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HomeMy WebLinkAbout251121 Rev Stormwater Report - - 243 GREAT POND ROAD STORM WATER ANALYSIS AND CACLUATIONS FOR 243 GREAT POND ROAD IN PREPARED BY: PATRIOT Engineering PO BOX 362 Lexington, Massachusetts 02420 DATE: October 29 2025 MIO �. wIAL Revised November 21 , 202 No� 50696 E1t'�0\ kA ����'���N��^ ��� � ����� � Engineering * ���������� N������0N��m�� ��@�� PD BOX 3O2 Lexington, MAO242O VIA: Hand Delivery October 28,JO25 Revised November 21, 2025 Ms.Jean Enright Director of Planning-North Andover 120 Main Street North Andover,O184S Re: 243 Great Pond Road North Andover,Massachusetts Dear Members of the Planning Board: Patriot Engineering LLC(Patriot) is pleased to submit this letter with accompanying documentation in support of the Watershed Special Permit application for the project located at 243 Great Pond Road.The proposed site improvements will involve the removal of an existing sports court area and gravel edge support of a proposed greenhouse structure.This project will not be any significant degradation of the quality or quantity of water in or entering Lake Cochichewick.The proposed greenhouse project will not result in any overcrowding or increase in traffic, is an appropriate use of the existing property and does not cause any hazards from fire or other dangers. This project does not increase the leviable area of the structure therefore overcrowding is not an issue. The existing topography for the subject parcel results in water runoff toward the west portion of the site (toward the delineated wetland); this location has been chosen as the design point for the stormwater analysis.The proposed site improvements will mimic existing drainage patterns.To mitigate any increase in stormwater runoff,the entire roof area of the proposed greenhouse will be captured and directed to proposed stone trench drip edge.The stormwater runoff from the remainder of the disturbed areas will mimic existing conditions. The proposed stone trench drip edge has been sized to capture the stormwater runoff for the 1-year, 2-year, and 10-year design storms and have a small overflow discharge in the 100-yeaar storm.The HydroCAD analysis results summarized below show that with proposed mitigation,the site improvements will not result in an increase in peak rate of stormwater surface runoff for the 1, 2, 10 and 100-year design storm. DP-1/100 Existing(Pre)_ Proposed ( Storm Event Rate(cfs) VmKurme(c0 Rotefofs\ Vokmrme(cf) 1-Year(2.64in./hr] 0.22 935 0.16 767 2-Year/3.2in/hc\ 0.42 1,521 0i33 1,287 10-YearMi8hl./hd 1.12 3,609 0.98 3,180 100-\ear(0.8in/hc) 3.28 10,203 I01 9\426 Accompanying this letter is: � A"Greenhouse Site Plan"dated October 2g. 2O26. Revised November 21. 2O25 * "Stormwater Analysis and Calculations for dated October 29,2025, Revised November 21,2025 � An"Operation&Maintenance Program"dated October 2B. 2O25. Revised November 21.2D2S PATRIOT Engineering PO BOX 362 Lexington, MA 02420 We anticipate this information meets the requirements of the Town of North Andover.Should you have anything further detail, please feel welcome to request via email at rm'o ak2p,� b f(lpaL�2m PATRIOT Engineering LLC, L#" PATRIOT T,'] Engineering PO BOX 362 Lexington, MA 02420 Michael J Novak, P.E. EX STING DP- 1 ---i WETLAND Bobcat Re.......... H � Routing Diagram for 243 GREAT POND ROAD ..._...> Prepared by Patriot Engineering, Printed 11/21/2025 HydrpCADO 10.20-5c s/n 11576 O 2023 HydrpCAD Software Solutions PLC 243 GREAT POND ROAD Prepared by Patriot Engineering Printed 11/21/2025 HydroCADI 10,20-5c s/n 11576 (D 2023 HydroCAD Software Solutions LLC Page 2 Rainfall Events Listing Event# Event Storm Type Curve Mode Duration B/B Depth AMC Name (hours) (inches) I 1-Yr 24 Hr Type III 24-hr Default 24.00 1 164 2 2 2-Yr 24 Hr Type III 24-hr Default 24.00 1 3.20 2 3 10-Yr 24 Hr Type III 24-hr Default 24.00 1 4.80 2 4 100-Yr 24 Hr Type III 24-hr Default 24.00 1 8.80 2 243 GREAT POND ROAD Type11/24-hr1-Yr24KrRoinfo0=2.64" Prepared by Patriot Engineering Printed 