) Vwq =required water quality volume Dwq =water quality depth(1" for critical areas, 0.5" for non-critical areas) A=impervious area Proposed Subsurface Infiltration Facility Vwq=( 0.5"/12) (34,010)= 1,418 cubic feet(cf) The proposed subsurface infiltration facility provides a total water quality volume under the outlet pipe invert of 12,981 cf of stormwater. Proposed Infiltration Trench#1 Vwq=(0.5"/12) (2,438)= 102 cubic feet(cf) The proposed infiltration trench#1 provides a total water quality volume of 1,133 cf of stormwater. Proposed Infiltration Trench#2 Vwq=(0.5"/12)(2,400)= 100 cubic feet(cf) The proposed infiltration trench#2 provides a total water quality volume of 958 cf of stormwater. A separate document entitled"Operation and Long Term Maintenance Plan"dated September 19,2414 is included as part of this report. Suitable practices for source control and long term pollution prevention have been identified and shall be implemented as discussed. The utilization of pretreatment and treatment BMP's combined with the operation and maintenance plan provides compliance with this standard. Standard 5: Land Uses with Higher Potential Pollutant Loads (LUHPPLs)—Source control and pollution prevention shall be implemented in accordance with the Stormwater Handbook to eliminate or reduce the discharge of stormwater runoff from such land uses to the maximum extent practicable, Stormwater Standard 5 is not applicable to this project. The proposed development will not subject the site to higher potential pollutant loads as defined in the Massachusetts Department of Environmental protection Wetlands and Water Quality Regulations. LUHPPLs are identified in 310 CMR 22.20B(2) and C(2)(a)-(k) and (m) and CMR 22.21(2)(a)(1)-(8) and(b)(l)-(6), areas within a site that are the location of activities that 7 are subject to an individual National Pollutant Discharge Elimination System(NPDES) permit or the NPDES Multi-sector General Permit; auto fueling facilities, exterior fleet storage areas, exterior vehicle service and equipment cleaning areas; marinas and boatyards;parking lots with high-intensity-use; confined disposal facilities and disposal sites. Standard 6: Critical Areas—Stormwater discharges to critical areas require the use of specific source control and pollution prevention measures and specific structural stormwater best management practices determined by the Department to be suitable for managing discharges to such areas. Stormwater Standard 6 is not applicable to this project. The proposed development is not within the Zone II or Interim Wellhead Protection Area of a public water supply and the stormwater runoff does not discharge to a critical area as defined in the Massachusetts Department of Environmental protection Wetlands and Water Quality Regulations. Critical areas are Outstanding Resource Waters and Special Resource Waters as designated in 314 CMR 4.0,recharge areas for public water supplies as defined in 310 CMR 22.02,bathing beaches as defined in 105 CMR 445.000, cold-water fisheries and shellfish growing areas as defined in 314 CMR 9.02 and 310 CMR 10.04. Standard 7: Redevelopments—A redevelopment project is required to meet Standards 1-6 only to the maximum extent practicable. Remaining standards shall be met as well as the project shall improve the existing conditions. Stormwater Standard 7 is not applicable to this project. Within the Stormwater Management Handbook(volume 1. chapter 1 page 20), the definition of a redevelopment project includes, "development, rehabilitation, expansion and phased projects on previously developed sites,provided the redevelopment results in no net increase in impervious area". Standard 8: Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan shall be implemented. An Inspection and Maintenance Program for a Proposed Stormwater Management System is included with this report. The erosion and sediment control section of the program details the construction period operation and maintenance plan and sequencing for pollution prevention measures and erosion and sedimentation controls. Locations of erosion control measures for the project are depicted on the site plan set accompanying this report. Standard 9: A long term Operation and Maintenance Plan shall be implemented. An.Inspection and Maintenance Program for a Proposed Stormwater Management System is included with this report. The long term operation and maintenance section of 8 the program provides details and the schedule for routine and non-routine maintenance tasks to be implemented at the completion of the project. Standard 10: Prohibition of Illicit Discharges— Illicit discharges to the stormwater management system are prohibited. Illicit.discharges to the stormwater management system are discharges that are not entirely comprised of stormwater. Discharges to the stormwater management system from the following activities or facilities are permissible: Firefighting, water line flushing, landscape irrigation,uncontaminated groundwater,potable water sources, foundation drains, air conditioning condensation, footing drains, individual resident car washing, flows from riparian habitats and wetlands, dechlorinated water from swimming pools, water used for street washing and water used to clean residential buildings without detergents. All other illicit discharges are prohibited. There are no known illicit discharges anticipated through the completion of this project. During construction and post construction procedures are provided to dissipate the potential for illicit discharges to the drainage system. Post construction preventions of illicit discharges are described in the Inspection and Maintenance Plan under the Good Housekeeping Practices section of the report. 9 APPENDIX Non-automated:Mar.4,2008 INSTRUCTIONS: 1. Sheet is nonautomated. Print sheet and complete using hand calculations. Column A and B: See MassDEP Structureal BMP Table 2. The calcualtions must be completed using the Column Headings specified in Chart and Not the Excel Column Headings 3. To complete Chart Column D, multiple Column B value within Row x Column C value within Row 4.To complete Chart Column E value, subtract Column D value within Row from Column C within Row 5. Total TSS Removal =Sum All Values in Column D Location: 185 Terminal Road, North Andover, NIA Train 1 : Han ar rooftop, taxiway, parking area, driveway (Discharge point #1) .�+ A B C D E BMP TSS Removal Starting TSS Amount Remaining Rate Load* Removed (B*C) Load (C-D) !c Deep Sump O O Catchbasins ` 1 .00 0,25 0.75 E Subsurface ' 80°0 0.75 0.60 0.15 Cr. Infiltration Facility O (All •— r^ � V♦ Separate Form Needs to Total TSS Removal $50°o be Completed for Each Outlet or BMP Train y Project: 5659 *Equals remaining load from previous BMP(E) which enters the BMP Prepared By: Meridian Associates, Inc. Date: 9/19/2014 Non-automated TSS Calculation Sheet must be used if Proprietary BMP Proposed Mass. Dept. of Environmental Protection 1. From MassDEP Stormwater Handbook Vol. 1 P:\5659_Windover-Lawrence Airport\ADMIN\Reports\Stormwater Management\5659-Tss1 INSTRUCTIONS: Non-automated: Mar.4,2008 1. Sheet is nonautomated. Print sheet and complete using hand calculations. Column A and B: See MassDEP Structureal BMP Table 2. The calcualtions must be completed using the Column Headings specified in Chart and Not the Excel Column Headings 3. To complete Chart Column D, multiple Column B value within Row x Column C value within Row 4. To complete Chart Column E value,subtract Column D value within Row from Column C within Row 5. Total TSS Removal =Sum All Values in Column D Location: 1,85 Terminal Road, North Andover, MA Train 1 : Driveway (Discharge point #2) NA B C E BMP TSS Removal Starting TSS Amount Remaining Rate Load Removed (B*C) Load (C-D) �G Vegetated Filter /a° 1 .00 0805 0,95 O O Strips S Infiltration Trenches 80% 0.95 0.76 0.19 O Deep Sump (All Catchbasins 25% 0.19 0.05 0.14 V Separate Form Needs to Tota' TSS Remiova $5.8°�o be Completed for Each Outlet or BMP Train Project: 5659 *Equals remaining load from previous BMP(E) which enters the BMP Prepared By: Meridian Associates, Inc. Date: 911912014 Non-automated TSS Calculation Sheet must be used if Proprietary BMP Proposed Mass. Dept.of Environmental Protection 1. From MassDEP Stormwater Handbook Vol. 1 P:\5659_Windover-Lawrence Airport\ADMIN\Reports\Stormwater Management\5659-Tss1 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report A. Introduction Important:When A Stormwater Report must be submitted with the Notice of Intent permit application to document filling out forms compliance with the Stormwater Management Standards. The following checklist is NOT a substitute for on the computer, (which h h hi Report R S the Stormwater e wcsouprovide more substantive and detailed information), use only the tab p pbut is offered key to move your here as a tool to help the applicant organize their Stormwater Management documentation for their cursor-do not Report and for the reviewer to assess this information in a consistent format. As noted in the Checklist, use the return the Stormwater Report must contain the engineering computations and supporting information set forth in key. Volume 3 of the Massachusetts Stormwater Handbook. The Stormwater Report must be prepared and certified by a Registered Professional Engineer(RPE) licensed in the Commonwealth. The Stormwater Report must include: ® The Stormwater Checklist completed and stamped by a Registered Professional Engineer (see page 2)that certifies that the Stormwater Report contains all required submittals.' This Checklist is to be used as the cover for the completed Stormwater Report. a Applicant/Project Name ® Project Address ® Name of Firm and Registered Professional Engineer that prepared the Report ® Long-Term Pollution Prevention Plan required by Standards 4-6 ® Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan required by Standard 82 ® Operation and Maintenance Plan required by Standard 9 In addition to all plans and supporting information, the Stormwater Report must include a brief narrative describing stormwater management practices, including environmentally sensitive site design and LID techniques, along with a diagram depicting runoff through the proposed BMP treatment train. Plans are required to show existing and proposed conditions, identify all wetland resource areas, NRCS soil types, critical areas, Land Uses with Higher Potential Pollutant Loads (LUHPPL), and any areas on the site where infiltration rate is greater than 2.4 inches per hour. The Plans shall identify the drainage areas for both existing and proposed conditions at a scale that enables verification of supporting calculations. As noted in the Checklist,the Stormwater Management Report shall document compliance with each of the Stormwater Management Standards as provided in the Massachusetts Stormwater Handbook. The soils evaluation and calculations shall be done using the methodologies set forth in Volume 3 of the Massachusetts Stormwater Handbook. To ensure that the Stormwater Report is complete, applicants are required to fill in the Stormwater Report Checklist by checking the box to indicate that the specified information has been included in the Stormwater Report. If any of the information specified in the checklist has not been submitted,the applicant must provide an explanation. The completed Stormwater Report Checklist and Certification must be submitted with the Stormwater Report. The Stormwater Report may also include the Illicit Discharge Compliance Statement required by Standard 10. If not included in the Stormwater Report,the Illicit Discharge Compliance Statement must be submitted prior to the discharge of stormwater runoff to the post-construction best management practices. 