The URL can be used to link to this page

Home My WebLink AboutJuly 2024 - Stormwater Report - - 0 GREAT POND ROAD STORMWATER REPORT NORTH LAKE COCHICHEWICK BOAT LAUNCH Town of North Andover, MA J uly zoza ENVIRONMENTAL PARTNERS ENVIRONMENTAL &�a PARTNERS MEMORANDUM To Town of North Andover- Project Group From Ryan Paul, PE, CFM - Environmental Partners Jamie Veillette, EIT- Environmental Partners CC John Borgesi, PE,Town Engineer- North Andover Department of Public Works Jean Enright, Planning Director-Town of North Andover Peter Boynton, Planning Board and Harbormaster-Town of North Andover Amy Maxner, Conservation Administrator-Town of North Andover John Weir, Fire Chief-Town of North Andover Ted Kelley- Project Proponent Robert Rafferty, PE - Environmental Partners Subject Stormwater Report North Lake Cochichewick Boat Launch Town of North Andover, MA On behalf of the Town of North Andover, Environmental Partners (EP) has prepared this stormwater management report in support of design, and local and state permitting efforts for the redevelopment of the North Lake Cochichewick Boat Launch. This report has been prepared in accordance with the requirements of Massachusetts Wetland Regulations - 310 CM 10.00, Massachusetts Stormwater Management Standards, and The Town of North Andover Wetland Protection Regulations and Town of North Andover Planning Board Regulations. m m, mi o �� mitt III II„ it j e ct The North Lake Cochichewick Boat Launch (herein referred to as the Boat Launch) is located on the northern end of North Lake Cochichewick(the Lake), directly across from House #1939 on Great Pond Road in North Andover, MA. The Site,which is owned by the Town and is documented in Book Page of 689, Page 147, occupies the former extents of the North Sewer Pump Station that has since been demolished. Initially constructed to serve municipal needs during the operational period of the Old North Pump Station,the Boat Launch has since evolved into a valuable asset for the community. It now supports a range of recreational activities, including non-motorized boating during the spring, summer, and fall seasons.Additionally, the Boat Launch plays a critical role in emergency response, providing access for the North Andover Fire Department's boat in the event of water-based emergencies. The current configuration of the Boat Launch includes a paved driveway apron, a dirt/gravel driveway, lawn areas, moveable boat racks, and a bituminous concrete boat launch that extends into the Lake.The existing retaining wall, constructed from cobble and concrete, is failing and is currently being supported by overgrown tree roots.Additionally, portions of the asphalt launch have deteriorated into the Lake. During the conceptual design phase,the Project was reviewed by both the Conservation Commission and the Planning Board. The Conservation Commission recommended several design modifications, including the ability for vehicles to reverse towards the launch,the incorporation of "living wall"for the retaining structure, and the integration of a fishing line disposal facility. Concurrently,the Planning Board suggested adjustments to restrict trailers from directly accessing the launch by incorporating a narrower entrance and physical barriers to limit vehicle entry. In the 75% design phase,feedback from both the Conservation Commission and the Planning Board was carefully reviewed.Their recommendations were integrated into the design where feasible, while some suggestions were assessed as impractical for the Site. Comprehensive details of these considerations and the resulting key design decisions are documented in the Alternatives Analysis included in Appendix C of the Notice of Intent Application, submitted separately from this report. The design is currently progressing through the permitting phase. The primary objectives of the Project are to enhance the Site functionality and safety through practical, low-impact design methods while also contributing to the beautification of the area. The proposed site development includes the reconstruction of the existing boat launch, a new mechanically stabilized earth (MSE) concrete block retaining wall, permeable paver driveways and parking areas, recreational lawn space, site appurtenances, stormwater bioretention areas, native tree plantings, and native shrub plantings. The proposed stormwater management system consists of two (2) bioretention areas, an overflow structure, conveyance piping, and riprap-lined Swale to manage runoff quality and quantity. Design plans for the project, including detailed sequence of construction activities, are provided in Attachment 1. m mom I I m , N mlum, . mm.!ry Mod&�� Existing and proposed drainage calculations were prepared utilizing HydroCAD Version 10.20, design rainfall data from NOAA Atlas 14, and accepted engineering design practices. HydroCAD is a computer aided design program for modeling the hydrology and hydraulics(H-H) of stormwater runoff and conveyance. The software computes storm runoff volume, peak rate of discharge, ii1-i v p a Irt- s m c o ii hydrographs, storage volumes using TR-20 and TR-55 methodologies. HydroCAD Reports for both existing and proposed conditions for the 2-, 10-, and 1 00-year 24-hour storm events are provided in Attachments 6 and 7. Assa t„i irTI p t iii it--i s ain d III........ii iii'--i ii t a t iii o iin-,1 Prior to building the model,the following assumptions were made: • The project is considered a redevelopment project. • The watershed area for hydrologic analysis and BMP sizing calculations includes the site area and all upgradient areas from which stormwater runoff flows onto the site; • Per North Andover Stormwater Regulations, all pervious lands prior to redevelopment were modeled in good hydrologic condition regardless of the conditions existing at the time of computation; • The length of sheet flow used for the time of concentration calculations are limited to 50feet in length per North Andover Stormwater Regulations; and • Drainage swales are sized to accommodate the 10-year storm event and velocities below 4- fps. Model iii-i"o iiriiTi a tii o iin EP gathered data from the following sources for input into the stormwater model: • Drainage System -Topographic and utility information was gathered from the professional survey. • Elevations-Topographic information was gathered from professional survey as shown on the plans. • Soils - Soil information was gathered from soil boring logs as well as the United States Geological Survey(USGS)Web Soil Survey(WSS)website https://websoiIsurvey.sc.egov.usda.gov/App/HomePage.htm. The WSS provides soil data for stormwater analysis, such as soil types, hydraulic soil groups (HSG), and estimated infiltration rates.Attachment 5 provides the NRCS Soils Report and soil boring logs. • Land Use-Land use data was as observed in field. • Rainfall Events- Data for the 2-year, 10-year, and 100-year 24-hour rainfall events were gathered NOAA'sAtlas 14 online tool for the geographic location of the project. Model Setup Sub-catchment area(s)were delineated based on the limits of the project areas and the topographic survey. Land use and soil types were used to create a composite curve number(CN)for each sub- catchment area. The CN values used in the hydrologic analysis are listed in the existing and proposed HydroCAD reports provided in Attachments 6 and 7. Rainfall data was entered into the model for the 2-year, 10-year, and 1 00-year 24-hour rainfall events as shown in Table 1 on the following page.An SCS Type III rainfall distribution was selected to develop 24-hour rainfall distribution curves. ii1-i v p a iiI t 1-i e s m c o ii Table 1 - Ralnfall Events' 2-year,, 24-hour 3.16 10-year, 24-hour 5.00 100-year,, 24-hour 7.93 1. Obtained from NOAA's Atlas 14 online tool for the geographic location cf the project. Two (2) sub-catchments were created under existing conditions. Four(4) sub-catchments were created under proposed conditions. One (1) design point was modeled for both existing and proposed conditions. Existing and proposed catchment area maps can be found in Attachments 3 and4. Under existing and proposed conditions, storrnvvater runoff from the project areaprirnari|yrernains the same with flows discharging to Lake [ochichevvick. Existing groundcover consists of grass in good condition, paved and gravel areas, and woods in good condition. Proposed groundcover consists of grass in good condition, permeable pavers, bioretention areas, paved areas, and woods in good condition. Under proposed conditions,there has been a reduction in impervious area from 5'353'sfto 483'sf(approximately 91% reduction). Back-up information data is provided in Attachment 5 for permeable paver material. M o d 10 u-t p u t The peak flows and velocities were analyzed at design point 1 (DP-1). Tables 2 provides these results. Table 2_ EAstaing and Proposed Peak Results at DP-1 FIN milli I i e�vP a Irt 1-i e s.comm S)'t Sta��,id&�,,-ds mWI " i I �„nm iUIIII��'n,'. Wu�m ��, i�umi u m��ml U' W'u'uwmriiw Wt 11j IIII iiWWwwml ru.uutt Wruvu' The MassDEP Checklist for Stormwater Report is included in Attachment 2. The Checklist has been stamped and signed by a Registered Professional Engineer in the State of Massachusetts.All conveyed stormwater is considered as a mix of redevelopment and development project.All stormwater standards will be met or exceeded as a result of the proposed project. t 0 IIr III a te Ir'� to I@ a IIr' 1. No ( It,"i. III e a t e [.)ischarges or E Ilr osIIIoII�-i . oWetlatids No New Untreated Discharges The project will not result in any new stormwater conveyance discharging untreated stormwater directly to the waters of the Commonwealth. Under proposed conditions,the impervious area will be reduced on-site. Runoff will continue to be directed southerly towards the wetlands and edge of water. Except for the drainage areas directed to the rain gardens, existing and proposed drainage patterns remain unchanged. Any new discharges are properly treated to remove at least 80%TSS load from the stormwater flow. Further documentation pertaining to stormwater treatment is provided under Standard 4. Erosion to Wetlands from Discharges EP evaluated permissible velocities according to the MassDOT Chapter 8- Exhibit 8-23:"Permissible Velocities for Channels with Erodible Linings"for all storm events. EP selected a Graded (channel), with loam to cobbles as the discharge soil.According to MassDOT, the permissible velocity is up to 5- ft/sec.Table 2 above shows that this permissible velocity is not exceeded. The Project has been designed to comply With Standard 1. t III Ii,m- a te IIr°' t,a Ir--i da Ir,,,, 2: I„ ea [,, ate ,,,,,tt ru.j a t IIIo IIr-i Standard 2 of the Massachusetts Stormwater Handbook states that post-development peak discharge rates shall not exceed pre-development peak discharge rates for the 2-year and 10-year 24-hour storm events. It also states that peak discharges from the 100-year 24-hour storm must be evaluated to show that an increase in off-site flooding will not occur. Table 2 above indicates that existing peak discharge rates for the project area are attenuated for the 2-1 10-, and 100-year storm events for Design Point 1. Therefore,the Project is in compliance with Standard 2. StoIir-inwatei, to li" a III°` 3. t III'Ii ' a t III°` [��Zecliarge The project fully meets Standard 3 for stormwater recharge. The project will result in a reduction in paved and impervious surface area by replacing hard packed gravel surfaces with grass or permeable concrete pavers. Therefore,the sites'ability to recharge stormwater runoff will be improved. In addition, bioretention storage areas are provided to capture a portion of the Site's runoff and runoff from Great Pond Road. Calculations for the required recharge volume of 1-inch of runoff from the contributing impervious drainage area and BMP drawdown analysis are provided below. III-i v:p a IIr t 1-i e II m c oIl µmy Page(D Of Bioretention Area #1 Infiltration volume: Storage capacity= 11432 ft3(See Proposed HydroCAD report in Attachment 7) Paved area = 2,056 ft2(Including contributing paved areas of Great Pond Road outside of the project area) WQV target depth = 1.0 in Runoff Volume Required = (1-in / 12 in/ft) *(21056 ft2.) = 170.33 ft3< 1,432 ft3 The required infiltration runoff volume to the bioretention area is less than the storage capacity provided.Therefore,the infiltration volume is adequate and complies with Standard 3. Drawdown times: Bioretention area bottom area (Ba) = 398 ft2 Volume to be infiltrated (Rv) = 170.33 ft3 K=0.17 in/hrfor Hydrologic Soil Group C Drawdown time = Rv/(K* Ba) = 170.33 ft3/(0.17 in/hr* 398 ft2.) = 2.5 hr<72 hr The drawdown analysis indicates the entire volume will be drawn down in 2.5 hours,well within the 72-hour requirement. Therefore,the drawdown time is satisfactory and complies with Standard 3. Bioretention Area #2 Infiltration volume: Storage capacity= 11239 ft3(See Proposed HydroCAD report in Attachment 7) Paved area = 1,907 ft2(Including contributing paved areas of Great Pond Road outside of the project area) WQV target depth = 1.0 in Runoff Volume Required = (1-in / 12 in/ft) * 11907 ft2.) = 159 ft3< 1,239 ft3 The required infiltration runoff volume to the bioretention area is less than the storage capacity provided.Therefore,the infiltration volume is adequate and complies with Standard 3. Drawdown times: Bioretention area bottom area (Ba) =419 ft2 Volume to be infiltrated (Rv) = 159 ft3 K=0.17 in/hrfor Hydrologic Soil Group C Drawdown time = Rv/(K* Ba) = 159 ft3/(0.17 in/hr*419 ft2.) = 2.2 hr<72 hr The drawdown analysis indicates the entire volume will be drawn down in 2.2 hours,well within the 72-hour requirement. Therefore,the drawdown time is satisfactory and complies with Standard 3. III-i v p a II° IIn e l m c o Sty III Ii'm- eIII a III--i ard . „u�� .„�,IIP„ Lj a III t Standard 4 of the Massachusetts Stormwater Standards addresses stormwater quality requirements. This standard requires that new stormwater management systems be designed to achieve an 80%Total Suspended Solids (TSS) removal rate prior to discharge. Additionally,this standard addresses the required volume of stormwater runoff that is to be treated by the BMPs, as well as components of a long-term source control and pollution prevention plan. Currently,there are no stormwater management systems or BMPs on the property. Under proposed conditions, two (2) bioretention areas are designed to treat surface runoff. The treatment trains for these systems are described below. Treatment Train 1:This treatment train consists of capturing stormwater runoff from a portion of the Site and a portion of Great Pond Rd to Bioretention Area No. 2. The portion of runoff from the Site is a combination of runoff from grass-filled and stone-filled permeable pavers (5,275-sf),the paved driveway apron (235-sf), and lawn area (1,250-sf). The portion of off-site run-off directed to Bioretention Area No. 2 is from 1,672-sf of the paved roadway along Great Pond Rd. Excess water from Bioretention No. 2 will discharge to Bioretention No. 1 through an overflow structure and conveyance piping.The overall TSS removal for this train is90%. Treatment Train 2:This treatment train consists of capturing stormwater runoff from a portion of the Site, excess water from Bioretention No. 2, and a portion of Great Pond Rd to Bioretention Area No. 1. The portion of runoff from the Site is a combination of runoff from stone-filled permeable pavers(1,056-sf),the paved driveway apron (248-sf), and lawn area (1,781-sf). The portion of off-site run-off directed to Bioretention Area No. 1 is from 1,808-sf of paved roadway along Great Pond Rd. Lastly, any excess water directed from Bioretention No. 2 to Bioretention No. 1 provides pre- treatment. Overflow from Bioretention No. 1 is conveyed via a riprap-lined swale. The pretreatment requirement of 44%TSS removal prior to infiltration is met through the pretreatment features of this train. The overall TSS removal for this train is 99%. Based on MassDEP's published removal rates for bioretention areas,TSS removal prior to discharging is a minimum of 90%.The project has been designed such that all proposed impervious surfaces pass through one of the previously described treatment trains,which results in the required TSS removal for the project. The results from the MassDEP TSS Removal Worksheet from Treatment Train 1 and 2 are provided on the following pages. ii1-i v P a Irt-e s m c o Tµmy D-J ei I-e of TSS Removal Required for Treatment Train 1: Location. Treat mentTrain 1 B C D E F TSS Removal Starting TSS Amount Remaining BIMP' Rate' Load* Removed Q (D I Bioretention Area 0.90 1.00 0.90 0.10 M M 0 0.00 0.10 0.00 0.10 E C 01 IL 0.00 11 0.10 11 0.00 11 0.10 CI) L L L L Separate Form Needs to, be Completed for Each T to I T R m va 1 90% utlet o r BM P'ra i n N or#t L.*e Project: La-"- "Y Prepared By. iLv *Equ al s re m ai n i n g la a,-d f r cim pre v 1 Gu s E311-0 P(E') N Gm-autm ated TS S C a]aj I aticm Sh eet Date-..7rzg)2o24 which enters the BMP m u st be u sed-if P ropri eta ry RI M P P roposs-ed-I 1.F ran M a P Storm eater H andboctk Vd.1 Ma ss.DeD -OF En vr_-Orr 7er,ta pim re C t6n, e nVDartnersxom Dngp q of 11 TSS Removal Required for Treatment Train 2: Location'. TreatmentTrain 2 B C D E F TSS Removal Starting TSS Amount R emaining BMP1 R ate' Load* Removed (C*D) Load 4=0 Q Q Blor-etention Ar-ea 0.90 1.00 0.90 0.10 0 _0 Bitoretenflon Area Me 0.10 0.09 0.01 E 0 0.00 0.01 0.00 0.01 0.01 0.00 0.01 0.01 0.00 0.01 Separate- Form Needs to be Completed for Each Tota l TSS R m v I = t or BM P'ra in Nufth Lake Project: Laurlr`'I'ty Prepared By-, JLV wEqu Is remaining load fry prep iiaus BN-1 P(E) N Gm-autcn aled TS S C a]cu I atim Sh eet Date" Vrz9)zom which entersthe BMP m u st b-e u ss edr i f P r Gr p d et a ry R M P P m p ms ed 1. F ru m M ass D-LE P St i r m eater H a n V cl. 1 .VVV,- ss. -,-Iep t.