11/31/2025 Summary for SubcatchmmentSC-1: EXISTING Runoff = 0.22 cfs @ 12.11hrs, Vo|ume= 935ct Depth= 0.45" Routed to Reach DP-1:WETLAND Runoff bySC5TR-2O method,UH=S[S,VVeighted-CN,Time Span=O.00']O.UOho,dt=O.03hrs Type III 24'hr 1-Yr24HrRainfa||=2.64" Area(sf) CN Description * 4,340 98 Court,Roof,and Patio 229 96 Gravel surface,HSGB 2Good, 24,908 68 Weighted Average 20\568 82.5BY6 Pervious Area 4,340 17.42Y6 Impervious Area Tc Length Slope Velocity Capacity Description 6.0 Direct Entry, SmbcatchnmentSC-1: EXISTING Nydrmgraph u.24 o.ox ` 0.22 0.m Type III 24-hr 0.2 2� � u1 � un 243 GREAT POND ROAD Type///24-hr 1-Yr 24 Hr Rainfall=2.64" Prepared by Patriot Engineering Printed 11/21/2025 HydroCAD010.20-5c s/n11576 @ 2023 HydroCAD Software Solutions LLC Page 4 Summary for Reach DP-1:WETLAND Inflow Area= 24,908 sf, 17.42% Impervious, Inflow Depth= 0.45" for 1-Yr 24 Hr event Inflow = 0.22 cfs @ 12.11 hrs, Volume= 935 cf Outflow = 0.22 cfs @ 12.11 hrs, Volume= 935 cf, Atten=0%, Lag=0.0 min Routing by Stor-Ind+Trans method,Time Span=0.00-30.00 hrs,dt=0.03 hrs Reach DP-1:WETLAND Hydrograph M Inflow 0.24. IN outflow 0.23zi 0.22-' Inflow Area=24,908 sf 0.21 0.2-� 0.19 0.17 0.16." 0.15- 0.14 0.13, 3: 0.12-: 0 0.11 0.1 0.09, 0.08, 0.07' 0.061, 0.05- 0.04--, 0.03-- 0.02; 0.01 0:, ............ ......... ......... 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 6 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Time (hours) ` 243 GREAT POND ROAD Type/024h 2-Yr24HrRainfa8=120" Prepared by Patriot Engineering Printed 11/21/2025 Summary for Smbnat#hmment SC-1: EXISTING Runoff = 0.42cfs @ 17.10hs, Vm|ume= 1,521d, Depth= 0.73" Routed to Reach DP'1:WETLAND Runoff byS[6TR-2O method,UH=6[S,VVeiQhted'CN,Time Span=U.UO'3U.00hru,dt=O.V]hrs Type III 24-hr 2Yr24HrRainfaU=3.20" Area(sf) CN Description ~ 4`340 98 Court'Roo tand Pmdo 229 96 Graxe|su�aoe,HSGB 2Good, 24,908 68 Weighted Average 20,568 8Z.G8%Pervious Area 4,340 17.42%Impervious Area Tc Length Slope Velocity Capacity Description 6.0 Direct Entry, SuhcatchmnentSC-1: EXISTING Hydragmaph u.4m o.^* ----- ».*2 o.4 Type III 24-hr u.ao o.xa u.cw u.o2 o.o o.co 4u.uo /s � 0.24 Runoff Depth=0.73" 0 0.22- � «1 »1 243 GREAT POND ROAD Type///24-hr 2-Yr 24 Hr Rainfall=3.20" Prepared by Patriot Engineering Printed 11/21/2025 HydroCAD"10.20-5c s/n11576 @ 2023 HydroCAD Software Solutions LLC Page 6 Summary for Reach DP-1:WETLAND Inflow Area= 24,908 sf, 17.42%Impervious, Inflow Depth= 0.73" for 2-Yr 24 Hr event Inflow = 0.42 cfs @ 12.10 hrs, Volume= 1,521 cf Outflow = 0.42 cfs @ 12.10 hrs, Volume= 1,521 cf, Atten=0%, Lag=0.0 min Routing by Stor-Ind+Trans method,Time Span=0.00-30.00 hrs,dt=0.03 hrs Reach DP-1:WETLAND Hydro graph M Inflow 0.46 0 Outflow 0.44-- -24,908 sf 0.42: Inflow Area 0.4. 0.38 0.36: 0.34- 0.32� 0.31-1 0.28-, 0.26-: 0.24 0.22-: O.Z� 0.181': 0.16: 0.14-.- 0.12- 0.1 0.08 0.06' 1�14z 02 0 Ad 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Time (hours) ' ^ 243 GREAT POND ROAD Type 6V24-hr1O-H'24HrRoinfo8=48O" Prepared hy Patriot Engineering Printed 11/21/2025 Summary for SuboatchmwamtSC-1: EXISTING Runoff = 1.12dfs @ 12.10hrs, Vu|ume= 3,609d, Depth= 1.74" Routed Lo Reach DP-1:WETLAND Runoff by5[STR'2O method,UH=SCS,VVeighted-CN,Time Span=U.UU'3U.OUhrs,dL=0.03hrs Type III 24'hr 10'Yr24HrRainfa||=4.80" Area(sf) CN Description * 4,340 98 Court, Roof,and Patio 229 96 Gravel surface,HSG8 20339 61 >75%Grass cover,Good, 24,908 68 Weighted Average 20,568 82.5896 Pervious Area 4,340 17.42%Impervious Area Tc Length Slope Velocity Capacity Description 6.0 Direct Entry, Subcat#hmnemtSC-l: EXISTING Hydrmgmaph Type III 24-hr Runoff Depth=1.74" Tc=6.0 min � � � o Time (hours) 243 GREAT POND ROAD Type/024hr2&yiJ4HrRoinfa0=480" Prepared by Patriot Engineering Printed 11/21/2025 Summary for Reach DP-1:WETILAND Inflow Area 24'908s[ 17.4296Impervious, Inflow Depth= 1.74" for 1O-Yr24Hrevent Inflow = I.12cfs @ I2.10ho, Vo|ume= 3,609cf Outflow = I.12cfs @ I2.10hrs, Vo|ume= 5,609cf' Atten=OY6' bU=O.Omin Routing byStnr-|nd+Tons method,Time Span=0.00'3D.00hrs,dt=O.O3hrs Reach