2 For some complex projects,it may not be possible to include the Construction Period Erosion and Sedimentation Control Plan in the Stormwater Report. In that event,the issuing authority has the discretion to issue an Order of Conditions that approves the project and includes a condition requiring the proponent to submit the Construction Period Erosion and Sedimentation Control Plan before commencing any land disturbance activity on the site. 5659-stormwater checklist-04/01/08 Stormwater Report Checklist-Page 1 of 8 LlMassachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report S. Stormwater Checklist and Certification The following checklist is intended to serve as a guide for applicants as to the elements that ordinarily need to be addressed in a complete Stormwater Report. The checklist is also intended to provide conservation commissions and other reviewing authorities with a summary of the components necessary for a comprehensive Stormwater Report that addresses the ten Stormwater Standards. mote: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 r e sion 1 Engineer's Certification I have reviewed the Stormwater Report, including the soil evaluation, computations, Long-term Pollution Prevention Pian,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 v `�` �� 12 '45 arm 2 �2 s _10 � ..�w M ° igfre and Date Checklist Project Type: Is the application for new development, redevelopment, or a mix of new and redevelopment? ® New development ❑ Redevelopment ❑ Mix of New Development and Redevelopment 5659-stormwater checklist•04/01(08 Stormwater Report Checklist•Page 2 of 8 Massachusetts Department of Environmental Protection ❑' Bureau of Resource Protection - Wetlands Program ��, Checklist for Stormwater Report Checklist (continued) LID Measures: Stormwater Standards require LID measures to be considered. Document what environmentally sensitive design and LID Techniques were considered during the planning and design of the project: ® No disturbance to any Wetland Resource Areas ❑ Site Design Practices (e.g. clustered development, reduced frontage setbacks) ❑ Reduced Impervious Area (Redevelopment Only) ® Minimizing disturbance to existing trees and shrubs ❑ LID Site Design Credit Requested: ❑ Credit 1 ❑ Credit 2 ❑ Credit 3 ® Use of"country drainage"versus curb and gutter conveyance and pipe ❑ Bioretention Cells (includes Rain Gardens) ❑ Constructed Stormwater Wetlands (includes Gravel Wetlands designs) ❑ Treebox Filter ❑ Water Quality Swale ❑ Grass Channel ❑ Green Roof ❑ Other(describe): 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. 5655-stormwater checklist•04/01/08 Stormwater Report Checklist•Page 3 of 8 ! Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report Checklist (continued) Standard 2: Peak Rate Attenuation ❑ Standard 2 waiver requested because the project is located in land subject to coastal storm flowage and stormwater discharge is to a wetland subject to coastal flooding. Evaluation provided to determine whether off-site flooding increases during the 100-year 24-hour storm. ® Calculations provided to show that post-development peak discharge rates do not exceed pre- development rates for the 2-year and 10-year 24-hour storms. If evaluation shows that off-site flooding increases during the 100-year 24-hour storm, calculations are also provided to show that post-development peak discharge rates do not exceed pre-development rates for the 100-year 24- hour storm. Standard 3: Recharge Soil Analysis provided. ® Required Recharge Volume calculation provided. ❑ Required Recharge volume reduced through use of the LID site Design Credits. ® Sizing the infiltration, BMPs is based on the following method: Check the method used. ® Static ❑ Simple Dynamic ❑ Dynamic Field' ❑ Runoff from all impervious areas at the site discharging to the infiltration BMP. ® Runoff from all impervious areas at the site is not discharging to the infiltration BMP and calculations are provided showing that the drainage area contributing runoff to the infiltration BMPs is sufficient to generate the required recharge volume. ® Recharge BMPs have been sized to infiltrate the Required Recharge Volume. ❑ Recharge BMPs have been sized to infiltrate the Required Recharge Volume only to the maximum extent practicable for the following reason: ❑ Site is comprised solely of C and D soils and/or bedrock at the land surface ❑ M.G.L. c. 21 E sites pursuant to 310 CMR 40.0000 ❑ Solid Waste Landfill pursuant to 310 CMR 19.000 ❑ Project is otherwise subject to Stormwater Management Standards only to the maximum extent practicable. ® Calculations showing that the infiltration BMPs will drain in 72 hours are provided. ❑ Property includes a M.G.L. c. 21 E site or a solid waste landfill and a mounding analysis is included. '80%TSS removal is required prior to discharge to infiltration BMP if Dynamic Field method is used. 5859-stormwater checklist-04/01/08 Stormwater Report Checklist Page 4 of 8 Massachusetts Department of Environmental Protection �-' Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report Checklist (continued) Standard 3: Recharge (continued) ❑ The infiltration BMP is used to attenuate peak flows during storms greater than or equal to the 10- year 24-hour storm and separation to seasonal high groundwater is less than 4 feet and a mounding analysis is provided. ❑ Documentation is provided showing that infiltration BMPs do not adversely impact nearby wetland resource areas. Standard 4: Water Quality The Long-Term Pollution Prevention Plan typically includes the following: • Good housekeeping practices; • Provisions for storing materials and waste products inside or under cover; • Vehicle washing controls; • Requirements for routine inspections and maintenance of Stormwater BMPs; • Spill prevention and response plans; • Provisions for maintenance of lawns, gardens, and other landscaped areas; • Requirements for storage and use of fertilizers, herbicides, and pesticides; • Pet waste management provisions; • Provisions for operation and management of septic systems; • Provisions for solid waste management; • Snow disposal and plowing plans relative to Wetland Resource Areas; • Winter Road Salt and/or Sand Use and Storage restrictions; • Street sweeping schedules; • Provisions for prevention of illicit discharges to the stormwater management system; • Documentation that Stormwater BMPs are designed to provide for shutdown and containment in the event of a spill or discharges to or near critical areas or from LUHPPL; • Training for staff or personnel involved with implementing Long-Term Pollution Prevention Plan; • List of Emergency contacts for implementing Long-Term Pollution Prevention Plan. ® A Long-Term Pollution Prevention Plan is attached to Stormwater Report and is included as an attachment to the Wetlands Notice of Intent. ❑ Treatment BMPs subject to the 44%TSS removal pretreatment requirement and the one inch rule for calculating the water quality volume are included, and discharge: ❑ is within the Zone II or Interim Wellhead Protection Area ❑ is near or to other critical areas ❑ is within soils with a rapid infiltration rate (greater than 2.4 inches per hour) ❑ involves runoff from land uses with higher potential pollutant loads. ❑ The Required Water Quality Volume is reduced through use of the LID site Design Credits. ® Calculations documenting that the treatment train meets the 80%TSS removal requirement and, if applicable, the 44%TSS removal pretreatment requirement, are provided. 5659-stormwater checklist•04/01/08 Stormwater Report Checklist•Page 5 of 8 LIMassachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checklist for Stormwater Report Checklist (continued) Standard 4: Water Quality (continued) ® The BMP is sized (and calculations provided) based on: Z 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 5: Land Uses With Higher Potential Pollutant Loads(LUHPPLs) ❑ The NPDES Multi-Sector General Permit covers the land use and the Stormwater Pollution Prevention Plan (SWPPP) has been included with the Stormwater Report. ❑ The NPDES Multi-Sector General Permit covers the land use and the SWPPP will be submitted prior to the discharge of stormwater to the post-construction stormwater BMPs. ❑ The NPDES Multi-Sector General Permit does not cover the land use. ❑ LUHPPLs are located at the site and industry specific source control and pollution prevention measures have been proposed to reduce or eliminate the exposure of LUHPPLs to rain, snow, snow melt and runoff, and been included in the long term Pollution Prevention Plan. ❑ All exposure has been eliminated. ❑ All exposure has not been eliminated and all BMPs selected are on MassDEP LUHPPL list. ❑ The LUHPPL has the potential to generate runoff with moderate to higher concentrations of oil and grease (e.g. all parking lots with >1000 vehicle trips per day) and the treatment train includes an oil grit separator, a filtering bioretention area, a sand filter or equivalent. Standard 6: Critical Areas ❑ The discharge is near or to a critical area and the treatment train includes only BMPs that MassDEP has approved for stormwater discharges to or near that particular class of critical area. ❑ Critical areas and BMPs are identified in the Stormwater Report. *The calculations utilize the half-inch rule for BMP's (as noted in the treatment calculations provided). 5659-stormwater checklist-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. 5659-Stormwater checklist-04/01/08 Stormwater Report Checklist-Page 7 of 8 Massachusetts Department of Environmental Protection LL1 Bureau of Resource Protection - Wetlands Program p 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 g: Operation and Maintenance Plan ® The Post Construction Operation and Maintenance Plan is included in the Stormwater Report and includes the following information: 0 Name of the stormwater management system owners; ® Party responsible for operation and maintenance; ® Schedule for implementation of routine and non-routine maintenance tasks; ® Plan showing the location of all stormwater BMPs maintenance access areas; ❑ Description and delineation of public safety features; ❑ Estimated operation and maintenance budget; and ® Operation and Maintenance Log Form. ❑ The responsible party is not the owner of the parcel where the BMP is located and the Stormwater Report includes the following submissions: ❑ A copy of the legal instrument(deed, homeowner's association, utility trust or other legal entity) that establishes the terms of and legal responsibility for the operation and maintenance of the project site stormwater BMPs; ❑ A plan and easement deed that allows site access for the legal entity to operate and maintain BMP functions. Standard 10: Prohibition of Illicit Discharges ® The Long-Term Pollution Prevention Plan includes measures to prevent illicit discharges; ❑ An Illicit Discharge Compliance Statement is attached; ® NO Illicit Discharge Compliance Statement is attached but will be submitted prior to the discharge of any stormwater to post-construction BMPs. 5659-stormwater checklist•04/01/08 Stormwater Report Checklist•Page 8 of 8 CONSTRUCTION PERIOD POLLUTION PREVENTION PLAN CONSTRUCTION PERIOD POLLUTION PREVENTION PLAN FOR A STORMWATER MANAGEMENT SYSTEM located at 85 TERMINAL ROAD NORTH ANDOVER, MASSACHUSETTS Applicant: Great Circle Central, LLC 54 Logan Lane, Unit C Santa Rosa Beach, Florida 32459 Prepared by: Meridian Associates, Inc. 500 Cummings Center, Suite 5950 Beverly, Massachusetts 01915 (978) 299-0447 September 19, 2014 Project Name: 85 Terminal Road North Andover, MA 01845 Owner Name: City of Lawrence 492 Sutton Street North Andover, MA 01845 Applicant Name: Great Circle Central, LLC 54 Logan Lane, Unit C Santa Rosa Beach, FL 32459 Party Responsible for Maintenance: Windover Construction, LLC 66 Cherry Hill Drive Beverly, MA 01915 Project Description: The lease area is located at 85 Terminal Road in North Andover, Massachusetts. The lease area will be accessed from the terminal access road. The topography includes a mixture of brush, woods and grass with mostly gradual slopes. The applicant is proposing to construct an airport hangar. This also includes a driveway, parking area, subsurface infiltration facility, vegetated filter strips, infiltration trenches, utilities and retaining wall. This proposal utilizes several different stormwater management techniques. Incorporated in this design are deep sump catchbasins, vegetated filter strips, infiltration trenches and a subsurface infiltration facility for the treatment and mitigation of the stormwater runoff. Erosion and Sedimentation Control Measures During Construction Activities FilterMitt FilterMitt are proposed to be installed, as shown on the site plan. The barriers are burlap fabric mitts filled with compost blends and shall be installed