-0 If En V fflhofyj PM te C t envDa-tne-..,I--om Stormwater quality calculations for compliance with Standard 4 are provided below. On-Site Infiltration: VWQ = (DwQ/12 in/ft)* (Aimp) VwQ = (1-in / 12 in/ft) *(483-sf) = 40.25 ft3 required <20,553 ft3 provided As demonstrated within Standard 3 in the section above,the stormwater management BMPs are capable of providing 2,553-cf(1,121 cubic feet for bioretention area #2 and 1,432 cubic feet for bioretention area #1) of infiltration for the first 1-inch of rainfall using the static method. Combined Off-Site and On-Site Infiltration: VwQ = (DwQ/12 in/ft)* (Aimp) VwQ = (1-in / 12 in/ft) *(5,147-sf) = 430 ft3 required <20,553 ft3 provided As demonstrated within Standard 3 in the section above,the stormwater management BMPs are capable of providing 2,553-cf(1,121 cubic feet for bioretention area #2 and 1,432 cubic feet for bioretention area #1) of infiltration for the first 1-inch of rainfall using the static method. The project has been designed to meet the full requirements of Standard 4. t&II"`III"" a t I--Statid&rd '. III.........a III"i"„ Use III t, i III°°°°°III III "i I-- I° ,t, III t III a [°� L„jII t a III, t III,,,,,,,,,;;a d The project site is zoned in a residential district and will not generate more than 1,000 vehicle trips per day. Therefore, it is not considered a Land Use with Higher Potential Pollutant Loads (LUHPPL) and additional requirements of Standard 5 are not applicable. St III°"Ill, te IIr", t,a Ir-i( a Ir"" -. „�f IIr"III t IIIc a hir" a The proposed redevelopment discharges stormwater runoff to Lake Cochichewick(MA84008). Lake Cochichewick is the Town's public drinking water supply source and is an Outstanding Water Resource (OWR). The proposed stormwater management system includes BMPs to treat runoff prior to discharging to Lake Cochichewick.The project has been designed in compliance with Standard 6. tUr III a te Ir'� to Ir-- a IIr- - [, ed eve I o IIr-n el III'l The project is the redevelopment of the existing driveway, parking area, boat ramp, and stone retaining walls. The project proposes to improve stormwater management through the implementation of BMPs and provide a net reduction in impervious areas. In general,the project has been designed to fully comply with all Standards. t,oIII"`III"n a t IIPm'" t a IIP'ida III"`d � C o III""'i s t IIr III t,III oIII" III°� ,,,,III"°III ;; w oInt,III"`ols The Design Plans in Attachment 1 provide construction period control details for the project. There will be less than one acre of land disturbed as a result of this project; therefore, an EPA NPDES Construction General Permit(CGP)will not be required for the construction of this project. The project has been designed to comply with Standard 8. t Ir Ii a te III,- t&r- d Ir 9- Ope Ira t III Iti &r,id II a III IIIei te Ii,i aIII ;a III° a III" The Town of North Andover will continue to be responsible for the operation and maintenance of the stormwater systems post-construction. Per NPDES permit(#MAR041214), the Town currently IIIIfPa III t 1-i e s m c o Tµmy provides preventative O&M procedures that are optimized for effective maintenance of the stormwater system. Specific O&M procedures for the bioretention areas are provided in Attachment 8.The project has been designed to comply with Standard 9. ,&ire iii'r a to iiP-- a it &rd 1 Illicit IIC,,, iii a ii ges to IC;;;, iiP--a iii in a e ,s to iii 'l To EP's knowledge, based on the best available information of the existing project area,there are no illicit discharges on site and the proposed project does not propose any illicit discharges.A signed Illicit Discharge Statement is provided in Attachment 9.The project has been designed to comply with Standard 10. At C 1h rn e ints 1. Design Plans(Half-Size Plans) 2. MassDEP Stormwater Checklist 3. Existing Catchment Area Map 4. Proposed Catchment Area Map 5. H-H Model Backup Information NRCS Soils Report Boring Logs NOAA Atlas 14,Volume 10 Version 3 for North Andover, MA(Precipitation Frequency Data) Permeable Paver Data 6. Existing Model Report 7. Proposed Model Report 8. Bioretention Area O&M 9. Illicit Discharge Compliance Statement IIIIfPa Irt-e s m c o Tµmy ATTACHMENT oilDESIGNI PLANS (HALF-SIZE PLANS) A............................... ..........12 ..............MASSI�',"I IIIIIIIIIII C°II S CIIIIIIII GIIIIRIMWA CIIIIIIII C�.............. C�K 1�............IS CIIIIIIII Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checkl'ist 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, Report Stormwater the Stter Re which should provide more substantive and detailed information but is offered use only the tab p ( p ) key to move your here as a tool to help the applicant organize their Stormwater Management documentation for their cursor-do not Report and for the reviewer to assess this information in a consistent format. As noted in the Checklist, use the return the Stormwater Report must contain the engineering computations and supporting information set forth in key. Volume 3 of the Massachusetts Stormwater Handbook. The Stormwater Report must be prepared and certified by a Registered Professional Engineer(RPE) licensed in the Commonwealth. The Stormwater Report must include: • The Stormwater Checklist completed and stamped by a Registered Professional Engineer(see page 2)that certifies that the Stormwater Report contains all required submittals.' This Checklist is to be used as the cover for the completed Stormwater Report. • Applicant/Project Name • Project Address • Name of Firm and Registered Professional Engineer that prepared the Report • Long-Term Pollution Prevention Plan required by Standards 4-6 • Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan required by Standard 82 • Operation and Maintenance Plan required by Standard 9 In addition to all plans and supporting information, the Stormwater Report must include a brief narrative describing stormwater management practices, including environmentally sensitive site design and LID techniques, along with a diagram depicting runoff through the proposed BMP treatment train. Plans are required to show existing and proposed conditions, identify all wetland resource areas, NRCS soil types, critical areas, Land Uses with Higher Potential Pollutant Loads (LUHPPL), and any areas on the site where infiltration rate is greater than 2.4 inches per hour. The Plans shall identify the drainage areas for both existing and proposed conditions at a scale that enables verification of supporting calculations. As noted in the Checklist, the Stormwater Management Report shall document compliance with each of the Stormwater Management Standards as provided in the Massachusetts Stormwater Handbook. The soils evaluation and calculations shall be done using the methodologies set forth in Volume 3 of the Massachusetts Stormwater Handbook. To ensure that the Stormwater Report is complete, applicants are required to fill in the Stormwater Report Checklist by checking the box to indicate that the specified information has been included in the Stormwater Report. If any of the information specified in the checklist has not been submitted, the applicant must provide an explanation. The completed Stormwater Report Checklist and Certification must be submitted with the Stormwater Report. 1 The Stormwater Report may also include the Illicit Discharge Compliance Statement required by Standard 10. If not included in the Stormwater Report,the Illicit Discharge Compliance Statement must be submitted prior to the discharge of stormwater runoff to the post-construction best management practices. 2 For some complex projects,it may not be possible to include the Construction Period Erosion and Sedimentation Control Plan in the Stormwater Report. In that event,the issuing authority has the discretion to issue an Order of Conditions that approves the project and includes a condition requiring the proponent to submit the Construction Period Erosion and Sedimentation Control Plan before commencing any land disturbance activity on the site. 02 SW Checklist•04/01/08 Stormwater Report Checklist•Page 1 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program � Checklist for Stormwater Report B. Stormwater Checklist and Certification The following checklist is intended to serve as a guide for applicants as to the elements that ordinarily need to be addressed in a complete Stormwater Report. The checklist is also intended to provide conservation commissions and other reviewing authorities with a summary of the components necessary for a comprehensive Stormwater Report that addresses the ten Stormwater Standards. Note: Because stormwater requirements vary from project to project, it is possible that a complete Stormwater Report may not include information on some of the subjects specified in the Checklist. If it is determined that a specific item does not apply to the project under review, please note that the item is not applicable (N.A.)and provide the reasons for that determination. A complete checklist must include the Certification set forth below signed by the Registered Professional Engineer who prepared the Stormwater Report. Registered Professional Engineer's Certification I have reviewed the Stormwater Report, including the soil evaluation, computations, Long-term Pollution Prevention Plan, the Construction Period Erosion and Sedimentation Control Plan (if included), the Long- term Post-Construction Operation and Maintenance Plan, the Illicit Discharge Compliance Statement(if included)and the plans showing the stormwater management system, and have determined that they have been prepared in accordance with the requirements of the Stormwater Management Standards as further elaborated by the Massachusetts Stormwater Handbook. I have also determined that the information presented in the Stormwater Checklist is accurate and that the information presented in the Stormwater Report accurately reflects conditions at the site as of the date of this permit application. Registered Professional Engineer Block and Signature µ OF Mgssq RYAN J. cyG PAUt m v GVlL N0.5112J' -o AL 7/30/2024 Signature and Date Checklist Project Type: Is the application for new development, redevelopment, or a mix of new and redevelopment? ❑ New development M Redevelopment ❑ Mix of New Development and Redevelopment 02 SW 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) M 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 M Other(describe): Pervious Pavers (9,991 sf) 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. 02 SW Checklist•04/01/08 Stormwater Report Checklist•Page 3 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checkl'ist 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. 1 80%TSS removal is required prior to discharge to infiltration BMP if Dynamic Field method is used. 02 SW Checklist•04/01/08 Stormwater Report Checklist•Page 4 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program Checkl'ist 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. Z A Long-Term Pollution Prevention Plan is attached to Stormwater Report and is included as an attachment to the Wetlands Notice of Intent. Z 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 Z 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. Z Calculations documenting that the treatment train meets the 80% TSS removal requirement and, if applicable, the 44% TSS removal pretreatment requirement, are provided. 02 SW Checklist•04/01/08 Stormwater Report Checklist•Page 5 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program � Checklist for Stormwater Report Checklist (continued) Standard 4: Water Quality (continued) � The BMP is sized (and calculations provided) based on: M The'/2' or 1"Water Quality Volume or ❑ The equivalent flow rate associated with the Water Quality Volume and documentation is provided showing that the BMP treats the required water quality volume. El 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. 02 SW 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 amulti-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 amulti-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 M 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. 02 SW Checklist•04/01/08 Stormwater Report Checklist•Page 7 of 8 Massachusetts Department of Environmental Protection Bureau of Resource Protection - Wetlands Program � Checklist for Stormwater Report Checklist (continued) Standard 8: Construction Period Pollution Prevention and Erosion and Sedimentation Control (continued) ❑ The project is highly complex and information is included in the Stormwater Report that explains why it is not possible to submit the Construction Period Pollution Prevention and Erosion and Sedimentation Control Plan with the application. A Construction Period Pollution Prevention and Erosion and Sedimentation Control has not been included in the Stormwater Report but will be submitted before land disturbance begins. � The project is not covered by a NPDES Construction General Permit. ❑ The project is covered by a NPDES Construction General Permit and a copy of the SWPPP is in the Stormwater Report. ❑ The project is covered by a NPDES Construction General Permit but no SWPPP been submitted. The SWPPP will be submitted BEFORE land disturbance begins. Standard 9: Operation and Maintenance Plan � The Post Construction Operation and Maintenance Plan is included in the Stormwater Report and includes the following information: ❑ Name of the stormwater management system owners; El Party responsible for operation and maintenance; M 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: El 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; M 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. 02 SW Checklist•04/01/08 Stormwater Report Checklist•Page 8 of 8 ATTACHMENT EXISTING CATCHMENT AREA MAP N e Q WF—2 - d W F 5 WF-6 I; F? TOB-1 roe 2 Toe AL. SUBCATCHMENT 1S �w>-4 TvB 4 TOB-3 TO W—2 AREA=21,643 SF SUBCATCHMENT 2S 1 (� TOB-36 _ WF 3 _ CN=82 AREA=18,155 SF — CN=76 e 6 N TOB-34 T0B > w y- ,. ,. TOB 33 TOB 2�► e TOBg 31 0 TOB-29 TOB-30 d 8- TOB-32 TOB 2 TOB—-26 TOB 8 0 a E TO .. TO T08 19 TOB 24 SA� OB 17 .. TOB 2 B 16 TOB-23 w \ TOB-10 'TOB 12 TOB-13- TOB-1� TOB-21 0 TOB-11 TOB 22 DESIGN POINT 1 0 (LAKE COCHICHEWICK) - LEGEND SUBCATCHMENT BOUNDARY o TIME OF CONCENTRATION PATH .--_ ---.- 'm m 0 m N E a' r 0 Z O N O M M ENVIRONMENTAL Scale AY202 NORTH LAKE COCHICHEWICK BOAT LAUNCH 75%DESIGN N Date MAY 2023 M Job No. 22003302 TOWN OF NORTH ANDOVER,MA Sheet No. PARTNERS \,` \ Designed by JLV THIS LINE IS ONE INCH \\\\ LONG WHEN PLOTTED AT O Drawn by AES FULL SCALE ON A 22"X z Checked by RJP 34'DRAWING EXISTING CONDITIONS v— CATCHMENT AREA MAP ° MARK DATE DESCRIPTION Approved by RJP ATTACHMENT 4 1� MAPPROPOSED CATCHMEN N SUBCATCHMENT 4S 5,884 SF - CN=83 SUBCATCHMENT 3S 9,610 SF BIORETENTION AREA NO.1 CN=82 OVERFLOW=116.50 PRECAST CONCRETE OVERFLOW STRUCTURE FLARED END 12"RCP PIPE ®�v BOT.=115.00 INV.OUT=115.20 S=0.45%,L=44' RIM.ELEV.=116.50 BIORETENTION AREA NO.2 --`�""� =' INV.OUT=115.50 BOT.=115.50 r Q v 65 _ D b - \ D , x 115.50 x 115.50 x 1 ._ _ 1 WF 2 117.20 e e e 11 - ' \o WF 5 WF-6 - 18.0 WF-1 r T v - / I TOB 1 TOB 2 TOB .- \ o 30.0 - _ - x 116.50 = �x 4-0 OB 11.50 e e e TOB-3 TOB- WF 2 F a e T 1 T - _ Fx o e SUBCATCHMENT 1S ��- 1NF 3 TOB-6. 13,643 SF SUBCATCHMENT 2S CN=76 11730_ 13.0 R360 117.50 10,661 SF TOB-34 TOB- CN=75 V = e e e e e _ F T TOB 33 / aa - e e e e e e e e 17.74 TOBg 31 0 a _ + - I f9�` �� 29 TOB-30 \ TOB 28 T 34} 12� B a TOB-32 d T T: m T 2 6 TOB-8 e- a 1R 0 �. E TOE 18 x 116.25 x 116.25 TOB 19 TOB 112.00 113.00 m TOB-24 TO 22 U OB 16 � TOB--1___ TOB-21 TO B-23 TOB-10 TOB 11 tbB 12 TOB-13 m TOB 22 v _ `o DESIGN POINT 1 0 (LAKE COCHICHEWICK) - LEGEND SUBCATCHMENT BOUNDARY o TIME OF CONCENTRATION PATH m 0 m N E a' r 0 Z O N O M M ENVIRONMENTAL Scale 1"=20' NORTH LAKE COCHICHEWICK BOAT LAUNCH 75%DESIGN N Date MAY 2023 M Job No. 22003302 TOWN OF NORTH ANDOVER,MA Sheet No. �� PARTNERS \ Designed by JLV THIS LINE IS ONE INCH \\\\ LONG WHEN PLOTTED AT O Drawn by AES FULL SCALE ON A 22"X z 34"DRAWING PROPSOED CONDITIONS Checked by RJP ti v : CATCHMENT AREA MAP ° MARK DATE DESCRIPTION Approved by RJP ATTACHMENT 5 H-H IM O D E L BACKUP INFORMATION NRCS Soils Report Boring Logs NOAA Atlas 14,Volume 10 Version 3 for North Andover, MA(Precipitation Frequency Data) Permeable Paver Data US'DA United States A product of the National Custom Soil Resource Department of Cooperative Soil Survey, Agriculture a joint effort of the United Report for States Department of RIC Agriculture and other S� Essex Count Federal agencies, State Y, Natural agencies including the Resources Agricultural Experiment Massachusetts Conservation Stations and local Service participants Northern ar ro P �% � � ,a�arrrroramrrrrmurnarrrurrrrrrrr�ararr.!a,zrRrm dr rR i rJg�/dui April 27, 2023 Preface Soil surveys contain information that affects land use planning in survey areas. They highlight soil limitations that affect various land uses and provide information about the properties of the soils in the survey areas. Soil surveys are designed for many different users, including farmers, ranchers, foresters, agronomists, urban planners, community officials, engineers, developers, builders, and home buyers. Also, conservationists, teachers, students, and specialists in recreation, waste disposal, and pollution control can use the surveys to help them understand, protect, or enhance the environment. Various land use regulations of Federal, State, and local governments may impose special restrictions on land use or land treatment. Soil surveys identify soil properties that are used in making various land use or land treatment decisions. The information is intended to help the land users identify and reduce the effects of soil limitations on various land uses. The landowner or user is responsible for identifying and complying with existing laws and regulations. Although soil survey information can be used for general farm, local, and wider area planning, onsite investigation is needed to supplement this information in some cases. Examples include soil quality assessments (http://www.nres.usda.gov/wps/ portal/nres/main/soils/health/)and certain conservation and engineering applications. For more detailed information, contact your local USDA Service Center (https://offices.sc.egov.usda.gov/locator/app?agency=nres)or your NRCS State Soil Scientist (http://www.nres.usda.gov/wps/portal/nres/detail/soils/contactus/? cid=nres142p2_053951). Great differences in soil properties can occur within short distances. Some soils are seasonally wet or subject to flooding. Some are too unstable to be used as a foundation for buildings or roads. Clayey or wet soils are poorly suited to use as septic tank absorption fields. A high water table makes a soil poorly suited to basements or underground installations. The National Cooperative Soil Survey is a joint effort of the United States Department of Agriculture and other Federal agencies, State agencies including the Agricultural Experiment Stations, and local agencies. The Natural Resources Conservation Service (NRCS) has leadership for the Federal part of the National Cooperative Soil Survey. Information about soils is updated periodically. Updated information is available through the NRCS Web Soil Survey, the site for official soil survey information. The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or a part of an individual's income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require 2 alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA's TARGET Center at(202) 720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue, S.W., Washington, D.C. 20250-9410 or call (800) 795-3272 (voice) or(202) 720-6382 (TDD). USDA is an equal opportunity provider and employer. 3 Contents Preface....................................................................................................................2 HowSoil Surveys Are Made..................................................................................5 SoilMap..................................................................................................................8 SoilMap................................................................................................................9 Legend................................................................................................................10 MapUnit Legend................................................................................................ 11 MapUnit Descriptions.........................................................................................11 Essex County, Massachusetts, Northern Part................................................ 13 1—Water..................................................................................................... 13 310B—Woodbridge fine sandy loam, 3 to 8 percent slopes....................... 13 311 B—Woodbridge fine sandy loam, 0 to 8 percent slopes, very stony..... 14 References............................................................................................................17 4 How So'll Surve Are Made Soil surveys are made to provide information about the soils and miscellaneous areas in a specific area. They include a description of the soils and miscellaneous areas and their location on the landscape and tables that show soil properties and limitations affecting various uses. Soil scientists observed the steepness, length, and shape of the slopes; the general pattern of drainage; the kinds of crops and native plants; and the kinds of bedrock. They observed and described many soil profiles. A soil profile is the sequence of natural layers, or horizons, in a soil. The profile extends from the surface down into the unconsolidated material in which the soil formed or from the surface down to bedrock. The unconsolidated material is devoid of roots and other living organisms and has not been changed by other biological activity. Currently, soils are mapped according to the boundaries of major land resource areas (MLRAs). MLRAs are geographically associated land resource units that share common characteristics related to physiography, geology, climate, water resources, soils, biological resources, and land uses (USDA, 2006). Soil survey areas typically consist of parts of one or more MLRA. The soils and miscellaneous areas in a survey area occur in an orderly pattern that is related to the geology, landforms, relief, climate, and natural vegetation of the area. Each kind of soil and miscellaneous area is associated with a particular kind of landform or with a segment of the landform. By observing the soils and miscellaneous areas in the survey area and relating their position to specific segments of the landform, a soil scientist develops a concept, or model, of how they were formed. Thus, during mapping, this model enables the soil scientist to predict with a considerable degree of accuracy the kind of soil or miscellaneous area at a specific location on the landscape. Commonly, individual soils on the landscape merge into one another as their characteristics gradually change. To construct an accurate soil map, however, soil scientists must determine the boundaries between the soils. They can observe only a limited number of soil profiles. Nevertheless, these observations, supplemented by an understanding of the soil-vegetation-landscape relationship, are sufficient to verify predictions of the kinds of soil in an area and to determine the boundaries. Soil scientists recorded the characteristics of the soil profiles that they studied. They noted soil color, texture, size and shape of soil aggregates, kind and amount of rock fragments, distribution of plant roots, reaction, and other features that enable them to identify soils. After describing the soils in the survey area and determining their properties, the soil scientists assigned the soils to taxonomic classes (units). Taxonomic classes are concepts. Each taxonomic class has a set of soil characteristics with precisely defined limits. The classes are used as a basis for comparison to classify soils systematically. Soil taxonomy, the system of taxonomic classification used in the United States, is based mainly on the kind and character of soil properties and the arrangement of horizons within the profile. After the soil 5 Custom Soil Resource Report scientists classified and named the soils in the survey area, they compared the individual soils with similar soils in the same taxonomic class in other areas so that they could confirm data and assemble additional data based on experience and research. The objective of soil mapping is not to delineate pure map unit components; the objective is to separate the landscape into landforms or landform segments that have similar use and management requirements. Each map unit is defined by a unique combination of soil components and/or miscellaneous areas in predictable proportions. Some components may be highly contrasting to the other components of the map unit. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The delineation of such landforms and landform segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, onsite investigation is needed to define and locate the soils and miscellaneous areas. Soil scientists make many field observations in the process of producing a soil map. The frequency of observation is dependent upon several factors, including scale of mapping, intensity of mapping, design of map units, complexity of the landscape, and experience of the soil scientist. Observations are made to test and refine the soil-landscape model and predictions and to verify the classification of the soils at specific locations. Once the soil-landscape model is refined, a significantly smaller number of measurements of individual soil properties are made and recorded. These measurements may include field measurements, such as those for color, depth to bedrock, and texture, and laboratory measurements, such as those for content of sand, silt, clay, salt, and other components. Properties of each soil typically vary from one point to another across the landscape. Observations for map unit components are aggregated to develop ranges of characteristics for the components. The aggregated values are presented. Direct measurements do not exist for every property presented for every map unit component. Values for some properties are estimated from combinations of other properties. While a soil survey is in progress, samples of some of the soils in the area generally are collected for laboratory analyses and for engineering tests. Soil scientists interpret the data from these analyses and tests as well as the field-observed characteristics and the soil properties to determine the expected behavior of the soils under different uses. Interpretations for all of the soils are field tested through observation of the soils in different uses and under different levels of management. Some interpretations are modified to fit local conditions, and some new interpretations are developed to meet local needs. Data are assembled from other sources, such as research information, production records, and field experience of specialists. For example, data on crop yields under defined levels of management are assembled from farm records and from field or plot experiments on the same kinds of soil. Predictions about soil behavior are based not only on soil properties but also on such variables as climate and biological activity. Soil conditions are predictable over long periods of time, but they are not predictable from year to year. For example, soil scientists can predict with a fairly high degree of accuracy that a given soil will have a high water table within certain depths in most years, but they cannot predict that a high water table will always be at a specific level in the soil on a specific date. After soil scientists located and identified the significant natural bodies of soil in the survey area, they drew the boundaries of these bodies on aerial photographs and 6 Custom Soil Resource Report identified each as a specific map unit. Aerial photographs show trees, buildings, fields, roads, and rivers, all of which help in locating boundaries accurately. 7 Soil Map The soil map section includes the soil map for the defined area of interest, a list of soil map units on the map and extent of each map unit, and cartographic symbols displayed on the map. Also presented are various metadata about data used to produce the map, and a description of each soil map unit. 8 Custom Soil Resource Report Soil Map 0 OD Ln rn ZID zo 0 0 326920 326940 326960 326980 327000 327020 327040 327060 327080 327100 327120 327140 327160 420 42'56"N N 420 42'56"N V C'I C') RIP PD- CI) C, E31 O C) cy') C") CO C") 10 C814 CO � Soil Map may not be valid at this scale. 10 420 42'50"N 44 1 1 1 1 1 1 1 1 1 1 1 1 1 420 42'50"N 326900 326920 326940 326960 326980 327000 327020 327040 327060 327080 327100 3271 220 327140 327160 0 00 Ln M ZID Map Scale:1:1,220 if printed on A landscape(11"x 8.5")sheet. zo 0 Meters 0 N 0 15 30 60 90 i Feet 0 50 100 200 300 Map projection:Web Mercator Comer coordinates:WGS84 Edge tics:UTM Zone 19N WGS84 9 Custom Soil Resource Report MAP LEGEND MAP INFORMATION Area of Interest(AOI) Spoil Area The soil surveys that comprise your AOI were mapped at Area of Interest(AOI) 1:15,800. Stony Spot Soils Very Stony Spot Soil Map Unit Polygons Warning:Soil Map may not be valid at this scale. Wet Spot Soil Map Unit Lines Enlargement of maps beyond the scale of mapping can cause Other misunderstanding of the detail of mapping and accuracy of soil Soil Map Unit Points g pp g y _ Special Line Features line placement.The maps do not show the small areas of Special Point Features contrasting soils that could have been shown at a more detailed Blowout Water Features scale. Streams and Canals E Borrow Pit Transportation Please rely on the bar scale on each map sheet for map Clay spot -_ Rails measurements. £ �� Closed Depression Interstate Highways Gravel Pit Source of Map: Natural Resources Conservation Service US Routes Web Soil Survey URL: r Gravelly Spot Major Roads Coordinate System: Web Mercator(EPSG:3857) 4 AlLandfill Local Roads Maps from the Web Soil Survey are based on the Web Mercator Lava Flow Background projection,which preserves direction and shape but distorts distance and area.A projection that preserves area,such as the _€ Marsh or swamp Aerial Photography Albers equal-area conic projection,should be used if more Mine or Quarry accurate calculations of distance or area are required. Miscellaneous Water This product is generated from the USDA-NRCS certified data as Perennial Water of the version date(s)listed below. Rock Outcrop Soil Survey Area: Essex County, Massachusetts, Northern Part Saline Spot Survey Area Data: Version 18,Sep 9,2022 Sandy Spot Soil map units are labeled(as space allows)for map scales -�_ Severely Eroded Spot 1:50,000 or larger. Sinkhole Date(s)aerial images were photographed: May 22,2022—Jun Slide or Slip 5,2022 Sodic Spot The orthophoto or other base map on which the soil lines were compiled and digitized probably differs from the background imagery displayed on these maps.As a result,some minor shifting of map unit boundaries may be evident. 10 Custom Soil Resource Report MapLegendUnit Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI 1 Water 1.7 22.5% 310B Woodbridge fine sandy loam,3 5.3 72.3% to 8 percent slopes 311 B Woodbridge fine sandy loam,0 0.4 5.1% to 8 percent slopes,very stony Totals for Area of Interest 7.3 100.0% MapDescriptionsUnit The map units delineated on the detailed soil maps in a soil survey represent the soils or miscellaneous areas in the survey area. The map unit descriptions, along with the maps, can be used to determine the composition and properties of a unit. A map unit delineation on a soil map represents an area dominated by one or more major kinds of soil or miscellaneous areas. A map unit is identified and named according to the taxonomic classification of the dominant soils. Within a taxonomic class there are precisely defined limits for the properties of the soils. On the landscape, however, the soils are natural phenomena, and they have the characteristic variability of all natural phenomena. Thus, the range of some observed properties may extend beyond the limits defined for a taxonomic class. Areas of soils of a single taxonomic class rarely, if ever, can be mapped without including areas of other taxonomic classes. Consequently, every map unit is made up of the soils or miscellaneous areas for which it is named and some minor components that belong to taxonomic classes other than those of the major soils. Most minor soils have properties similar to those of the dominant soil or soils in the map unit, and thus they do not affect use and management. These are called noncontrasting, or similar, components. They may or may not be mentioned in a particular map unit description. Other minor components, however, have properties and behavioral characteristics divergent enough to affect use or to require different management. These are called contrasting, or dissimilar, components. They generally are in small areas and could not be mapped separately because of the scale used. Some small areas of strongly contrasting soils or miscellaneous areas are identified by a special symbol on the maps. If included in the database for a given area, the contrasting minor components are identified in the map unit descriptions along with some characteristics of each. A few areas of minor components may not have been observed, and consequently they are not mentioned in the descriptions, especially where the pattern was so complex that it was impractical to make enough observations to identify all the soils and miscellaneous areas on the landscape. The presence of minor components in a map unit in no way diminishes the usefulness or accuracy of the data. The objective of mapping is not to delineate pure taxonomic classes but rather to separate the landscape into landforms or 11 Custom Soil Resource Report landform segments that have similar use and management requirements. The delineation of such segments on the map provides sufficient information for the development of resource plans. If intensive use of small areas is planned, however, onsite investigation is needed to define and locate the soils and miscellaneous areas. An identifying symbol precedes the map unit name in the map unit descriptions. Each description includes general facts about the unit and gives important soil properties and qualities. Soils that have profiles that are almost alike make up a soil series. Except for differences in texture of the surface layer, all the soils of a series have major horizons that are similar in composition, thickness, and arrangement. Soils of one series can differ in texture of the surface layer, slope, stoniness, salinity, degree of erosion, and other characteristics that affect their use. On the basis of such differences, a soil series is divided into soil phases. Most of the areas shown on the detailed soil maps are phases of soil series. The name of a soil phase commonly indicates a feature that affects use or management. For example, Alpha silt loam, 0 to 2 percent slopes, is a phase of the Alpha series. Some map units are made up of two or more major soils or miscellaneous areas. These map units are complexes, associations, or undifferentiated groups. A complex consists of two or more soils or miscellaneous areas in such an intricate pattern or in such small areas that they cannot be shown separately on the maps. The pattern and proportion of the soils or miscellaneous areas are somewhat similar in all areas. Alpha-Beta complex, 0 to 6 percent slopes, is an example. An association is made up of two or more geographically associated soils or miscellaneous areas that are shown as one unit on the maps. Because of present or anticipated uses of the map units in the survey area, it was not considered practical or necessary to map the soils or miscellaneous areas separately. The pattern and relative proportion of the soils or miscellaneous areas are somewhat similar. Alpha-Beta association, 0 to 2 percent slopes, is an example. An undifferentiated group is made up of two or more soils or miscellaneous areas that could be mapped individually but are mapped as one unit because similar interpretations can be made for use and management. The pattern and proportion of the soils or miscellaneous areas in a mapped area are not uniform. An area can be made up of only one of the major soils or miscellaneous areas, or it can be made up of all of them. Alpha and Beta soils, 0 to 2 percent slopes, is an example. Some surveys include miscellaneous areas. Such areas have little or no soil material and support little or no vegetation. Rock outcrop is an example. 12 Custom Soil Resource Report Essex County, Massachusetts, Northern Part 1—Water Map Unit Setting National map unit symbol: vjx4 Frost-free period: 125 to 165 days Farmland classification: Not prime farmland Map Unit Composition Water. 100 percent Estimates are based on observations, descriptions, and transects of the mapunit. 31013—Woodbridge fine sandy loam, 3 to 8 percent slopes Map Unit Setting National map unit symbol: 2t2gl Elevation: 0 to 1,470 feet Mean annual precipitation: 36 to 71 inches Mean annual air temperature: 39 to 55 degrees F Frost-free period: 140 to 240 days Farmland classification: All areas are prime farmland Map Unit Composition Woodbridge, fine sandy loam, and similar soils: 82 percent Minor components: 18 percent Estimates are based on observations, descriptions, and transects of the mapunit. Description of Woodbridge, Fine Sandy Loam Setting Landform: Ground moraines, drumlins, hills Landform position (two-dimensional): Summit, backslope, footslope Landform position (three-dimensional): Side slope Down-slope shape: Concave Across-slope shape: Linear Parent material: Coarse-loamy lodgment till derived from gneiss, granite, and/or schist Typical profile Ap- 0 to 7 inches: fine sandy loam Bw1 - 7 to 18 inches: fine sandy loam Bw2- 18 to 30 inches: fine sandy loam Cd-30 to 65 inches: gravelly fine sandy loam Properties and qualities Slope: 3 to 8 percent Depth to restrictive feature: 20 to 39 inches to densic material Drainage class: Moderately well drained Runoff class: Medium Capacity of the most limiting layer to transmit water(Ksat):Very low to moderately low (0.00 to 0.14 i n/h r) 13 Custom Soil Resource Report Depth to water table:About 18 to 30 inches Frequency of flooding: None Frequency of ponding: None Maximum salinity. Nonsaline (0.0 to 1.9 mmhos/cm) Available water supply, 0 to 60 inches: Low(about 3.6 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 2w Hydrologic Soil Group: C/D Ecological site: F144AY037MA- Moist Dense Till Uplands Hydric soil rating: No Minor Components Paxton Percent of map unit: 10 percent Landform: Drumlins, ground moraines, hills Landform position (two-dimensional): Summit, shoulder, backslope Landform position (three-dimensional): Nose slope, side slope, crest Down-slope shape: Convex, linear Across-slope shape: Convex Hydric soil rating: No Ridgebury Percent of map unit: 8 percent Landform: Depressions, ground moraines, hills, drainageways Landform position (two-dimensional):Toeslope, backslope, footslope Landform position (three-dimensional): Base slope, head slope, dip Down-slope shape: Concave Across-slope shape: Concave Hydric soil rating: Yes 311 B—Woodbridge fine sandy loam, 0 to 8 percent slopes, very stony Map Unit Setting National map unit symbol: 2t2q r Elevation: 0 to 1,440 feet Mean annual precipitation: 36 to 71 inches Mean annual air temperature: 39 to 55 degrees F Frost-free period: 140 to 240 days Farmland classification: Farmland of statewide importance Map Unit Composition Woodbridge, very stony, and similar soils: 82 percent Minor components: 18 percent Estimates are based on observations, descriptions, and transects of the mapunit. 14 Custom Soil Resource Report Description of Woodbridge, Very Stony Setting Landform: Ground moraines, hills, drumlins Landform position (two-dimensional): Summit, backslope, footslope Landform position (three-dimensional): Side slope Down-slope shape: Concave Across-slope shape: Linear Parent material: Coarse-loamy lodgment till derived from gneiss, granite, and/or schist Typical profile Oe - 0 to 2 inches: moderately decomposed plant material A -2 to 9 inches: fine sandy loam Bwl - 9 to 20 inches: fine sandy loam Bw2-20 to 32 inches: fine sandy loam Cd-32 to 67 inches: gravelly fine sandy loam Properties and qualities Slope: 0 to 8 percent Surface area covered with cobbles, stones or boulders: 1.6 percent Depth to restrictive feature:20 to 43 inches to densic material Drainage class: Moderately well drained Runoff class: Medium Capacity of the most limiting layer to transmit water(Ksat):Very low to moderately low (0.00 to 0.14 i n/h r) Depth to water table:About 19 to 27 inches Frequency of flooding: None Frequency of ponding: None Maximum salinity: Nonsaline (0.0 to 1.9 mmhos/cm) Available water supply, 0 to 60 inches: Low(about 4.0 inches) Interpretive groups Land capability classification (irrigated): None specified Land capability classification (nonirrigated): 6s Hydrologic Soil Group: C/D Ecological site: F144AY037MA- Moist Dense Till Uplands Hydric soil rating: No Minor Components Paxton, very stony Percent of map unit: 10 percent Landform: Ground moraines, hills, drumlins Landform position (two-dimensional): Summit, shoulder, backslope Landform position (three-dimensional): Side slope, crest Down-slope shape: Convex, linear Across-slope shape: Linear, convex Hydric soil rating: No Ridgebury, very stony Percent of map unit: 8 percent Landform: Hills, drainageways, drumlins, depressions, ground moraines Landform position (two-dimensional): Toeslope Landform position (three-dimensional): Head slope, base slope Down-slope shape: Concave 15 Custom Soil Resource Report Across-slope shape: Concave Hydric soil rating: Yes 16 References American Association of State Highway and Transportation Officials (AASHTO). 2004. Standard specifications for transportation materials and methods of sampling and testing. 24th edition. American Society for Testing and Materials (ASTM). 2005. Standard classification of soils for engineering purposes. ASTM Standard D2487-00. Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of wetlands and deep-water habitats of the United States. U.S. Fish and Wildlife Service FWS/OBS-79/31. Federal Register. July 13, 1994. Changes in hydric soils of the United States. Federal Register. September 18, 2002. Hydric soils of the United States. Hurt, G.W., and L.M. Vasilas, editors. Version 6.0, 2006. Field indicators of hydric soils in the United States. National Research Council. 1995. Wetlands: Characteristics and boundaries. Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service. U.S. Department of Agriculture Handbook 18. http://www.nres.usda.gov/wps/portal/ nres/detail/national/soils/?cid=nres 142p2_054262 Soil Survey Staff. 1999. Soil taxonomy: A basic system of soil classification for making and interpreting soil surveys. 2nd edition. Natural Resources Conservation Service, U.S. Department of Agriculture Handbook 436. http:H www.nres.usda.gov/wps/portal/nres/detail/national/soils/?cid=nresl42p2_053577 Soil Survey Staff. 2010. Keys to soil taxonomy. 11 th edition. U.S. Department of Agriculture, Natural Resources Conservation Service. http:// www.nres.usda.gov/wps/portal/nres/detail/national/soils/?cid=nresl42p2_053580 Tiner, R.W., Jr. 1985. Wetlands of Delaware. U.S. Fish and Wildlife Service and Delaware Department of Natural Resources and Environmental Control, Wetlands Section. United States Army Corps of Engineers, Environmental Laboratory. 1987. Corps of Engineers wetlands delineation manual. Waterways Experiment Station Technical Report Y 87-1. United States Department of Agriculture, Natural Resources Conservation Service. National forestry manual. http://www.nres.usda.gov/wps/portal/nres/detail/soils/ home/?cid=nres 142p2_053374 United States Department of Agriculture, Natural Resources Conservation Service. National range and pasture handbook. http://www.nres.usda.gov/wps/portal/nres/ detail/national/landuse/rangepasture/?cid=stelprdb1043084 17 Custom Soil Resource Report United States Department of Agriculture, Natural Resources Conservation Service. National soil survey handbook, title 430-VI. http://www.nres.usda.gov/wps/portal/ nres/detail/soils/scientists/?cid=nres 142p2_054242 United States Department of Agriculture, Natural Resources Conservation Service. 