DP-1:WETLAND Hydmm0maPh M Inflow � � � o Time (hours) 243 GREAT POND ROAD Type0J4-hr20)M24HrRmirifia0=880" Prepared by Patriot Engineering Printed 11/21/2025 Summary forSubcatchmnemt SC-l: EXISTING Runoff = 8.38dfs@ 1I.09hrs, Vo|ume= 10,203ct Depth= 4.92" Routed to Reach DP-I :WETLAND Runoff bySCSTR'2O method,UH=SC5,VVeighted-CN,Time 3pan=O.00-3O.DOhrs,dt=O.V3hrs Type III%/|hr 100-Yr24HrRainta||=8.80" Area(sf) CN Description * 4,340 98 Court,Roof,and Patio 329 96 Gravel surface,HSG8 2 24,908 68 Weighted Average I0,568 82.58%Pervious Area 4,340 17.4296 Impervious Area 7i Length Slope Velocity Capacity Description 6.0 Direct Entry, SwbratchmnentSC-1: EXISTING ll�ydrwgnaph Type III 24-hr u � � U. Tc=6.0 min Time (hours) 243 GREAT POND ROAD Type hV24-hr100-Yr24HrRuinfaK=0BO" Prepared by Patriot Engineering Printed 11/21/2025 Summary for Reach DP-1:WETLAND Inflow Area 24,908s[ l7.4296Impervious, Inflow Depth= 4.92" for 1On4r24Hrevent Inflow = 3J8dfs @ I2.09ho, Vo|ume= 10,203cf Outflow = 3]8cfs @ 12.09hrs, Vo|ume= lO,2O8cf' Auen=OY6' Lag=0.0min Routing byStop|nd+Trans method,Time Span=0DO'3O.OUhrs'dt=O.O3ho Reach DP-8:WETILAND Hydrmgmaph M Inflow 'eu � w .2 U. Time (hours) BARN SC-100 PROPOSE PT STONE TRENCH DP-100 WETLAND SUbCat Reach an nk Routing Diagram for 243 GREAT POND ROAD_POST Prepared by Patriot Engineering, Printed 11/21/2025 EHydroCADO 10.20-5c s/n 11576 O 2023 HydroCAD Software Solutions LLC 243 GREAT POND ROAD—POST Prepared by Patriot Engineering Printed 11/21/2025 HydroCAD110.20-5c s/n11576 @ 2023 HydroCAD Software Solutions LILC Page 2 Rainfall Events Listing Event# Event Storm Type Curve Mode Duration B/B Depth AMC Name (hours) (inches) 1 1-Yr 24 Hr Type III 24-hr Default 24.00 1 2.64 2 2 2-Yr 24 Hr Type III 24-hr Default 24.00 1 3.20 2 3 10-Yr 24 Hr Type III 24-hr Default 24.00 1 4.80 2 4 100-Yr 24 Hr Type III 24-hr Default 24.00 1 8.80 2 . ` 243 GREAT POND Type/024-h/ 2-Yr24Hr8oinfo0=2.64" Prepared by Patriot Engineering Printed 11/21/2025 Summary for Subuatchmment 3S: BARN Runoff = 0.05cb@ 12D8hrs, Vu|ume= 179cf, Depth= 2.41" Routed to Pond PT:STONE TRENCH Runoff by5{STR-2O method,VH=SCG,VVeighted-[N,Time 5pan=0.00-3O.0Ohrs,dt=O.O3ho Type III 24'hr 1'Y/24HrRminfa||=2.64" Area(sf) CN Description * 890 98 DRIVE 890 IO0.00%Impervious Area Tc Length Slope Velocity Capacity Description 6.0 Direct Entry, Swbmmtchrnemt3S: BARN Hydrograph 0.05., Type III 24-hr 0.055- ouu Runoff Depth=2.41 � � o.ouu uou uo1s »»1 uma Time (hours) 243 GREAT POND ROAD—POST Type/024-hr1'M'24HrRoinfa0=2.64" Prepared by Patriot Engineering Printed11/21/2025 Summary for Subcatohmnemt SC-100: PROPOSED Runoff = 016dfs @ 12.12hrs, Vo|ome= 767c[ De[*h= 0.38" Routed to Reach DP-1DO:WETLAND Runoff by5[STR'2O method,UH=SCS'VVeighted'CN'Time 6pan=O.On-3O.ODhrs,dt=O.O3hrs Type III 24'hr1'Yr24HrRainfa||=2.G4" Area(sf) CN Description * 3,050 98 Ex. Roof,Ex. Patio,Prop Wall and Landings 156 85 Gravel roads,H5G8 20812 61 >75%Grass cover,Good,HS8B 24,018 66 Weighted Average 20,968 87.3O%Pervious Area 3,050 12.7U%Impervious Area Tc Length Slope Velocity Capacity Description &O Direct Entry, Swbcatchmment SC-100; PROPOSED Hydrm0raph u.m 0. r Type III 24-hr 42 0.1" o� � � � Runoff Depth=0.38" uom um uuo u05 u uoo u 0.01 0 I { 243 GREAT POND ROAD—POST Type 111 24-hr 1-Yr 24 Hr Rainfall=2.64" Prepared by Patriot Engineering Printed 11/21/2025 HydroCAD0 10.20-5c s/n 11576 @ 2023 HydroCAD Software Solutions LLC Page 5 Summary for Reach DP-100:WETLAND Inflow Area= 24,908 sf, 15.82%Impervious, Inflow Depth= 0.37" for 1-Yr 24 Hr event Inflow = 0.16 cfs @ 12.12 hrs, Volume= 767 cf Outflow = 0.16 cfs @ 12.12 hrs, Volume= 767 cf, Atten=0%, Lag=0.0 min Routing by Stor-Ind+Trans method,Time Span=0.00-30.00 hrs,dt=0.03 hrs Reach DP-100:WETLAND Hydrograph 0.1&, M Inflow 4.16 cfs /� QQ//.'��QQ. 0 oufflow 0.17 0.16 o:1sols Inflow Area-2 ww 1,908 Sf 0.15' 0.14- 0.13-. 