prior to the commencement of any work on-site and in accordance with the design plans. An additional supply of mitts shall be on-site to replace and/or repair FilterMitts that have been disturbed. The lines of mitts shall be inspected and maintained on a weekly basis during construction. Deposited sediments shall be removed when the level of deposition reaches approximately one-half the height of the FilterMitt. Surface Stabilization The surface of all disturbed areas shall be stabilized during and after construction. Temporary measures shall be taken during construction to prevent erosion and siltation.No 2 construction sediment shall be allowed to enter the infiltration basin. All disturbed slopes will be stabilized with a permanent vegetative cover. Some or all of the following measures will be utilized on this project as conditions may warrant. a. Temporary Seeding b. Temporary Mulching C. Permanent Seeding d. Placement of Sod e. Hydroseeding f. Placement of Hay g. Placement of Jute Netting Storm Drain Inlet Protection A temporary storm inlet protection filter will be placed around all catchbasin units. The purpose of the filter is to prevent the inflow of sediments into the closed drainage system. The filter shall remain in place until a pen-nanent vegetative cover is established and the transport of sediment is no longer visibly apparent. The filter shall be inspected and maintained on a weekly basis and after every stone.of 0.25 inches or more of rainfall/precipitation. Vegetated Filter Strips The vegetated filter strips shall be checked weekly and after major storm events during construction for rilling and erosion. Implement soil stabilization measures until permanent vegetation is established. Infiltration Trenches The performance of the infiltration trenches shall be checked weekly and after every major storm event during construction. No construction period runoff should be directed into the infiltration trenches. Subsurface Infiltration Facility The performance of the subsurface infiltration facility shall be checked weekly and after every major storm event during construction. No construction period runoff should be directed into the subsurface infiltration facility. Topsoil Stockpile The topsoil stockpile shall be checked weekly and after major storm events during construction for rilling and erosion. Place temporary seed and mulch to establish growth on stockpile during construction. 3 STORMWATER MANAGEMENT CONSTRUCTION PHASE INSPECTION SCHEDULE AND EVALUATION CHECKLIST PROJECT LOCATION: 85 Terminal Road,North Andover,Massachusetts Inspection Inspector Area Inspected Best Management Required Inspection Comments Recommendation Follow-up Inspection Date Practice es/no Frequencl if BMP Required es/no) FilterMitt No Weekly and After Major Storm Events Storm Drain Inlet No Weekly and After Protection Major Storm Events Vegetated Filter Yes Weekly and After Strips Major Storm Events Infiltration Trenches Yes Weekly and After Major Storm Events Subsurface Yes Weekly and After Infiltration Facility Ma'or Storm Events Topsoil stockpile No Weekly and After Major Storm Events (1) Refer to the Massachusetts Stormwater Handbook, Volume Two: Stormwater Technical Handbook(February 2008) for recommendations regarding frequency for inspection and maintenance of specific BMP's. (2) Inspections to be conducted by a qualified professional such as an environmental scientist or civil engineer. Limited or no use of sodium chloride salts, fertilizers or pesticides recommended. Other notes: (Include deviations from: Con. Comm. Order of Conditions, PB Approval, Construction Sequence and Approved Plan) Stormwater Control Manager: 4 OPERATION AND LONG TERM MAINTENANCE PLAN OPERATION AND LONG TERM MAINTENANCE PLAN located at 85 TERMINAL ROAD NORTH ANDOVER, MASSACHUSETTS Applicant: Great Circle Central, LLC 54 Logan Lane, Unit C Santa Rosa Beach, Florida 32459 Prepared by: Meridian Associates, Inc. 500 Cummings Center, Suite 5950 Beverly, Massachusetts 01915 (978) 299-0447 September 19, 2014 Project Name: 85 Terminal Road North Andover, MA 01845 Owner Name: City of Lawrence 492 Sutton Street North Andover, MA 01845 Applicant Name: Great Circle Central, LLC 54 Logan Lane, Unit C Santa Rosa Beach, FL 32459 Party Responsible for Maintenance: Windover Construction, LLC 66 Cherry Hill Drive Beverly, MA 01915 Project Description: The lease area is located at 85 Terminal Road in North Andover,Massachusetts. The lease area will be accessed from the terminal access road. The topography includes a mixture of brush, woods and grass with mostly gradual slopes. The applicant is proposing to construct an airport hangar. This also includes a driveway,parking area, subsurface infiltration facility, vegetated filter strips, infiltration trenches,utilities and retaining wall. This proposal utilizes several different stormwater management techniques. Incorporated in this design are deep sump catchbasins, vegetated filter strips, infiltration trenches and a subsurface infiltration facility for the treatment and mitigation of the stormwater runoff. Inspection and Maintenance Measures After Construction Erosion Control Eroded sediments can adversely affect the performance of the stormwater management system. Eroding or barren areas should be immediately re-vegetated. Subsurface Infiltration Facility The infiltration facility should be inspected after the first several rainfall events or first few months after construction, after all major storms (3.1" and greater), and on regular semi- annual scheduled dates. Ponded water inside the system (as visible from the observation well) after several days often indicates that the bottom of the system is clogged. 2 Vegetated Filter Strips Regular maintenance is critical for filter strips to be effective and to ensure that flow does not bypass the system. Conduct inspections every six months during the first year and then annually thereafter. Inspect the level spreader for sediment buildup and the vegetation for signs of erosion, bare spots, and overall health. Regular, frequent mowing of the grass is required. Remove sediment from the toe of the slope or level spreader, reseed bare spots as necessary. Periodically,remove sediment that accumulates near the top of the strip to maintain the appropriate slope and prevent formation of a berm that could impede the distribution of stormwater runoff as sheet flow. Deep Sump Oatchbasins The catchbasins shall be inspected four(4)times per year, and if necessary, any maintenance shall be performed so that it functions as designed. The catchbasins shall be cleaned twice per year, or when sediment in the bottom of the sump reaches 24 inches below the bottom of the outlet. Inlet and outlet pipes should be checked for clogging. At a minimum,inspection of the catchbasin shall be performed during the last week of April and the first week of October each year. Infiltraton'Trenches Infiltration trenches are prone to failure due to clogging and therefore it is imperative that they are aggressively maintained on a regular schedule. Inspect the infiltration trench after the first several rainfall events, after all major storms, and on regularly scheduled dates every six months. Routinely remove grass clippings, leaves and accumulated sediment from the surface of the trench. If water is ponded at the surface several days after a rain event then the infiltration trench is most likely clogged and will have to be replaced. Debris and Litter Removal Trash may collect in the BMP's, potentially causing clogging of the facilities. All debris and litter shall be removed when necessary, and after each stone event. Good Housekeeping Practices (in accordance with Standard 10 of the Stormwater Management Handbook to prevent illicit discharges) Provisions for storing paints, cleaners, automotive waste and other potentially hazardous household waste products inside or under cover • All materials on site will be stored inside in a neat, orderly,manner in their appropriate containers with the original manufacturer's label. • Only store enough material necessary. Whenever possible, all of a product shall be used up before disposing of container • Manufacturer, local, and State recommendations for proper use and disposal shall be followed. 3 Vehicle washing controls • A commercial car wash shall be used when possible. Car washes treat and/or recycle water. • Cars shall be washed on gravel, grass, or other permeable surfaces to allow filtration to occur. • Use biodegradable soaps. • A water hose with a nozzle that automatically turns off when left unattended. Airplane washing and deicing controls • Use biodegradable soaps. • A water hose with a nozzle that automatically turns off when left unattended. • Airplanes shall be deiced in accordance with the airport regulations. Requirements for routine inspection and maintenance of stormwater BMPs • See Inspection and Maintenance Measures after Construction. Spill prevention and response plans • Spill Control Practices shall be in conformance with the guidelines set forth in the National Pollutant Discharge Elimination System(NPDES) Stormwater Pollution Prevention Plan(SWPPP) Provisions for maintenance of lawns, gardens, and other landscaped areas • Grass shall not be cut shorter than 2 to 3 inches and mulch clipping should be left on lawn as a natural fertilizer. • Use low volume water approaches such as drip-type or sprinkler systems. Water plants only when needed to enhance root growth and avoid runoff problems. • The use of mulch shall be utilized where possible. Mulch helps retain water and prevents erosion. Requirements for storage and use of fertilizers,herbicides and pesticides • Fertilizers used will be applied only in the minimum amounts recommended by the manufacturer. Once applied, fertilizer will be worked into the soil to limit exposure to storm water. Storage will be in a covered shed. The contents of any partially used bags of fertilizer will be transferred to a sealable plastic bin to avoid spills. • Do not fertilize before a rainstorm. • Consider using organic fertilizers. They release nutrients more slowly. • Pesticides shall be applied on lawns and gardens only when necessary and applied only in the minimum amounts recommended by the manufacturer. Pet waste management • Scoop up and seal pet wastes in a plastic bag. Dispose of properly, in the garbage. Provisions for operation and management of septic systems 4 Not Applicable Provisions for solid waste management • All solid waste shall be disposed of or recycled in accordance with local town regulations. Snow disposal and plowing plans relative to Wetland Resource Area • Snow shall be plowed and stored on gravel, grass, or other permeable surfaces to allow filtration to occur. • Once snow.melts all sand salt and debris shall be extracted from surface and properly disposed of. • Snow shall not be disposed of in any wetland resource area or waterbody. • Avoid disposing snow on top of storm drain catchbasins or stormwater drainage Swale. Winter Road Salt and/or Sand use and storage restrictions • Salt storage piles should be located outside the 100-year buffer zone and shall be covered at all tunes. • The amount of road salt applied should be regulated to prevent over salting of roadways and increasing runoff concentrations. Alternative materials, such as sand or gravel, should be used in especially sensitive areas. Roadway and Parking Lot sweeping schedule • Pavement sweeping shall be conducted at a frequency of not less than once per year. • Removal of any accumulated sand, grit, and debris from driveway after the snow melts shall be completed shortly after snow melts for the season. 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 Not Applicable Training for staff or personnel involved with implementing Long-Term Pollution Prevention Plan To be determined by the owner. List of Emergency contacts for implementing Long-Term Pollution Prevention Plan To be determined by the owner. 