2006. Land resource regions and major land resource areas of the United States, the Caribbean, and the Pacific Basin. U.S. Department of Agriculture Handbook 296. http://www.nres.usda.gov/wps/portal/nres/detail/national/soils/? cid=nres 142p2_053624 United States Department of Agriculture, Soil Conservation Service. 1961. Land capability classification. U.S. Department of Agriculture Handbook 210. http:// www.nrcs.usda.gov/lnternet/FSE—DOCUMENTS/nrcsl42p2—O52290.pdf 18 BORING LOG J111l�lllllll«' f 111 Project:Old North Pump Station Boat Ram ' J p p Location: North Andover, MA Boring No: B-1 Client:Town of North Andover Location: Near entrance to boat ramp Driller: Northern Drill Service, Inc. Approx. Ground Elevation: N/A Drilling Methods: Drive&Wash - Approx. Groundwater Elevation: N/A Weather: 50s, light rain Date/Time of Groundwater Elevation: N/A Performed By: AET Date: 10/24/22 Datum: N/A Checked By: Date: Boring Locus Map Project No. NOR120-0628071-22003302 Pen./ Blow Stratum Depth Sample Rec. Counts per Soil Description Change Note (feet) No. (Inch) 6 inch Depth (feet) B-1 0- 1 0-6"Dark brown,organic soil, moist Soil 0- 1.25 1.25 11 /15 11 6-11 Medium dense,grey, POORLY GRADED SAND WITH 100+ SILT, moist,few gravel,trace organics,white rock dust in tip Sand with Silt 1 2 1.25-9 N/A N/A N/A Roller bit used to through 8-foot Boulder Boulder 3 6 9- 11 B-1 9 9/24 4 Medium,grey,SILT,wet,some fine sand,trace gravel 11 4 4 Silt 11 - 14 N/A N/A N/A Unknown 51 14- 16 B-1 14- 14/24 21 Hard,grey,SANDY SILT,wet,little gravel, rock fragment in 16 30 tip p 28 Sandy Silt 16-19 N/A N/A N/A Unknown 21 B-1 19- 11 Silt with Sand 19-21 21 20/24 15 6 Hard,grey/light brown,SILT WITH SAND,wet,little gravel 25 4 END OF BORING NOTES: LEGEND 1.Split spoon refusal encountered at 1.25 feet Trace-Approximately<5% Few-Approximately 6%to 15% below ground surface(bgs) 2. Driller stated that boulder felt like it had a flat Little-Approximately 16%to 30% Some-Approximately 31%to 49% top and was fairly easy to drill through,indicating 0-4 Coarse Soil N Value-Very Loose 5-10 Coarse Soil N Value-Loose 11-29 Coarse Soil N Value-Medium Dense that it could be an old retaining wall 30-49 Coarse Soil NValue-Dense >50 Coarse Soil NValue-very Dense 3.Water table measured at 6.5 feet bgs 4. Boring terminated at predetermined depth of 21 0-3 Fine Soil N Value-Very Soft 3-4 Fine Soil N Value-Soft 5-8 Fine Soil N Value-Medium feet bgs 9-15 Fine Soil N Value-Stiff 16-30 Fine Soil N Value-Very Stiff >30 Fine Soil N Value-Hard ENVIRONMENTAL PARTNERS Page 1 of 1 BORING LOG J111l�lllllll«' f 111 Project:Old North Pump Station Boat Ram ' J p p Location: North Andover, MA Boring No: B-2 Client:Town of North Andover Location: Near boat ramp Driller: Northern Drill Service, Inc. Approx. Ground Elevation: N/A Drilling Methods: Drive&Wash - Approx. Groundwater Elevation: N/A Weather: 50s, light rain Date/Time of Groundwater Elevation: N/A Performed By: AET Date: 10/24/22 Datum: N/A Checked By: Date: Boring Locus Map Project No. NOR120-0628071-22003302 Pen./ Blow Stratum Depth Sample Rec. Counts per Soil Description Change Note (feet) No. (Inch) 6 inch Depth (feet) 5 0-6"Dark brown,organic soil Soil 0-2 B-2 0-2 8.5/24 9 6-8.5"Medium dense, light brown/dark brown/orange 8 POORLY GRADED SAND WITH SILT, moist,some organics Sand with silt 5 2-4 N/A N/A N/A Unknown 10 7 Silty Sand 4-6 B-2 4-6 11 /24 7 Medium dense,light brown SILTY SAND, moist, little gravel 8 1 6-9 N/A N/A N/A Unknown 34 9- 11 B-2 9 4/24 53 Very dense,light brown fine POORLY GRADED SAND WITH 11 57 SILT,wet, rock fragments in tip 55 11 - 14 N/A N/A N/A Unknown Sand with Silt 4 14- 16 B 2 14 14.5/24 4 Loose,light brown, POORLY GRADED SAND WITH SILT, 16 6 wet 11 16-19 N/A N/A N/A Unknown Silt with Sand, 4 0-101,Stiff,light brown,SILT WITH SAND,wet, laminated Laminated 19-21 B_2 19_ 17/24 6 10-17"Medium dense, light brown WELL GRADED SAND 21 10 15 WITH SILT,wet,some small gravel Sand with Silt 2 END OF BORING NOTES: LEGEND 1.Water table measured at 6.5 feet bgs Trace-Approximately<5% Few-Approximately 6%to 15% 2. Boring terminated at predetermined depth of 21 Little-Approximately 16%to 30% Some-Approximately 31%to 49% feet bgs 0-4 Coarse Soil N Value-Very Loose 5-10 Coarse Soil N Value-Loose 11-29 Coarse Soil N Value-Medium Dense 30-49 Coarse Soil N Value-Dense >50 Coarse Soil N Value-Very Dense 0-3 Fine Soil N Value-Very Soft 3-4 Fine Soil N Value-Soft 5-8 Fine Soil N Value-Medium 9-15 Fine Soil N Value-Stiff 16-30 Fine Soil N Value-Very Stiff >30 Fine Soil N Value-Hard ENVIRONMENTAL PARTNERS Page 1 of 1 BORING LOG J p p J1i1111I1 Project:Old North Pump Station Boat Ram Jll�,��lylll��l�flll111l1111�111111111��, „I;JJJ %;,n o,, Location: North Andover, MA Boring No: B-3 Client:Town of North Andover Location:On gravel in between B-1 and B-2 Driller: Northern Drill Service, Inc. Approx. Ground Elevation: N/A Drilling Methods: Drive&Wash - Approx. Groundwater Elevation: N/A Weather: 50s, light rain Date/Time of Groundwater Elevation: N/A Performed By: AET Date: 10/24/22 Datum: N/A Checked By: Date: Boring Locus Map Project No. NOR120-0628071-22003302 Pen./ Blow Stratum Depth Sample Rec. Counts per Soil Description Change Note (feet) No. (Inch) 6 inch Depth (feet) 8 Medium dense, brown lightening downwards, POORLY 0-2 B-3 0-2 14/24 7 GRADED SAND, moist, little gravel,trace silt,with 1" 8 7 organics layer at 4" Sand 2-4 N/A N/A N/A Unknown No 11 10 Medium dense, light brown,SILTY SAND,wet,little gravel, 4-6 sample 2/24 10 rock fragment in tip collected 8 Silty Sand 1 6-9 N/A N/A N/A Unknown 17 9- 11 B-3 9 15/24 21 Dense,light brown, POORLY GRADED GRAVEL WITH 11 20 SAND,wet,little silt Gravel with Sand 18 11 - 14 N/A N/A N/A Unknown 17 14- 16 B-3 14- 17/24 15 Dense,light brown, POORLY GRADED SAND WITH SILT, 16 15 wet,trace gravel,sections with thin laminations Sand with Silt 17 16-19 N/A N/A N/A Unknown 28 Sand with Gravel B-3 19- 34 0-10"Very dense,light brown, POORLY GRADED SAND 19-21 21 24/24 42 WITH GRAVEL,wet,trace silt 67 10-24 Hard,light brown,SILT WITH SAND,wet,trace gravel Silt with Sand 2 END OF BORING NOTES: LEGEND 1.Water table measured at 6.5 feet bgs Trace-Approximately<5% Few-Approximately 6%to 15% 2. Boring terminated at predetermined depth of 21 Little-Approximately 16%to 30% Some-Approximately 31%to 49% feet bgs 0-4 Coarse Soil N Value-Very Loose 5-10 Coarse Soil N Value-Loose 11-29 Coarse Soil N Value-Medium Dense 30-49 Coarse Soil N Value-Dense >50 Coarse Soil N Value-Very Dense 0-3 Fine Soil N Value-Very Soft 3-4 Fine Soil N Value-Soft 5-8 Fine Soil N Value-Medium 9-15 Fine Soil N Value-Stiff 16-30 Fine Soil N Value-Very Stiff >30 Fine Soil N Value-Hard ENVIRONMENTAL PARTNERS Page 1 of 1 4/27/23, 11:11 AM Precipitation Frequency Data Server NOAAAtlas 14,Volume 10,Version 3 Location name: North Andover, Massachusetts, , USA* Latitude:42.71460 Longitude: -71.11270 ` Elevation: m/ft** *source:ESRI Maps **source:USGS POINT PRECIPITATION FREQUENCY ESTIMATES Sanja Perica,Sandra Pavlovic,Michael St.Laurent,Carl Trypaluk,Dale Unruh,Orlan Wilhite NOAA,National Weather Service,Silver Spring,Maryland PF tabular I PF graphical I Maps & aerials PF tabular PDS-based point precipitation frequency estimates with 90% confidence intervals (in inches)' Duration Average recurrence interval (years) 1 2 5 10 25 1 50 1 100 IL 200 L 500 1000 5-min 0.310 0.370 0.467 0.548 0.659 0.743 0.831 0.928 1.07 1.18 (0.244-0.384) (0.291-0.458) (0.366-0.582) (0.427-0.686) (0.496-0.861) (0.547-0.992) (0.592-1.15) (0.627-1.32) (0.691-1.56) (0.744-1.76) 10-min 0.439 0.524 0.662 0.777 0.934 1.05 1.18 1.31 1.51 1.67 (0.346-0.544) (0.412-0.649) (0.518-0.823) (0.604-0.972) (0.703-1.22) (0.776-1.40) (0.839-1.63) (0.888-1.86) (0.979-2.21) (1.06-2.50) 15-min 0.517 0.616 0.778 0.913 1.10 1.24 1.38 1.55 1.77 1.96 (0.407-0.640) (0.484-0.764) (0.610-0.968) (0.711-1.14) (0.827-1.44) (0.912-1.65) (0.987-1.91) (1.05-2.19) (1.15-2.61) (1.24-2.94) 30-min 0.711 0.848 1.07 1.26 1.51 1.71 1.91 2.13 2.44 2.70 (0.560-0.881)L(O-667-1.05) (0.840-1.33) (0.979-1.58) (1.14-1.98) (1.26-2.28) (1.36-2.64) (1.44-3.02) (1.59-3.59) (1.71-4.05) 60-min 0.906 1.08 1.37 1.60 1.93 2.17 2.43 2.71 3.11 3.44 (0.713-1.12) (0.850-1.34) (1.07-1.70) (1.25-2.01) (1.45-2.52) (1.60-2.90) (1.73-3.36) (1.83-3.84) (2.02-4.57) (2.18-5.15) 2-hr 1.17 1.40 1.78 2.10 2.53 2.86 3.20 3.62 4.24 4.77 (0.925-1.43) (1.11-1.72) (1.41-2.20) (1.65-2.61) (1.93-3.30) (2.13-3.81) (2.32-4.45) (2.45-5.10) (2.76-6.19) (3.03-7.10) 3-hr 1.35 1.62 2.07 2.45 2.96 3.35 3.76 4.27 5.05 5.72 (1.07-1.65) (1.29-1.99) (1.65-2.55) (1.93-3.03) (2.27-3.86) (2.51-4.46) (2.74-5.23) (2.90-5.99) (3.29-7.34) (3.64-8.47) 6-hr 1.72 2.08 2.68 3.18 3.86 4.36 4.91 5.60 6.66 7.59 (1.38-2.09) (1.67-2.54) (2.15-3.28) (2.53-3.91) (2.98-5.00) (3.30-5.79) (3.61-6.81) (3.82-7.81) (4.36-9.63) (4.84-11.2) 12-hr 2.15 2.63 3.41 4.06 4.96 5.61 6.33 7.22 8.61 9.80 (1.75-2.60) (2.13-3.19) (2.76-4.15) (3.26-4.97) (3.85-6.37) (4.27-7.40) (4.68-8.72) (4.95-10.0) (5.65-12.4) (6.27-14.3) 24-h r 2.54 3.16 4.16 5.00 6.15 7.00 7.93 9.10 10.9 12.6 (2.08-3.05) (2.58-3.80) (3.40-5.03) 4.05-6.07 (4.82-7.88) (5.37-9.19) L(5.91-10.9) (6.27-12.5) (7.21-15.6) (8.06-18.3) 2-day 2.84 3.60 L(3 85 5.89 7.31 8.35 9.51 11.0 13.5 15.6 (2.35-3.39) (2.98-4.31) -5.82) (4.81-7.10) (5.78-9.33) (6.47-10.9) (7.18-13.1) (7.61-15.1) (8.90-19.1) (10.1-22.6) 3-day 3.12 3.93 5.27 6.38 7.91 9.02 10.3 11.9 14.6 16.9 (2.59-3.71) (3.27-4.68) (4.36-6.30) (5.24-7.67) (6.29-10.1) (7.02-11.8) (7.79-14.1) (8.25-16.3) (9.64-20.6) (10.9-24.4) 4-day 3.39 4.23 5.61 6.75 8.32 9.47 10.8 12.4 15.2 17.6 (2.83-4.02) (3.53-5.02) (4.66-6.68) (5.57-8.09) (6.64-10.6) (7.39-12.3) (8.17-14.7) 1(8.64-16.9) (10.1-21.4) 1(11.4-25.3) 7-day 4.13 5.00 6.43 7.61 9.23 10.4 L(895-15.9) 1.7 13.5 L(10'8-22-8) 6.3 18.8 (3.48-4.87) (4.20-5.91) (5.38-7.62) (6.32-9.07) (7.41-11.6) (8.17-13.5) (9.40-18.2) (12.2-26.8) 10-day 4.80 5.70 7.16 8.37 10.0 11.3 12.6 14.3 17.1 19.6 (4.06-5.65) (4.81-6.70) (6.02-8.45) (6.98-9.94) (8.07-12.5) (8.85-14.4) (9.60-16.9) (10.0-19.3) (11.4-23.9) (12.7-27.8) 20-day 6.70 7.69 9.30 10.6 12.5 13.9 15.3 17.0 19.5 21.6 (5.72-7.82) (6.55-8.99) (7.89-10.9) (8.96-12.6) (10.1-15.4) (10.9-17.5) (11.6-20.0) (12.0-22.7) (13.1-27.0) (14.0-30.4) 30-day 8.28 9.35 11.1 12.5 14.5 16.0 17.6 19.2 21.5 23.3 (7.11-9.64) (8.01-10.9) (9.46-13.0) (10.6-14.7) (11.8-17.7) (12.6-20.0) (13.2-22.7) (13.6-25.6) (14.5-29.6) (15.2-32.7) 45-day 10.3 11.5 13.3 14.9 17.1 18.7 20.4 22.0 24.1 25.6 (8.89-11.9) (9.87-13.3) F(l .4-15.5) (12.7-17.4) (13.9-20.7) (14.8-23.1) (15.3-25.9) (15.7-29.1) (16.3-33.0) (16.7-35.9) 60-day 12.0 13.3 15.2 16.9 19.2 21.0 22.7 24.3 26.3 27.7 (10.4-13.9) (11.5-15.3) (13.1-17.7) (14.4-19.7) (15.6-23.1) (16.6-25.8) (17.0-28.7) (17.3-32.0) (17.8-35.9) (18.1-38.7) 1 Precipitation frequency(PF)estimates in this table are based on frequency analysis of partial duration series(PDS). Numbers in parenthesis are PF estimates at lower and upper bounds of the 90%confidence interval.The probability that precipitation frequency estimates (for a given duration and average recurrence interval)will be greater than the upper bound(or less than the lower bound)is 5%.Estimates at upper bounds are not checked against probable maximum precipitation(PMP)estimates and may be higher than currently valid PMP values. Please refer to NOAAAtlas 14 document for more information. Back to Top PF graphical https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=42.7146&Ion=-71.1127&data=depth&units=english&series=pds 1/4 4/27/23, 11:11 AM Precipitation Frequency Data Server D "- " el p'tII,i- uto�n- °_ Icy DDF curves, L ti Li e: 4. . , 4 I,"', L,o,nI etude -71,1127 30 Average re,��ijirrpm�we, W ry r �W Yr 2 _ �Ifl �..... I,.•...� ��. �� . 1 „.� II Y �.II IV.....� ,,� �, A W W WMl flp q r';Iw, byp;, r y,[ IV% 9 yff•'IMIIVyti u N u ! 91 u 91 u w 91 u u I i�' VV,'+Y, G J d M II G II G LL II d G J II M IM�W Il�lldlfdflAmlWAFfWl�lldlflAml��l�llf(RdflAmlAFf�Af�tld fdfldl�I�IIdNAllfdflAmlWAFf�l�lld fdflAmlWAFf�l�lldlfdflAmlWAFf�l�lld fdflAmlWAFf�l�lldlfdflAmlWAFf�l�lldlfdf(R II 1 4 1 YI II VI II IV VI 4 II 1 YI �N X�''A W Y I ta Ir W Ir W Po Ir I W Y I 4 . � 1!W�IWWwwWWWWWN9'WW'4 ya-r-Yr W w W ul w m w W m w II W w '1100,I IA 11✓ v w smuyw�M A ii iiiii. iu x i. u..iii W ii iiiii.� Wu.iii iu. i iiiin W u Ti µIYIWIW" iiiiii r. e o W LL..IIII"" III . i�,�e n . — r �n I NY • �Y .. .r I „Ty, ii i 1 NA N NIIi'� IM1 MJ F II II YI A ^� ,17 �� W W W W YI W W W VI V�IIw „YI..+YIµlllV. w m M z a w ¢ y ml� a i V,V�' �ry lu�nnllllllllllllllllllllllllluuiwr� �, Wv .. »rn��. .0 v �w�„ ��. wW .� u w ,A fur✓°wmvv� 1 u A �w,� r�l I Imrv" � ��i1P P elf r ro lA 0 Ia d�rA 4-4 ul +r My W ei or d „dV p qyu4i"" L Ir�pI�A .li� IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII Nm""�u ulw) LNd" 4 N w w VI 4 VI 4 �W VI �wwimlYWll,*!s s u:,l p°ry �� m nHl W ry u n u u II W i,,r' dal�aW�Wwll ldludN w ,�,e n / ��vu !w,l�� III uul�r, � w �v u u AI I vl":.�rWu�W i,y"' rrn�vl a;�� r)re W�I��I -k''"", �y JVG.., I.�. ^ ��,,��, rv, ��m�. ��e .m a m "�� J � al J Iwu Ww'° �, V �� rr,.✓ ""IIF rl„�'v�,uli^ry rr a dr Y�l�a�� Ir W ea"MI, 0A 'ry L r00 7n u v rulYrA"w lw rlr'uq IWV �"�y' I��ar yr lu�v'rN" � r '��,. �tr:.✓rwurA ,14�n✓are,.,r r III � m.d!�vl��Iwrl„�+„ 4vvIII I1d..�,,,�,,.Y I uw�,iYuJ��,,, e'U w� ��,�e — .1 u 0 j� why-y',�' r.................. u wuaf v... tt ul uc.wwIrca�uil>naa^w.y uu�Irw��dur�mu.wN "'wr" @ G A u 7u, "�,um w ry m u >�I � wwuu� „( % .arrwv»„rrrorlrw,.rm .u;avi, rrarvw�«m,�"^�y��vvvvvvvrrmr�" u� u u m u u n'i u Y ®Y,ry r rn mw r M cvi, e � ��l� ,(mY,um..iQ4v,L,ww„urunn»v vvvvv�clnw r I 11,��AJ'� 11AIW�a '1@I.V,NW QmANIDYI �WWtlk L., ',,'', ..IIP'% }A� A,RMAAI 9 AAA NI I 0 RA^AAIA IANGPIIW Id WWA M W 0Ln 0 M n M fu ra 30 N I I I G d d G M II II II II 'L A II 9 VI VI YI Ji Ji I W W W �9'II��'I� Wiwi.II � uNIY "• " III W�. M III I IIIwSIP�IWiw"w"I*""� V m v '1� up �,IHuu'AwAP'rIIMu S Il N li li Ai Ai � I,�til' � W W W W W WmdWrxYtll W. ,.,A �rdm�i G io io G Ji w r1 NWWI"Y Y IWW"° ul N �mu �' a .Il w rrl.YluuNYwVY"'Y!Y N'" J o� 11110 �� .w w 20 m N W W A I.w+"r w mm°Wi �r '—dly "e e ray. .W auvA v" I�,ulN�mlr'"��w uN•ur dl A aIN„mr'"'° a W u^wuu r V'�" °rar�v u Iva 10-4jynin . a �� w�v vvv vv, r V ' a r°✓ m Iwu�wwn u u u r,H.' u;w"'• A wr m � a A,'aII II i..v.... a rr` a'� r�,v W�%IV^ 'w,wAwwwN;uuw>'ww;wr>'uv r �N Ir � W rv� iidYB �� dAW." e ^ uW�i Fl"'�uU,�dl sill,IM`d Mw' " vAvx"'""'W'�o"Illvw ^Iwmrvraumm m � � o„r uu ,I .au � mA uu1,. n uJJtii0000000000m P �6 y m uuuaWlrm v�vralm•�u a „.,,,, �vvv mrIN v.»mvv✓r rw L.v..»m.✓invmm.".-,'dui''I w'r'�'"am Iwr.al e rA w vvI,I I rn�r..—^'^mWvY r rtuaVL°�°mr',u��vsm�vrrv,.!�Wlw.uu!w ;'ry,�,wwwiv�,..e�u wrrrdur r�°va,�a'ua'r Yrw""IIAlevvr w.d..,..r+,I�nI7��Irn^W'I°''v'.',,w u,''�✓r m IUv^'Iw�a uvwv v ulµry^,'rr i.rNa nmr��uW,��irr,,,.,,,m,llrl"';.., r rr ahAw,,,,,,.w,x�l n�ro,,�c a, ..�irrnr,lr,n�,o,,,l l .��vWu.w, �uI�wYaYu>hmYWyWyyMyYyWy ylWl'IWYwr III'v V IUpk _G 10 W �Aw '9 , . day e 1, IL x m Ia. � wr a w r e �� r nW rrrrrw �w4NN _d lyrvnr, LL✓'""v,✓" rdl.W�'�'� ll.;,,,iii „c... - '� w mmuummw' �uuvAl�"timu 'aouw'Wr"i—rrmllmlr,w i Wl un� ^ 'uumormru0 ... ,,,A" a I�. w. y r r ;;,,,,,�„ �r worrfm;rm nWv ��;v,,vu. �mr m lo/ ..,. ,,,c,,;.. ,.,,,MIU�I ..., �, ,,,, 4�,,,.. - � 60—m�u�iv��i� II it un � � w�Mm�r�r�ror � �,j�iil IIOWr1ryP �lr.di y„�, OVII � rwl,Iflll,,�'°a',;o„ wuum �nmmul .....,,,,,., ,,,,,,i ... ,,,,,, m„ v.wv� r r rmnWu«vwvvvvvvv�wwwwwwv�vvvv.;rrralaartnirrrrc:r,° ,ii„ r .,,,;,,,,,,, y w rVr �L4f/IIIIN...AAW r«lfVialYlJlylr!�. i�i iiiii,i l(llllll l%%%/%J/) ii.rlrW///////flPf)Yll ......... .. it �i�P&I,,�rrn�.v oo mv�u�irrnn;�r.....r......ririwww,it »i✓/ �///f �"'"v',rx f/a ,,,,,,,,,,,,,...., �NJMI m 2 �.r . 21"15 50 1010 2,00 5 Average j"-eA a rrei eY inte,rval (yeacris) t I a s 1.4,Vol me 10,"Vel,rs,io n, 3 C11 related(G M T) T h u AP r 7 15: ..1.34 Back to Top 11 Maps & aerials Small scale terrain https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?Iat=42.7146&Ion=-71.1127&data=depth&units=engiish&series=pds 2/4 4/27/23, 11:11 AM Precipitation Frequency Data Server rJ/��/�� r,/✓%,:. n��/y,"wpNW!f i/r �� io/, �/J rf rm+✓ Iu,rr. �/ ,Iv,.r:Jl �a,% / ..,n ,v r""/ / llj/', ,, rj„r na na ior+v,/rardrwvr lu fe l ,k!`r >/ci�G�f✓mvr rri n+r�fFF' �// fi�� ,r// ✓'r// �faa nm w YI �,' //i /�'% ,;vn6'9a yrv;,,r^ �1naurliiD'➢,� rum ��jl r,rinrr rl „erdNlrulNI X, r;,,'h' JvJNr>y',Id,Wr� "'I;,." J �"` �` �`ri' �J�l <�r d1 111/98 f Imo, pg rdJ V /(/ FRI / /4y Sit ; /l m+y!>✓ fl r, k Sul f�3 w^�VIvVI.: ,,?r�,urr airF I,v /'11i! �„,,�w I� p 7 'li of ofi r„ 1f,i W irPfiJi� 1u��6 4 v ter.. "irrpao rr/rrciiir,.. wI r, ,� % "%/i% '�IV(✓ .t.. ,..IW1), /'�,, a �'If �/////��,,r,",;, ,rihoP r o J4d/� / r� �t 4ry Jm. ■�M 11,V�:,,.#vie„ 4N, ,! "�rrw lPl' 1i Iy "///'' �r b IG ,a w. 4 P¢�%/� ,, �J liGu,zalJ?,f �° d I' r.Auu,: Ip 01 % i%' ...... 1111 Large scale terrain r,,,/J�(1.,r///1i/� /�r/�J�// //�, r�✓ r 1 ///�y�;ri�o� %///r,,,� '%/ � ��," �Gi '4 .',r. " 1 /,.,%/1 .,�,� � �i ,.//i /r/f�„:. /� ;r/.flll/sari%,/o ,r r,,,,�iiii/.r/,r ,,,, cr,✓.,. ,,,i� ,".rrr U///�I,ar f�✓ / i/,,, i� � /,;, ? /,/ /iiiri�i, vro,r, ,,,of it f/,r,��,//�v/P i ,,,,///� /.,/�� ..,,, / ✓// 'ci�, .// ,;, ,, r r �✓m,.,� a �/ ,;,,/J ,e>.:,, r��,,,,, / ,rr /i/„,'' �/ rrrr„/,/ %%////f%%.� /�'��.,r ,,/ G;:r�� rr,.I�/..///,�//// ,o ,irr ";,` ,rr.: ,�:/%�/ ✓/ r,,,,, ;�i/ r,, //// rr, ,/. %, � e � / ,-r/,/!/,�/r,rr, � or/ / /„rrrr,✓/, /, / IVJi ../ 1, / r%r/✓.. ,r �"r�/r. / r r /, Y /,.,.,.. :,,; r,.,/ /..., ✓r /r....... rrr/ / / j f r 1�/r d r/�i�,r//,., r/• /.-,�„ r�Al a rrr,/ I! :,:, ,iii, ., //, ,,,,,.,/� /ii I ./��.////�i„�,.r..✓,rr I� rr r..,i//% /,::.,, r r �, ,,,;,rii / 1, .✓ ,: ,///// � � // r I.. r,/,... �,. /✓�,/,,, ,/,r „�r r r / rrrr, ,,, :..r �.. ,� / rr: /,„�.,✓ri v/e i r/��;r o,,//r ////�r 1....,, /� ,i, ,,,, i„rrr,: �/ �/ „,,r ✓rr,...,,,, /,,. r,,,.., v�, /„ / ,,, /r„r,,,,rrrr,,,,,,/.r� ..� � /jj / 1 /I ,.. / ,/�„/,,./r�r,,,,sr„ rr r/%r rv,r ../rr,,, rrrr a„✓„ / :r � .../j /l�IrI��,,,,,n;,✓,Jr�l//i/rlr/ii;/�Ir.,a..%r�/ii r/i I/��r/�r1fc:,..,.G�'�i Y(ryi,,/r,,�,./,Ir///r ID y,p/f!r rial:l/ "/r,/,rr;i a;;,,/ir/�,,k/r, I�fr"n�I,ri,ll/.,.,.r.:.a,eNrr,%.,fi�/>��,r nlr r,,,, ,fir , ,, �r ;:�,/�//i/�/i�/'�/I/�//%ii� 1/0"ii;_ b nit � , /i„.. r,r, Hi�flf fl', lYr L' ,J Vi➢1 i ,a/iiii/, / ,,rJ//0 iii///,,,.." rr ,r //� .i{ / r, / /,,,,rrr,,,,/��,. i//% ✓ r,'J, N ,, ,r � ,.,J //! /,� / lr�,Ii ��<,l,/,,,,,>r" ,, r ri,r 'j r1IP, '�//j%//%/ f� 9;;i" 10 0 11k, irn y dAi.'Mr�l Large scale map %rr�r�Y I I i Pf r,,Jrd 1II�4.I�,� ��n,',iii�u,p��la�,..@ u'iu iw o�� , I I y ufi µHall, ( U' II I Y awl 0'n C O n N�Iw J r u �001 dfi if Y�"r Jl f J�, / 1 r yy l s h u „I,�r J � I P, If falls; (gip ulOF, ,rrrr gamU/nori,�A� wr,vm�� n rcl Ju nine„arrr�r �. rmvlfhmur��lkuww�u 4rf µ 8 � v II V Ieladul. r wr r anrllr ryeH wd 0 4a es 1) 11 Il1ki L a a 1.1 w Bec J/10/01 rw Large scale aerial https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=42.7146&Ion=-71.1127&data=depth&units=english&series=pds 3/4 4/27/23, 11:11 AM Precipitation Frequency Data Server e r i e e Ini III Back to Top US Department of Commerce National Oceanic and Atmospheric Administration National Weather Service National Water Center 1325 East West Highway Silver Spring, MD 20910 Questions?: HDSC.Questions@noaa.gov Disclaimer https://hdsc.nws.noaa.gov/hdsc/pfds/pfds_printpage.html?lat=42.7146&Ion=-71.1127&data=depth&units=english&series=pds 4/4 CS iii,od r ry , 4 Number's (CN) Y I "V Rational ,;,V, runoffcoeff V I Ipe,nid on, the so,11;� infiltration 'rate,, "ba,se, storage anddesign storm, In G urr ", Y i ^IW. a ', N values, than r" ""Vr,.."" y"`"" us I e.p 'u, f6`p ( ",l`, e table, ry i „I. below,,,-, ,,,, Land I j i i i r (mmfhri(d) ., " 0.00 Interiocking (1,270 ...10.30 Pavement Irv""-ii w" r" °„ "ii, '(I h " 1,00 airn,"1011)''r) wit"17 Manufacturer value ............. i i (Ou 'n Ih rW,- 98 01,1190 Asphalt ,or 0.95 d Pavement f y �, r RUNOFF FI VALUES r used t�� -w u e�kl� � r��i�._.� �� wa,t,e�r� t.ruris off differ �, rf �� °�� .