0.12 i 0.11 4 0.1- 0.09 �—°° 0.087: 0.07' 0.06=, 0.05-m 0.04 0.03 0.02 0.01 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Time (hours) 243 GREAT PONQROAD_POST Type 024hr1-Yr24HrRoinfa0=264" Prepared by Patriot Engineering Printed 11/21/2025 Summary for Pond PT:STONE TRENCH Inflow Area O90s[1OO.OU% Impervious, Inflow Depth= 2.41" for I4r24Hrevent Inflow = 0.05cfs@ 12D8ho, Vo|ume= 179cf Outflow = 0.01dfs @ 11J0hrs, Vn|ume= 179ct Auen=D5%. Lag=U.Omin Discarded = 0.01db@ 1170hn, Vo|ume= 179cf Primary = 0.08dfs@ 0.00hrs, Vo|ume= Ucf Routed to Reach DP-1O0:WETLAND Routing byStor'|nd method,Time Span=O.OU-3O.OUhrs,dt=0.O3hrs Peak E|ev= 152.91' @1Z.57hm 5urf.Area=14Osf StoraDe=51cf Plug-Flow detention time=39.8 min calculated for I79cf(100%ofinflow) Center-ofyMassdet.time= 89.7 min(8UD.4-75O.d) Volume Invert Avail.Storage Stora e Description #1 15I00' 224cf Custom Stage Data(Phsmmatic) Listed below(Reca|c) 56OcfOverall x4O.0%Voids Elevation Surf.Area |nc.Store Cum.Store 152.00 140 O O 156.00 140 560 560 Device Routing Invert Outlet Devices #1 Discarded 152.00' 2.41Oin/hrExfbrationover Surface area #2 Primary 155.95' 1n.0'long x1.o'breadth Broad-Crested Rectangular Weir Head(feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 3.00 [oef. (English) 2.69 2.72 2.75 3.85 2.98 3.08 120 3.28 3.31 330 3.31 3.32 Discarded OutFloow yNax=0.01cfs @ 11.70hrs HVV=152.04' (Free Discharge) t-I=Exfiltmtion (Exfi|tration Controls O.O1dfs) PrimaryOutF|om/ K8ax=0.00dy @8.00hrs HVV=152.00' (Free Discharge) t-2=Broed'Cnested Rectangular Weir (Controls 0.00cfs) 243 GREAT POND ROAD—POST Type///24-hr 1-Yr 24 Hr Rainfall=2.64" Prepared by Patriot Engineering Printed 11/21/2025 HydroCAD1 10.20-5c s/n 11576 O 2023 HydroCAD Software Solutions LLC Page 7 Pond PT: STONE TRENCH Hyrdrograph Inflow [0.05 afs /^� J� p Q(�("� �+; Outflow Inflow Area-890 sf ggDiscarded IDl Primary 0.055: 0,05-'(1 Peak Elev=152.91 ' 0.045 Storage=51 cf 0.04 _ 0.035- 0.03 a u 0.025- 0.02= 0.015- 0,01 ds�> a.ot ora 0.01..: 0.005 �4,40 cfs 0.. 0 1 2 3 4 5 6 7 8 9 101112131415161718192021222324252627282930 Time (hours) 243 GREAT POND ROAD—POST Type/I/24-hr 2-Yr 24Hr8ainfo8=3.20" Prepared 6y Patriot Engineering Printed 11/21/2025 Summary for Subcatchmmemt3S: BARN Runoff = 0.06 cfs @ 12.08hrs, Vo|ume= 720cf, Depth= 2.97" Routed to Pond PT:STONE TRENCH Runoff bySCSTR-2O method,UH=SCS'VVe|ghted-CN,Time 5pan=O.00-3O.00hrs'dt=O.O3ho Type III 24'hr 2-Yr24HrRoinfaU=3.20" Area(sf) CN Description ' * 890 98 DRIVE 890 1UU.00%Impervious Area Tc Length Slope Velocity Capacity Description 6.0 Direct Entry, Subcatchmnemt3S: BARN Hyd*mgraph nur o.oes 0.06- Type III 24-hr noss 0.05 0.045: 0.04 2� 3; 0.035 Runoff Depth=2.97" .2 U. oox Tc=6.0 min oouo oou 0.015: nu/ o.me Time (hours) 243 GREAT POND Type///J4-h 2-Yr 24HrKainfall=3.20" Prepared by Patriot Engineering Printed 1I/21/2025 Summary for Smbcatchmmen1SC-100: PROPOSED Runoff = 0.33cb@ 17.11hrs, Vo|uma= 1,287cf, Depth= 0.64" Routed to Reach DP'lOO:WETLAND Runoff by5C3TR'ZO method,UH=SC5,VVeiQhted'CN,Time Span=0.00'3O.00hn,dt=O.OShrs Type III 24-hrZ-Yr24HrRaintaU=I2O" Area(sf) CN Description , 3,050 98 Ex.Roof, Ex.Patio,Prop Wall and Landings 156 85 Gravel roads,HSGB 2Good, 24,0I8 66 Weighted Average 20,968 87.JO96 Pervious Area 3'050 l3.7U%Impervious Area Tc Length Slope Velocity Capacity Description 6.0 Direct Entry, Sm6#atchrment SC-100: PROPOS2D Hydrograpi� 0.36 n.o* OM Type III 24-hr o.o o.uo o.xo 0.24 ».22 u.2 3: o.18 U- 0.16 01 Time (hours) 243 GREAT POND ROAD—POST Type H/24-hr 2-Yr 24 Hr Rainfall=3.20" Prepared by Patriot Engineering Printed 11/21/2025 HydroCAD610.20-5c s/n11576 @ 2023 HydroCAD Software Solutions LLC Page 10 Summary for Reach DP-100:WETLAND Inflow Area= 24,908 sf, 15.82% Impervious, Inflow Depth= 0.62" for 2-Yr 24 Hr event Inflow = 0.33 cfs @ 12.11 hrs, Volume= 1,287 cf Outflow = 0.33 cfs @ 12.11 hrs, Volume= 1,287 cf, Atten=0%, Lag=0.0 min Routing by Stor-Ind+Trans method,Time Span=0.00-30.00 hrs,dt=0.03 hrs Reach DP-100:WETLAND Hydro graph M Inflow 0.36- 0.33 ds 0 Outflow 0 C 0.34 S: Inflow Area-24,908 sf 0.32- 0.3-r. 0.28-: 0.26": 0.24 0.22 0.2. 0.18-. 0 LL O.W 014': 0.12 0.1 0.08 0.06� 0.04�, 0.02".0 ........ ....... 