5 STORMWATER MANAGEMENT POST-CONSTRUCTION PHASE INSPECTION SCHEDULE AND EVALUATION CHECKLIST PROJECT LOCATION: 85 Terminal Road,North Andover, Massachusetts InspectionInspector Area Inspected Best Management Required Inspection. Comments IRecommendation Follow-up Inspection Date F Practice(yes/no) Frequency if BMP Required es/no) Subsurface Yes Twice a year Infiltration Facility Vegetated Filter Yes Twice a year for first Strips year and annually thereafter Deep Sump Yes Four times a year Catchbasins Infiltration Trenches Yes Twice a year (1) Refer to the Massachusetts Stormwater Handbook, Volume Two: Stormwater Technical Handbook(February 2008) for recommendations regarding frequency for inspection and maintenance of specific BMP's. (2) Inspections to be conducted by a qualified professional such as an environmental scientist or civil engineer. Limited or no use of sodium chloride salts, fertilizers or pesticides recommended. Other notes: (Include deviations from: Con. Comm. Order of Conditions, PB Approval, Construction Sequence and Approved Plan) Stormwater Control Manager: 6 STORMWATER ANALYSIS AND CALCULATIONS STORMWATER ANALYSIS AND CALCULATIONS for 85 TERMINAL ROAD NORTH ANDOVER, MASSACHUSETTS Prepared for: Great Circle Central,t I a LLC 54 Logan Lane, Unit C Santa Rosa Beach, Florida 32459 Prepared • p d by. Meridian Associates, Inc. 500 Cummings Center, Suite 5950 Beverly, Massachusetts 01915 (978) 299-0447 September 19, 2014 MERIDIAN 'INASSOCI ' ' TABLE OF CONTENTS Calculation Methods: Source of Data: Report Summary: Calculation Objectives Selection of Storm Events Classification of Soils Existing Conditions Overview Proposed Conditions Overview Performance of Stormwater Management Facilities Performance of Peak Rate Runoff Conclusion Stormwater Analysis: Existing Conditions • Watershed Routing Diagram • 2, 10, 100-Year 24 Hour Storm Event Analysis Proposed Conditions • Watershed Routing Diagram • 2, 10, 100-Year 24 Hour Storm Event Analysis Proposed Storm Drain Analysis • 100-Year Storm Event Appendix: Soils Information Pre Development Drainage Plan Post Development Drainage Plan Storm Drain Plan CALCULATION METHODS — TR 20 SCS Unit Hydrograph Procedure — Runoff Curve Numbers — Time of Concentration by TR55 Methodology — Pond Rating by the Storage-Indication Method — Manning Equation SOURCE OF DATA — Technical Report No. 20 — Technical Report No. 55 — Technical Paper No. 40 — Partial Field Survey by MAI — Massachusetts Stormwater Management Handbook, February 2008 REPORT SUMMARY: Calculation Obiectives The objective of these calculations is to document that the proposed project described in the Stormwater Management Report does not result in an increase of offsite rates of stormwater runoff or flooding down gradient of the site, The analysis is separated into existing and proposed conditions. Drainage plans have been incorporated into this report to depict existing and proposed drainage areas. Selection of Storm Events The storm events have been compiled from the Soil Conservation Service Technical Report No. 55 and the U.S. Department of Commerce Technical Paper No. 40. Rainfall frequency data has been provided as follows: Freouency (Years) Rainfall [24-flour Event(inches)] 2 3.1 10 4.5 100 6.5 Classification of Soils Drainage classes have been established based on soil maps provided by the web soil survey website as well as onsite soil testing. According to the Natural Resources Conservation Service, the following soil types, parent materials and hydrologic groups are delineated within the project site: 305B: Paxton fine sandy loam, 3 to 8 percent slopes—hydrologic soil group C 602: Urban land There is no hydrologic soil group rating for urban land therefore hydrologic soil group C has been used in the calculations to be conservative. Hydrologic soil groups are assigned to each soil type by NRCS based on their potential rate of water infiltration. Group C soils have slow infiltration rates when thoroughly wet and generally consist of soils that have a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture. Existing Conditions Overview The lease area will be accessed from the terminal access road. The topography includes a mixture of brush, woods and grass with mostly gradual slopes. For the purpose of analyzing existing and proposed stormwater runoff, two design points have been designated for comparison. One subcatchment area has been delineated based ontopography which will contribute stormwater flow to the design point. Existing Design Points and Subcatchment Area Design Point#1 is a point at the edge of the taxiway which collects stormwater runoff from the majority of the project site. The subcatchment area flows overland and into a closed storm sewer system before reaching the design point. Design Point#2 is a point at the edge of the existing parking area for the airport terminal. The subcatchment area flows overland before reaching the design point. Pro used Conditions Overview The applicant is proposing to construct an airport hangar on the lease area. This also includes a driveway,parking area, subsurface infiltration facility, vegetated filter strips, infiltration trenches,utilities and retaining wall. Storrnwater Mann ern This proposal utilizes conventional stormwater management techniques. Incorporated in this design are a subsurface infiltration facility, vegetated filter strips, infiltration trenches and deep sump catchbasins for treatment, recharge and peak rate control of the stormwater runoff. Design strategies for the stormwater systems follow methods from the Massachusetts Stormwater Handbook. Vegetated Filter Strip Vegetated filter strips are uniformly graded vegetated surfaces that receive stormwater runoff from adjacent impervious areas. Vegetated filter strips typically treat sheet flow or small concentrated flows that can be distributed along the width of the strip using a level spreader. Vegetated filter strips are designed to slow stormwater runoff velocities, trap sediment and promote infiltration, thereby reducing stormwater runoff volumes. Vegetated filter strips are pretreating the stormwater runoff before it enters the infiltration trenches. Variable TSS removal efficiencies have been reported for filter strips. A TSS removal rate of 5%was used for this BMP because the filter strips are less than 25' wide. Infiltration Trench The infiltration trenches can be designed for either complete or partial exfiltration of the stormwater runoff. Infiltration trenches provide control of peak discharges and water quality treatment for all storm events. Infiltration trenches are constructed with multiple 2 layers to allow infiltration and prevent from clogging. The infiltration trenches are treating and controlling the peak discharge rate of the stormwater runoff from a portion of the driveway. A TSS removal rate of 80%is achieved by this BMP with adequate pretreatment. Deep Sump Catchbasin Similar to an ordinary catchbasin but fitted with an outlet hood to separate floatables such as oil, grease, trash and debris. They also have four foot deep sumps that promote settling of suspended solids. The catchbasin are pretreating the stormwater runoff from the impervious areas. A TSS removal rate of 25% is achieved by this :BMP. Subsurface Infiltration Facilitv A subsurface infiltration facility has been incorporated into this design to provide recharge and peak rate control of the stormwater runoff. The facility consists of plastic chambers with open bottoms placed on a bed of stone. The chambers are constructed to store the stormwater runoff temporarily to allow it to infiltrate into the underlying soil. During the larger storm events stormwater runoff does discharge from the facility. The facility has been designed to treat the stormwater runoff from the hangar rooftop, taxiway,parking area and a portion of the driveway. A TSS removal rate of 80% is achieved by this BMP. Proposed Design Points and Subcatchment Areas Design Point#1 is a point at the edge of the taxiway which collects stormwater runoff from the majority of the project site. The subcatchment area flows into a driveway Swale and into a closed storm sewer system and then into the subsurface infiltration facility reaching the design point. Design Point#2 is a point at the edge of the existing parking area for the airport terminal which collects stormwater runoff from a portion of the proposed driveway. The subcatchment area flows overland and then into the infiltration trenches before reaching the design point. Proposed Storm Drain Analysis The proposed storm drain system has been analyzed using the Hydraflow Storm Sewers Extension for Civil3D. The storm drain system has been analyzed for the 100 year storm event and no surcharging occurred at any of the manholes or catchbasins. 3 Summary of Flows and Volumes at Design Point (CFS) A detailed analysis of existing and proposed subcatchment areas and infiltration trenches and subsurface infiltration facility is included in the HydroCAD analysis section of this report. Design Point#1 Storm Event Existing Conditions (Pre) Proposed Conditions (Post) Peak Flow(CFS) Peak Flow (CFS) 2-Year(3.1 in./hr.) 1.34 0.93 10-Year(4.5 in./hr.) 3.02 1.89 100-Year(6.5 in./hr.) 5.79 3.42 Design Point#2 Storm Event Existing Conditions LPrej Proposed Conditions (Post) Peak Flow (CFS) Peak Flow(CFS) 2-Year(3.1 in./hr.) 1.96 1.47 10-Year(4.5 in./hr.) 4.10 3.48 100-Year(6.5 in./hr.) 7.50 6.35 Design Point#1 Storm Event Existing—Conditions (Pre) Proposed Conditions (Post) Volume (CF) Volume (CE) 2-Year(3.1 in./hr.) 6,055 3,659 10-Year(4.5 in./hr.) 12,676 7,492 100-Year(6.5 in./hr.) 23,740 22,956 Design Point#2 Storm Event Existiny,Conditions (Pre) Proposed Conditions (Post) Volume (CE) Volume (CF) 2-Year(3.1 in./hr.) 10,062 7,231 10-Year(4.5 in./hr.) 20,125 15,682 100-Year(6.5 in./hi.) 36,416 29,229 4 Conclusion The calculations indicate peaks and volume have been met or reduced for the 2-year, 10- year, and 100-year storm events. We can therefore anticipate no adverse impacts or downstream flooding with the completion of this project. In addition the design provides for the required TSS removal, recharge volumes and water quality treatment required by the MA DEP Stormwater Management Requirements. 5 WATERSHED ROUTING IA AM Subcatchm nt area #1 Subcatchmr iDP1 S� e P € k i D■ Z it Pre development Pre development (Discharge point #1 ) (Discharge point #2) Bobcat IReach[ onti Link' Routing Diagram for 5659 PRE Prepared by Meridian Associates, Printed 11/7/2014 HydroCAD®10.00 s/n 00814 00 2011 HydroCAD Software Solutions LLC EXISTING 2-YEAR 24-HOUR STORM EVENT ANALYSIS 5659 PRE Type 111 24-hr 2 year storm Rainfall=3.10" Prepared by Meridian Associates Printed 11/7/2014 HydroCAD® 10,00 s/n 00814.@ 2011 HydroCAD Software Solutions LLC Page 2 Summary for Subcatchment SC1: Subcatchment area#1 Runoff = 1.34 cfs @ 12.23 hrs, Volume= 0.139 af, Depth= 0.87" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Type III 24-hr 2 year storm Rainfall=3.10" Area (sf) CN Description - 50,763 74 >75% Grass cover, Good, HSG C 2,047 98 Paved parking, HSG C 1,263 96 Gravel surface, HSG C 784 98 Unconnected roofs, HSG C 28,816 65 Brush, Good, HSG C 83,673 72 Weighted Average 80,842 96.62% Pervious Area 2,831 3.38% Impervious Area 784 27.69% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.5 100 0.0450 0.16 Sheet Flow, Sheet through brush Grass: Dense n= 0.240 P2= 3.10" 1.5 44 0.0050 0.49 Shallow Concentrated Flow, SCF through brush Short Grass Pasture Kv= 7.0 fps 1.9 216 0.0728 1.89 Shallow Concentrated Flow, SCF through grass Short Grass Pasture Kv= 7.0 fps 1.1 207 0.0050 3.21 2.52 Pipe Channel, Pipe flow 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.013 Corrugated PE, smooth interior 15.0 567 Total Summary for Subcatchment SC2: Subcatchment area#2 Runoff = 1.96 cfs @ 12.34 hrs, Volume= 0.231 af, Depth= 1.03" Runoff by SGS TR-20 method, UH=SCS, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Type III 24-hr 2 year storm Rainfall=3.10" Area (sf) CN Description 10,132 98 Paved parking, HSG C 1,220 98 Roofs, HSG C 76,063 74 >75% Grass cover, Good, HSG C 5,619 65 Brush, Good, HSG C 24,632 70 Woods Good HSG C 117,666 75 Weighted Average 106,314 90.35% Pervious Area 11,352 9.65% Impervious Area 5659 PRE Type Ill 24-hr 2 year storm Rainfall=3.10" Prepared by Meridian Associates Printed 11/7/2014 HydroCAD® 10.00 s/n 00814 ©2011 HydroCAD Software Solutions LLC Page 3 Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) ft/sec) (cfs) 14.1 100 0.0600 0.12 Sheet Flow, Sheet through woods Woods: Light underbrush n= 0.400 P2= 3,10" 4.0 115 0.0090 