��,� example, brturfi),ous asph,alt h,asiiCvalue-o 5.Thi rir7i,,I, 5 percent of tl wat. r i[I ru n Off the u f �I, ,, r n CDesfign in Coils';uc i(ari&Saiii-iitary an . ri ,Sewer s,A.miericanSociety f Cl °il,,,',",Fz'n,g,irieers,, New Yrark, p., III i1 C,O,M a i i„s oG,G t L,r rf'ha,s a C,vak,i,ei,of 0,1 S or 1551 P rn�t_The C ki f perim�eable p v i g, with, up zi 5 per,cent, :L pe,i n �, s e, ta� zero, ,I� t.f� rm��f��.11� i� t��r�G�r+ �� .I �� ,� d,irl �� i r . �� I �i��i�� r �_I r� � ��G�� Icapacity i i , r� � r _ m � ic � � � �� . _�I T � � � r �i � � r face� fg l �� r�z rea � r �ap ATTACHMENT 6 EXISTING MODEL REPORT is) 2S SC-01 SC-02 1 R DP-1 - Lake Cochichewick Subcat Reach Pond Link Routing Diagram for Existing_N.Andover Boat Launch Prepared by Apex Companies, Printed 5/12/2023 HydroCAD®10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Existing_N. Andover Boat Launch Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 2 Rainfall Events Listing (selected events) Event# Event Storm Type Curve Mode Duration B/B Depth AMC Name (hours) (inches) 1 2-yr, 24-hr Type II 24-hr Default 24.00 1 3.16 2 2 10-yr, 24-hr Type II 24-hr Default 24.00 1 5.00 2 3 100-yr, 24-hr Type II 24-hr Default 24.00 1 7.93 2 Existing_N. Andover Boat Launch Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 3 Area Listing (all nodes) Area CN Description (sq-ft) (subcatchment-numbers) 217593 74 >75% Grass cover, Good, HSG C (1 S, 2S) 51074 96 Gravel, HSG C (1 S) 41843 98 Paved, HSG C (1 S, 2S) 81288 70 Woods, Good, HSG C (1 S, 2S) 3%798 79 TOTAL AREA Existing_N. Andover Boat Launch Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 4 Soil Listing (all nodes) Area Soil Subcatchment (sq-ft) Group Numbers 0 HSG A 0 HSG B 39798 HSG C 1 S, 2S 0 HSG D 0 Other 3%798 TOTAL AREA Existing_N. Andover Boat Launch Prepared by Apex Companies Printed 5/12/2023 HydroCAD® 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 5 Ground Covers (all nodes) HSG-A HSG-B HSG-C HSG-D Other Total Ground Su (sq-ft) (sq-ft) (sq-ft) (sq-ft) (sq-ft) (sq-ft) Cover NL 0 0 21,593 0 0 21593 >75% Grass cover, Good 0 0 5,074 0 0 5,074 Gravel 0 0 4,843 0 0 4,843 Paved 0 0 8,288 0 0 8,288 Woods, Good 0 0 39,798 0 0 393798 TOTAL AREA Existing_N. Andover Boat Launch Type //24-hr 2-yr, 24-hr Rainfall=3.16" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 6 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1S: SC-01 Runoff Area=21,643 sf 13.26% Impervious Runoff Depth=1.51" Flow Length=206' Tc=5.0 min CN=82 Runoff=1.39 cfs 2,716 cf Subcatchment 2S: SC-02 Runoff Area=18,155 sf 10.87% Impervious Runoff Depth=1.12" Flow Length=141' Tc=5.8 min CN=76 Runoff=0.84 cfs 1,701 cf Reach 1 R: DP-1 - Lake Cochichewick Inflow=2.22 cfs 4,417 cf Outflow=2.22 cfs 4,417 cf Total Runoff Area= 39,798 sf Runoff Volume =4,417 cf Average Runoff Depth = 1.33" 87.83% Pervious= 34,955 sf 12.17% Impervious =4,843 sf Existing_N. Andover Boat Launch Type //24-hr 2-yr, 24-hr Rainfall=3.16" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 7 Summary for Subcatchment 1 S: SC-01 A Tc of 5-min min. was used Runoff = 1.39 cfs @ 11.96 hrs, Volume= 2,716 cf, Depth= 1.51" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 2-yr, 24-hr Rainfall=3.16" Area (sf) CN Description 51074 96 Gravel, HSG C 21870 98 Paved, HSG C 47233 70 Woods, Good, HSG C 97466 74 >75% Grass cover, Good, HSG C 211643 82 Weighted Average 181773 86.74% Pervious Area 2,870 13.26% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.3 28 0.0380 1.37 Sheet Flow, Sheet flow, first 50', paved Smooth surfaces n= 0.011 P2= 3.16" 0.4 23 0.0164 0.94 Sheet Flow, Sheet flow, first 50', gravel Smooth surfaces n= 0.011 P2= 3.16" 1.4 139 0.0070 1.70 Shallow Concentrated Flow, SCF, gravel driveway Paved Kv= 20.3 fps 0.0 16 0.1400 7.60 Shallow Concentrated Flow, SCF, paved boat ramp Paved Kv= 20.3 fps 2.1 206 Total, Increased to minimum Tc = 5.0 min Existing_N. Andover Boat Launch Type 1124-hr 2-yr, 24-hr Rainfall=3.16" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 O 2022 HydroCAD Software Solutions LLC Page 8 Subcatchment 1 S: SC-01 Hydrograph 1.39 cfs —Runoff Ylow, � 24, h r ai f l = .1------------- ' Ru f .............. ---------------- e 1641 N w 3 f lu 271 LL f p oL.e th 6 T =8 U.M.p... III III U 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Existing_N. Andover Boat Launch Type //24-hr 2-yr, 24-hr Rainfall=3.16" Prepared by Apex Companies Printed 5/12/2023 HydroCAD® 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 9 Summary for Subcatchment 2S: SC-02 Runoff = 0.84 cfs @ 11.98 hrs, Volume= 1,701 cf, Depth= 1.12" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 2-yr, 24-hr Rainfall=3.16" Area (sf) CN Description 11973 98 Paved, HSG C 4,055 70 Woods, Good, HSG C 125127 74 >75% Grass cover, Good, HSG C 181155 76 Weighted Average 161182 89.13% Pervious Area 17973 10.87% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.3 14 0.0200 0.92 Sheet Flow, Sheet flow, first 50', paved Smooth surfaces n= 0.011 P2= 3.16" 4.4 36 0.0190 0.13 Sheet Flow, Sheet flow, first 50' Grass: Short n= 0.150 P2= 3.16" 0.7 56 0.0400 1.40 Shallow Concentrated Flow, SCF, lawn Short Grass Pasture Kv= 7.0 fps 0.4 35 0.0900 1.50 Shallow Concentrated Flow, SCF, woods Woodland Kv= 5.0 fps 5.8 141 Total Existing_N. Andover Boat Launch Type //24-hr 2-yr, 24-hr Rainfall=3.16" Prepared by Apex Companies Printed 5/12/2023 HydroCAD® 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 10 Subcatchment 2S: SC-02 Hydrograph 0.9 .......... ..... .............. ................. ..........................--------------- 0.84 cfs —Runoff 0.85 0.8 0.75 .............:,.......... .....................'..... .............,..............' 0.7 0.65 . ........ 3 ......................... 1914---hr a ----- 1 0.6 ........................................ ......................................... 0.55 e 0 1 .... ...............''..............''.....................:' 0.5 ', 1-117101 3 0.45 .......................... ...................................... 0 f. a p .1 . ...................... ........................................................................................................................................ ................................................................ .................................................. .........._...... e. 5 � 0.3 ............. ———------------- 0.2 5 ....................'......'..............' ..........................................'..............' ................................................................................................'.............'..............' T rini ----- 0.2 ....... ............ 0.15 ........... ......................... 0.1 .......................'............' .............................'... ........................................'..........'...................................................................................................:....... ..:'....................'................................................................ 0.05 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Existing_N. Andover Boat Launch Type //24-hr 2-yr, 24-hr Rainfall=3.16" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 11 Summary for Reach 1 R: DP-1 - Lake Cochichewick DP-1 is used as a common point (Lake C.) to analyze peak flows in existing and proposed conditions [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 39,798 sf, 12.17% Impervious, Inflow Depth = 1.33" for 2-yr, 24-hr event Inflow = 2.22 cfs @ 11.97 hrs, Volume= 4,417 cf Outflow = 2.22 cfs @ 11.97 hrs, Volume= 4,417 cf, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Reach 1 R: DP-1 - Lake Cochichewick Hydrograph 2.22 cfs Inflow Outflow f Are. f 3 0 1 ........................-------............... .'' ....................................................... ........................................... ..............'....................................... 0 t 7]117117117117117]11 17171717 1�71�71�717 1111117117]11 711MIMIMIrIl 711711711711711 U... MIM111MMIM117117]JI711 1"� M"�FMM"711 Ill,Ill,m m U u u u u U� 711" �1711111117 4p��"" 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Existing_N. Andover Boat Launch Type //24-hr 10-yr, 24-hr Rainfall=5.00" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 12 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1S: SC-01 Runoff Area=21,643 sf 13.26% Impervious Runoff Depth=3.08" Flow Length=206' Tc=5.0 min CN=82 Runoff=2.78 cfs 5,553 cf Subcatchment 2S: SC-02 Runoff Area=18,155 sf 10.87% Impervious Runoff Depth=2.54" Flow Length=141' Tc=5.8 min CN=76 Runoff=1.90 cfs 3,836 cf Reach 1 R: DP-1 - Lake Cochichewick Inflow=4.66 cfs 9,389 cf Outflow=4.66 cfs 9,389 cf Total Runoff Area= 39,798 sf Runoff Volume =9,389 cf Average Runoff Depth =2.83" 87.83% Pervious= 34,955 sf 12.17% Impervious =4,843 sf Existing_N. Andover Boat Launch Type //24-hr 10-yr, 24-hr Rainfall=5.00" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 13 Summary for Subcatchment 1 S: SC-01 A Tc of 5-min min. was used Runoff = 2.78 cfs @ 11.96 hrs, Volume= 5,553 cf, Depth= 3.08" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 10-yr, 24-hr Rainfall=5.00" Area (sf) CN Description 51074 96 Gravel, HSG C 21870 98 Paved, HSG C 47233 70 Woods, Good, HSG C 97466 74 >75% Grass cover, Good, HSG C 211643 82 Weighted Average 181773 86.74% Pervious Area 2,870 13.26% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.3 28 0.0380 1.37 Sheet Flow, Sheet flow, first 50', paved Smooth surfaces n= 0.011 P2= 3.16" 0.4 23 0.0164 0.94 Sheet Flow, Sheet flow, first 50', gravel Smooth surfaces n= 0.011 P2= 3.16" 1.4 139 0.0070 1.70 Shallow Concentrated Flow, SCF, gravel driveway Paved Kv= 20.3 fps 0.0 16 0.1400 7.60 Shallow Concentrated Flow, SCF, paved boat ramp Paved Kv= 20.3 fps 2.1 206 Total, Increased to minimum Tc = 5.0 min Existing_N. Andover Boat Launch Type 1124-hr 10-yr, 24-hr Rainfall=5.00" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 O 2022 HydroCAD Software Solutions LLC Page 14 Subcatchment 1 S: SC-01 Hydrograph 3 2.78 cfs —Runoff ylow, � 1 z r ai f I ..... = .0 ' o f e 1 64,43 N 11 w 3 fd 5553 LL f p = .0 ' o e th:=206............................... T 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Existing_N. Andover Boat Launch Type //24-hr 10-yr, 24-hr Rainfall=5.00" Prepared by Apex Companies Printed 5/12/2023 HydroCAD® 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 15 Summary for Subcatchment 2S: SC-02 Runoff = 1.90 cfs @ 11.97 hrs, Volume= 3,836 cf, Depth= 2.54" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 10-yr, 24-hr Rainfall=5.00" Area (sf) CN Description 11973 98 Paved, HSG C 4,055 70 Woods, Good, HSG C 125127 74 >75% Grass cover, Good, HSG C 181155 76 Weighted Average 161182 89.13% Pervious Area 17973 10.87% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.3 14 0.0200 0.92 Sheet Flow, Sheet flow, first 50', paved Smooth surfaces n= 0.011 P2= 3.16" 4.4 36 0.0190 0.13 Sheet Flow, Sheet flow, first 50' Grass: Short n= 0.150 P2= 3.16" 0.7 56 0.0400 1.40 Shallow Concentrated Flow, SCF, lawn Short Grass Pasture Kv= 7.0 fps 0.4 35 0.0900 1.50 Shallow Concentrated Flow, SCF, woods Woodland Kv= 5.0 fps 5.8 141 Total Existing_N. Andover Boat Launch Type 1124-hr 10-yr, 24-hr Rainfall=5.00" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 O 2022 HydroCAD Software Solutions LLC Page 16 Subcatchment 2S: SC-02 Hydrograph 2 1.90 cfs —Runoff y � 1 T' 24=I:: r a f I = .0 ' Ru o A e 18 15 N w f I 3181 ....................................... ....... LL 1 ------------------------ ... ...... ............. ff p = .5 ' o e th 1 T 0saw= 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Existing_N. Andover Boat Launch Type //24-hr 10-yr, 24-hr Rainfall=5.00" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 17 Summary for Reach 1 R: DP-1 - Lake Cochichewick DP-1 is used as a common point (Lake C.) to analyze peak flows in existing and proposed conditions [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 39,798 sf, 12.17% Impervious, Inflow Depth = 2.83" for 10-yr, 24-hr event Inflow = 4.66 cfs @ 11.96 hrs, Volume= 9,389 cf Outflow = 4.66 cfs @ 11.96 hrs, Volume= 9,389 cf, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Reach 1 R: DP-1 - Lake Cochichewick Hydrograph 5 4.66 cfs Inflow —Outflow f mf r 9,7 f 4-— ———— ------------....--- ....................... ........................ ............'.............'... ...................... ............................... 3 0 2 -.-.-.-.-.-.-.-.-.-.-.-.-:'-.-.-.-.-.-._'-.-.-.-.-.-.-.'-.-.............................................................................................'...............-.-.-.-.-.-.-.-.-.-.-.-.-.--------..-.-.-.-.-.-.--.-.-.-.-.-..'.......'.......'....................................................................................'..............'..............'....................................'.......'................................ ............................' -.-.-.-.-.-.-.--------..------. 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Existing_N. Andover Boat Launch Type //24-hr 100-yr, 24-hr Rainfall=7.93" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 18 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1S: SC-01 Runoff Area=21,643 sf 13.26% Impervious Runoff Depth=5.79" Flow Length=206' Tc=5.0 min CN=82 Runoff=5.04 cfs 10,449 cf Subcatchment 2S: SC-02 Runoff Area=18,155 sf 10.87% Impervious Runoff Depth=5.09" Flow Length=141' Tc=5.8 min CN=76 Runoff=3.72 cfs 7,707 cf Reach 1 R: DP-1 - Lake Cochichewick Inflow=8.74 cfs 18,156 cf Outflow=8.74 cfs 18,156 cf Total Runoff Area= 39,798 sf Runoff Volume = 18,156 cf Average Runoff Depth = 5.47" 87.83% Pervious= 34,955 sf 12.17% Impervious =4,843 sf Existing_N. Andover Boat Launch Type //24-hr 100-yr, 24-hr Rainfall=7.93" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 19 Summary for Subcatchment 1 S: SC-01 A Tc of 5-min min. was used Runoff = 5.04 cfs @ 11.96 hrs, Volume= 10,449 cf, Depth= 5.79" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 100-yr, 24-hr Rainfall=7.93" Area (sf) CN Description 51074 96 Gravel, HSG C 21870 98 Paved, HSG C 47233 70 Woods, Good, HSG C 97466 74 >75% Grass cover, Good, HSG C 211643 82 Weighted Average 181773 86.74% Pervious Area 2,870 13.26% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.3 28 0.0380 1.37 Sheet Flow, Sheet flow, first 50', paved Smooth surfaces n= 0.011 P2= 3.16" 0.4 23 0.0164 0.94 Sheet Flow, Sheet flow, first 50', gravel Smooth surfaces n= 0.011 P2= 3.16" 1.4 139 0.0070 1.70 Shallow Concentrated Flow, SCF, gravel driveway Paved Kv= 20.3 fps 0.0 16 0.1400 7.60 Shallow Concentrated Flow, SCF, paved boat ramp Paved Kv= 20.3 fps 2.1 206 Total, Increased to minimum Tc = 5.0 min Existing_N. Andover Boat Launch Type //24-hr I 00-yr, 24-hr Rainfall=7.93 IFF Prepared by Apex Companies Printed 5/12/2023 HydroCAD® 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 20 Subcatchment 1S: SC-01 Hydrograph 5.04 cfs Runoff 5 ----------------- ......... .............. Tylle I Mill 1 ...................................... ............................. 4 ------------------------ ... ................................... :al cal -' 9: is,� Ru f e 164 3 U f Iu 0 4 407 I off ep t U 2 ............ ....................... ...... A. :6 W e : T ............... ............................ .............. .... ............. ---------------- 0 1....U....U 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Existing_N. Andover Boat Launch Type //24-hr 100-yr, 24-hr Rainfall=7.93" Prepared by Apex Companies Printed 5/12/2023 HydroCAD® 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 21 Summary for Subcatchment 2S: SC-02 Runoff = 3.72 cfs @ 11.97 hrs, Volume= 7,707 cf, Depth= 5.09" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 100-yr, 24-hr Rainfall=7.93" Area (sf) CN Description 11973 98 Paved, HSG C 4,055 70 Woods, Good, HSG C 125127 74 >75% Grass cover, Good, HSG C 181155 76 Weighted Average 161182 89.13% Pervious Area 17973 10.87% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.3 14 0.0200 0.92 Sheet Flow, Sheet flow, first 50', paved Smooth surfaces n= 0.011 P2= 3.16" 4.4 36 0.0190 0.13 Sheet Flow, Sheet flow, first 50' Grass: Short n= 0.150 P2= 3.16" 0.7 56 0.0400 1.40 Shallow Concentrated Flow, SCF, lawn Short Grass Pasture Kv= 7.0 fps 0.4 35 0.0900 1.50 Shallow Concentrated Flow, SCF, woods Woodland Kv= 5.0 fps 5.8 141 Total Existing_N. Andover Boat Launch Type //24-hr I 00-yr, 24-hr Rainfall=7.93 FIF Prepared by Apex Companies Printed 5/12/2023 HydroCAD® 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 22 Subcatchment 2S: SC-02 Hydrograph ........................................................................................................................................................ ------------------------------------------------------------...................... 4 3.72cfsRunoff y I _ L I ............. ...................................................... ................................................. .......... 3 ----------------- 4 :4ir ai ill"Cal 9 ,� Ru :k e 18 15 0 o il] =7 70, ...................... ........ ............ 2 ------------------------ 0 ................. .... ............ ...............—" ............... U:ff ep h .p low L.e th: :1 =5.8 .................................. -------------------------- --- ------------------- T- U....U 7�7�7�77r�7�7�77FFV-V7FIF-97117117117117111IIIIIIIII]II 0 11�711`11`11`117111 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Existing_N. Andover Boat Launch Type //24-hr 100-yr, 24-hr Rainfall=7.93" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 23 Summary for Reach 1 R: DP-1 - Lake Cochichewick DP-1 is used as a common point (Lake C.) to analyze peak flows in existing and proposed conditions [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 39,798 sf, 12.17% Impervious, Inflow Depth = 5.47" for 100-yr, 24-hr event Inflow = 8.74 cfs @ 11.96 hrs, Volume= 18,156 cf Outflow = 8.74 cfs @ 11.96 hrs, Volume= 18,156 cf, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Reach 1 R: DP-1 - Lake Cochichewick Hydrograph 9 8.74 cfs Inflow ...... ........... .......... Outflow 8 Irif Mf Ar 91744 7 ................. ... ----------------------------------- ........................................ 6 .... ... ...... 3 0 UL 4 ------..-------.-------.'.........',........' ...............................'........:'..................' ...................................................:...........'.............' ................................'................................' ............................... 3 2 ...... ...... ....... ........ .... ........ ...... ........ ...... ....... ...... ...... .... .......... . 1 ------..------- ..............'....... 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Existing_N. Andover Boat Launch Multi-Event Tables Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 24 Events for Subcatchment 1 S: SC-01 Event Rainfall Runoff Volume Depth (inches) (cfs) (cubic-feet) (inches) 2-yr, 24-hr 3.16 1.39 2716 1.51 10-yr, 24-h r 5.00 2.78 5,553 3.08 100-yr, 24-h r 7.93 5.04 10,449 5.79 Existing_N. Andover Boat Launch Multi-Event Tables Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 25 Events for Subcatchment 2S: SC-02 Event Rainfall Runoff Volume Depth (inches) (cfs) (cubic-feet) (inches) 2-yr, 24-hr 3.16 0.84 1701 1.12 10-yr, 24-h r 5.00 1.90 3,836 2.54 100-yr, 24-h r 7.93 3.72 71707 5.09 Existing_N. Andover Boat Launch Multi-Event Tables Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 26 Events for Reach 1 R: DP-1 - Lake Cochichewick Event Inflow Outflow Elevation Storage (cfs) (cfs) (feet) (cubic-feet) 2-yr, 24-hr 2.22 2.22 0.00 0 10-yr, 24-h r 4.66 4.66 0.00 0 100-yr, 24-h r 8.74 8.74 0.00 0 Existing_N. Andover Boat Launch Table of Contents Prepared by Apex Companies Printed 5/12/2023 HydroCAD® 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC TABLE OF CONTENTS Project Reports 1 Routing Diagram 2 Rainfall Events Listing (selected events) 3 Area Listing (all nodes) 4 Soil Listing (all nodes) 5 Ground Covers (all nodes) 2-yr, 24-hr Event 6 Node Listing 7 Subcat 1 S: SC-01 9 Subcat 2S: SC-02 11 Reach 1 R: DP-1 - Lake Cochichewick 10-yr,24-h r Event 12 Node Listing 13 Subcat 1 S: SC-01 15 Subcat 2S: SC-02 17 Reach 1 R: DP-1 - Lake Cochichewick 100-yr, 24-hr Event 18 Node Listing 19 Subcat 1 S: SC-01 21 Subcat 2S: SC-02 23 Reach 1 R: DP-1 - Lake Cochichewick Multi-Event Tables 24 Subcat 1 S: SC-01 25 Subcat 2S: SC-02 26 Reach 1 R: DP-1 - Lake Cochichewick A..........Iuumm� ..................... ..... 