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Time (hours) 243 GREAT POND ROAD—POST Type8/24-hr2-Y,24HrRoin/a8=I2O" Prepared by Patriot Engineering Printed 11/21/2025 Summary for Pond PT: STONE TRENCH Inflow Area 89Osf,1UO.000 Impervious, Inflow Depth= 2.97" for Z-Yr24Hrevent Inflow = 0.06di @ 12.08hrs, Vo|umm= 220cf Outflow = 0.01cfs @ 1I.64hrs' Vo|ume= 230ct Atten=DQ%, LaQ=O.Omin Discarded = 0.01cfs @ 1I.54hn' Vo|ume= 220d Primary = ODOcb@ DDUhrs' Vo|ume= Ocf Routed to Reach DP'1OO:WETLAND Routing byStnr-|nd method,Time Span=U.0O-3O.00hrs,dt=0.O3hn Peak Bev=1B.22' @12.64hrs Surf.Area=140 sf 9torage=6@cf Plug-Flow detention dme=55.0 min calculated for 2ZOcf(1UOY6ofinflow) Center-of-Massdet.dme=55.9 min(81I.3-756.4) Volume Invert Avail.Storage Storage Description #1 152.00' 224of Custom Stage Data(Priamadd Listed below(Reca|c) 56OcfOverall x40.UY6Voids Elevation Surf.Area |nc3tore [um.5tore 152.00 140 O O 156.00 I40 560 560 Device Routing Invert Outlet D i #1 Discarded I52M' 2.41Oin/hrExfi|tradun over Surface area #2 Primary 155.95' 1V.D'long xl.0'breadth Broad-Crested Rectangular Weir Head(fcet) O.2O04OO.5UO.8U1DO12Ol.4O1.6O1.8UI.002.5OS.00 Coef. (English) 2.69 2.72 2.75 2.85 2.98 3.08 3.20 3.28 331 3.30 9.31 3.32 DiscardedOutF|ow K8ax=0.01cfs@1I.64hrs HVV=152.04' (Free Discharge) t—I=ExO|tradon (Exf|hration Controls 8.Olcfs) PrimaryOutF|ovx Max=O.00ofs @pO.00ho HYV=152D0' (Free Discharge) —2=Bnmad'CrestedRactangu|arVVe|r (Controls O.U0cfs) 243 GREAT POND ROAD POST Type///24-hr 2-Yr 24 Hr Rainfall=3.20" Prepared by Patriot Engineering Printed 11/21/2025 HydroCAD'10.20-5c s/n 11576 O 2023 HydroCAD Software Solutions LLC Page 12 Pond PT: STONE TRENCH Hydro graph h Q Inflow 4.4s ors p::1,Outflow Inflow Area=890 sf 01�Discarded 0.07- Primary 0.065 0.06 Peak Elev=1 e2 ' 0.055 Storage=68 cf 0.05 0.045. 0.04 0.035 c LL 0.03- 0.025; 0.02 0.01 afs Z �s� k 0.015.7 4.41 as 0.0. 0 04 afs_. 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Time (hours) 243 GREAT POND ROAD—POST Type///24-hr 10-Yr 24 Hr Rainfall=4.80" Prepared by Patriot Engineering Printed 11/21/2025 HydroCAD610.20-5c s/n11576 @ 2023 HydroCAD Software Solutions LLC Page 13 Summary for Subcatchment 3S: BARN Runoff = 0.10 cfs @ 12.08 hrs, Volume= 338 cf, Depth= 4.56" Routed to Pond PT:STONE TRENCH Runoff by SCS TR-20 method,UH=SCS,Weighted-CN,Time Span=0.00-30.00 hrs,dt=0.03 hrs Type III 24-hr 10-Yr 24 Hr Rainfall=4.80" Area(sf) CN Description 890 98 DRIVE 890 100.00%Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 3S: BARN Hydrograph 0.105- VN1 Runoff 0.1 0.095' 0.09 Type III 24-hr 0.085: 10-Yr 24 Hr Rainfall=4.80" 0.08 0.075� Runoff Area=890 sf 0.07-- 0.065-- Runoff Volume=338 cf j 0.06--. 4�0.055 Runoff Depth=4.56" 0.05-- U-0.045 Tc=6.0 min 0.04- 0.035-: CN=98 0.03- 0.02& 0.02, 0.015- 0.01' 0.005.0 .......-TT-7 0 1 2 3 4 5 6 7 8 9 10 11 77777715 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Time (hours) 243 GREAT POND ROAD—POST Type/024-hr1O-Yi24HiRohnfrll=4.60" Prepared by Patriot Engineering Printed 11/21/2025 Summary for SubcabchnmemtSC-100: PROPOSED Runoff = 0.98cfs @ 12.10hrs, Vu|ume= 3,188cf, Depth= 1.59" Routed to Reach DP-1OO:WETLAND Runoff by5CSTR-2D method,UH=SC5,VVeighted-CN'Time 5pan=O.O0'3O.00ho,dt=O.O3ho Type III Z4-hr 10-Yr24HrKainfa||=4.80" Area(sf) CN Description * 3,050 98 Ex. Roof,Ex.Patio, Prop Wall and Landings 156 85 Gravel roads, HSG8 208I2 61 >75%Grass cover,Good, HSG8 24,018 66 Weighted Average 20,968 87.30Y6 Pervious Area 3,050 12.7OY6 Impervious Area Tc Length Slope Velocity Capacity Description 6.0 Direct Entry, SwbcatchnmentSC-100: PROPOSED Hydrogvaph Type Ill 24-hr Runoff Depth=1.59" Tc=6.0 min � � � � o Time (hours) 243 GREAT POND ROAD—POST Type///24-hr 10-Yr 24 Hr Rainfafi=4.80" Prepared by Patriot Engineering Printed 11/21/2025 HydroCAD*10.20-5c s/n11576 @ 2023 HydroCAD Software Solutions LLC Page 15 Summary for Reach DP-100:WETLAND Inflow Area= 24,908 sf, 15.82%Impervious, Inflow Depth= 1.54" for 10-Yr 24 Hr event Inflow = 0.98 cfs @ 12.10 hrs, Volume= 3,188 cf Outflow = 0.98 cfs @ 12.10 hrs, Volume= 3,188 cf, Atten=0%, Lag=0.0 