0.47 Shallow Concentrated Flow, SCF through woods Woodland Kv= 5.0 fps 4.7 232 0.0140 0.83 Shallow Concentrated Flow, SCF through grass Short Grass Pasture Kv= 7.0 fps 22.8 447 Total Summary for Link P1: Pre development (Discharge point 1) Inflow Area = 1.921 ac, 3.38% Impervious, Inflow Depth = 0.87" for 2 year storm event Inflow = 1.34 cfs @ 12.23 hrs, Volume= 0.139 of Primary = 1.34 cfs @ 12.23 hrs, Volume= 0.139 af, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span=0.00-50.01 hrs, dt=0.03 hrs Summary for Lank : Pre development (Discharge point ) Inflow Area = 2.701 ac, 9.65% Impervious, Inflow Depth = 1.03`° for 2 year storm event Inflow = 1.96 cfs @ 12.34 hrs, Volume= 0.231 of Primary = 1.96 cfs @ 12.34 hrs, Volume= 0.231 af, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span= 0.00-50.01 hrs, dt=0.03 hrs EXISTING 10-YEAR 24-HOUR STORM EVENT ANALYSIS 5659 PRE Type 11124-hr 10 year storm Rainfall=4.50" Prepared by Meridian Associates Printed 11/7/2014 HydroCADO 10.00 s/n 00814 ©2011 HydroCAD Software Solutions LLC Page 4 Summary for Subcatchment SC1: Subcatchment area #1 Runoff = 3.02 cfs @ 12.22 hrs, Volume= 0.291 af, Depth= 1.82" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Type III 24-hr 10 year storm Rainfall=4.50" Area (sf) CN Description 50,763 74 ' >75% Grass cover, Good, HSG C 2,047 98 Paved parking, HSG C 1,263 96 Gravel surface, HSG C 784 98 Unconnected roofs, HSG C 28,816 65 Brush, Good, HSG C 83,673 72 Weighted Average 80,842 96.62% Pervious Area 2,831 3.38% Impervious Area 784 27.69% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.5 100 0.0450 0.16 Sheet Flow, Sheet through brush Grass: Dense n=0.240 P2= 3.10" 1.5 44 0.0050 0.49 Shallow Concentrated Flow, SCF through brush Short Grass Pasture Kv= 7.0 fps 1.9 216 0.0728 1.89 Shallow Concentrated Flow, SCF through grass Short Grass Pasture Kv= 7.0 fps 1.1 207 0.0050 3.21 2.52 Pipe Channel, Pipe flow 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.013 Corrugated PE, smooth interior 15.0 567 Total Summary for Subcatchment SC2: Subcatchment area#2 Runoff = 4.10 cfs @ 12.33 hrs, Volume= 0.462 af, Depth= 2.05" Runoff by SGS TR-20 method, UH=SCS, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Type III 24-hr 10 year storm Rainfall=4.50" Area (sf) CN Description 10,132 98 Paved parking, HSG C 1,220 98 Roofs, HSG C 76,063 74 >75% Grass cover, Good, HSG C 5,619 65 Brush, Good, HSG C 24,632 70 Woods Good, HSG C 117,666 75 Weighted Average 106,314 90.35% Pervious Area 11,352 9.65% Impervious Area 5659 PRE Type 11124-hr 10 year storm Rainfall=4.50" Prepared by Meridian Associates Printed 11/7/2014 HydroCADO 10.00 s/n 00314 ©2011 HydroCAD Software Solutions LLC Pam Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 14.1 100 0.0600 0.12 Sheet Flow, Sheet through woods Woods: Light underbrush n= 0,400 P2= 3.10" 4.0 115 0.0090 0.47 Shallow Concentrated Flow, SCF through woods Woodland Kv= 5.0 fps 4.7 232 0.0140 0.83 Shallow Concentrated Flow, SCF through grass Short Grass Pasture Kv= 7.0 fps 22.8 447 Total Summary for Link DPI: Pre development (Discharge point 1) Inflow Area = 1.921 ac, 3.38% Impervious, Inflow Depth = 1.82" for 10 year storm event Inflow = 3.02 cfs @ 12.22 hrs, Volume= 0.291 of Primary = 3.02 cfs @ 12.22 hrs, Volume= 0.291 af, Atten= 0%, Lag= 0.0 min Primary outflow= inflow, Time Span= 0.00-50.01 hrs, dt=0.03 hrs Summary for Link P re development (Discharge point ) Inflow Area = 2.701 ac, 9.65% Impervious, Inflow Depth = 2.05" for 10 year storm event Inflow = 4.10 cfs @ 12.33 hrs, Volume= 0.462 of Primary = 4.10 cfs @ 12.33 hrs, Volume= 0.462 af, Atten=0%, Lag=0.0 min Primary outflow= Inflow, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs 100-YEAR 24-HOUR STORM EVENT ANALYSIS 5659 PRE Type 11124-hr 900 year storm Rainfall=6.50" Prepared by Meridian Associates Printed 11/7/2014 HydroCAD® 10.00 s/n 00814 ©2011 HydroCAD Software Solutions LLC Page 6 Summary for Subcatchment SCI: Subcatchment area #1 Runoff = 5.79 cfs @ 12.21 hrs, Volume= 0.545 af, Depth= 3.41" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Type III 24-hr 100 year storm Rainfall=6.50" Area (sf) CN Description 50,763 74 >75% Grass cover, Good, HSG C 2,047 98 Paved parking, HSG C 1,263 96 Gravel surface, HSG C 784 98 Unconnected roofs, HSG C 28,816 65 Brush Good HSG C 83,673 72 Weighted Average 80,842 96.62% Pervious Area 2,831 3.38% Impervious Area 784 27.69% Unconnected Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 10.5 100 0.0450 0.16 Sheet Flow, Sheet through brush Grass: Dense n= 0.240 P2= 3.10" . 1.5 44 0.0050 0.49 Shallow Concentrated Flow, SCF through brush Short Grass Pasture Kv= 7.0 fps 1.9 216 0.0728 1.89 Shallow Concentrated Flow, SCF through grass Short Grass Pasture Kv= 7.0 fps 1.1 207 0.0050 3.21 2.52 Pipe Channel, Pipe flow 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.013 Corrugated PE smooth interior 15.0 567 Total Summary for Subcatchment SC2: Subcatchment area #2 Runoff = 7.50 cfs @ 12.32 hrs, Volume= 0.836 af, Depth= 3.71" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Type III 24-hr 100 year storm Rainfall=6.50" Area (sf) CN Description 10,132 98 Paved parking, HSG C 1,220 98 Roofs, HSG C 76,063 74 >75% Grass cover, Good, HSG C 5,619 65 Brush, Good, HSG C 24,632 70 Woods, Good, HSG C 117,666 75 Weighted Average 106,314 90.35% Pervious Area 11,352 9.65% Impervious Area 5659 PRE Type 11124-hr 100 year storm Rainfall=6.50" Prepared by Meridian Associates Printed 11/7/2014 HydroCADO 10.00 s/n 00814 ©2011 HydroCAD Software Solutions LLC Page 7 Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 14.1 100 0.0600 0.12 Sheet Flow, Sheet through woods Woods: Light underbrush n= 0.400 P2= 3.10" 4.0 115 0.0090 0.47 Shallow Concentrated Flow, SCF through woods Woodland Kv= 5.0 fps 4.7 232 0.0140 0.83 Shallow Concentrated Flow, SCF through grass Short Grass Pasture Kv= 7.0 fps 22.8 447 Total Summary for Link DPI: Pre development (Discharge point 1) Inflow Area = 1.921 ac, 3.38% Impervious, Inflow Depth = 3.41" for 100 year storm event Inflow = 5.79 cfs @ 12.21 hrs, Volume= 0.545 of Primary - 5.79 cfs @ 12.21 hrs, Volume= 0.545 af, Atten= 0%, Lag=0.0 min Primary outflow = Inflow, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Summary for Link a Pre development (Discharge point# ) Inflow Area = 2.701 ac, 9.65% Impervious, Inflow Depth = 3.71" for 100 year storm event Inflow - 7.50 cfs @ 12.32 hrs, Volume= 0.836 of Primary = 7.50 cfs @ 12.32 hrs, Volume= 0.836 af, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span= 0.00-50.01 hrs, dt=0.03 hrs PROPOSED CONDITIONS WATERSHED ROUTING DIAGRAM `f $f R JII I a't ; 2 ; Subcatchmen area#1a Subcatchment a#2a 11 - Subcatchrhent area#2b are Subsurface infi ation Subcahment area#1 b facilit Infiltr ion trench#2 Y Infiltration tren #1 ,DP1" dP2 � Subcatchment area#2c Post development Post development (Discharge point#1) (Discharge point#2) �,SiubCBtjReach end Ljnk; Routing Diagram for 5659 POST Prepared by Meridian Associates, Printed 11/7/2014 HydroCAD®10.00 s/n 00814 ©2011 HydroCAD Software Solutions LLC 2-YEAR 24-HOUR STORM EVENT ANALYSIS 5659 POST Type 111 24-hr 2 year storm Rainfall=3.10" Prepared by Meridian Associates Printed 11/7/2014 HydroCAD® 10.00 s/n 00814 @2011 HydroCAD Software Solutions LLC Page 2 Summary for Subcatchment SCIa: Subcatchment area #1a Runoff = 2.98 cfs @ 12.10 hrs, Volume= 0.219 af, Depth= 1.75" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Type III 24-hr 2 year storm Rainfall=3.10" Area (sf) CN Description 17,994 98 Paved parking, HSG C 19,289 74 >75% Grass cover, Good, HSG C 15,825 98 Roofs, HSG C * 191 98 Retaining wall, HSG C 12,268 70 Woods, Good, HSG C 65,567 86 Weighted Average 31,557 48.13% Pervious Area 34,010 51.87%Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.8 80 0.0490 0.23 Sheet Flow, Grass: Short n= 0.150 P2= 3.10" 0.2 99 0.0480 7.73 38.63 TrapNee/Rect Channel Flow, Bot.W=2.00' D=1.00' Z= 3.0 '/' Top.W=8.00' n= 0.030 Short grass 0.9 258 0.0100 4.54 3.56 Pipe Channel, 12.0" Round.Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.013 Corrugated PE, smooth interior 6.9 437 Total Summary for Subcatchment SCI b: Subcatchment area#1 b Runoff = 0.93 cfs @ 12.17 hrs, Volume= 0.084 af, Depth= 1.08" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Type III 24-hr 2 year storm Rainfall=3.10" Area (sf) CN Description 3,383 98 Paved parking, HSG C 781 98 Roofs, HSG C 36,170 74 >75% Grass cover, Good, HSG C 40,334 76 Weighted Average 36,170 89.68% Pervious Area 4,164 10.32% Impervious Area 5659 POST Type 111 24-hr 2 year storm Rainfall=3.10" Prepared by Meridian Associates Printed 11/7/2014 HydroCADO 10.00 s/n 00814 ©2011 HydroCAD Software Solutions LLC Page 3 Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.4 100 0.0600 0.26 Sheet Flow, Grass: Short n= 0.150 P2= 3.10" 4,3 277 0.0230 1.06 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 1.1 207 0.0050 3.21 2.52 Pipe Channel, 12.0" Round Area=0.8 sf Perim= 3.1' r= 0.25' n= 0.013 Corrugated PE, smooth interior 11.8 584 Total Summary for Subcatchment SCa: Subcatchment area# a Runoff = 0.90 cfs @ 12.34 hrs, Volume= 0.107 af, Depth= 0.97" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Type 111 24-hr 2 year storm Rainfall=3.10" Area (sf) CN Description 2,438 98 Paved parking, HSG C 42,735 74 >75% Grass cover, Good, HSG C 12,365 70 Woods, Good, HSG C 57,538 74 Weighted Average 55,100 95.76% Pervious Area 2,438 4.24% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 21.8 100 0.0200 0.08 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.10" 0.7 43 0.0400 1.00 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 22.5 143 Total Summary for Subcatchment SC2b: Subcatchment area#2b Runoff = 0.34 cfs @ 12.11 hrs, Volume= 0.026 af, Depth= 1.26" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Type III 24-hr 2 year storm Rainfall=3.10" Area (sf) CN Description 8,347 74 >75% Grass cover, Good, HSG C 2,400 98 Paved parking, HSG C 10,747 79 Weighted Average 8,347 77.67% Pervious Area 2,400 22.33% Impervious Area 5659 POST Type 11124-hr 2 year storm Rainfall=3.10" Prepared by Meridian Associates Printed 11/7/2014 HydroCADO 10.00 s/n 00814 ©2011 I'HydroCAD Software Solutions LLC Page 4 To Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.5 56 0.0180 0.14 Sheet Flow, Grass: Short n= 0.150 P2= 3.10" 0.5 44 0.0450 1.59 Sheet Flow, Smooth surfaces n= 0.011 P2= 3.10" 0.3 71 0.0350 3.80 Shallow Concentrated Flow, Paved Kv= 20.3 fps 7.3 171 Total Summary for Subcatchment S2c: Subcatchment area##2c Runoff = 1.03 cfs @ 12.14 hrs, Volume= 0.083 af, Depth= 1.60" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Type III 24-hr 2 year storm Rainfall=3.10" Area (sf) CN Description 15,826 74 >75% Grass cover, Good, HSG C 11,328 98 Paved parking, HSG C 27,154 84 Weighted Average 15,826 58.28% Pervious Area 11,328 41.72% Impervious Area To Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (fUsec) (cfs) 8.5 58 0.0100 0.11 Sheet Flow, Grass: Short n= 0.150 P2= 3.10" 0:6 42 0.0240 1.22 Sheet Flow, Smooth surfaces n= 0.011 P2= 3.10" 0.4 74 0.0200 2.87 Shallow Concentrated Flow, Paved Kv= 20.3 fps 9.5 174 Total Summary for Pond 1P: Subsurface infiltration facility Inflow Area = 1.505 ac, 51.87% Impervious, Inflow Depth = 1.75" for 2 year storm event Inflow = 2.98 cfs @ 12.10 hrs, Volume= 0.219 of Outflow = 0.05 cfs @ 10.35 hrs, Volume= 0.156 af, Atten= 98%, Lag= 0.0 min Discarded = 0.05 cfs @ 10.35 hrs, Volume= 0.156 of Primary = 0.00 cfs @ 0.00 hrs, Volume= 0.000 of Routing by Stor-Ind method, Time Span= 0.00-50.01 hrs, dt=0.03 hrs Peak Elev= 145.49' @ 21.41 hrs Surf.Area= 0.171 ac Storage= 0.164 of Plug-Flow detention time= 1,054.4 min calculated for 0.156 of(71% of inflow) Center-of-Mass det. time= 960.0 min ( 1,784.8- 824.8 ) 5659 POST Type ll/24-hr 2 year storm Rainfall=3.10" Prepared by Meridian Associates Printed 11/7/2014 HydroCAD® 10.00 s/n 00814 ©2011 HydroCAD Software Solutions LLC Page 5 Volume Invert Avall.Storage Storage Description #1A 144.10' 0.142 of 40.17'W x 185.50'L x 3.54'H Field A 0.606 of Overall - 0.251 of Embedded = 0.355 of x 40.0% Voids #2A 144.60' 0.251 of Cultec R-330XL x 208 Inside#1 Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.001 = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50'x 7.45 sf x 8 rows 0.393 of Total Available Storage Storage