0 P 0 S D IM 0 D 1�............. (4S 3S SC-04 Sd-03 B /2\P CAP 1 P Bio. Ret.1 Area #1 12" RCP Bio. Ret. Area #2 1 S 3R 2S SC-01 Rip-Ra Swale SC-02 1R DP-1 - Lake Cochichewick Subcat Reach Pond Link Routing Diagram for Proposed_N.Andover Boat Launch S u 4bcat Reach /Po n\d Link Prepared by Apex Companies, Printed 5/12/2023 HydroCAD®10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Proposed—N. Andover Boat Launch Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 2 Rainfall Events Listing (selected events) Event# Event Storm Type Curve Mode Duration B/B Depth AMC Name (hours) (inches) 1 2-yr, 24-hr Type II 24-hr Default 24.00 1 3.16 2 2 10-yr, 24-hr Type II 24-hr Default 24.00 1 5.00 2 3 100-yr, 24-hr Type II 24-hr Default 24.00 1 7.93 2 Proposed—N. Andover Boat Launch Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 3 Area Listing (all nodes) Area CN Description (sq-ft) (subcatchment-numbers) 167764 74 >75% Grass cover, Good, HSG C (1 S, 2S7 3S7 4S) 483 98 Paved, HSG C (3S7 4S) 97991 80 Permeable Pavers, HSG C (1 S, 2S7 3S, 4S) 11196 74 Rain Garden, Good, HSG C (3S) 991 74 Rain garden, Good, HSG C (4S) 41664 98 Roadway, HSG C (1 S, 2S7 3S7 4S) 51709 70 Woods, Good, HSG C (1 S, 2S) 3%798 78 TOTAL AREA Proposed—N. Andover Boat Launch Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 4 Soil Listing (all nodes) Area Soil Subcatchment (sq-ft) Group Numbers 0 HSG A 0 HSG B 39798 HSG C 1 S, 2S, 3S, 4S 0 HSG D 0 Other 3%798 TOTAL AREA Proposed—N. Andover Boat Launch Prepared by Apex Companies Printed 5/12/2023 HydroCAD® 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 5 Ground Covers (all nodes) HSG-A HSG-B HSG-C HSG-D Other Total Ground Su (sq-ft) (sq-ft) (sq-ft) (sq-ft) (sq-ft) (sq-ft) Cover NL 0 0 161764 0 0 16764 >75% Grass cover, Good 0 0 483 0 0 483 Paved 0 0 9,991 0 0 9,991 Permeable Pavers 0 0 11196 0 0 1,196 Rain Garden, Good 0 0 991 0 0 991 Rain garden, Good 0 0 4,664 0 0 47664 Roadway 0 0 5709 0 0 5709 Woods, Good 0 0 39,798 0 0 39,798 TOTAL AREA Proposed—N. Andover Boat Launch Prepared by Apex Companies Printed 5/12/2023 HydroCAD® 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 6 Pipe Listing (all nodes) Line# Node In-Invert Out-Invert Length Slope n Width Diam/Height Inside-Fill Number (feet) (feet) (feet) (ft/ft) (inches) (inches) (inches) 1 5P 115.50 115.30 44.0 0.0045 0.012 0.0 12.0 0.0 Proposed-N. Andover Boat Launch Type //24-hr 2-yr, 24-hr Rainfall=3.16" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 7 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1S: SC-01 Runoff Area=13,643 sf 4.25% Impervious Runoff Depth=1.12" Flow Length=131' Tc=5.0 min CN=76 Runoff=0.65 cfs 1,278 cf Subcatchment 2S: SC-02 Runoff Area=10,661 sf 5.67% Impervious Runoff Depth=1.07" Flow Length=97' Tc=5.0 min CN=75 Runoff=0.48 cfs 948 cf Subcatchment 3S: SC-03 Runoff Area=9,610 sf 19.84% Impervious Runoff Depth=1.51" Flow Length=63' Slope=0.0100 '/' Tc=5.0 min CN=82 Runoff=0.62 cfs 1,206 cf Subcatchment 4S: SC-04 Runoff Area=5,884 sf 34.94% Impervious Runoff Depth=1.58" Flow Length=52' Tc=5.0 min CN=83 Runoff=0.39 cfs 773 cf Reach 1 R: DP-1 - Lake Cochichewick Inflow=1.14 cfs 2,226 cf Outflow=1.14 cfs 2,226 cf Reach 3R: Rip-Rap Swale Avg. Flow Depth=0.00' Max Vet=0.00 fps Inflow=0.00 cfs 0 cf n=0.041 L=13.0' S=0.0500 '/' Capacity=4.54 cfs Outflow=0.00 cfs 0 cf Pond 1 P: Bio. Ret. Area#2 Peak Elev=116.51' Storage=743 cf Inflow=0.62 cfs 1,206 cf Discarded=0.00 cfs 671 cf Primary=0.02 cfs 270 cf Outflow=0.03 cfs 941 cf Pond 2P: Bio. Ret. Area#1 Peak Elev=116.46' Storage=846 cf Inflow=0.39 cfs 1,043 cf Discarded=0.00 cfs 810 cf Primary=0.00 cfs 0 cf Outflow=0.00 cfs 810 cf Pond 5P: 12" RCP Peak Elev=116.50' Inflow=0.02 cfs 270 cf 12.0" Round Culvert n=0.012 L=44.0' S=0.0045 '/' Outflow=0.02 cfs 270 cf Total Runoff Area= 39,798 sf Runoff Volume =4,205 cf Average Runoff Depth = 1.27" 87.07% Pervious= 34,651 sf 12.93% Impervious = 5,147 sf Proposed—N. Andover Boat Launch Type //24-hr 2-yr, 24-hr Rainfall=3.16" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 8 Summary for Subcatchment 1 S: SC-01 Runoff = 0.65 cfs @ 11.97 hrs, Volume= 1,278 cf, Depth= 1.12" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 2-yr, 24-hr Rainfall=3.16" Area (sf) CN Description 27459 80 Permeable Pavers, HSG C 580 98 Roadway, HSG C 17813 70 Woods, Good, HSG C 87791 74 >75% Grass cover, Good, HSG C 137643 76 Weighted Average 13,063 95.75% Pervious Area 580 4.25% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.8 50 0.0150 1.06 Sheet Flow, Sheet flow, first 50' Smooth surfaces n= 0.011 P2= 3.16" 0.4 66 0.0300 2.79 Shallow Concentrated Flow, SCF, driveway Unpaved Kv= 16.1 fps 0.0 15 0.1200 5.58 Shallow Concentrated Flow, SCF, paved boat ramp Unpaved Kv= 16.1 fps 1.2 131 Total, Increased to minimum Tc = 5.0 min Subcatchment 1S: SC-01 Hydrograph ............ ....... 0.7 ....... 0.65 cfs —Runoff 0.65 ............. ............................ IL2 T 0.6 ..... ....... 0.55 ............................,............._,......... . ....................I...........................................................:',�..............',... .........................,.............I..............',......................' �...............' ......:',..................'......�;� .......................... 0.5 24 r a fal 1 0.45 ....... ............. .. f e 1� S......... ...... . ............. f I 1 270 0 0.35 -------- ------------ ........... .............. WN e = 1... .2 ..........................'................................................................................................................................................................................... 0.253 0.2 .............._..... ...................................................: T. . .... i.... 0.15 ...............I...................................................................................................................... .............' 0.1 0.05 0mob 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch Type //24-hr 2-yr, 24-hr Rainfall=3.16" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 9 Summary for Subcatchment 2S: SC-02 Runoff = 0.48 cfs @ 11.97 hrs, Volume= 948 cf, Depth= 1.07" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 2-yr, 24-hr Rainfall=3.16" Area (sf) CN Description 11219 80 Permeable Pavers, HSG C 3,896 70 Woods, Good, HSG C 4,942 74 >75% Grass cover, Good, HSG C 604 98 Roadway, HSG C 101661 75 Weighted Average 101057 94.33% Pervious Area 604 5.67% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.3 15 0.0200 0.94 Sheet Flow, Sheet flow, first 50% roadway Smooth surfaces n= 0.011 P2= 3.16" 2.6 35 0.0714 0.23 Sheet Flow, Sheet flow, first 50', woods Grass: Short n= 0.150 P2= 3.16" 0.2 15 0.0350 1.31 Shallow Concentrated Flow, SCF, lawn Short Grass Pasture Kv= 7.0 fps 0.3 32 0.1060 1.63 Shallow Concentrated Flow, SCF, woods Woodland Kv= 5.0 fps 3.4 97 Total, Increased to minimum Tc = 5.0 min Proposed—N. Andover Boat Launch Type //24-hr 2-yr, 24-hr Rainfall=3.16" Prepared by Apex Companies Printed 5/12/2023 HydroCAD® 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 10 Subcatchment 2S: SC-02 Hydrograph 0.54 0.52 Runoff 0.5 0.48 cfs ----------------- ....................i ....... .... ..,........ .............. ......................................... ........... 0.48 . 0.46 ........................................_.............'..............................................................................................'............................'............................................................................!.............................. ..... MIN 0.44 ........................................_'............'................................................................................................................'..............'... ...... 0.42 ...................... ...........................' ....................................._.......�.�.�.�.�. .............................................. ....--........'... ...................................................... ..............................................�..........--..........� ...........J........................... 0.4 0.38 .......................... ------ ........... ...... .... 0.36 4 r a f 1 .1 0.3 ......................................... ............................ 4 ............................ 0.32 ... ....... e... 0-...66 ...................... ......................... -- 0.28 199+ c0.26 .... ..............................I..... ....................................... ................... .... ............ 0.24 ............ V MEMO 0.22 .......................... ............................ ... ............ ............ ................................... 0.2 ........................................_'.............'..............',....................................................................................'............................'.................................................................... 0.18 .............. .....................'........'... ........................... 0.16 --- ........ .............. 0.14 .. ... ... ... .... .... ....... ...... ..........................................................'...... 0.12 ............... ...................... ...................... 0.1loom 0.08 ................................_...... ...................................--------------------------------------------......................................................................................--------- 0.06 0.04 0.02 ............ .. -------............................._.................. ........ .................................' -- -.-.-.-.- 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch Type //24-hr 2-yr, 24-hr Rainfall=3.16" Prepared by Apex Companies Printed 5/12/2023 HydroCAD® 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 11 Summary for Subcatchment 3S: SC-03 Runoff = 0.62 cfs @ 11.96 hrs, Volume= 1,206 cf, Depth= 1.51" Routed to Pond 1 P : Bio. Ret. Area #2 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 2-yr, 24-hr Rainfall=3.16" Area (sf) CN Description 11672 98 Roadway, HSG C 235 98 Paved, HSG C 51257 80 Permeable Pavers, HSG C 11196 74 Rain Garden, Good, HSG C 17250 74 >75% Grass cover, Good, HSG C 97610 82 Weighted Average 7,703 80.16% Pervious Area 11907 19.84% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.9 50 0.0100 0.90 Sheet Flow, Sheet flow, first 50' Smooth surfaces n= 0.011 P2= 3.16" 0.1 10 0.0100 1.61 Shallow Concentrated Flow, SCF, pavers Unpaved Kv= 16.1 fps 0.1 3 0.0100 0.70 Shallow Concentrated Flow, SCF, lawn Short Grass Pasture Kv= 7.0 fps 1.1 63 Total, Increased to minimum Tc = 5.0 min Proposed—N. Andover Boat Launch Type //24-hr 2-yr, 24-hr Rainfall=3.16" Prepared by Apex Companies Printed 5/12/2023 HydroCAD® 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 12 Subcatchment 3S: SC-03 Hydrograph 0.65 0.62 cfs ................ Runoff 0.6 ............ ...................... . e 1121 hl 0.5512 .............:......... ........................... y 0.5 ' '',... .............�................,.......�..............................................................................................................................................................................,............................,...................................................................................................',.............,.......�..................... 0.45 ........ 4''- rRi a131 ' of r a 10 s 0.4 .... .................................................. ............. .................................................... .................................. o f I e 016 c 0.35 .... ..................................... .................... -.-.-.-.-.-.............................._......................... ......: 0 i R no 0.3 F-0 I 0.25 n t''h 3. ............................ ...................................... o 00 0 / 0.2 p.... 0.15 .............. .................... =156 M in ..................... ...... 0.1 ................................... .......................................................................................................................................................................... N 3; 0.05 IT7 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch Type //24-hr 2-yr, 24-hr Rainfall=3.16" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 13 Summary for Subcatchment 4S: SC-04 Runoff = 0.39 cfs @ 11.96 hrs, Volume= 773 cf, Depth= 1.58" Routed to Pond 2P : Bio. Ret. Area #1 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 2-yr, 24-hr Rainfall=3.16" Area (sf) CN Description 11808 98 Roadway, HSG C 248 98 Paved, HSG C 11056 80 Permeable Pavers, HSG C 991 74 Rain garden, Good, HSG C 17781 74 >75% Grass cover, Good, HSG C 57884 83 Weighted Average 37828 65.06% Pervious Area 2,056 34.94% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.5 33 0.0200 1.10 Sheet Flow, Sheet flow, pavers Smooth surfaces n= 0.011 P2= 3.16" 0.6 6 0.0750 0.16 Sheet Flow, Grass: Short n= 0.150 P2= 3.16" 0.0 13 0.0500 4.43 7.54 Channel Flow, Swale Area= 1.7 sf Perim= 4.2' r= 0.40' n= 0.041 Riprap, 2-inch 1.1 52 Total, Increased to minimum Tc = 5.0 min Proposed—N. Andover Boat Launch Type //24-hr 2-yr, 24-hr Rainfall=3.16" Prepared by Apex Companies Printed 5/12/2023 HydroCAD® 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 14 Subcatchment 4S: SC-04 Hydrograph 0.44 0.42 ................ ....... 0.39 cfs —Runoff 0.4 0.38 ............... .... .......................... Ez 0.36 .......................'............'.................................................................................................:........'... 0.34 ..............'...............'....................'......................'.................................................................................................'..... .......................... 2 0.3 ------. r"" ... ....... . L. 1 ...... 0.28 ...................... ....................... ...... 0.26Sil 8184 0.24 3 ............. ..... . ... . ............ .......... ...�..... . .... 7 3 : 0.22 _o 0.2 .............. 0.18 ............. e 0.16 .................................. ---..------- -------.'........'............................................................................ ..'.......'.... 2 ..... 0.14 0.12 ................'........'............'...............' ......................................'.............'..............' "In 0.1 ...... ................... ..... ................ ....................... ... 0.08 ,,,,,,,,.I.,,,,,,, 0.06 0.04 .............: .............' .............'..................',......................' 0.02 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 6668 70 72 Time (hours) Proposed—N. Andover Boat Launch Type //24-hr 2-yr, 24-hr Rainfall=3.16" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 15 Summary for Reach 1 R: DP-1 - Lake Cochichewick [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 39,798 sf, 12.93% Impervious, Inflow Depth = 0.67" for 2-yr, 24-hr event Inflow = 1.14 cfs @ 11.97 hrs, Volume= 2,226 cf Outflow = 1.14 cfs @ 11.97 hrs, Volume= 2,226 cf, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Reach 1 R: DP-1 - Lake Cochichewick Hydrograph 1.14 cfs Inflow Outflow f 1A r 98 f 3 0 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch Type //24-hr 2-yr, 24-hr Rainfall=3.16" Prepared by Apex Companies Printed 5/12/2023 HydroCAD® 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 16 Summary for Reach 3R: Rip-Rap Swale Inflow Area = 15,494 sf, 25.58% Impervious, Inflow Depth = 0.00" for 2-yr, 24-hr event Inflow = 0.00 cfs @ 0.00 hrs, Volume= 0 cf Outflow = 0.00 cfs @ 0.00 hrs, Volume= 0 cf, Atten= 0%, Lag= 0.0 min Routed to Reach 1 R : DP-1 - Lake Cochichewick Routing by Stor-Ind+Trans method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Max. Velocity= 0.00 fps, Min. Travel Time= 0.0 min Avg. Velocity= 0.00 fps, Avg. Travel Time= 0.0 min Peak Storage= 0 cf @ 0.00 hrs Average Depth at Peak Storage= 0.00' Bank-Full Depth= 0.50' Flow Area= 1.3 sf, Capacity= 4.54 cfs 1.00' x 0.50' deep channel, n= 0.041 Riprap, 2-inch Side Slope Z-value= 3.0 '/' Top Width= 4.00' Length= 13.0' Slope= 0.0500 T Inlet Invert= 116.50', Outlet Invert= 115.85' Reach 3R: Rip-Rap Swale Hydrograph 1 Inflow Outflow f a F th:ixi .0 s 1 3 L ' o . =0105 it s 0.00 cfs 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch Type //24-hr 2-yr, 24-hr Rainfall=3.16" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 17 Summary for Pond 1P: Bio. Ret. Area #2 nflow Area = 9,610 sf, 19.84% Impervious, Inflow Depth = 1.51" for 2-yr, 24-hr event Inflow = 0.62 cfs @ 11.96 hrs, Volume= 1,206 cf Outflow = 0.03 cfs @ 13.25 hrs, Volume= 941 cf, Atten= 95%, Lag= 77.1 min Discarded = 0.00 cfs @ 13.25 hrs, Volume= 671 cf Primary = 0.02 cfs @ 13.25 hrs, Volume= 270 cf Routed to Pond 5P : 12" RCP Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 116.51' @ 13.25 hrs Surf.Area= 974 sf Storage= 743 cf Flood Elev= 117.00' Surf.Area= 1,176 sf Storage= 1,269 cf Plug-Flow detention time= 1,073.6 min calculated for 941 cf(78% of inflow) Center-of-Mass det. time= 984.2 min ( 1,816.9 - 832.7 ) Volume Invert Avail.Storage Storage Description #1 115.50' 1,269 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 115.50 419 0 0 419 116.00 784 296 296 787 117.00 17176 973 11269 17194 Device Routing Invert Outlet Devices #1 Discarded 115.50' 0.170 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 112.00' Phase-In= 1.00' #2 Primary 116.50' 24.0" Horiz. Top of Riser C= 0.600 Limited to weir flow at low heads Discarded Outflow Max=0.00 cfs @ 13.25 hrs HW=116.51' (Free Discharge) L1=Exfi1tration ( Controls 0.00 cfs) Primary OutFlow Max=0.02 cfs @ 13.25 hrs HW=116.51' (Free Discharge) L2=Top of Riser (Weir Controls 0.02 cfs @ 0.33 fps) Proposed—N. Andover Boat Launch Type //24-hr 2-yr, 24-hr Rainfall=3.16" Prepared by Apex Companies Printed 5/12/2023 HydroCAD® 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 18 Pond 1 P: Bio. Ret. Area #2 Hydrograph 0.65 0.62 cfs Inflow Outflow 0.6 ...... ...................... ...... Discarded ............_..... rea1,O'', f', —Primary 0.55 0.5 .........................................................''............'............................... I. .... 0.45 f 0.4 0.35 .....------..-------..-------.'.------:'-------'.----..........'....................................................'.......'........IT....',.. 0 0.3 0.25 0.2 0.15 -----.-------- ...................... 0.1 0.05 0.02 cfs . cs 0 t U"..�77r�,Fr�U U 11 U U 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 7072 Time (hours) Proposed—N. Andover Boat Launch Type //24-hr 2-yr, 24-hr Rainfall=3.16" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 19 Summary for Pond 2P: Bio. Ret. Area #1 [81] Warning: Exceeded Pond 5P by 0.54' @ 12.95 hrs Inflow Area = 15,494 sf, 25.58% Impervious, Inflow Depth = 0.81" for 2-yr, 24-hr event Inflow = 0.39 cfs @ 11.96 hrs, Volume= 1,043 cf Outflow = 0.00 cfs @ 24.04 hrs, Volume= 810 cf, Atten= 99%, Lag= 724.9 min Discarded = 0.00 cfs @ 24.04 hrs, Volume= 810 cf Primary = 0.00 cfs @ 0.00 hrs, Volume= 0 cf Routed to Reach 3R : Rip-Rap Swale Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 116.46' @ 24.04 hrs Surf.Area= 974 sf Storage= 846 cf Flood Elev= 117.00' Surf.Area= 1,201 sf Storage= 1,432 cf Plug-Flow detention time= 1,529.7 min calculated for 810 cf(78% of inflow) Center-of-Mass det. time= 1,440.2 min ( 2,305.9 - 865.7 ) Volume Invert Avail.Storage Storage Description #1 115.00' 1,432 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 115.00 0 0 0 0 115.50 590 98 98 590 116.00 787 343 441 793 116.50 991 444 885 17003 117.00 17201 547 17432 11222 Device Routing Invert Outlet Devices #1 Discarded 115.00' 0.170 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 112.00' Phase-In= 1.00' #2 Primary 116.50' Channel/Reach using Reach 3R: Rip-Rap Swale Discarded OutFlow Max=0.00 cfs @ 24.04 hrs HW=116.46' (Free Discharge) L1=Exfi1tration ( Controls 0.00 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=115.00' (Free Discharge) L2=Channel/Reach ( Controls 0.00 cfs) Proposed-N. Andover Boat Launch Type //24-hr 2-yr, 24-hr Rainfall=3.16" Prepared by Apex Companies Printed 5/12/2023 HydroCAD® 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 20 Pond 2P: Bio. Ret. Area #1 Hydrograph 0.44 0.42 ............ ...................................... ................. 0.39 cfs Inflow Outflow 0.4 Discarded 0.38 Primary ..... ............................1 ......... 0.36 -M f6 A .............. ........ 0.34 ————..........................------ ................................................... 0.32 0.3 ------------- 0.26 0.24 ————------------------- .............. ...................-——------------------- ................... 0.22 .............. ................... 0 0.2 ............. ......................................... 0.18 ............................................ ........... ............ ............. ................................................................................ ............................ ........................... 0.16 ————------------------- ............................... . ......................................... 0.14 0.12 ................................... .................... ................................... 0.1 .................... . .......................... ------ ............. .......... .............. 0.08 .................. ———— ------------------------ ............................................ .................................................... 0.06 ------- 0.04 f ------------ .0.00 cfs . 0.00 c ..... -Ell MMEMM I F�7ro W-F-F-F1117117]IF111�IN 11,1111 111�I I I U I...I U U I I 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed-N. Andover Boat Launch Type //24-hr 2-yr, 24-hr Rainfall=3.16" Prepared by Apex Companies Printed 5/12/2023 HydroCAD® 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 21 Summary for Pond 5P: 12" RCP Inflow Area = 9,610 sf, 19.84% Impervious, Inflow Depth = 0.34" for 2-yr, 24-hr event Inflow = 0.02 cfs @ 13.25 hrs, Volume= 270 cf Outflow = 0.02 cfs @ 13.25 hrs, Volume= 270 cf, Atten= 0%, Lag= 0.0 min Primary = 0.02 cfs @ 13.25 hrs, Volume= 270 cf Routed to Pond 2P : Bio. Ret. Area #1 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 116.50' @ 13.25 hrs Flood Elev= 117.00' Device Routing Invert Outlet Devices #1 Primary 115.50' 12.0" Round Culvert L= 44.0' RCP, sq.cut end projecting, Ke= 0.500 Inlet/ Outlet Invert= 115.50' / 115.30' S= 0.0045 T Cc= 0.900 n= 0.012 Concrete pipe, finished, Flow Area= 0.79 sf Primary OutFlow Max=0.07 cfs @ 13.25 hrs HW=116.50' TW=116.50' (Fixed TW Elev= 116.50') L1=Culvert (Outlet Controls 0.07 cfs, @ 0.12 fps) Pond 5P: 12" RCP Hydrograph 0.027 0.026 Inflow 0.025 0.02 cfs 0.024 -Primary 0.023 0.022 L.. .�+1...�. .... f 0.021 -------- 0.02 ................ Pea. .... 0.019 ........... ..................... .... .................................................. ■ 0.018 �................ 0.017 � 0.015 0.014 ------------------......... ------ n goo" J- .......................... .............................. ...........................................------..-.-.-.-.-.-.-......-........................... ..............,........................................................................................ ................,............................�.�.�.�.�. c 0.013 ...................'.............'..............''....................................................................................'...............' ...............................................'.-.-.-.-.-.-.'.-.-.-.-.-.-.-........................................ 0.012 1-:2 0.011 .. ...... .............,.. 0.01 .�. ----- 0.009AM 0.008 0.007 ...................... 0-006M Al 0.005 0.004 0.003 0.002 .................... .'.........'......................'. 0.001 ...................'...............' ........................................................................................' 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed-N. Andover Boat Launch Type //24-hr 10-yr, 24-hr Rainfall=5.00" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 22 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1S: SC-01 Runoff Area=13,643 sf 4.25% Impervious Runoff Depth=2.54" Flow Length=131' Tc=5.0 min CN=76 Runoff=1.47 cfs 2,883 cf Subcatchment 2S: SC-02 Runoff Area=10,661 sf 5.67% Impervious Runoff Depth=2.45" Flow Length=97' Tc=5.0 min CN=75 Runoff=1.11 cfs 2,176 cf Subcatchment 3S: SC-03 Runoff Area=9,610 sf 19.84% Impervious Runoff Depth=3.08" Flow Length=63' Slope=0.0100 '/' Tc=5.0 min CN=82 Runoff=1.23 cfs 2,466 cf Subcatchment 4S: SC-04 Runoff Area=5,884 sf 34.94% Impervious Runoff Depth=3.17" Flow Length=52' Tc=5.0 min CN=83 Runoff=0.77 cfs 1,556 cf Reach 1 R: DP-1 - Lake Cochichewick Inflow=2.58 cfs 7,011 cf Outflow=2.58 cfs 77011 cf Reach 3R: Rip-Rap Swale Avg. Flow Depth=0.22' Max Vet=2.31 fps Inflow=0.84 cfs 1,953 cf n=0.041 L=13.0' S=0.0500 '/' Capacity=4.54 cfs Outflow=0.84 cfs 1,953 cf Pond 1 P: Bio. Ret. Area#2 Peak Elev=116.64' Storage=874 cf Inflow=1.23 cfs 2,466 cf Discarded=0.00 cfs 681 cf Primary=1.08 cfs 1,519 cf Outflow=1.09 cfs 2,200 cf Pond 2P: Bio. Ret. Area#1 Peak Elev=116.72' Storage=1,112 cf Inflow=1.79 cfs 3,075 cf Discarded=0.01 cfs 869 cf Primary=0.84 cfs 1,953 cf Outflow=0.84 cfs 2,821 cf Pond 5P: 12" RCP Peak Elev=116.59' Inflow=1.08 cfs 1,519 cf 12.0" Round Culvert n=0.012 L=44.0' S=0.0045 '/' Outflow=1.08 cfs 1,519 cf Total Runoff Area= 39,798 sf Runoff Volume =9,081 cf Average Runoff Depth =2.74" 87.07% Pervious= 34,651 sf 12.93% Impervious = 5,147 sf Proposed—N. Andover Boat Launch Type //24-hr 10-yr, 24-hr Rainfall=5.00" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 23 Summary for Subcatchment 1 S: SC-01 Runoff = 1.47 cfs @ 11.96 hrs, Volume= 2,883 cf, Depth= 2.54" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 10-yr, 24-hr Rainfall=5.00" Area (sf) CN Description 27459 80 Permeable Pavers, HSG C 580 98 Roadway, HSG C 17813 70 Woods, Good, HSG C 87791 74 >75% Grass cover, Good, HSG C 137643 76 Weighted Average 13,063 95.75% Pervious Area 580 4.25% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.8 50 0.0150 1.06 Sheet Flow, Sheet flow, first 50' Smooth surfaces n= 0.011 P2= 3.16" 0.4 66 0.0300 2.79 Shallow Concentrated Flow, SCF, driveway Unpaved Kv= 16.1 fps 0.0 15 0.1200 5.58 Shallow Concentrated Flow, SCF, paved boat ramp Unpaved Kv= 16.1 fps 1.2 131 Total, Increased to minimum Tc = 5.0 min Subcatchment 1S: SC-01 Hydrograph 1.47 cfs —Runoff Y 1 441 r ai fl = .0 ' .......................... ................................................................................................................................. .._ 1 Flu f e f I 2 1883 0 Rt ffElep I 0L.e th 1 ILT i 117117117117117117117117]117117117117117]IIFI11711,11,11IF, 71 71 17]F7117117117117 F7117117117117 F111711 11� 711MIMI 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch Type //24-hr 10-yr, 24-hr Rainfall=5.00" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 24 Summary for Subcatchment 2S: SC-02 Runoff = 1.11 cfs @ 11.96 hrs, Volume= 2,176 cf, Depth= 2.45" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 10-yr, 24-hr Rainfall=5.00" Area (sf) CN Description 17219 80 Permeable Pavers, HSG C 37896 70 Woods, Good, HSG C 47942 74 >75% Grass cover, Good, HSG C 604 98 Roadway, HSG C 107661 75 Weighted Average 107057 94.33% Pervious Area 604 5.67% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.3 15 0.0200 0.94 Sheet Flow, Sheet flow, first 50% roadway Smooth surfaces n= 0.011 P2= 3.16" 2.6 35 0.0714 0.23 Sheet Flow, Sheet flow, first 50', woods Grass: Short n= 0.150 P2= 3.16" 0.2 15 0.0350 1.31 Shallow Concentrated Flow, SCF, lawn Short Grass Pasture Kv= 7.0 fps 0.3 32 0.1060 1.63 Shallow Concentrated Flow, SCF, woods Woodland Kv= 5.0 fps 3.4 97 Total, Increased to minimum Tc = 5.0 min Proposed—N. Andover Boat Launch Type 1124-hr 10-yr, 24-hr Rainfall=5.00" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 O 2022 HydroCAD Software Solutions LLC Page 25 Subcatchment 2S: SC-02 Hydrograph 1.11 cfs —Runoff e '2 1 ............ —————-------------- ......... 'P4 41 1 r ai fal = .0Aim ' Ru 0 k e 10 66: N w 3 01 2 17 0 t 0ffrre p L t 7 T 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch Type //24-hr 10-yr, 24-hr Rainfall=5.00" Prepared by Apex Companies Printed 5/12/2023 HydroCAD® 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 26 Summary for Subcatchment 3S: SC-03 Runoff = 1.23 cfs @ 11.96 hrs, Volume= 2,466 cf, Depth= 3.08" Routed to Pond 1 P : Bio. Ret. Area #2 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 10-yr, 24-hr Rainfall=5.00" Area (sf) CN Description 11672 98 Roadway, HSG C 235 98 Paved, HSG C 51257 80 Permeable Pavers, HSG C 11196 74 Rain Garden, Good, HSG C 17250 74 >75% Grass cover, Good, HSG C 97610 82 Weighted Average 7,703 80.16% Pervious Area 11907 19.84% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.9 50 0.0100 0.90 Sheet Flow, Sheet flow, first 50' Smooth surfaces n= 0.011 P2= 3.16" 0.1 10 0.0100 1.61 Shallow Concentrated Flow, SCF, pavers Unpaved Kv= 16.1 fps 0.1 3 0.0100 0.70 Shallow Concentrated Flow, SCF, lawn Short Grass Pasture Kv= 7.0 fps 1.1 63 Total, Increased to minimum Tc = 5.0 min Proposed—N. Andover Boat Launch Type 1124-hr 10-yr, 24-hr Rainfall=5.00" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 O 2022 HydroCAD Software Solutions LLC Page 27 Subcatchment 3S: SC-03 Hydrograph 1.23 cfs —Runoff T, pie 112:1 -h ............................................ ............................................---------------------------------------- ...... ............. .......... ...... 4-hr R in a 1 1:5 Elm 009 0 ' R ff r a 1 0s u f I e66::c LL 0 De t 30 ' I n h 3 Sl 0011 Ol/ =5.0 i CP t J.U 0U....U III U 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch Type //24-hr 10-yr, 24-hr Rainfall=5.00" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 28 Summary for Subcatchment 4S: SC-04 Runoff = 0.77 cfs @ 11.96 hrs, Volume= 1,556 cf, Depth= 3.17" Routed to Pond 2P : Bio. Ret. Area #1 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 10-yr, 24-hr Rainfall=5.00" Area (sf) CN Description 17808 98 Roadway, HSG C 248 98 Paved, HSG C 17056 80 Permeable Pavers, HSG C 991 74 Rain garden, Good, HSG C 17781 74 >75% Grass cover, Good, HSG C 57884 83 Weighted Average 37828 65.06% Pervious Area 27056 34.94% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.5 33 0.0200 1.10 Sheet Flow, Sheet flow, pavers Smooth surfaces n= 0.011 P2= 3.16" 0.6 6 0.0750 0.16 Sheet Flow, Grass: Short n= 0.150 P2= 3.16" 0.0 13 0.0500 4.43 7.54 Channel Flow, Swale Area= 1.7 sf Perim= 4.2' r= 0.40' n= 0.041 Riprap, 2-inch 1.1 52 Total, Increased to minimum Tc = 5.0 min Proposed—N. Andover Boat Launch Type 1124-hr 10-yr, 24-hr Rainfall=5.00" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 O 2022 HydroCAD Software Solutions LLC Page 29 Subcatchment 4S: SC-04 Hydrograph 0.85 �g 0.77 cfs —Runoff 0.75 I I 0.7 .......................... .......................... Y 0.65 0.6 r a 0.55 ............................ ..................................................................................... ..................... y0.5 . ........................... .................... R, ri, ff r -----5 "88:, �fil 1 1- 5 . ...... .................. = 0.45 0 0.4 LL ....... 0.35 o f ep-h= .1 ' 0.3 .... ......................... ..................... =:`2 0.25 In: 0.2 .... ................................ ....................................... ........................................ . ..... 0.15 ............ ....... .............. 0.1 0.05 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch Type //24-hr 10-yr, 24-hr Rainfall=5.00" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 30 Summary for Reach 1 R: DP-1 - Lake Cochichewick [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 39,798 sf, 12.93% Impervious, Inflow Depth = 2.11" for 10-yr, 24-hr event Inflow = 2.58 cfs @ 11.96 hrs, Volume= 77011 cf Outflow = 2.58 cfs @ 11.96 hrs, Volume= 77011 cf, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Reach 1 R: DP-1 - Lake Cochichewick Hydrograph 2.58 cfs Inflow —Outflow f re. 9 f 2 .... .. ................................... ....................................... 3 0 1 ----------------. ........................ 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed_N. Andover Boat Launch Type 1124-hr 10-yr, 24-hr Rainfall=5.00" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 O 2022 HydroCAD Software Solutions LLC Page 31 Summary for Reach 3R: Rip-Rap Swale Inflow Area = 15,494 sf, 25.58% Impervious, Inflow Depth = 1.51" for 10-yr, 24-hr event Inflow = 0.84 cfs @ 12.07 hrs, Volume= 1,953 cf Outflow = 0.84 cfs @ 12.07 hrs, Volume= 1,953 cf, Atten= 0%, Lag= 0.2 min Routed to Reach 1 R : DP-1 - Lake Cochichewick Routing by Stor-Ind+Trans method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Max. Velocity= 2.31 fps, Min. Travel Time= 0.1 min Avg. Velocity= 0.76 fps, Avg. Travel Time= 0.3 min Peak Storage= 5 cf @ 12.07 hrs Average Depth at Peak Storage= 0.22' , Surface Width= 2.31' Bank-Full Depth= 0.50' Flow Area= 1.3 sf, Capacity= 4.54 cfs 1.00' x 0.50' deep channel, n= 0.041 Riprap, 2-inch Side Slope Z-value= 3.07' Top Width= 4.00' Length= 13.0' Slope= 0.0500 '/' Inlet Invert= 116.50', Outlet Invert= 115.85' Reach 3R: Rip-Rap Swale Hydrograph 0'9 Inflow 0.84 cfs 0.85 -Outflow 0.8 fl 0 re 0.75 ..... 0.7 � ;2 0.65 0.6PS 0.55 '41 ..... y V 0.5 0 0.45 LL 0.4 0.35 , 0.3 0.25 0.2 0.15 0.1 0.05 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch Type //24-hr 10-yr, 24-hr Rainfall=5.00" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 32 Summary for Pond 1P: Bio. Ret. Area #2 Inflow Area = 9,610 sf, 19.84% Impervious, Inflow Depth = 3.08" for 10-yr, 24-hr event Inflow = 1.23 cfs @ 11.96 hrs, Volume= 2,466 cf Outflow = 1.09 cfs @ 12.00 hrs, Volume= 2,200 cf, Atten= 12%, Lag= 2.1 min Discarded = 0.00 cfs @ 12.00 hrs, Volume= 681 cf Primary = 1.08 cfs @ 12.00 hrs, Volume= 1,519 cf Routed to Pond 5P : 12" RCP Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 116.64' @ 12.00 hrs Surf.Area= 1,026 sf Storage= 874 cf Flood Elev= 117.00' Surf.Area= 1,176 sf Storage= 1,269 cf Plug-Flow detention time= 486.3 min calculated for 2,200 cf(89% of inflow) Center-of-Mass det. time= 432.6 min ( 1,244.9 - 812.3 ) Volume Invert Avail.Storage Storage Description #1 115.50' 1,269 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 115.50 419 0 0 419 116.00 784 296 296 787 117.00 17176 973 11269 17194 Device Routing Invert Outlet Devices #1 Discarded 115.50' 0.170 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 112.00' Phase-In= 1.00' #2 Primary 116.50' 24.0" Horiz. Top of Riser C= 0.600 Limited to weir flow at low heads Discarded Outflow Max=0.00 cfs @ 12.00 hrs HW=116.64' (Free Discharge) L1=Exfi1tration ( Controls 0.00 cfs) Primary OutFlow Max=1.08 cfs @ 12.00 hrs HW=116.64' (Free Discharge) L2=Top of Riser (Weir Controls 1.08 cfs @ 1.23 fps) Proposed—N. Andover Boat Launch Type //24-hr 10-yr, 24-hr Rainfall=5.00" Prepared by Apex Companies Printed 5/12/2023 HydroCAD® 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 33 Pond 1 P: Bio. Ret. Area #2 Hydrograph 1.23 cfs717 Inflow uuuuuuuuuuuuuu1 Outflow Discarded 1.08 cfs I I a O' f —Primary 1 -.-.-.-.-.---------------------------------- ...................... ............................................................................................. ......... ea .............. t to 4' f 7! 77 0 i UL 0.0 .............. ................................. L I P!1111�"11711711`11`11`11711711 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch Type //24-hr 10-yr, 24-hr Rainfall=5.00" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 34 Summary for Pond 2P: Bio. Ret. Area #1 [81] Warning: Exceeded Pond 5P by 0.52' @ 11.91 hrs Inflow Area = 15,494 sf, 25.58% Impervious, Inflow Depth = 2.38" for 10-yr, 24-hr event Inflow = 1.79 cfs @ 11.98 hrs, Volume= 3,075 cf Outflow = 0.84 cfs @ 12.07 hrs, Volume= 2,821 cf, Atten= 53%, Lag= 5.3 min Discarded = 0.01 cfs @ 12.07 hrs, Volume= 869 cf Primary = 0.84 cfs @ 12.07 hrs, Volume= 1,953 cf Routed to Reach 3R : Rip-Rap Swale Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 116.72' @ 12.07 hrs Surf.Area= 1,080 sf Storage= 1,112 cf Flood Elev= 117.00' Surf.Area= 1,201 sf Storage= 1,432 cf Plug-Flow detention time= 516.7 min calculated for 2,821 cf(92% of inflow) Center-of-Mass det. time= 474.1 min ( 1,300.5 - 826.4 ) Volume Invert Avail.Storage Storage Description #1 115.00' 1,432 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 115.00 0 0 0 0 115.50 590 98 98 590 116.00 787 343 441 793 116.50 991 444 885 17003 117.00 17201 547 17432 11222 Device Routing Invert Outlet Devices #1 Discarded 115.00' 0.170 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 112.00' Phase-In= 1.00' #2 Primary 116.50' Channel/Reach using Reach 3R: Rip-Rap Swale Discarded OutFlow Max=0.01 cfs @ 12.07 hrs HW=116.72' (Free Discharge) L1=Exfi1tration ( Controls 0.01 cfs) Primary OutFlow Max=0.83 cfs @ 12.07 hrs HW=116.72' (Free Discharge) L2=Channel/Reach (Channel Controls 0.83 cfs @ 2.31 fps) Proposed—N. Andover Boat Launch Type //24-hr 10-yr, 24-hr Rainfall=5.00" Prepared by Apex Companies Printed 5/12/2023 HydroCAD® 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 35 Pond 2P: Bio. Ret. Area #1 Hydrograph 2 El9.7 cfs Inflow Outflow Disd Acarded I f r e —Primary I i 7 ' t or 1 1 ......................................................'.............:'............!.................................................................................................'..............' ............................................................:'..............'... 3 0.84 cfs 0.0 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch Type //24-hr 10-yr, 24-hr Rainfall=5.00" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 36 Summary for Pond 5P: 12" RCP [79] Warning: Submerged Pond 1 P Primary device#2 by 0.09' Inflow Area = 9,610 sf, 19.84% Impervious, Inflow Depth = 1.90" for 10-yr, 24-hr event Inflow = 1.08 cfs @ 12.00 hrs, Volume= 1,519 cf Outflow = 1.08 cfs @ 12.00 hrs, Volume= 1,519 cf, Atten= 0%, Lag= 0.0 min Primary = 1.08 cfs @ 12.00 hrs, Volume= 1,519 cf Routed to Pond 2P : Bio. Ret. Area #1 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 116.59' @ 12.00 hrs Flood Elev= 117.00' Device Routing Invert Outlet Devices #1 Primary 115.50' 12.0" Round Culvert L= 44.0' RCP, sq.cut end projecting, Ke= 0.500 Inlet/ Outlet Invert= 115.50' / 115.30' S= 0.0045 '/' Cc= 0.900 n= 0.012 Concrete pipe, finished, Flow Area= 0.79 sf Primary OutFlow Max=1.08 cfs @ 12.00 hrs HW=116.59' TW=116.50' (Fixed TW Elev= 116.50') L1=Culvert (Outlet Controls 1.08 cfs @ 1.57 fps) Pond 5P: 12" RCP Hydrograph 1.08 cfs Inflow Primary 1 .......... ............................................. . I U IV 1 0 1:2 00 ii LM u u u u U v v v 111 1111 W W N 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed-N. Andover Boat Launch Type //24-hr 100-yr, 24-hr Rainfall=7.93" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 37 Time span=0.00-72.00 hrs, dt=0.01 hrs, 7201 points Runoff by SCS TR-20 method, UH=SCS, Weighted-CN Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment 1S: SC-01 Runoff Area=13,643 sf 4.25% Impervious Runoff Depth=5.09" Flow Length=131' Tc=5.0 min CN=76 Runoff=2.88 cfs 5,792 cf Subcatchment 2S: SC-02 Runoff Area=10,661 sf 5.67% Impervious Runoff Depth=4.98" Flow Length=97' Tc=5.0 min CN=75 Runoff=2.21 cfs 4,423 cf Subcatchment 3S: SC-03 Runoff Area=9,610 sf 19.84% Impervious Runoff Depth=5.79" Flow Length=63' Slope=0.0100 '/' Tc=5.0 min CN=82 Runoff=2.24 cfs 4,639 cf Subcatchment 4S: SC-04 Runoff Area=5,884 sf 34.94% Impervious Runoff Depth=5.91" Flow Length=52' Tc=5.0 min CN=83 Runoff=1.39 cfs 2,898 cf Reach 1 R: DP-1 - Lake Cochichewick Inflow=8.35 cfs 15,640 cf Outflow=8.35 cfs 15,640 cf Reach 3R: Rip-Rap Swale Avg. Flow Depth=0.44' Max Vet=3.37 fps Inflow=3.42 cfs 5,425 cf n=0.041 L=13.0' S=0.0500 '/' Capacity=4.54 cfs Outflow=3.41 cfs 5,425 cf Pond 1 P: Bio. Ret. Area#2 Peak Elev=116.72' Storage=960 cf Inflow=2.24 cfs 4,639 cf Discarded=0.01 cfs 700 cf Primary=2.16 cfs 3,673 cf Outflow=2.17 cfs 4,374 cf Pond 2P: Bio. Ret. Area#1 Peak Elev=116.94' Storage=1,358 cf Inflow=3.53 cfs 6,572 cf Discarded=0.01 cfs 891 cf Primary=3.42 cfs 5,425 cf Outflow=3.42 cfs 6,316 cf Pond 5P: 12" RCP Peak Elev=116.83' Inflow=2.16 cfs 3,673 cf 12.0" Round Culvert n=0.012 L=44.0' S=0.0045 '/' Outflow=2.16 cfs 3,673 cf Total Runoff Area= 39,798 sf Runoff Volume = 17,752 cf Average Runoff Depth = 5.35" 87.07% Pervious= 34,651 sf 12.93% Impervious = 5,147 sf Proposed—N. Andover Boat Launch Type //24-hr 100-yr, 24-hr Rainfall=7.93" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 38 Summary for Subcatchment 1 S: SC-01 Runoff = 2.88 cfs @ 11.96 hrs, Volume= 5,792 cf, Depth= 5.09" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 100-yr, 24-hr Rainfall=7.93" Area (sf) CN Description 27459 80 Permeable Pavers, HSG C 580 98 Roadway, HSG C 17813 70 Woods, Good, HSG C 87791 74 >75% Grass cover, Good, HSG C 137643 76 Weighted Average 13,063 95.75% Pervious Area 580 4.25% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.8 50 0.0150 1.06 Sheet Flow, Sheet flow, first 50' Smooth surfaces n= 0.011 P2= 3.16" 0.4 66 0.0300 2.79 Shallow Concentrated Flow, SCF, driveway Unpaved Kv= 16.1 fps 0.0 15 0.1200 5.58 Shallow Concentrated Flow, SCF, paved boat ramp Unpaved Kv= 16.1 fps 1.2 131 Total, Increased to minimum Tc = 5.0 min Subcatchment 1S: SC-01 Hydrograph 3 2.88 cfs ..... ..�. ....... ..... ........ ....... ..... ......... ....... ....... ..... ...... .... ............. Runoff v 4 1 - r ai f l = .9 ' 2 .........................................' ............................................................'...........'................................................................... ...........................................................',.............'... Ru f e 13 6 4is ..... f 011J 5179:2 : 0 ff e = .0 0; p Io a th 1 1 ——— ..................................... .............................................. ........................................................ ............................................................................. T i 0 JM9.�.r"?"T"17117117]117117117117117]llr7ll7ll7ll7ll7 M11111111 1711[7117117117117]11[711711711711711[71IM?�M��'?%RT 4,1�11 11 11,1111 1111 1111 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch Type //24-hr 100-yr, 24-hr Rainfall=7.93" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 39 Summary for Subcatchment 2S: SC-02 Runoff = 2.21 cfs @ 11.96 hrs, Volume= 4,423 cf, Depth= 4.98" Routed to Reach 1 R : DP-1 - Lake Cochichewick Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 100-yr, 24-hr Rainfall=7.93" Area (sf) CN Description 17219 80 Permeable Pavers, HSG C 37896 70 Woods, Good, HSG C 47942 74 >75% Grass cover, Good, HSG C 604 98 Roadway, HSG C 107661 75 Weighted Average 107057 94.33% Pervious Area 604 5.67% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.3 15 0.0200 0.94 Sheet Flow, Sheet flow, first 50% roadway Smooth surfaces n= 0.011 P2= 3.16" 2.6 35 0.0714 0.23 Sheet Flow, Sheet flow, first 50', woods Grass: Short n= 0.150 P2= 3.16" 0.2 15 0.0350 1.31 Shallow Concentrated Flow, SCF, lawn Short Grass Pasture Kv= 7.0 fps 0.3 32 0.1060 1.63 Shallow Concentrated Flow, SCF, woods Woodland Kv= 5.0 fps 3.4 97 Total, Increased to minimum Tc = 5.0 min Proposed—N. Andover Boat Launch Type 1124-hr 100-yr, 24-hr Rainfall=7.93" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 O 2022 HydroCAD Software Solutions LLC Page 40 Subcatchment 2S: SC-02 Hydrograph 2.21 cfs —Runoff 2 I 1 r ai fia I = .9 ' u f e 10 661 N w 3 f I 44,21 tj ..........0 e hLL 1 .................. ............................ ......................... 9 � L ti 7 T 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch Type //24-hr 100-yr, 24-hr Rainfall=7.93" Prepared by Apex Companies Printed 5/12/2023 HydroCAD® 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 41 Summary for Subcatchment 3S: SC-03 Runoff = 2.24 cfs @ 11.96 hrs, Volume= 4,639 cf, Depth= 5.79" Routed to Pond 1 P : Bio. Ret. Area #2 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 100-yr, 24-hr Rainfall=7.93" Area (sf) CN Description 11672 98 Roadway, HSG C 235 98 Paved, HSG C 51257 80 Permeable Pavers, HSG C 11196 74 Rain Garden, Good, HSG C 17250 74 >75% Grass cover, Good, HSG C 97610 82 Weighted Average 7,703 80.16% Pervious Area 11907 19.84% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.9 50 0.0100 0.90 Sheet Flow, Sheet flow, first 50' Smooth surfaces n= 0.011 P2= 3.16" 0.1 10 0.0100 1.61 Shallow Concentrated Flow, SCF, pavers Unpaved Kv= 16.1 fps 0.1 3 0.0100 0.70 Shallow Concentrated Flow, SCF, lawn Short Grass Pasture Kv= 7.0 fps 1.1 63 Total, Increased to minimum Tc = 5.0 min Proposed—N. Andover Boat Launch Type 1124-hr 100-yr, 24-hr Rainfall=7.93" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 O 2022 HydroCAD Software Solutions LLC Page 42 Subcatchment 3S: SC-03 Hydrograph 2.24 cfs —Runoff e 112: -h 2 —— ------------ —————------------——————------------ ............. 0 4: y rR in a 1 7.93' R ciff r a 10S u f I rne= 39 c LL o De t =51.7.......................... ' n h 3 SI P =:01.01 01/ =5.0 ::nl:i CP 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch Type //24-hr 100-yr, 24-hr Rainfall=7.93" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 43 Summary for Subcatchment 4S: SC-04 Runoff = 1.39 cfs @ 11.96 hrs, Volume= 2,898 cf, Depth= 5.91" Routed to Pond 2P : Bio. Ret. Area #1 Runoff by SCS TR-20 method, UH=SCS, Weighted-CN, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Type II 24-hr 100-yr, 24-hr Rainfall=7.93" Area (sf) CN Description 17808 98 Roadway, HSG C 248 98 Paved, HSG C 17056 80 Permeable Pavers, HSG C 991 74 Rain garden, Good, HSG C 17781 74 >75% Grass cover, Good, HSG C 57884 83 Weighted Average 37828 65.06% Pervious Area 27056 34.94% Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.5 33 0.0200 1.10 Sheet Flow, Sheet flow, pavers Smooth surfaces n= 0.011 P2= 3.16" 0.6 6 0.0750 0.16 Sheet Flow, Grass: Short n= 0.150 P2= 3.16" 0.0 13 0.0500 4.43 7.54 Channel Flow, Swale Area= 1.7 sf Perim= 4.2' r= 0.40' n= 0.041 Riprap, 2-inch 1.1 52 Total, Increased to minimum Tc = 5.0 min Proposed—N. Andover Boat Launch Type 1124-hr 100-yr, 24-hr Rainfall=7.93" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 O 2022 HydroCAD Software Solutions LLC Page 44 Subcatchment 4S: SC-04 Hydrograph 1.39 cfs —Runoff y � 1:0 24 , h.............---------------- r a i f I =.......7,93' y ............. f 5, 8 3 f Iu 2189 LLt off ep h=! I L t 2 T =8 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch Type //24-hr 100-yr, 24-hr Rainfall=7.93" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 45 Summary for Reach 1 R: DP-1 - Lake Cochichewick [40] Hint: Not Described (Outflow=Inflow) Inflow Area = 39,798 sf, 12.93% Impervious, Inflow Depth = 4.72" for 100-yr, 24-hr event Inflow = 8.35 cfs @ 11.97 hrs, Volume= 15,640 cf Outflow = 8.35 cfs @ 11.97 hrs, Volume= 15,640 cf, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind+Trans method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Reach 1 R: DP-1 - Lake Cochichewick Hydrograph ............. -.-..----- --- 35 cfs Inflow —Outflow 8 .................... fAed% ........... . ......... . ............ . . ............. 7 . ......................... ........................... .. ..... 7..................... 3 0 3 ..... ............. ...... 2 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch Type 1124-hr 100-yr, 24-hr Rainfall=7.93" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 O 2022 HydroCAD Software Solutions LLC Page 46 Summary for Reach 3R: Rip-Rap Swale Inflow Area = 15,494 sf, 25.58% Impervious, Inflow Depth = 4.20" for 100-yr, 24-hr event Inflow = 3.42 cfs @ 11.99 hrs, Volume= 5,425 cf Outflow = 3.41 cfs @ 11.99 hrs, Volume= 5,425 cf, Atten= 0%, Lag= 0.1 min Routed to Reach 1 R : DP-1 - Lake Cochichewick Routing by Stor-Ind+Trans method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Max. Velocity= 3.37 fps, Min. Travel Time= 0.1 min Avg. Velocity= 0.98 fps, Avg. Travel Time= 0.2 min Peak Storage= 13 cf @ 11.99 hrs Average Depth at Peak Storage= 0.44' , Surface Width= 3.63' Bank-Full Depth= 0.50' Flow Area= 1.3 sf, Capacity= 4.54 cfs 1.00' x 0.50' deep channel, n= 0.041 Riprap, 2-inch Side Slope Z-value= 3.07' Top Width= 4.00' Length= 13.0' Slope= 0.0500 '/' Inlet Invert= 116.50', Outlet Invert= 115.85' Reach 3R: Rip-Rap Swale Hydrograph 3.41 cfs Inflow —Outflow f0 a , Zof 3 . ................................... ....................................... .... .................... ............ Fth .4 ' s w 1 2 3 L ' 0 LL = 05 c6p C it s ———— -------------------------.............................. 7"' .. L11171171rT71 ��!nj�i n?npnqnqnqnn 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch Type //24-hr 100-yr, 24-hr Rainfall=7.93" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 47 Summary for Pond 1P: Bio. Ret. Area #2 Inflow Area = 9,610 sf, 19.84% Impervious, Inflow Depth = 5.79" for 100-yr, 24-hr event Inflow = 2.24 cfs @ 11.96 hrs, Volume= 4,639 cf Outflow = 2.17 cfs @ 11.98 hrs, Volume= 4,374 cf, Atten= 3%, Lag= 1.1 min Discarded = 0.01 cfs @ 11.98 hrs, Volume= 700 cf Primary = 2.16 cfs @ 11.98 hrs, Volume= 3,673 cf Routed to Pond 5P : 12" RCP Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 116.72' @ 11.98 hrs Surf.Area= 1,059 sf Storage= 960 cf Flood Elev= 117.00' Surf.Area= 1,176 sf Storage= 1,269 cf Plug-Flow detention time= 261.4 min calculated for 4,373 cf(94% of inflow) Center-of-Mass det. time= 229.2 min ( 1,023.6 - 794.4 ) Volume Invert Avail.Storage Storage Description #1 115.50' 1,269 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 115.50 419 0 0 419 116.00 784 296 296 787 117.00 17176 973 11269 17194 Device Routing Invert Outlet Devices #1 Discarded 115.50' 0.170 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 112.00' Phase-In= 1.00' #2 Primary 116.50' 24.0" Horiz. Top of Riser C= 0.600 Limited to weir flow at low heads Discarded Outflow Max=0.01 cfs @ 11.98 hrs HW=116.72' (Free Discharge) L1=Exfi1tration ( Controls 0.01 cfs) Primary OutFlow Max=2.16 cfs @ 11.98 hrs HW=116.72' (Free Discharge) L2=Top of Riser (Weir Controls 2.16 cfs @ 1.54 fps) Proposed—N. Andover Boat Launch Type //24-hr 100-yr, 24-hr Rainfall=7.93" Prepared by Apex Companies Printed 5/12/2023 HydroCAD® 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 48 Pond 1 P: Bio. Ret. Area #2 Hydrograph ?24 rf Inflow 2.16 cfsI � Outflow Discarded ''�, ''�, ''�, I I A ��'�� a 10 �� f' —Primary 2 ........ .......................... ......................... e a 1 to: 0' f O 1 .......................... ........................ 0.0 0 L711717171� 111�111�N v U u U u u u u U u u 4 111 ..0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch Type //24-hr 100-yr, 24-hr Rainfall=7.93" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 49 Summary for Pond 2P: Bio. Ret. Area #1 [81] Warning: Exceeded Pond 5P by 0.52' @ 11.66 hrs Inflow Area = 15,494 sf, 25.58% Impervious, Inflow Depth = 5.09" for 100-yr, 24-hr event Inflow = 3.53 cfs @ 11.97 hrs, Volume= 6,572 cf Outflow = 3.42 cfs @ 11.99 hrs, Volume= 6,316 cf, Atten= 3%, Lag= 1.1 min Discarded = 0.01 cfs @ 11.99 hrs, Volume= 891 cf Primary = 3.42 cfs @ 11.99 hrs, Volume= 5,425 cf Routed to Reach 3R : Rip-Rap Swale Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 116.94' @ 11.99 hrs Surf.Area= 1,174 sf Storage= 1,358 cf Flood Elev= 117.00' Surf.Area= 1,201 sf Storage= 1,432 cf Plug-Flow detention time= 242.4 min calculated for 6,316 cf(96% of inflow) Center-of-Mass det. time= 219.8 min ( 1,026.4 - 806.7 ) Volume Invert Avail.Storage Storage Description #1 115.00' 1,432 cf Custom Stage Data (Conic) Listed below (Recalc) Elevation Surf.Area Inc.Store Cum.Store Wet.Area (feet) (sq-ft) (cubic-feet) (cubic-feet) (sq-ft) 115.00 0 0 0 0 115.50 590 98 98 590 116.00 787 343 441 793 116.50 991 444 885 17003 117.00 17201 547 17432 11222 Device Routing Invert Outlet Devices #1 Discarded 115.00' 0.170 in/hr Exfiltration over Surface area Conductivity to Groundwater Elevation = 112.00' Phase-In= 1.00' #2 Primary 116.50' Channel/Reach using Reach 3R: Rip-Rap Swale Discarded OutFlow Max=0.01 cfs @ 11.99 hrs HW=116.94' (Free Discharge) L1=Exfi1tration ( Controls 0.01 cfs) Primary OutFlow Max=3.41 cfs @ 11.99 hrs HW=116.94' (Free Discharge) L2=Channel/Reach (Channel Controls 3.41 cfs @ 3.37 fps) Proposed-N. Andover Boat Launch Type //24-hr I 00-yr, 24-hr Rainfall=7.93 F1 Prepared by Apex Companies Printed 5/12/2023 HydroCAD® 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 50 Pond 2P: Bio. Ret. Area #1 Hydrograph Inflow 11111111111111111111111111111P 3.42 cfs Outflow Discarded AM If Primary f 3 .............. .......................... ......... ... ... ... L e • t rc1 o ......................................... .................................... 2 0 --------------------------..................... ....................................... .............................................. ................................................ 0.0 1............... 0 L711nln"117]F711711 ?T1 I �""O 111 111 i !III:;;: I !III I 0 2 4 6 8 10 12 14 16 1820 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch Type //24-hr 100-yr, 24-hr Rainfall=7.93" Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 51 Summary for Pond 5P: 12" RCP [81] Warning: Exceeded Pond 1 P by 0.10' @ 11.98 hrs Inflow Area = 9,610 sf, 19.84% Impervious, Inflow Depth = 4.59" for 100-yr, 24-hr event Inflow = 2.16 cfs @ 11.98 hrs, Volume= 3,673 cf Outflow = 2.16 cfs @ 11.98 hrs, Volume= 3,673 cf, Atten= 0%, Lag= 0.0 min Primary = 2.16 cfs @ 11.98 hrs, Volume= 3,673 cf Routed to Pond 2P : Bio. Ret. Area #1 Routing by Stor-Ind method, Time Span= 0.00-72.00 hrs, dt= 0.01 hrs Peak Elev= 116.83' @ 11.98 hrs Flood Elev= 117.00' Device Routing Invert Outlet Devices #1 Primary 115.50' 12.0" Round Culvert L= 44.0' RCP, sq.cut end projecting, Ke= 0.500 Inlet/ Outlet Invert= 115.50' / 115.30' S= 0.0045 7' Cc= 0.900 n= 0.012 Concrete pipe, finished, Flow Area= 0.79 sf Primary OutFlow Max=2.16 cfs @ 11.98 hrs HW=116.83' TW=116.50' (Fixed TW Elev= 116.50') L1=Culvert (Inlet Controls 2.16 cfs @ 2.75 fps) Pond 5P: 12" RCP Hydrograph 2.16 cfs Inflow Primary 2 ---------------- re 1 f CO,JIM IV I 0 1 ........................................ .......................................... ...........................,............ Lm 401) A 1) :12 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 68 70 72 Time (hours) Proposed—N. Andover Boat Launch Multi-Event Tables Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 52 Events for Subcatchment 1 S: SC-01 Event Rainfall Runoff Volume Depth (inches) (cfs) (cubic-feet) (inches) 2-yr, 24-hr 3.16 0.65 1,278 1.12 10-yr, 24-h r 5.00 1.47 2,883 2.54 100-yr, 24-h r 7.93 2.88 51792 5.09 Proposed—N. Andover Boat Launch Multi-Event Tables Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 53 Events for Subcatchment 2S: SC-02 Event Rainfall Runoff Volume Depth (inches) (cfs) (cubic-feet) (inches) 2-yr, 24-hr 3.16 0.48 948 1.07 10-yr, 24-h r 5.00 1.11 2,176 2.45 100-yr, 24-h r 7.93 2.21 41423 4.98 Proposed—N. Andover Boat Launch Multi-Event Tables Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 54 Events for Subcatchment 3S: SC-03 Event Rainfall Runoff Volume Depth (inches) (cfs) (cubic-feet) (inches) 2-yr, 24-hr 3.16 0.62 1,206 1.51 10-yr, 24-hr 5.00 1.23 2,466 3.08 100-yr, 24-h r 7.93 2.24 41639 5.79 Proposed—N. Andover Boat Launch Multi-Event Tables Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 55 Events for Subcatchment 4S: SC-04 Event Rainfall Runoff Volume Depth (inches) (cfs) (cubic-feet) (inches) 2-yr, 24-hr 3.16 0.39 773 1.58 10-yr, 24-h r 5.00 0.77 1,556 3.17 100-yr, 24-h r 7.93 1.39 21898 5.91 Proposed—N. Andover Boat Launch Multi-Event Tables Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 56 Events for Reach 1 R: DP-1 - Lake Cochichewick Event Inflow Outflow Elevation Storage (cfs) (cfs) (feet) (cubic-feet) 2-yr, 24-hr 1.14 1.14 0.00 0 10-yr, 24-h r 2.58 2.58 0.00 0 100-yr, 24-h r 8.35 8.35 0.00 0 Proposed—N. Andover Boat Launch Multi-Event Tables Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 57 Events for Reach 3R: Rip-Rap Swale Event Inflow Outflow Elevation Storage (cfs) (cfs) (feet) (cubic-feet) 2-yr, 24-hr 0.00 0.00 116.50 0 10-yr, 24-hr 0.84 0.84 116.72 5 100-yr, 24-h r 3.42 3.41 116.94 13 Proposed—N. Andover Boat Launch Multi-Event Tables Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 58 Events for Pond 1 P: Bio. Ret. Area#2 Event Inflow Outflow Discarded Primary Elevation Storage (cfs) (cfs) (cfs) (cfs) (feet) (cubic-feet) 2-yr, 24-hr 0.62 0.03 0.00 0.02 116.51 743 10-yr, 24-h r 1.23 1.09 0.00 1.08 116.64 874 100-yr, 24-h r 2.24 2.17 0.01 2.16 116.72 960 Proposed—N. Andover Boat Launch Multi-Event Tables Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 59 Events for Pond 2P: Bio. Ret. Area#1 Event Inflow Outflow Discarded Primary Elevation Storage (cfs) (cfs) (cfs) (cfs) (feet) (cubic-feet) 2-yr, 24-hr 0.39 0.00 0.00 0.00 116.46 846 10-yr, 24-h r 1.79 0.84 0.01 0.84 116.72 17112 100-yr, 24-h r 3.53 3.42 0.01 3.42 116.94 17358 Proposed—N. Andover Boat Launch Multi-Event Tables Prepared by Apex Companies Printed 5/12/2023 HydroCADO 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC Page 60 Events for Pond 5P: 12" RCP Event Inflow Primary Elevation Storage (cfs) (cfs) (feet) (cubic-feet) 2-yr, 24-hr 0.02 0.02 116.50 0 10-yr, 24-h r 1.08 1.08 116.59 0 100-yr, 24-h r 2.16 2.16 116.83 0 Proposed—N. Andover Boat Launch Table of Contents Prepared by Apex Companies Printed 5/12/2023 HydroCAD® 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC TABLE OF CONTENTS Promect Reports 1 Routing Diagram 2 Rainfall Events Listing (selected events) 3 Area Listing (all nodes) 4 Soil Listing (all nodes) 5 Ground Covers (all nodes) 6 Pipe Listing (all nodes) 2-yr, 24-hr Event 7 Node Listing 8 Subcat 1 S: SC-01 9 Subcat 2S: SC-02 11 Subcat 3S: SC-03 13 Subcat 4S: SC-04 15 Reach 1 R: DP-1 - Lake Cochichewick 16 Reach 3R: Rip-Rap Swale 17 Pond 1 P: Bio. Ret. Area #2 19 Pond 2P: Bio. Ret. Area #1 21 Pond 5P: 12" RCP 10-yr,24-h r Event 22 Node Listing 23 Subcat 1 S: SC-01 24 Subcat 2S: SC-02 26 Subcat 3S: SC-03 28 Subcat 4S: SC-04 30 Reach 1 R: DP-1 - Lake Cochichewick 31 Reach 3R: Rip-Rap Swale 32 Pond 1 P: Bio. Ret. Area #2 34 Pond 2P: Bio. Ret. Area #1 36 Pond 5P: 12" RCP 100-yr, 24-hr Event 37 Node Listing 38 Subcat 1 S: SC-01 39 Subcat 2S: SC-02 41 Subcat 3S: SC-03 43 Subcat 4S: SC-04 45 Reach 1 R: DP-1 - Lake Cochichewick 46 Reach 3R: Rip-Rap Swale 47 Pond 1 P: Bio. Ret. Area #2 49 Pond 2P: Bio. Ret. Area #1 51 Pond 5P: 12" RCP Multi-Event Tables 52 Subcat 1 S: SC-01 53 Subcat 2S: SC-02 54 Subcat 3S: SC-03 55 Subcat 4S: SC-04 56 Reach 1 R: DP-1 - Lake Cochichewick Proposed_N. Andover Boat Launch Table of Contents Prepared by Apex Companies Printed 5/12/2023 HydroCAD® 10.20-2g s/n 04044 ©2022 HydroCAD Software Solutions LLC 57 Reach 3R: Rip-Rap Swale 58 Pond 1 P: Bio. Ret. Area #2 59 Pond 2P: Bio. Ret. Area #1 60 Pond 5P: 12" RCP ATTACHMENT 8 BIORETENTION AREA O&M ENVIRONMENTAL PARTNERS 0 ��RA11111111111111F�1 0 A�N�D �NA A�1��N 11111111111111111111111111111 �N A�N C ......................AIN 1111113 0 �1 0 11111111111111111111111111111�1 �N Aomum 1 A�N��111111111111111) 2 �N 0 z .....................A�K C 0 C C��11111111111111111111111��::::Iw C OA11111111111111F �1..................... 111111FO WN G�F �No I Premature failure of bioretention areas is a significant issue caused by lack of regular maintenance. Ensuring long-term maintenance involves sustained public education and deed restrictions or covenants for privately owned cells. Bioretention areas require careful attention while plants are being established and seasonal landscaping maintenance thereafter.Table 1 shows the bioretention maintenance schedule below. ��IIIII II 1 1 JJ ll 1 1 111�� l»>aaal a �aa� I » r , r L uu, 11 ffff ��IIII IIII 11 IIII. 111 Ill ..III IIIIIIIIIIIIIIIIIIIIIIII�IIIIIIIII((�IIIIIIIIIIJ�IIIIIIIIIIIIII�(I1111111111fllllllllllll�lllllllllllll�IIIIIIII�IIIII�IIIIIIIIIIIIIIIIIIIIIIIIIIIII IIIIIIII��IIIIIIIIIIIII�IIIIIIII(IIIIIIIIIII IIIIIIIIIIIIII11111111111f(IIIIIIIIIIIIIIIIIIIIIIIIIIII�IIIIIIIIIIIII IIIIIIIIIIIIIII�IIIIIIIIIIIII��IIIIIIIIIIII�IIIIIIIIIIII�((IIIIIIII((IIIIIIIIIIIIIIIII�IIIIIIIIIIII�IIlfllllllllllll IIIIIIIIIIIIIII IIIII�IIIIIIIIIIII IIII; Activity Time of Year Frequency Inspect and remove trash Year round Monthly Mulch Spring Annually Replace dead vegetation' Spring Annually Prune Spring or Fall Annually Replace entire media and all Late Spring/early Summer As needed vegetation 1. See Planting List in Drawing Plans 2. Paying careful attention to operation and maintenance can extend the life of the soil media. Inspect soil and repair eroded areas monthly. Re-mulch void areas as needed. Remove litter and debris monthly.Treat diseased vegetation as needed. Remove and replace dead vegetation twice per year(spring and fall). Remove invasive species as needed to prevent these species from spreading into the bioretention area. Replace mulch every two years, in the early spring. Upon failure, excavate bioretention area, scarify bottom and sides, replace filter fabric and soil, replant, and mulch.A summary of maintenance activities can be found in Table 1. Because the soil medium filters contaminants from runoff,the cation exchange capacity of the soil media will eventually be exhausted.When the cation exchange capacity of the soil media decreases, change the soil media to prevent contaminants from migrating to the groundwater, or from being discharged via an underdrain outlet. Using small shrubs and plants instead of larger trees will make it easier to replace the media with clean material when needed. tl ei Cold Climate Considerations Never store snow in bioretention areas. The Operation and Maintenance plan must specify where on-site snow will be stored.All snow dumps must comply with MassDEP's guidance. When bioretention areas are located along roads, care must be taken during plowing operations to prevent snow from being plowed into the bioretention areas. If snow is plowed into the cells, runoff may bypass the cell and drain into downgradient wetlands without first receiving the required water quality treatment, and without recharging the groundwater. ATTACHMENT COMPLIANCEILLICIT . ........... ` t Ilr`III" ' to Ilr' o Irt v m IN o irt IIC,,,,,,,a e Co c[-i III c,,,i e wIII c IIE;;;Co a-t a a Ir'i c >r o III III Ilr`t,"i Ir'i d o e Ilr', MA C��I illillililluuuuumu uuuuumu S C A G CI 0 JAlll � m uuuuuuuuuumumu uuuuuum ............... IIIIIIIIIIIIIIIuuuuumu To the best of my knowledge,there are no known illicit discharge connections to the North Lake Cochichewick Boat Launch Facility off Great Pond Road. Site investigation and survey of the existing drainage system did not reveal any illicit discharge connections within the extent of the surveyed area as shown on the Design Plans.Additionally, no new illicit discharges are expected to occur as a result of this work. I hereby certify that the preceding is accurate. Ryan J. Paul, PE Environmental Partners Group, LLC.