min Routing by Stor-Ind+Trans method,Time Span=0.00-30.00 hrs,dt=0.03 hrs Reach DP-100:WETLAND I-fydrograph M Inflow o se cfs" M Outflow 1 Inflow Area-24,908 sf LL 01 0 1 2 3 4 5 6 7 8 9 10 11 12 13 114 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Time (hours) 243 GREAT POND ROAD-POST Type///24-hr10Yr 24 Hr Rainfall=4.80" Prepared by Patriot Engineering Printed 11/21/2025 Summary for Pond PT:STONE TRENCH Inflow Area 89Osf,100.UOY6 Impervious, Inflow Depth= 4.56' for 1O'Yr24Hrevent Inflow = O.IOdfs @ 13D8hrs' Vo|ume= 338cf Outflow = 0.01cfs @ 11.25 hrs' Vo|ume= 338cf, Atten=92%, Lag=O.Omin Discarded = 0.01cb@ 12.25he' Vo|ume= 338cf Primary = O.ODcfs @ 0.00h,a' Vo|ume= Ocf Routed to Reach DP-1U0:WETLAND Routing by8tnr-|nd method,Time Span=0.DO-3O.00hrs'dt=O.O3hrs Peak E|ev=154.19' @13.O3hrs 5urf.Area=140sf gto/age=1Z]cf Plug-Flow detention dme= I1Z.O min calculated for 93@d(IOU%ufinflow) [enter-of-K8assdet.time= 11I.5 min(B51.2 748.7) Volume Invert Avail.Storage Storage Descrietion #1 152.00' 224cf Custom Stage Data(Prismadc) Listed below(Reca|c) 56OcfOverall x4O.O%Voids Elevation 6urf.Area |ncStore Cum.Store 152.00 140 O 0 156.00 140 560 560 Device Routing Invert Outlet Devices #1 Discarded 152.00' 2.410in/hrExfihret|on over Surface area #2 Primary 155.95' l0.0'long x1.o'breadth Broad-Crested Rectangular Weir Head(feet) 0.20 040 0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.50 100 Coef. (English) 2.69 2.72 2.75 2.85 2.98 3.08 3.20 3.28 3.31 330 3.32 3.32 Discarded0uuRoxv K4ax=0.01dfs @ 11.25 hrs HVV=152D4' (Free Discharge) t� -`=Exfi|tration (Exfi|tmdon Controls U.Olcfs) PrimaryOutFloxw N1ax=0.00cfs @O.00hn HVV=153.00' (Free Discharge) t-2=Broad-Cnestad Rectangular Weir (Controls O.O0dfs) 243 GREAT POND ROAD—POST Type Ill 24-hr 10-Yr 24 Hr Rainfall=4.80" Prepared by Patriot Engineering Printed 11/21/2025 HydroCAD"10.20-5c s/n 11576 O 2023 HydroCAD Software Solutions LLC Page 17 Pond PT:STONE TRENCH Hydro graph Inflow DJO cf5 / dutrinw Inflow Area=890 sf Discarded 0.105 IIDW Primary 0.1 0.095 Peak Elev=154.191 0.09- °oo$ Storage-123 cf 0.075 0.07 _0.065.? 0.06 0.055 0 0.05 0.045.. 0.04 0.035 0.03 0.025-` 0. 0.015, 0,01 cts e u"r 0,01, 0. 0.40 cfs 0' 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Time (hours) 243 GREAT POND ROAD—POST Type///24-hr 100-Yr 24 Hr Rainfafl=8.80" Prepared by Patriot Engineering Printed 11/21/2025 HydroCAD"10.20-5c s/n11576 @ 2023 HydroCAD Software Solutions LLC Page 18 Summary for Subcatchment 3S: BARN Runoff = 0.18 cfs @ 12.08 hrs, Volume= 635 cf, Depth= 8.56" Routed to Pond PT:STONE TRENCH Runoff by SCS TR-20 method,UH=SCS,Weighted-CN,Time Span=0.00-30.00 hrs,dt=0.03 hrs Type III 24-hr 100-Yr 24 Hr Rainfall=8.80" Area(sf) CN Description 890 98 DRIVE 890 100.00%Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 3S: BARN Hydro rapes 0.19: Runoff 0.18-: 0.1 7; Type III 24-hr 0.15 0.1 6: I 00-Yr 24 Hr Rainfall=8.80" 0.14- Runoff Area=890 sf 0.13 0.12- Runoff Volume=635 d °.11 : Runoff Depth=8.56" .2 0'09; Tc=6.0 min U. 0.08 0.07 CN=98 0.06' 0.05' 0.04 0.03 0.02 100% 0.01- :11:10 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Time (hours) . . " 243 GREAT POND ROAD—POST Type 6VJ4-hr200-Yr248rRoinfa&=8.&D" Prepared by Patriot Engineering Printed 11/21/2025 Summary for Subcatchmmemt SC-100: PROPOSED Runoff = 3.02cfs @ 12.09ho, Vo|ume= 9,351ct Dep1h= 4.67" Routed to Reach DP'IOO:WETLAND Runoff by5CSTR-2U method,UH=SCS,VVeiAhted'CN,Time Span=U.00'3O.00hrs,dt=O.O3hm Type III 24'hr 100-Yr24HrRainfa||=8.80" Area(sf) CN Description * 3,050 98 Ex.Roof,Ex. Patio,Prop Wall and Landings 156 85 Gravel roads,H5G B 208I2 61 7 9&Grass cover,Good, 24`018 66 Weighted Average 20,968 O7.3OY6 Pervious Area 3,050 lZ.70Y6 Impervious Area Tc ian[¢h Slope Velocity Capacity Description 6.0 Direct Entry, Swbcat#hnmemtSC-100: PROPOSED Hyd"ogmmp�'� u Type III 24-hr 2- Runoff Volume=9,351 d � Runoff Depth=4.67" � � � Tc=6.0 min LL 1 Time (hours) 243 GREAT POND ROAD—POST Type///24-hr 100-Yr 24 Hr Rainfall=8.80" Prepared by Patriot Engineering Printed 11/21/2025 HydroCAD11 