Group A created with Chamber Wizard Device Routing Invert Outlet Devices #1 Primary 146.50' 4.0" Round Culvert L= 18.5' CPP, square edge headwall, Ke= 0.500 Inlet/Outlet Invert= 146.50'/ 143.70' S= 0.1514'/' Cc= 0.900 n=0.012, Flow Area=0.09 sf #2 Discarded 144.10' 0.2701n/hr Exflltration over Surface area Discarded®utFlow Max=0.05 cfs @ 10.35 hrs HW=144.14' (Free Discharge) t--2=Exfiltration (Exfiltration Controls 0.05 cfs) Primary®utFlow Max=0.00 cfs @ 0.00 hrs HW=144.10' (Free Discharge) L1=Culvert ( Controls 0.00 cfs) Summary for Pond 2P: Infiltration trench #1 Inflow Area = 1.321 ac, 4.24% Impervious, Inflow Depth = 0.97" for 2 year storm event Inflow = 0.90 cfs @ 12.34 hrs, Volume= 0.107 of Outflow = 1.00 cfs @ 12.40 hrs, Volume= 0.097 af, Atten= 0%, Lag= 3.5 min Discarded = 0.01 cfs @ 12.39 hrs, Volume= 0.017 of Primary - 0.99 cfs @ 12.40 hrs, Volume= 0.080 of Routing by Stor-Ind method, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Peak Elev= 156.11' @ 12.39 hrs Surf.Area= 0.026 ac Storage= 0.021 of Plug-Flow detention time= 213.8 min calculated for 0.097 of(90% of inflow) Center-of-Mass det. time= 166.3 min ( 1,045.7 -879.4 ) Volume Invert Avail.Storage Storage Description #1 153.00' 0.020 of 4.00'W x')81.00'L x 3.00'H infiltration trench 0.050 of Overall x 40.0% Voids #2 156.00' 0.006 of 4.00'W x 90.001 x 0.50'H storage above infiltration trench Z=3.0 0.026 of Total Available Storage Device Routing Invert Outlet Devices #1 Primary 153.00' 12.0" Round Culvert L= 9.0' CPP, square edge headwall, Ke= 0.500 Inlet/Outlet Invert= 153.00'/ 152.30' S= 0.0778 '/' Cc= 0.900 n= 0.012, Flow Area= 0.79 sf #2 Device 1 156.00' 24.0"x 24.0" Horiz. Grate C= 0.600 Limited to weir flow at low heads 5659 POST Type 11124-hr 2 year storm Rainfall=3.10" Prepared by Meridian Associates Printed 11/7/2014 HydroCADO 10.00 s/n 00814 ©2011 HydroCAD Software Solutions LLC Page 6 #3 Discarded 153.00' 0.270 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.01 cfs @ 12.39 hrs HW=156.11' (Free Discharge) L3=Exfiltration (Exfiltration Controls 0.01 cfs) Primary OutFlow Max=0.92 cfs @ 12.40 hrs HW=156.11' (Free Discharge) L1=Culvert (Passes 0.92 cfs of 6.11 cfs potential flow) L2=Grate (Weir Controls 0.92 cfs @ 1.07 fps) Summary for Pond 3Po Infiltration trench #2 Inflow Area = 0.247 ac, 22.33% Impervious, Inflow Depth = 1.26" for 2 year storm event Inflow = 0.34 cfs @ 12.11 hrs, Volume= 0.026 of Outflow = 0.02 cfs @ 14.90 hrs, Volume= 0.017 af, Atten=94%, Lag= 167.2 min Discarded = 0.01 cfs @ 14.90 hrs, Volume= 0.014 of Primary = 0.02 cfs @ 14.90 hrs, Volume= 0.003 of Routing by Stor-Ind method, Time Span=0.00-50.01 hrs, dt= 0.03 hrs Peak Elev= 156.01' @ 14.90 hrs Surf.Area=0.022 ac Storage= 0.017 of Plug-Flow detention time= 884.8 min calculated for 0.017 of(66% of inflow) Center-of-Mass det. time= 777.2 min ( 1,626.1 -848.9 ) Volume Invert Avail.Storage Storage Description #1 153.00' 0.017 of 4.00'W x 157.00'L x 3.00'H infiltration trench 0.043 of Overall x 40.0% Voids #2 156.00' 0.005 of 4.00'W x 78.00'L x 0.50'H storage above infiltration trench Z=3.0 0.022 of Total Available Storage Device Routing Invert Outlet Devices #1 Primary 153.00' 12.0" Round Culvert L= 11.0' CPP, square edge headwall, Ke= 0.500 Inlet/Outlet Invert= 153.00'1151.90' S= 0.1000 T Cc= 0.900 n=0.012, Flow Area=0.79 sf #2 Device 1 156.00' 24.0"x 24.0" Horiz. Grate C= 0.600 Limited to weir flow at low heads #3 Discarded 153.00' 0.270 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.01 cfs @ 14.90 hrs HW=156.01' (Free Discharge) L3=Exfiltration (Exfiltration Controls 0.01 cfs) Primary OutFlow Max=0.01 cfs @ 14.90 hrs HW=156.01' (Free Discharge) L1=Culvert (Passes 0.01 cfs of 5.99 cfs potential flow) L2=Grate (Weir Controls 0.01 cfs @ 0.25 fps) 5659 POST Type Ill 24-hr 2 year storm Rainfall=3.10" Prepared by Meridian Associates Printed 11/7/2014 HydroCAD® 10.00 s/n 00814 ©2011 HydroCAD Software Solutions LLC Page 7 Summary for Link DP1: Post development (Discharge point 1) Inflow Area = 2.431 ac, 36.05% Impervious, Inflow Depth = 0.41" for 2 year storm event Inflow = 0.93 cfs @ 12.17 hrs, Volume= 0.084 of Primary = 0.93 cfs @ 12.17 hrs, Volume= 0.084 af, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span=0.00-50.01 hrs, dt=0.03 hrs Summary for Link DP2: Post development (Discharge point# ) Inflow Area = 2.191 ac, 16.94% Impervious, Inflow Depth = 0.91" for 2 year storm event Inflow = 1.47 cfs @ 12.40 hrs, Volume= 0.166 of Primary = 1.47 cfs @ 12.40 hrs, Volume= 0.166 af, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span= 0.00-50.01 hrs, dt=0.03 hrs 10-YEAR 24-HOUR STORM EVENT ANALYSIS 5659 POST Type 111 24-hr 10 year storm Rainfall=4.50" Prepared by Meridian Associates Printed 11/7/2014 HydroCAD® 10.00 s/n 00814 ©2011 HydroCAD Software Solutions LLC Page 8 Summary for Subcatchment SC1a: Subcatchment area #1a Runoff = 5.07 cfs @ 12.10 hrs, Volume= 0.377 af, Depth= 3.00" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Type III 24-hr 10 year storm Rainfall=4.50" Area (sf) CN Description 17,994 98 Paved parking, HSG C 19,289 74 >75% Grass cover, Good, HSG C 15,825 98 Roofs, HSG C 191 98 Retaining wall, HSG C 12,268 70 Woods, Good, HSG C 65,567 86 Weighted Average 31,557 48.13% Pervious Area 34,010 51.87% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.8 80 0.0490 0.23 Sheet Flow, Grass: Short n= 0.150 P2= 3.10" 0.2 99 0.0480 7.73 38.63 TrapNeelRect Channel Flow, Bot.W=2.00' D=1.00' Z= 3.07' Top.W=8.00' n= 0.030 Short grass 0.9 258 0.0100 4.54 3.56 Pipe Channel, 12.0" Round Area= 0.8 sf Perim= 3.1' r=0.25' n= 0.013 Corrugated PE, smooth interior 6.9 437 Total Summary for Subcatchment SC1 b: Subcatchment area #1 b Runoff = 1.89 cfs @ 12.17 hrs, Volume= 0.164 af, Depth= 2.13" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Type III 24-hr 10 year storm Rainfall=4.50" Area (sf) CN Description 3,383 98 Paved parking, HSG C 781 98 Roofs, HSG C 36,170 74 >75% Grass cover, Good, HSG C 40,334 76 Weighted Average 36,170 89.68% Pervious Area 4,164 10.32% Impervious Area 5659 POST Type 11124-hr 10 year storm Rainfall=4.50" Prepared by Meridian Associates Printed 11/7/2014 HydroCAD® 10.00 s/n 00814 O 2011 HydroCAD Software Solutions LLC Page 9 Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.4 100 0.0600 0.26 Sheet Flow, Grass: Short n= 0.1.50 P2= 3.10" 4.3 277 0.0230 1.06 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 1.1 207 0.0050 3.21 2.52 Pipe Channel, 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.013 Corrugated PE, smooth interior 11.8 584 Total Summary for Subcatchment SC2a: Subcatchment area#2a Runoff = 1.93 cfs @ 12.32 hrs, Volume= 0.217 af, Depth= 1.97" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Type Iii 24-hr 10 year storm Rainfali=4.50' Area (sf) CN Description 2,438 98 Paved parking, HSG C 42,735 74 >75% Grass cover, Good, HSG C 12,365 70 Woods, Good, HSG C 57,538 74 Weighted Average 55,100 95.76% Pervious Area 2,438 4.24% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 21.8 100 0.0200 0.08 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.10" 0.7 43 0.0400 1.00 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 22.5 143 Total Summary for Subcatchment SM: Subcatchment area#2b Runoff = 0.65 cfs @ 12.11 hrs, Volume= 0.049 af, Depth= 2.38" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Type III 24-hr 10 year storm Rainfall=4.50" Area (sf) CN Description 8,347 74 >75% Grass cover, Good, HSG C 2,400 98 Paved parking, HSG C 10,747 79 Weighted Average 8,347 77.67% Pervious Area 2,400 22.33% Impervious Area 5659 POST Type 11124-hr 10 year storm Rainfall=4.50" Prepared by Meridian Associates Printed 11/7/2014 HydroCADO 10.00 s/n 00814 O 2011 HydroCAD Software Solutions LLC Page 10 Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.5 56 0.0180 0.14 Sheet Flow, Grass: Short n= 0.150 P2= 3.10" 0.5 44 0.0450 1.59 Sheet Flow, Smooth surfaces n= 0.011 P2= 3.10" 0.3 71 0.0350 3.80 Shallow Concentrated Flow, Paved Kv= 20.3 fps 7.3 171 Total Summary for Subcatchment SC2c: Subcatchment area#2c Runoff = 1.82 cfs @ 12.13 hrs, Volume= 0.146 af, Depth= 2.82`° Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Type III 24-hr 10 year storm Rainfall=4.50" Area (sf) CN Description 15,826 74 >75% Grass cover, Good, HSG C 11,328 98 Paved parking, HSG C 27,154 84 Weighted Average 15,826 58.28% Pervious Area 11,328 41.72% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 8.5 58 0.0100 0.11 Sheet Flow, Grass: Short n= 0.150 P2= 3.10" 0.6 42 0.0240 1.22 Sheet Flow, Smooth surfaces n= 0.011 P2= 3.10" 0.4 74 0.0200 2.87 Shallow Concentrated Flow, Paved Kv= 20.3 fps 9.5 174 Total Summary for Pond 1P: Subsurface infiltration facility Inflow Area = 1.505 ac, 51.87% Impervious, Inflow Depth = 3.00" for 10 year storm event Inflow = 5.07 cfs @ 12.10 hrs, Volume= 0.377 of Outflow = 0.07 cfs @ 22.33 hrs, Volume= 0.170 af, Aften= 99%, Lag= 614.1 min Discarded = 0.05 cfs @ 8.97 hrs, Volume= 0.162 of Primary - 0.02 cfs @ 22.33 hrs, Volume= 0.008 of Routing by Stor-Ind method, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Peak Elev= 146.59' @ 22.33 hrs Surf.Area= 0.171 ac Storage= 0.308 of Plug-Flow detention time= 1,028.7 min calculated for 0.170 of(45% of inflow) Center-of-Mass det. time= 911.5 min ( 1,720.9-809.3 ) 5659 POST Type ///24-hr 10 year storm Rainfall=4.50" Prepared by Meridian Associates Printed 11/7/2014 HydroCAD010.00 s/n 00814 ©2011 HydroCAD Software Solutions LLC Page 11 Volume Invert Avail.Storage Storage Description #1A 144.10' 0.142 of 40.17'W x 185.501 x 3.54'H Field A 0.606 of Overall - 0.251 of Embedded = 0.355 of x 40.0% Voids #2A 144.60' 0.251 of Cultec R-330XL x 208 Inside#1 Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.00'L = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.50'L with 1.50' Overlap Row Length Adjustment= +1.50' x 7.45 sf x 8 rows 0.393 of Total Available Storage Storage Group A created with Chamber Wizard Device Routing Invert Outlet Devices #1 Primary 146.50' 4.0" Round Culvert L= 18.5' CPP, square edge headwall, Ke= 0.500 Inlet/Outlet Invert= 146.50' / 143.70' S= 0.1514'/' Cc= 0.900 n= 0.012, Flow Area= 0.09 sf #2 Discarded 144.10' 0.270 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.05 cfs @ 8.97 hrs HW=144.14' (Free Discharge) t--2=Exfiitration (Exfiltration Controls 0.05 cfs) Primary OutFlowa Max=0.02 cfs @ 22.33 hrs HW=146.59' (Free Discharge) t-1=Culvert (Inlet Controls 0.02 cfs @ 1.02 fps) Summary for Pond 2P: Infiltration trench #1 Inflow Area = 1.321 ac, 4.24% Impervious, Inflow Depth = 1.97" for 10 year storm event Inflow = 1.93 cfs @ 12.32 hrs, Volume= 0.217 of Outflow = 1.93 cfs @ 12.33 hrs, Volume= 0.207 af, Atten= 0%, Lag= 0.4 min Discarded = 0.01 cfs @ 12.33 hrs, Volume= 0.017 of Primary = 1.92 cfs @ 12.33 hrs, Volume= 0.189 of Routing by Stor-Ind method, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Peak Elev= 156.18' @ 12.33 hrs Surf.Area= 0.027 ac Storage= 0.022 of Plug-Flow detention time= 105.2 min calculated for 0.207 of(95% of inflow) Center-of-Mass det. time= 80.0 min ( 938.1 - 858.0 ) Volume Invert Avail.Storage Storage Description #1 153.00" 0.020 of 4.00'W x 181.00'L x 3.00'H infiltration trench 0.050 of Overall x 40.0% Voids #2 156.00' 0.006 of 4.00'W x 90.00%x 0.50'H storage above infiltration trench Z=3.0 0.026 of Total Available Storage Device Routing Invert Outlet Devices #1 Primary 153.00' 12.0" Round Culvert L= 9.0' CPP, square edge headwall, Ke= 0.500 Inlet/Outlet Invert= 153.00'/ 152.30' S= 0.0778 '/' Cc= 0.900 n= 0.012, Flow Area= 0.79 sf #2 Device 1 156.00' 24.0" x 24.0" Horiz. Grate C= 0.600 Limited to weir flow at low heads 5659 POST Type 111 24-hr 10 year storm Rainfall=4.50" Prepared by Meridian Associates Printed 11/7/2014 HydroCADO 10.00 s/n 00814 O 2011 HydroCAD Software Solutions LLC Page 12 #3 Discarded 153.00' 0.270 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.01 cfs @ 12.33 hrs HW=156.18' (Free Discharge) t-3=Exfiltration (Exfiltration Controls 0.01 cfs) Primary OutFlow Max=1.92 cfs @ 12.33 hrs HW=156.18' (Free Discharge) t-1=Culvert (Passes 1.92 cfs of 6.19 cfs potential flow) '-2=Grate (Weir Controls 1.92 cfs @ 1.37 fps) Summary for Pond 3P: Infiltration trench #2 Inflow Area= 0.247 ac, 22.33% Impervious, Inflow Depth = 2.38" for 10-year storm event Inflow = 0.65 cfs @ 12.11 hrs, Volume= 0.049 of Outflow = 0.47 cfs @ 12.25 hrs, Volume= 0.040 af, Atten= 28%, Lag= 8.5 min Discarded = 0.01 cfs @ 12.24 hrs, Volume= 0.015 of Primary = 0.46 cfs @ 12.25 hrs, Volume= 0.025 of Routing by Stor-Ind method, Time Span= 0.00-50.01 hrs, dt=0.03 hrs Peak Elev= 156.07' @ 12.25 hrs Surf.Area= 0.022 ac Storage= 0.018 of Plug-Flow detention time= 419.6 min calculated for 0.040 of(82% of inflow) Center-of-Mass det. time= 346.8 min ( 1,177.2-830.4) Volume Invert Avail.Storage Storage Description #1 153.00' 0.017 of 4.00'W x 157.00'L x 3.00'H infiltration trench 0.043 of Overall x 40.0% Voids #2 156.00' 0.005 of 4.00'W x 78.00'L x 0.50'H storage above infiltration trench Z=3.0 0.022 of Total Available Storage Device Routing Invert Outlet Devices #1 Primary 153.00' 12.0" Round Culvert L= 11.0' CPP, square edge headwall, Ke= 0.500 Inlet/Outlet Invert= 153.00'/ 151.90' S= 0.1000 '/' Cc= 0.900 n= 0.012, Flow Area= 0.79 sf #2 Device 1 156.00' 24.0"x 24.0" Horiz. Grate C= 0.600 Limited to weir flow at low heads #3 Discarded 153.00' 0.270 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.01 cfs @ 12.24 hrs HW=156.06' (Free Discharge) L3=Exfiltration (Exfiltration Controls 0.01 cfs) Primary OutFlow Max=0.40 cfs @ 12.25 hrs HW=156.06' (Free Discharge) t-1=Culvert (Passes 0.40 cfs of 6.05 cfs potential flow) L2=Grate (Weir Controls 0.40 cfs @ 0.81 fps) 5659 POST Type 11124-hr 10 year storm Rainfall=4.50" Prepared by Meridian.Associates Printed 11/7/2014 HydroCADO 10,00 s/n 00814 ©2011 HydroCAD Software Solutions LLC Page 13 Summary for Link DP1: Post development (Discharge point #1) Inflow Area = 2.431 ac, 36.05% Impervious, Inflow Depth = 0.85" for 10 year storm event Inflow = 1.89 cfs @ 12.17 hrs, Volume= 0.172 of Primary = 1.89 cfs @ 12.17 hrs, Volume= 0.172 af, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Summary for Link DP2: Post development (Discharge point#2) Inflow Area = 2.191 ac, 16.94% Impervious, Inflow Depth = 1.97" for 10 year storm event Inflow = 3.48 cfs @ 12.25 hrs, Volume= 0.360 of Primary = 3.48 cfs @ 12.25 hrs, Volume= 0.360 af, Atten=0%, Lag= 0.0 min Primary outflow= Inflow, Time Span= 0.00-50.01 hrs, dt=0.03 hrs PROPOSED CONDITIONS 100-YEAR 24-HOUR STORM EVENT ANALYSIS 5659 POST Type 111 24-hr 100 year storm Rainfall=6.50" Prepared by Meridian Associates Printed 11/7/2014 HydroCADO 10.00 s/n 00814 ©2011 HydroCAD Software Solutions LLC Page 14 Summary for Subcatchment SC1a: Subcatchment area#1a Runoff = 8.09 cfs @ 12.10 hrs, Volume= 0.613 af, Depth= 4.89" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Type III 24-hr 100 year storm Rainfall=6.50" Area (sf) CN Description 17,994 98 Paved parking, HSG C 19,289 74 >75% Grass cover, Good, HSG C 15,825 98 Roofs, HSG C 191 98 Retaining wall, HSG C 12,268 70 Woods, Good, HSG C 65,567 86 Weighted Average 31,557 48.13% Pervious Area 34,010 51.87% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.8 80 0.0490 0.23 Sheet Flow, Grass: Short n= 0.150 P2= 3.10" 0.2 99 0.0480 7.73 38.63 Trap/Vee/Rett Channel Flow, Bot.W=2.00' D=1.00' Z= 3.0 '/' Top.W=8.00' n= 0.030 Short grass 0.9 258 0.0100 4.54 3.56 Pipe Channel, 12.0" Round Area= 0.8 sf Perim= 3.1' r= 0.25' n= 0.013 Corrugated PE, smooth interior 6.9 437 Total Summary for Subcatchment SCI b: Subcatchment area#1 b Runoff = 3.42 cfs @ 12.16 hrs, Volume= 0.294 af, Depth= 3.82" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Type 111 24-hr 100 year storm Rainfall=6.50" Area (sf) CN Description 3,383 98 Paved parking, HSG C 781 98 Roofs, HSG C 36,170 74 >75% Grass cover, Good, HSG C 40,334 76 Weighted Average 36,170 89.68% Pervious Area 4,164 10.32% Impervious Area 5659 POST Type 111 24-hr 100 year storm Rainfall=6.50" Prepared by Meridian Associates Printed 11/7/2014 HydroCADO 10.00 s/n 00814 ©2011 HydroCAD Software Solutions LLC Page 15 To Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.4 100 0.0600 0.26 Sheet Flow, Grass: Short n= 0.150 P2= 3.10" 4.3 277 0.0230 1.06 Shallow Concentrated Flow, Short Grass Pasture Kv= 7.0 fps 1.1 207 0.0050 3.21 2.52 Pipe Channel, 12.0" Round Area= 0.8 sf Perim= 3.1' r=0.25' n= 0.013 Corrugated PE, smooth interior 11.8 584 Total Summary for Subcatchment SCa: Subcatchment area#2a Runoff = 3.58 cfs @ 12.31 hrs, Volume= 0.397 af, Depth= 3.61" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Type III 24-hr 100 year storm Rainfall=6.50" Area(sf) CN Description 2,438 98 Paved parking, HSG C 42,735 74 >75% Grass cover, Good, HSG C 12,365 70 Woods, Good, HSG C 57,538 74 Weighted Average 55,100 95.76% Pervious Area 2,438 4.24% Impervious Area To Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 21.8 100 0.0200 0.08 Sheet Flow, Woods: Light underbrush n= 0.400 P2= 3.10" 0.7 43 0.0400 1.00 Shallow Concentrated Flow, Woodland Kv= 5.0 fps 22.5 143 Total Summary for Subcatchment SC2b: Subcatchment area#2b Runoff = 1.13 cfs @ 12.10 hrs, Volume= 0.085 af, Depth= 4.13" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Type III 24-hr 100 year storm Rainfall=6.50" Area (sf) CN Description 8,347 74 >75% Grass cover, Good, HSG C 2,400 98 Paved parking, HSG C 10,747 79 Weighted Average 8,347 77.67% Pervious Area 2,400 22.33% Impervious Area 5659 POST Type Ill 24-hr 100 year storm Rainfall=6.50" Prepared by Meridian Associates Printed 11/7/2014 HydroCADO 10,00 s/n 00814 ©2011 HydroCAD Software Solutions LLC Page 16 Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.5 56 0.0180 0.14 Sheet Flow, Grass: Short n= 0.150 P2= 3.10" 0.5 44 0.0450 1.59 Sheet Flow, Smooth surfaces n= 0.011 P2= 3.10" 0.3 71 0.0350 3.80 Shallow Concentrated Flow, Paved Kv= 20.3 fps 7.3 171 Total Summary for Subcatchment SC2c: Subcatchment area#2c Runoff = 2.97 cfs @ 12.13 hrs, Volume= 0.242 af, Depth= 4.67" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Type III 24-hr 100 year storm Rainfall=6.50" Area (sf) CN Description 15,826 74 >75% Grass cover, Good, HSG C 11,328 98 Paved parking, HSG C 27,154 84 Weighted Average 15,826 58.28% Pervious Area 11,328 41.72% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 8.5 58 0.0100 0.11 Sheet Flow, Grass: Short n= 0.150 P2= 3.10" 0.6 42 0.0240 1.22 Sheet Flow, Smooth surfaces n= 0.011 P2= 3.10" 0.4 74 0.0200 2.87 Shallow Concentrated Flow, Paved Kv= 20.3 fps 9..5 174 Total Summary for Pond 1 P: Subsurface infiltration facility Inflow Area = 1.505 ac, 51.87% Impervious, Inflow Depth = 4.89" for 100 year storm event Inflow = 8.09 cfs @ 12.10 hrs, Volume= 0.613 of Outflow = 0.44 cfs @ 14.20 hrs, Volume= 0.401 af, Atten= 95%, Lag= 126.0 min Discarded = 0.05 cfs @ 7.47 hrs, Volume= 0.168 of Primary = 0.40 cfs @ 14.20 hrs, Volume= 0.233 of Routing by Stor-Ind method, Time Span=0.00-50.01 hrs, dt= 0.03 hrs Peak Elev= 147,56' @ 14.20 hrs Surf.Area= 0.171 ac Storage= 0.388 of Plug-Flow detention time= 598.3 min calculated for 0.401 of(65% of inflow) Center-of-Mass det. time= 500.4 min ( 1,296.1 - 795.7 ) 5659 POST Type 11124-hr 100 year storm Rainfall=6.50" Prepared by Meridian Associates Printed 11/7/2014 HydroCADO 10.0.0 s/n 00814 ©2011 HydroCAD Software Solutions LLC Page 17 Volume Invert Avail.Storage Storage Description #1A 144.10' 0.142 of 40.17'W x 185.501 x 3.54'H Field A 0.606 of Overall - 0.251 of Embedded = 0.355 of x 40.0% Voids #2A 144.60' 0.251 of Cultec R-330XL x 208 Inside#1 Effective Size= 47.8"W x 30.0"H => 7.45 sf x 7.001 = 52.2 cf Overall Size= 52.0"W x 30.5"H x 8.501 with 1.50' Overlap Row Length Adjustment= +1.50'x 7.45 sf x 8 rows 0.393 of Total Available Storage Storage Group A created with Chamber Wizard Device Routing Invert Outlet Devices #1 Primary 146.50' 4.0" Round Culvert L= 18.5' CPP, square edge headwall, Ke= 0.500 Inlet/Outlet Invert= 146.50'/ 143.70' S= 0.1514'/' Cc=0.900 n= 0.012, Flow Area= 0.09 sf #2 Discarded 144.10' 0.270 inlhr Exfiltration over Surface area Discarded OutFlo Max=0.05 cfs @ 7.47 hrs HW=144.14' (Free Discharge) t-2=Exfiltration (Exfiltration Controls 0.05 cfs) rimary OutFlow Max=0.40 cfs @ 14.20 hrs HW=147.56' (Free Discharge) 1=Culvert (Inlet Controls 0.40 cfs @ 4.56 fps) Summary for Pond 2P: Infiltration trench #1 Inflow Area = 1.321 ac, 4.24% Impervious, Inflow Depth = 3.61" for 100 year storm event Inflow = 3.58 cfs @ 12.31 hrs, Volume= 0.397 of Outflow = 3.58 cfs @ 12.32 hrs, Volume= 0.387 af, Atten= 0%, Lag= 0.4 min Discarded = 0.01 cfs @ 12.32 hrs, Volume= 0.018 of Primary = 3.57 cfs @ 12.32 hrs, Volume= 0.369 of Routing by Stor-Ind method, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Peak Elev= 156.26' @ 12.32 hrs Surf.Area=0.028 ac Storage= 0.023 of Plug-Flow detention time= 61.3 min calculated for 0.387 of(97% of inflow) Center-of-Mass det. time= 46.0 min ( 886.5 - 840.5 ) Volume Invert Avail.Storage Storage Description #1 153.00' 0.020 of 4.00'W x 181.00'L x 3.00'H infiltration trench 0.050 of Overall x 40.0% Voids #2 156.00' 0.006 of 4.00'W x 90.00'L x 0.50'H storage above infiltration trench Z=3.0 0.026 of Total Available Storage Device Routing Invert Outlet Devices #1 Primary 153.00' 12.0" Round Culvert L= 9.0' CPP, square edge headwall, Ke= 0.500 Inlet/Outlet Invert= 153.00'/ 152.30' S=0.0778 '/' Cc= 0.900 n= 0.012, Flaw Area= 0.79 sf #2 Device 1 156.00' 24.0"x 24.0" Horiz. Grate C= 0.600 Limited to weir flow at low heads 5659 POST Type ///24-hr 900 year storm Rainfall=6.50" Prepared by Meridian Associates Printed 11/7/2014 HydroCAD® 10.00 s/n 00814 ©2011 HydroCAD Software Solutions LLC Page 18 #3 Discarded 153.00' 0.270 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.01 cfs @ 12.32 hrs HW=156.26' (Free Discharge) t-3=Exfiltration (Exfiltration Controls 0.01 cfs) Primary OutFlow Max=3.56 cfs @ 12.32 hrs HW=156.26' (Free Discharge) t-1=Culvert (Passes 3.56 cfs of 6.29 cfs potential flow) t-2=Grate (Weir Controls 3.56 cfs @ 1.68 fps) Summary for Pond 3P: Infiltration trench #2 Inflow Area = 0.247 ac, 22.33% Impervious, Inflow Depth = 4.13" for 100 year storm event Inflow = 1.13 cfs @ 12.10 hrs, Volume= 0.085 of Outflow = 1.13 cfs @ 12.11 hrs, Volume= 0.076 af, Atten= 0%, Lag= 0.5 min Discarded = 0.01 cfs @ 12.11 hrs, Volume= 0.016 of Primary = 1.12 cfs @ 12.11 hrs, Volume= 0.060 of Routing by Stor-Ind method, Time Span= 0.00-50.01 hrs, dt= 0.03 hrs Peak Elev= 156.12' @ 12.11 hrs Surf.Area= 0.023 ac Storage= 0.018 of Plug-Flow detention time=238.4 min calculated for 0.076 of(89% of inflow) Center-of-Mass det. time= 189.2 min ( 1,003.8 - 814.6 ) Volume Invert Avail.Storage Storage Description #1 153.00' 0.017 of 4.00'W x 157.00'L x 3.00'H infiltration trench 0.043 of Overall x 40.0% Voids #2 156.00' 0.005 of 4.00'W x 78.00'L x 0.50'H storage above infiltration trench Z=3.0 0.022 of Total Available Storage Device Routing Invert Outlet Devices #1 Primary 153.00' 12.0" Round Culvert L= 11.0' CPP, square edge headwall, Ke= 0.500 Inlet/Outlet Invert= 153.00'/ 151.90' S= 0.10007' Cc= 0.900 n= 0.012, Flow Area= 0.79 sf #2 Device 1 156.00' 24.0" x 24.0" Horiz. Grate C= 0.600 Limited to weir flow at low heads #3 Discarded 153.00' 0.270 in/hr Exfiltration over Surface area Discarded OutFlow Max=0.01 cfs @ 12.11 hrs HW=156.12' (Free Discharge) L3=Exfiltration (Exfiltration Controls 0.01 cfs) Primary OutFlow Max=1.10 cfs @ 12.11 hrs HW=156.12' (Free Discharge) t-1=Culvert (Passes 1.10 cfs of 6.12 cfs potential flow) t -2=Grate (Weir Controls 1.10 cfs @ 1.14 fps) 5659 POST Type ///24-hr 100 year storm Rainfall=6.50" Prepared by Meridian Associates Printed 11/7/2014 HydroCADO 10.00 s/n 00814 ©2011 HydroCAD Software Solutions LLC Page 19 Summary for Link DP1 a Post development (Discharge point #1) Inflow Area = 2.431 ac, 36.05% Impervious, Inflow Depth = 2.60" for 100 year storm event Inflow = 3.42 cfs @ 12.16 hrs, Volume= 0.527 of Primary = 3.42 cfs @ 12.16 hrs, Volume= 0.527 af, Atten= 0%, Lag= 0.0 min Primary outflow= Inflow, Time Span= 0.00-50.01 hrs, dt=0.03 hrs Summary for Link DP2: Post development (Discharge point#2) Inflow Area = 2.191 ac, 16.94% Impervious, Inflow Depth = 3.68" for 100 year storm event Inflow = 6.35 cfs @ 12.16 hrs, Volume= 0.671 of Primary = 6.35 cfs @ 12.16 hrs, Volume= 0.671 af, Atten= 0%, Lag=4.0 min Primary outflow= Inflow, Time Span= 0.00-50.01 hrs, dt=0.03 hrs PROPOSE® STORM DRAINANALYSIS 100-YEAR STORM EVENT HydraoW Storm Sewers Extension for Autodesk(g) AutoCAD(g) Civil ME) Plan Ouf I Z . Z . \ - / / / . � . � . / / / . Z / / } 12 . � Project File: STORM DRAIN tkm Number @ lines:6 ok 11 f712014 Storm Sewm wan Storm Sewer Inventory Report Page Line Alignment Flow Data Physical Data Line ID No. Dnstr Line Defl Junc Known Drng Runoff Inlet Invert Line Invert Line Line N J-Loss Inlet/ Line Length angle Type Q Area Coeff Time EI Dn Slope EI Up Size Shape Value Coeff Rim EI (deg) (cfs) (ac) (C) (min) (ft) N (ft) (in) (n) (K) (ft) 1 End 89.966 118.91 MH 0.00 0.00 0.00 0.0 144.60 1.11 145.60 12 Cir 0.012 1,00 149.00 PDMH3-INFILTRATION 2 1 50.287 -31.123 MH 0.00 0.00 0.00 0.0 145.80 0.99 146.30 12 Cir 0.012 0.64 150.00 PDMH4-PDMH3 3 2 112.36 36.349 Grate 0.00 0.36 0.35 5.0 146.50 0.98 147.60 12 Cir 0.012 1.00 150.50 PCB3-PDMH4 4 1 8.458 -88.750 Grate 0.00 0.21 0.50 5.0 145.80 1.18 145.90 12 Cir 0.012 1.00 148.90 PCB5-PDMH3 5 2 9.309 -25.389 Grate 0.00 0.28 0.71 5.0 146.50 1.07 146.60 12 Cir 0.012 1,00 150.00 PCB4-PDMH4 6 1 39.636 10.774 None 0.00 0.36 0.90 5.0 146.60 1.01 147.00 12 Cir 0.012 1.00 151.00 ROOF DRAIN-PDMH3 Project File: STORM DRAIN 1.stm Number of lines:6 Date: 11/7/2014 Storm Sewers v10.30 Storm Sewer Summary Report Page, Line Line ID Flow Line Line Line Invert Invert Line HGL HGL Minor HGL Dns Junction No. rate Size shape length EL Dn EL Up Slope Down Up loss Junct Line Type (cfs) (in) (ft) (ft) (ft) N (ft) (ft) (ft) (ft) No. 1 PDMH3-INFILTRATION 5.17 12 Cir 89.966 144.60 145.60 1.112 145.60* 147.22* 0.67 147.89 End Manhole 2 PDMH4-PDMH3 2.25 12 Cir 50.287 145.80 146.30 0.994. 