10.20-5c s/n 11576 @ 2023 HydroCAD Software Solutions LLC Page 20 Summary for Reach DP-100:WETLAND Inflow Area= 24,908 sf, 15.82%impervious, Inflow Depth= 4.54" for 100-Yr 24 Hr event Inflow = 3.01 cfs @ 12.09 hrs, Volume= 9,426 cf Outflow = 3.01 cfs @ 12.09 hrs, Volume= 9,426 cf, Atten=0%, Lag=0.0 min Routing by Star-Ind+Trans method,Time Span=0.00-30.00 hrs,dt=0.03 hrs Reach DP-100:WETLAND Hydrograph 0 Inflow "K67ors Outflow 3- Inflow Area-24,908 sf 2-- 0 0 1 2 3 4 5 6 7 8 9 101 12 13 14 1 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Time (hours) ' 243 GREAT POND ROAD-POST Type0V24-hr100-YrJ4HrRoinfo8=B8D" Prepared by Patriot Engineering Printed 11/21/2025 Summary for Pond PT:STONE TRENCH Inflow Area 89Osf,1OU.00Y6Impervious, Inflow Depth= 8.56" for IOO-YrZ4Hrevent Inflow = 0.18cfs @ 12.08hn, Vo|ume= 635cf Outflow = 0D9dfs@ 22.31hrs' Vo|ume= 635cf, Atten=4g%, Lag=133min Discarded = 0.01cfs @ 9J2hrs, Vo|ume= 560cf Primary = 0.08cfs @/ 12.31ho, Vo|ume= 75cf Routed tn Reach DP'1OO:WETLAND Routing byStor'|nd method,Time Span=0.UO-3O.ODho,dt=OD]hm Peak E|ev=155.97' @12.3Uhn 5urf.Areu=140sf Stn/age=22Id Plug-Flow detention dme=2O4.l min calculated for b54d(1OU%ofinflow) Centerof-W1asydet.dme= 204.1min(944.1 740.I) Volume Invert Avail.Storage Storage Description #1 152.00' 224cf Custom Stage Data(prismatic) Listed below(Reca|c) 560cfOverall x40.0YSVoids Elevation 6urf.Area |nc.Store Cum.Store 152.00 140 O O 156.00 140 560 560 Device Routing Invert Outlet D i #1 Discarded 152.00' 2.410|n/brExM|tration over Surface area #2 Primary 155.95' 10.0'|ong x1.O'breadth Broad-Crested Rectangular Weir Head(feet) 0.20 0.40 0.60 0.80 1.00 1.20 1.40 2.60 1.80 ZDO 2S0 3D0 [oef. (English) 2.69 2.72 2.75 2.85 2.98 3.08 3.20 3.28 331 3.30 3.31 3.32 Discarded OutF|ow yNax=O.Olcfs @9.72 hrs HVV=153.04' (Free Discharge) -l=Exfi|tration (Exfi|trodon Controls 0.U1cfs) PrimaryCxutF|ow Max=0.06cfs @ 12.31 hrs HVV=155.97' (Free Discharge) -2=Wroa6'CestedRectangu|arVVeir (VVeirCnntrn|s0.06cfs @0.35fps) 243 GREAT POND ROAD—POST Type///24-hr 100-Yr 24 Hr Rainfall=8.80" Prepared by Patriot Engineering Printed 11/21/2025 HydroCAD"10.20-5c s/n 11576 Q 2023 HydroCAD Software Solutions LLC Page 22 Pond PT: STONE TRENCH Hydro graph Inflow �0.18 cfs Inflow Area- Q ';�QUtfIOW 890 sf �V3Discarded 0.19- Primary 0.17 Peak Elev=155.97' 0.16: 014 Storage=222 cf 0.13j OM CIS 0.11. 0.1 O 0.09-' e 0.08 0.07: 0.06r �y t 0.05 0.04 0.03 sP tltl1 ofs 0.01 0' . 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Time (hours) Project Name: 243 Great Pond Road North Andover, MA Applicants: Stephen and Judi Boyko 243 Great Pond Road North Andover, MA Party Responsible for Maintenance During Construction: Contractor Party Responsible for Maintenance After Construction: Property Owner Erosion and Sedimentation Qgatrgi Measures during Qgogtrugfign Activities Filtermitt Filtermitt will be installed along the down gradient limit of work as depicted on the Site Construction Plan. The Filtermitt will be installed prior to the commencement of any work on- site. An additional supply of Filtermitt shall be on-site to replace and/or repair Filtermitt that is disturbed. The lines of Filtermitt shall be inspected and maintained on a weekly basis during construction. No construction activities are to occur beyond the Filtermitt at any time. Sediment shall be removed once the volume reaches % to Y2 the height of the Filtermitt. Surface Stabilization The surface of all disturbed areas shall be stabilized during and after construction. Disturbed areas remaining idle for more than 14 days shall be stabilized. Temporary measures shall be taken during construction to prevent erosion and siltation. No construction sediment shall be allowed to enter any infiltration system or formal drainage system. All disturbed slopes will be stabilized with a permanent vegetative cover. Some or all of the following measures will be utilized on this project as conditions may warrant. a. Temporary Seeding b. Temporary Mulching C. Permanent Seeding d. Placement of Sod