147.89* 148.06* 0.08 148.14 1 Manhole 3 PCB3-PDMH4 0.93 12 Cir 112.365 146.50 147.60 0.979 148.14 148.21 0.05 14827 2 Grate 4 PCB5-PDMH3 0.78 12 Cir 8.458 145.80 145.90 1.182 147.89* 147.89* 0.02 147.91 1 Grate 5 PCB4-PDMH4 1.47 12 Cir 9.309 146.50 146.60 1.074 148.14* 148.16* 0.05 14821 2 Grate 6 ROOF DRAIN-PDMH3 2.40 12 Cir 39.636 146.60 147.00 1.009 147.89 148.00 0.14 148.14 1 None Project File: STORM DRAIN 1.stm Number of lines:6 Run Date: 11/7!2014 NOTES: Return period= 100 Yrs. ;*Surcharged(HGL above crown). ° Storm Sewers 00.30 Storm Sewer Tabulation Pagel Station Len Drng Area Rnoff Area x C Tc Rain Total Cap Vel Pipe Invert Elev HGL Elev Grnd/Rim Elev Line ID coeff (1) flow full Line To Incr Total Incr Total Inlet Syst Size Slope Dn Up Dn Up Dn Up Line (ft) (ac) (ac) (C) (min) (min) (in/hr) (cfs) (cfs) (ft/s) (in) (%) (ft) (ft) (ft) (ft) (ft) (ft) 1 End 89.966 0.00 1.21 0.00 0.00 0.75 0.0 6.9 6.9 5.17 4.07 6.58 12 1.11 144.60 145.60 145.60 147.22 145.60 149.00 PDMH3-INFILTR 2 1 50.287 0.00 0.64 0.00 0.00 0.32 0.0 6.6 6.9 2.25 3.85 2.87 12 0.99 145.80 146.30 147.89 148.06 149.00 150.00 PDMH4-PDMH3 3 2 12.36E 0.36 0.36 0.35 0.13 0.13 5.0 5.0 7.4 0.93 3.82 1.52 12 0.98 146.50 147.60 148.14 148.21 150.00 150.50 PCB3-PDMH4 4 1 8.458 0.21 0.21 0.50 0.11 0.11 5.0 5.0 7.4 0.78 4.19 0.99 12 1.18 145.80 145.90 147.89 147.89 149.00 148.90 PCB5-PDMH3 5 2 9.309 0.28 0.28 0.71 0.20 0.20 5.0 5.0 7.4 1.47 4.00 1.87 12 1.07 146.50 146.60 148.14 '148.16 150.00 150.00 PCB4-PDMH4 6 1 39.636 0.36 0.36 0.90 0.32 0.32 5.0 5.0 7.4 2.40 3.88 3.05 12 1.01 146.60 147.00 147.89 148.00 149.00 151.00 ROOF DRAIN-P Project File: STORM DRAIN 1.stm Number of lines:6 Run Date: 11/7/2014 NOTES:Intensity=44.87/(inlet time+10.30)^0.66; Return period=Yrs. 100 c=cir e=ellip b=box Storm Sewers 00.30 Inlet Report Page 1 Line Inlet ID Q= Q Q Q Junc Curb Inlet Grate Inlet Gutter Inlet Byp No CIA carry capt Byp Type Line Ht L Area L W So W Sw Sx n Depth Spread Depth Spread Depr No (cfs) (cfs) (cfs) (cfs) (in) (ft) (sqft) (ft) (ft) (ft/ft) (ft) (ftift). (ft/ft) (ft) (ft) (ft) (ft) (in) 1 PDMH3 0.00 0.00 0.00 0.00 MH 0.0 0.00 0.00 0.00 0.00 sag 0.00 0.000 0.000 0.000 0.00 0.00 0.00 0.00 0.0 Off 2 PDMH4 0.00 0.00 0.00 0.00 MH 0.0 0.00 0.00 0.00 0.00 Sag 0.00 0.000 0.000 0.000 0.00 0.00 0.00 0.00 0.0 Off 3 PCB3 0.93 0.00 0.93 0.00 Grate 0.0 0.00 4.00 2.00 2.00 Sag 2.00 0.050 0.020 0.000 0.19 6.44 0.19 6.44 0.0 Off 4 PC65 0.78 0.00 0.78 0.00 Grate 0.0 0.00 4.00 2.00 2.00 Sag 2.00 0.050 0.020 0.000 0.17 5.64 0.17 5.64 0.0 if 5 PCB4 1.47 0.00 1.47 0.00 Grate 0.0 0.00 4.00 2.00 2.00 Sag 2.00 0.050 0.020 0.000 0.24 8.91 0.24 8.91 0.0 Off 6 ROOF DRAIN 2.40 0.00 0.00 2.40 None 0.0 0.00 0.00 0.00 0.00 Sag 0.00 0.000 0.000 0.000 0.00 0.00 0.00 0.00 0.0 Off Project File: STORM DRAIN 1.stm Number of lines:6 Run Date: 11/7/2014 NOTES: Inlet N-Values=0.016;Intensity=44.87/(Inlet time+10.30)^0.66; Return period=100 Yrs. ; *Indicates Known Q added.All curb inlets are Horiz throat. Storm Sewers v10.30 Hydraflow Storm Sewers Extension for Autodesk@ AutoCADO Civil 3®® Plan f� Project File: STORM DRAIN 2.stm Number of lines: 1 Date:11/7/2014 Storm Sewers v10.30 Storm Sewer Inventory Report Pagel Line Alignment Flow Data Physical Data Line ID No. Dnstr Line Defl Junc Known Drng Runoff Inlet Invert Line Invert Line Line N J-Loss Inlet( Line Length angle Type Q Area Coeff Time EI Dn Slope EI Up Size Shape Value Coeff Rim EI No. (ft) (deg) (cfs) (ac) (C) (min) (ft) N (ft) (in) (n) (K) (ft) 1 End 13.000 152.22C Grate 0.00 0.28 0.83 5.0 144.60 9.23 145.80 12 Cir 0.012 1.00 148.80 PCB6-INFILTRATION Project File: STORM DRAIN 2.stm Number of lines:1 Date: 11/7/2014 Storm Sewers v10.30 Storm Sewer Summary Report Pagel Line Line ID Flow Line Line Line Invert Invert Line HGL HGL Minor HGL Dns Junction No. rate Size shape length EL Dn EL Up Slope Down Up loss Junct Line Type (cfs) (in) (ft) (ft) (ft) N (ft) (ft) (ft) (ft) No. 1 PC136-INFILTRATION 1.72 12 Cir 13.000 144.60 145.80 9.231 144.86 146.36 n/a 146.36 End Grate I Project File: STORM DRAIN 2.stm Number of lines: 1 Run Date:11/7/2014 NOTES: Return period=100 Yrs. Storm Severs 00.30 Storm Sewer Tabulation Pagel Station Len Drng Area Rnoff Area x C Tc Rain Total Cap Vel Pipe Invert Elev HGL Elev Grnd i Rim Elev Line ID coeff (1) flow full Line To Incr Total Incr Total Inlet Syst Size Slope Dn Up Dn Up Dn Up Line (ft) (ac) (ac) (C) (min) (min) (in/hr) (cfs) (cfs) (ft/s) (in) (%j (ft) (ft) (ft) (ft) (ft) (ft) 1 End 13.000 0.28 0.28 0.83 0.23 0.23 5.0 5.0 7.4 1.72 11.72 7.24 12 9.23 144.60 145.80 144.86 146.36 145.60 148.80 PCB6-INFILTRA i Project File: STORM DRAIN 2.stm Number of lines: 1 Run Date: 11/7/2014 NOTES:Intensity=44.87/(Inlet time+10.30)^0.66; Return period=Yrs. 100 c=cir e=eliip b=box Storm Sewers 00.30 Inlet Report Pagel Line Inlet ID Q= Q Q Q Junc Curb Inlet Grate Inlet Gutter Inlet Byp No CIA carry capt Byp Type Line Ht L Area L W So W SW Sx n Depth Spread Depth Spread Depr No (cfs) (cfs) (cfs) (cfs) (in) (ft) (sqft) (ft) (ft) (ft/ft) (ft) (ft/ft) (ft/ft) (ft) (ft) (ft) (ft) (in) 1 PCB6 1.72 0.00 0.51 1.21 Grate 0.0 0.00 0.00 2.00 2.00 0.010 2.00 0.005 0.005 0.013 0.10 19.62 0.10 19.62 0.0 off i Project File: STORM DRAIN 2.stm Number of lines: 1 Run Date: 11/7/2014 NOTES: Inlet N-Values=0.016;Intensity=44.87/(Inlet time+10.30)^0.66; Return period=100 Yrs.; *Indicates Known Q added.All curb inlets are Horiz throat_ Storm Sewers v10.30 APPENDIX Hydrologic Soil Group—Essex County,Massachusetts,Northern Part (Lawrence airport hangar) io 42'43'UN 326000 326100 326200 326300 326400 326500 326600 326700 326800 326900 42'43 O"N J. 4Z'42!39"N 326000 326100 326200 326500 326600 326700 326800 326900 42*4Z 39N N Map Scale:1:4,600 if printed on A landscape(11"x 8.5)sheet NMeters ZD 0 50 100 200 300 0200 _�Feet 400 800 1200 Map projection:Web Mercator Comer ooDrchnates:WGSM Edge tics:UTM Zone 19N WGS84 USDA Natural Resources Web Soil Survey Conservation Service 9110/2014 National Cooperative Soil Survey Page 1 of 4 Hydrologic Soil Group—Essex County,Massachusetts,Northern Part (Lawrence airport hangar) MAP LEGEND MAP INFORMATION Area of Interest(AOI) 0 C The soil surveys that comprise your AOI were mapped at 1:15,800. Area of Interest(AOI) 13 C/D Soils Warning:Soil Map may not be valid at this scale. D Soil Rating Polygons Enlargement of maps beyond the scale of mapping can cause 0 A p Not rated or not available misunderstanding of the detail of mapping and accuracy of soil line Water Features placement.The maps do not show the small areas of contrasting 0 A/D Streams and Canals soils that could have been shown at a more detailed scale. B Transportation Please rely on the bar scale on each map sheet for map BID Rails measurements. 0 C 0%0 Interstate Highways Source of Map: Natural Resources Conservation Service 0 C/D Web Soil Survey URL: http://websoilsurvey.nres.usda.gov US Routes Coordinate System: Web Mercator(EPSG:3857) 0 D Major Roads Maps from the Web Soil Survey are based on the Web Mercator 0 Not rated or not available Local Roads projection,which preserves direction and shape but distorts Soil Rating Lines distance and area.A projection that preserves area,such as the Background Albers equal-area conic projection,should be used if more accurate AWA Aerial Photography calculations of distance or area are required. AID This product is generated from the USDA-NRCS certified data as of B the version date(s)listed below. B/D Soil Survey Area: Essex County,Massachusetts,Northern Part Survey Area Data: Version 9,Dec 17,2013 Soil map units are labeled(as space allows)for map scales 1:50,000 „ter C/D or larger. D Date(s)aerial images were photographed: Mar 30,2011—May 1, r Not rated or not available 2011 Soil Rating Points The orthophoto or other base map on which the soil lines were A compiled and digitized probably differs from the background 13 imagery displayed on these maps.As a result,some minor shifting A/D of map unit boundaries may be evident. 13 e B/D UsDA Natural Resources Web Soil Survey 9/10/2014 Conservation Service National Cooperative Soil Survey Page 2 of 4 Hydrologic Soil Group—Essex County,Massachusetts,Northern Part Lawrence airport hangar Hydrologic Soil Group Hydrologic Soil Group—Summary by Map Unit—Essex County,Massachusetts,Northern Part(MA605) Map unit symbol Map unit name Rating Acres in AOI Percent of AOI 1 Water 0.01 0.0%1 6A "-------- - ;Scarboro mucky fine I D -"---- I 0.66 ---------"0.6°/% sandy loam,0 to 1 j ----- ------ --- ------ j percent slopes 52A Freetown muck,0 to 1 1 A/D 0.5 0.6% percent slopes 1260A Sudbury fine sandy —TB ---- —--- 1.1 --- ----- 1.2%° jloam,0 to 3 percent slopes j 3051 i Paxton fine sandy loam, C 21.41 24.4% 3 to 8 percent slopes 305C Paxton fine sandy loam, C — I 0.5 0.6%1 8 to 15 percent slopes 3108 Woodbridge fine sandy 1 C 3.81 4.3°/%I loam,3 to 8 percent I j slopes 311B Woodbridge fine sand C o loam,0 to 8 percent j slopes,very stony 421 B Canton fine sandy loam, �B 1.6 1, — 1.9%1 3 to 8 percent slopes, very stony 602 Urban land 52.3 59.7% 71513 Ridgebury and Leicester C 5.3 6.1 fine sandy foams,3 to 8 percent slopes, i extremely stony Totals for Area of Interest 87.61 100.0%1 USDA Natural Resources Web Soil Survey 9/10/2014 Conservation Service National Cooperative Soil Survey Page 3 of 4 Hydrologic Soil Group—Essex County,Massachusetts,Northern Part Lawrence airport hangar 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(A/D, B/D, and C/D).The groups are defined as follows: Group A. Soils having a high infiltration rate(low runoff potential)when thoroughly wet.These consist mainly of deep,well drained to excessively drained sands or gravelly sands.These soils have a high rate of water transmission. Group B. Soils having a moderate infiltration rate when thoroughly wet.These consist chiefly of moderately deep or deep,moderately well drained or well drained soils that have moderately fine texture to moderately coarse texture.These soils have a moderate rate of water transmission. Group C. Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils having a layer that impedes the downward movement of water or soils of moderately fine texture or fine texture.These soils have a slow rate of water transmission. Group D. Soils having a very slow infiltration rate(high runoff potential)when thoroughly wet.These consist chiefly of clays that have a high shrink-swell potential, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission. If a soil is assigned to a dual hydrologic group(A/D, B/D, or C/D), the first letter is for drained areas and the second is for undrained areas.Only the soils that in their natural condition are in group D are assigned to dual classes. Rating Options Aggregation Method: Dominant Condition Component Percent Cutoff. None Specified Tie-break Rule: Higher USDA Natural Resources Web Soil Survey 9/10/2014 21101 Conservation Service National Cooperative Soil Survey Page 4 of 4