e. Hydroseeding f. Placement of Hay 9. Placement of Jute Netting Dust shall be controlled at the site. Tree Protection Existing trees to be saved shall be protected with orange construction fence (offset from the tree trunk by professional standard based on canopy). Stone Edge Construction activity above and around the proposed location of the stone edge facility shall be limited to prevent compaction of the existing soil. Installation of this system shall occur under dry weather conditions and full stone depth shall be installed immediately to prohibit the introduction of fines or other material that would compromise the functionality of this system. Removal of Sediment and Erosion Controls At the completion of construction activities and after receiving approval from the Town of North Andover, all physical sediment and erosion controls shall be removed from the site. Lgaglecm Ins l2action and Maipt2liangp. MpgaguEegg after ronstruction Erosion Control Eroded sediments can adversely affect the performance of the stormwater management system. Eroding or barren areas should be immediately re-vegetated. Debris and Litter Removal Trash may collect in the BIVIP's, potentially causing clogging of the facilities. All debris and litter shall be removed when necessary, and after each storm event. Sediment and debris collected from vacuuming and/or sweeping should be disposed of at a permitted waste disposal facility. Avoid disposing of this material on site, where it could be washed into the proposed subsurface infiltration systems. Stone Drip Edge The drip edge shall be inspected after all major storms and on regular bi-annual scheduled dates. The drip edge shall be cleared of any debris on a biannual basis. The first '/2 inch of stone can be removed and replaced if the edge becomes clogged Debris and Litter Removal Trash may collect in the BIVIP's, potentially causing clogging of the facilities. All debris and litter shall be removed when necessary, and after each storm event. Sediment and debris collected from vacuuming and/or sweeping should be disposed of at a permitted waste disposal facility. Avoid disposing of this material on site, where it could be washed into the proposed subsurface infiltration systems. STORMWATER MANAGEMENT CONSTRUCTIQN PHASE INSPECTION SCHEDULE AND EVALUATION CHECKLIST PROJECT LOCATION: 243 Great Pond Road WEATHER: Inspecti Required Follow-up on Inspect Area Inspection Comments Recommends t Inspection or Inspected ion Required Date Frequency if (yes/no) BMP Filtermitt Weekly and After Major Storm Events (1) Refer to the Massachusetts Stormwater Handbook, Volume Two: Stormwater Technical Handbook (February 2008) for recommendations regarding frequency for inspection and maintenance of specific BMP's. (2) Inspections to be conducted by a qualified professional such as an environmental scientist or civil engineer. Limited or no use of sodium chloride salts, fertilizers or pesticides recommended. Other notes: (include deviations from: Con. Comm. Order of Conditions, PB Approval, Construction Sequence and Approved Plan) Stormwater Control Manager: a5TO RMWATER MANAGEMENT AFTER CONSTRUCTION INSPECTION SCHEDULE AND EVALUATION CHECKLIST PROJECT LOCATION: 243 Great Pond Road WEATHER: Inspecti Required Follow-up Inspect Area Inspected Ins Comments Recom men dal Inspection on or action ion Required Date Frequency if (yes1no) BMP Subsurface Bi-annually and After Infiltration System Major Storm Events Drip Edge Bi-annually and After Major Storm Events (3) Refer to the Massachusetts Stormwater Handbook, Volume Two: Stormwater Technical Handbook (February 2008) for recommendations regarding frequency for inspection and maintenance of specific BMP's. (4) Inspections to be conducted by a qualified professional such as an environmental scientist or civil engineer. Limited or no use of sodium chloride salts, fertilizers or pesticides recommended. Other notes: (include deviations from: Con. Comm. Order of Conditions, PB Approval, Construction Sequence and Approved Plan) Stormwater Control Manager: