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HomeMy WebLinkAbout243 GP_Stormwater Report - - 243 GREAT POND ROAD STORMWATER ANALYSIS AND CACLUATIONS FOR 243 GREAT POND ROAD IN NORTH ANDOVER, MASSACHUSETTS PREPARED BY: PATRIOT Engineering PO BOX 362 Lexington, Massachusetts 02420 NOVAK vas No. 50696 DATE: October 29, 2025 AL ° � itPATRIOT , i e e i PO BOX 362 Lexington, MA 02420 VIA: EMAIUVIEWPOINT October 29, 2025 Ms. Jean Enright Director of Planning-North Andover 120 Main Street North Andover, 01845 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 subsurface infiltration system has been sized to capture and fully infiltrate the stormwater runoff for the 1, and 2-year design storms. 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 2, 10 and 100-year design storm. DP-1/100 Existing (Pre) Proposed (Post) Storm Event Rate(cfs) Volume(cf) Rate(cfs) Volume(cf) 1-Year(2.64 in./hr.) 0 80 0.00 41 2-Year(3.2 in./hr.) 0.01 267 0.01 187 10-Year(4.8 in./hr.) 0.24 1,271 0.22 1,139 100-Year(8.8 in./hr.) 1.73 5,713 1.72 5,534 Accompanying this letter is: • A"Greenhouse Site Plan" dated October 29, 2025 • "Stormwater Analysis and Calculations for dated October 29, 2025 • An "Operation & Maintenance Program" dated October 29, 2025 tPATRIOT wEngineering 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 mnovak(c)_patriot-eng.com PATRIOT Engineering LLC, Michael J Novak, P.E. 2S EX 3R WETLAND Subcat Reach on Link Routing Diagram for 243 GREAT POND ROAD Prepared by Patriot Engineering, Printed 10/29/2025 HydroCAD®10.20-5c s/n 11576 ©2023 HydroCAD Software Solutions LLC 243 GREAT POND ROAD Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD°10.20-5c s/n 11576 ©2023 HydroCAD Software Solutions LLC 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 ROAD Type///24-hr 1-Yr 24 Hr Rainfall=2.64" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD°10.20-5c s/n 11576 ©2023 HydroCAD Software Solutions LLC Page 3 Summary for Subcatchment 2S: EX Runoff = 0.00 cfs @ 15.29 hrs, Volume= 80 cf, Depth= 0.04" Routed to Reach 3R :WETLAND 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 1-Yr 24 Hr Rainfall=2.64" Area (sf) CN Description 4,340 98 Paved parking, HSG A 229 76 Gravel roads, HSG A 20,339 39 >75%Grass cover,Good, HSG A 24,908 50 Weighted Average 20,568 82.58%Pervious Area 4,340 17.42%Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 2S: EX Hydrograph 0.003 Runoff 0.003.003 Type III 24-hr ' 0.002 1-Yr 24 Hr Rainfall=2 4 Runoff Area=24,908 0.002 %;� 0.002 0.002 Runoff Volume=80 ' 0.002 Runoff • °'%,, Depth=0.04•- _ 0 0.001 0.001 Tc=6.0 min 0.001 CN=50 0.001 0.001 0.000 0.000 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 Type///24-hr 1-Yr 24 Hr Rainfal1=2.64" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD®10.20-5c s/n 11576 @ 2023 HydroCAD Software Solutions LLC Page 4 Summary for Reach 3R: WETLAND Inflow Area = 24,908 sf, 17.42% Impervious, Inflow Depth= 0.04" for 1-Yr 24 Hr event Inflow = 0.00 cfs @ 15.29 hrs, Volume= 80 cf Outflow = 0.00 cfs @ 15.29 hrs, Volume= 80 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 3R:WETLAND Hydrograph Inflow 0.003. 0.00 ofs ElOutflow Cfs 0.003 Inflow Area=24,9 °° 0.003 e 0.002 0.002 0.002 0.002 0.002 �r a� i—°° 0.0010.001 i 0.001 0.001 i 0.001 /. 0.000 j 0.000 0 1 2 3 4 5 6 7 8 9 loll 12 1314 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Time (hours) 243 GREAT POND ROAD Type///24-hr 2-Yr 24 Hr Rainfall=3.20" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD°10.20-5c s/n 11576 ©2023 HydroCAD Software Solutions LLC Page 5 Summary for Subcatchment 2S: EX Runoff = 0.01 cfs @ 12.48 hrs, Volume= 267 cf, Depth= 0.13" Routed to Reach 3R :WETLAND 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 2-Yr 24 Hr Rainfall=3.20" Area (sf) CN Description 4,340 98 Paved parking, HSG A 229 76 Gravel roads, HSG A 20,339 39 >75%Grass cover,Good, HSG A 24,908 50 Weighted Average 20,568 82.58%Pervious Area 4,340 17.42%Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 2S: EX Hydrograph 0.015 Runoff 0.014 0.0 �r5 0.013 % Type III 24-hr 0.012 2-Yr 24 Hr Rainfall=3.20 0.011 ' %% Runoff Area=24 908 sf 0.017, O.009 %';.Runoff Volume=267 cf 0.008 Runoff Depth=0.13" Mo 0.007 O.006 � ,: Tc=6.0 On n O.00S % %,, CN=50 0.004 0.003 - 0.002 0.001 , s r" 0 1 2 3 4 5 6 7 8 9 10 11 12 13 1 11 4 1 11 5 16 17 18 19 20 21 22 23 2 11 4 25 26 27 28 29 30 Time (hours) 243 GREAT POND ROAD Type///24-hr 2-Yr 24 Hr Rainfal1=3.20" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD®10.20-5c s/n 11576 @ 2023 HydroCAD Software Solutions LLC Page 6 Summary for Reach 3R: WETLAND Inflow Area = 24,908 sf, 17.42% Impervious, Inflow Depth= 0.13" for 2-Yr 24 Hr event Inflow = 0.01 cfs @ 12.48 hrs, Volume= 267 cf Outflow = 0.01 cfs @ 12.48 hrs, Volume= 267 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 3R:WETLAND Hydrograph Inflow 0.015 0.0�ors 0 Outflow 0.014 ° Inflow Area=24,908 sf 0.013 - 0.012 / 0.011 0.01:: 0.009 0.008 .2 0.007 LL i 0.006 0.005 i1r/ 0.004 0.003 0.001 O,I 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///24-hr 10-Vr 24 Hr Rainfall=4.80" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD°10.20-5c s/n 11576 ©2023 HydroCAD Software Solutions LLC Page 7 Summary for Subcatchment 2S: EX Runoff = 0.24 cfs @ 12.13 hrs, Volume= 1,271 cf, Depth= 0.61" Routed to Reach 3R :WETLAND 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 4,340 98 Paved parking, HSG A 229 76 Gravel roads, HSG A 20,339 39 >75%Grass cover,Good, HSG A 24,908 50 Weighted Average 20,568 82.58%Pervious Area 4,340 17.42%Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 2S: EX Hydrograph 0.26 Runoff 0.25 0.24 cfs 0.23 % Type III 24-hr 0.2� 0.2 10-Yr 24 Hr Rainfall=4.80 0.18 j Runoff Area=24,908 sf 0.17 0.16 Runoff Volume=1,271 cf w 0.15 3 0.13 Runoff Depth=0 61 LL 0.11 % Tc=6.0 min 0 CN=50 0.08 0.07 0.05 0.04. 0.03 0.01 0,.. ,r i�,r i /,�i r 'eie 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///24-hr 10-Yr 24 Hr Rainfall=4.80" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD®10.20-5c s/n 11576 @ 2023 HydroCAD Software Solutions LLC Page 8 Summary for Reach 3R: WETLAND Inflow Area = 24,908 sf, 17.42% Impervious, Inflow Depth= 0.61" for 10-Yr 24 Hr event Inflow = 0.24 cfs @ 12.13 hrs, Volume= 1,271 cf Outflow = 0.24 cfs @ 12.13 hrs, Volume= 1,271 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 3R:WETLAND Hydrograph Inflow 0.26 oz4 ors _ El Outflow 0.24 o.z4°`S Inflow Area=24,908 sf 0.22 0.2 0.18 - 0.16 w 0.14 / - 0 0.12 LL 0.1 0.08 0.06 0 - 0.04.02 r 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 2722 23 24 25 26 27 28 29 30 Time (hours) 243 GREAT POND ROAD Type///24-hr 100-Yr 24 Hr Rainfall=8.80" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD°10.20-5c s/n 11576 ©2023 HydroCAD Software Solutions LLC Page 9 Summary for Subcatchment 2S: EX Runoff = 1.73 cfs @ 12.10 hrs, Volume= 5,713 cf, Depth= 2.75" Routed to Reach 3R :WETLAND 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 4,340 98 Paved parking, HSG A 229 76 Gravel roads, HSG A 20,339 39 >75%Grass cover,Good, HSG A 24,908 50 Weighted Average 20,568 82.58%Pervious Area 4,340 17.42%Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 2S: EX Hydrograph Runoff 1.73 cfs j Type III 24-hr 100-Yr 24 Hr Rainfall=8.80" j Runoff Area 24,908 sf j Runoff Volume=5,713 cf Runoff Depth=2.75"- LL j Tc=6.0 min CN=50 i,ri�,riri,ii�'' � " ,�",,�i✓%�'d ,r�%.,/�i�0,,�„r/,�/o;�i;/�/j�i;7,i!r, �r,ij 0...,,, epee ;ve,,, iei�i 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///24-hr 100-Yr 24 Hr Rainfall=8.80" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD®10.20-5c s/n 11576 @ 2023 HydroCAD Software Solutions LLC Page 10 Summary for Reach 3R: WETLAND Inflow Area = 24,908 sf, 17.42% Impervious, Inflow Depth= 2.75" for 100-Yr 24 Hr event Inflow = 1.73 cfs @ 12.10 hrs, Volume= 5,713 cf Outflow = 1.73 cfs @ 12.10 hrs, Volume= 5,713 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 3R:WETLAND Hydrograph Inflow 1.73 cfs p Outflow 1.73 cfs Inflow Area=24,908 sf r LL j �j 0,,, .�/;r� 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) 3S 5S BARN PRO 1P ST NE TRENCH 4R WETLAND Subcat Reach on Link Routing Diagram for 243 GREAT POND ROAD Prepared by Patriot Engineering, Printed 10/29/2025 HydroCAD®10.20-5c s/n 11576 ©2023 HydroCAD Software Solutions LLC 243 GREAT POND ROAD Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD°10.20-5c s/n 11576 ©2023 HydroCAD Software Solutions LLC 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 ROAD Type///24-hr 1-Yr 24 Hr Rainfall=2.64" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD°10.20-5c s/n 11576 ©2023 HydroCAD Software Solutions LLC Page 3 Summary for Subcatchment 3S: BARN Runoff = 0.05 cfs @ 12.08 hrs, Volume= 179 cf, Depth= 2.41" Routed to Pond 1P: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 1-Yr 24 Hr Rainfall=2.64" 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 0.055 0 Runoff 0.05 cfs 0.05 Type III 24-h r 0.045 j 1 -Yr 24 Hr Rainfall=2.64" 0.04 % Runoff Area=890 sf_ Runoff Volume=179 d 0.035 0.03 Runoff Depth=2.41 - a 0.025 Tc=6.0 min 0.02 - i CN=98- 0.015 � 0.01 / - 0.005 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 Type///24-hr 1-Yr 24 Hr Rainfall=2.64" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD°10.20-5c s/n 11576 ©2023 HydroCAD Software Solutions LLC Page 4 Summary for Subcatchment 5S: PROP Runoff = 0.00 cfs @ 17.03 hrs, Volume= 41 cf, Depth= 0.02" Routed to Reach 4R :WETLAND 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 1-Yr 24 Hr Rainfall=2.64" Area (sf) CN Description 3,691 98 Paved parking, HSG A 156 76 Gravel roads, HSG A 21,061 39 >75%Grass cover,Good, HSG A 24,908 48 Weighted Average 21,217 85.18%Pervious Area 3,691 14.82%Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 5S: PROP Hydrograph 0.002 Runoff 0.001 0.00 cfs 0.001 Type III 24-hr "1 1-Yr 24 Hr Rainfall=2.6 0.001 Runoff Area=24,908 sf 0001 Runoff Volume=41 cf 0.001 LL 0001 Runoff Depth=0.02" ' 0.001 Tc=6.0 min 0.0°0 CN=48 0.000 j 0.000 o i. 0 it er� 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 2071 22 23 24 25 26 27 28 29 30 Time (hours) 243 GREAT POND ROAD Type///24-hr 1-Yr 24 Hr Rainfal1=2.64" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD®10.20-5c s/n 11576 @ 2023 HydroCAD Software Solutions LLC Page 5 Summary for Reach 4R: WETLAND Inflow Area = 25,798 sf, 17.76% Impervious, Inflow Depth= 0.02" for 1-Yr 24 Hr event Inflow = 0.00 cfs @ 17.03 hrs, Volume= 41 cf Outflow = 0.00 cfs @ 17.03 hrs, Volume= 41 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 4R:WETLAND Hydrograph IM Inflow 0.002 0.00 cfs 0 Outflow 0.001 0.00 ofs 0.001 Inflow Area=25,798 0.001 0.001 0.001 0.001 rr, 0.001 0.001 LL 0.001 0.000 / 0.000 0.000 0.000 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 Type///24-hr 1-Yr 24 Hr Rainfall=2.64" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD°10.20-5c s/n 11576 ©2023 HydroCAD Software Solutions LLC Page 6 Summary for Pond 1P: STONE TRENCH Inflow Area = 890 sf,100.00% Impervious, Inflow Depth= 2.41" for 1-Yr 24 Hr event Inflow = 0.05 cfs @ 12.08 hrs, Volume= 179 cf Outflow = 0.00 cfs @ 10.89 hrs, Volume= 179 cf, Atten=94%, Lag=0.0 min Discarded = 0.00 cfs @ 10.89 hrs, Volume= 179 cf Primary = 0.00 cfs @ 0.00 hrs, Volume= 0 cf Routed to Reach 411 :WETLAND Routing by Stor-Ind method,Time Span=0.00-30.00 hrs,dt=0.03 hrs Peak Elev=155.32' @ 13.58 hrs Surf.Area=140 sf Storage=74 cf Plug-Flow detention time= 177.2 min calculated for 179 cf(100%of inflow) Center-of-Mass det.time= 177.1 min (937.7-760.6) Volume Invert Avail.Storage Storage Description #1 154.00' 112 cf Custom Stage Data(Prismatic) Listed below(Recalc) 280 cf Overall x 40.0%Voids Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 154.00 140 0 0 156.00 140 280 280 Device Routing Invert Outlet Devices #1 Discarded 154.00' 1.020 in/hr Exfiltration over Surface area #2 Primary 155.95' 20.0'long x 1.0'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 Coef. (English) 2.69 2.72 2.75 2.85 2.98 3.08 3.20 3.28 3.31 3.30 3.31 3.32 Discarded OutFlow Max=0.00 cfs @ 10.89 hrs HW=154.02' (Free Discharge) t1=Exfiltration (Exfiltration Controls 0.00 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=154.00' (Free Discharge) t2=Broad-Crested Rectangular Weir (Controls 0.00 cfs) 243 GREAT POND ROAD Type///24-hr 1-Yr 24 Hr Rainfall=2.64" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD°10.20-5c s/n 11576 ©2023 HydroCAD Software Solutions LLC Page 7 Pond 1P: STONE TRENCH Hydrograph Inflow o.os ifs ..l Outflow Inflow Area-890 sf Discarded p Primary 0.055 0.05 Peak Elev=155.32'- 0.045. Storage=74 cf 0.04... 0.035 a 0.03 3 a 0.025 0.02 0.015 0.01 0.0o cfs 0.00 cfs 0.005 0.00 cfs 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///24-hr 2-Yr 24 Hr Rainfall=3.20" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD°10.20-5c s/n 11576 ©2023 HydroCAD Software Solutions LLC Page 8 Summary for Subcatchment 3S: BARN Runoff = 0.06 cfs @ 12.08 hrs, Volume= 220 cf, Depth= 2.97" Routed to Pond 1P: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 2-Yr 24 Hr Rainfall=3.20" 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 0.07 0 Runoff 0.065 0.0s ors 0.06 Type III 24-h r 0.055 j 2-Yr 24 Hr Rainfall=3,20 0.05 % -Runoff Area=890 sf-- Runoff 0.045 0.04 - - �Ru f�Vo lu m cf e=220 u00 -- 3 0.035 - Runoff Depth=2.97 o - 0.03 Tc=6.0 min 0.025 j 0.02 CN=98 - / - 0.015 0.01 t �r 0.005 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 Type///24-hr 2-Yr 24 Hr Rainfall=3.20" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD°10.20-5c s/n 11576 ©2023 HydroCAD Software Solutions LLC Page 9 Summary for Subcatchment 5S: PROP Runoff = 0.01 cfs @ 14.56 hrs, Volume= 187 cf, Depth= 0.09" Routed to Reach 4R :WETLAND 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 2-Yr 24 Hr Rainfall=3.20" Area (sf) CN Description 3,691 98 Paved parking, HSG A 156 76 Gravel roads, HSG A 21,061 39 >75%Grass cover,Good, HSG A 24,908 48 Weighted Average 21,217 85.18%Pervious Area 3,691 14.82%Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 5S: PROP Hydrograph 0.007 Runoff °.°07 0 01 cfs r -hr Type III 24 o.00s. _ �' 0.006 � � r 24 Hr Rainfall=3,20" 0.005 Hoff Area=24,908 sf w 0.004 � ', off Volume=187 d 3 0.004 Depth=0.09" E0 0.003 0.003 � �� =6.0 min 0.002 CN=48 0.002 j 0.001 0.001 0.000 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///24-hr 2-Yr 24 Hr Rainfal1=3.20" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD®10.20-5c s/n 11576 @ 2023 HydroCAD Software Solutions LLC Page 10 Summary for Reach 4R: WETLAND Inflow Area = 25,798 sf, 17.76% Impervious, Inflow Depth= 0.09" for 2-Yr 24 Hr event Inflow = 0.01 cfs @ 14.56 hrs, Volume= 187 cf Outflow = 0.01 cfs @ 14.56 hrs, Volume= 187 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 4R:WETLAND Hydrograph Inflow 0.007 0.01 Cfs 0 Outflow 0.007 01 Cfs, flow Area=25,798 sf 0.006 0.006 j 0.005 " 0.005 i 0.004 - - - i �- 0.004 i a 0.003 i i 0.003 0.002 0.002 0.001 0.001 0.000 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///24-hr 2-Yr 24 Hr Rainfall=3.20" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD°10.20-5c s/n 11576 ©2023 HydroCAD Software Solutions LLC Page 11 Summary for Pond 1P: STONE TRENCH Inflow Area = 890 sf,100.00% Impervious, Inflow Depth= 2.97" for 2-Yr 24 Hr event Inflow = 0.06 cfs @ 12.08 hrs, Volume= 220 cf Outflow = 0.00 cfs @ 10.38 hrs, Volume= 220 cf, Atten=95%, Lag=0.0 min Discarded = 0.00 cfs @ 10.38 hrs, Volume= 220 cf Primary = 0.00 cfs @ 0.00 hrs, Volume= 0 cf Routed to Reach 411 :WETLAND Routing by Stor-Ind method,Time Span=0.00-30.00 hrs,dt=0.03 hrs Peak Elev=155.76' @ 14.03 hrs Surf.Area=140 sf Storage=98 cf Plug-Flow detention time= 245.5 min calculated for 220 cf(100%of inflow) Center-of-Mass det.time= 245.4 min ( 1,001.8-756.4) Volume Invert Avail.Storage Storage Description #1 154.00' 112 cf Custom Stage Data(Prismatic) Listed below(Recalc) 280 cf Overall x 40.0%Voids Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 154.00 140 0 0 156.00 140 280 280 Device Routing Invert Outlet Devices #1 Discarded 154.00' 1.020 in/hr Exfiltration over Surface area #2 Primary 155.95' 20.0'long x 1.0'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 Coef. (English) 2.69 2.72 2.75 2.85 2.98 3.08 3.20 3.28 3.31 3.30 3.31 3.32 Discarded OutFlow Max=0.00 cfs @ 10.38 hrs HW=154.02' (Free Discharge) t1=Exfiltration (Exfiltration Controls 0.00 cfs) Primary OutFlow Max=0.00 cfs @ 0.00 hrs HW=154.00' (Free Discharge) t2=Broad-Crested Rectangular Weir (Controls 0.00 cfs) 243 GREAT POND ROAD Type///24-hr 2-Yr 24 Hr Rainfall=3.20" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD°10.20-5c s/n 11576 ©2023 HydroCAD Software Solutions LLC Page 12 Pond 1P: STONE TRENCH Hydrograph Inflow 0.06 ofs ..Ill Outflow Inflow Area-890 sf Discarded 0.07 ®Primary 0.065(1 0.06 Peak Elev=155.76' 0.06 0.055 Storage=98 cf - 0.05 0.045 v 0.04 3 0.035 0 a 0.03 0.025 0.02 0.015 0.01 O.00 cfs 0.0 .: 0.00 cfs 0,,,;; I'llIlP, I'll ll 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///24-hr 10-Vr 24 Hr Rainfall=4.80" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD°10.20-5c s/n 11576 ©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 1P: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 0 Runoff 0.1. 0.10 cfs 0.095 j Type III 24-hr 10-Yr 24 Hr Rainfall=4.80 0.085 0.08 0.075 Runoff Area=890 sf 0.07 0.065 Runoff Vol ume=338 cf w 0.06 05 % Runoff Depth=4.516 0 0.0.05 u-0.045 Tc=6.0 m i n 0. 0 0035 ; CN=98 0.03 0.025 0.02 0.015 0.01 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///24-hr 10-Vr 24 Hr Rainfall=4.80" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD°10.20-5c s/n 11576 ©2023 HydroCAD Software Solutions LLC Page 14 Summary for Subcatchment 5S: PROP Runoff = 0.16 cfs @ 12.15 hrs, Volume= 1,069 cf, Depth= 0.51" Routed to Reach 4R :WETLAND 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 3,691 98 Paved parking, HSG A 156 76 Gravel roads, HSG A 21,061 39 >75%Grass cover,Good, HSG A 24,908 48 Weighted Average 21,217 85.18%Pervious Area 3,691 14.82%Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 5S: PROP Hydrograph 0.17. Runoff _.. 0.16 cfs 0.16 0.15: Type III 24-hr 0.14 % 10-Yr 24 Hr Rainfall=4.80 0.13 0.12 Runoff Area=24,968 sf Runoff Volume=1,069 cf w 0.1 3 0.09 % - Runoff Dep#h=0.51"- 0 0.08 LL 0.07 Tc=6.0 min 0.06 / CN=48 0.05 0.04 0.02 0.01 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///24-hr 10-Yr 24 Hr Rainfall=4.80" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD®10.20-5c s/n 11576 @ 2023 HydroCAD Software Solutions LLC Page 15 Summary for Reach 4R: WETLAND Inflow Area = 25,798 sf, 17.76% Impervious, Inflow Depth= 0.53" for 10-Yr 24 Hr event Inflow = 0.22 cfs @ 12.18 hrs, Volume= 1,139 cf Outflow = 0.22 cfs @ 12.18 hrs, Volume= 1,139 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 4R:WETLAND Hydrograph 0.25 Inflow 0.24 0.22 ors El Outflow 0.23 0.22 ors Inflow Area=25 798 sf 0.22 0.21 0.19 0.18 0.17 0.16 , 0.15 w 0.14 0.13 0 0.12 a 0.11 0.1 0.08 r 0.07 0.06 0.05 0.04 0.03 0.01 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///24-hr 10-Yr 24 Hr Rainfall=4.80" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD°10.20-5c s/n 11576 ©2023 HydroCAD Software Solutions LLC Page 16 Summary for Pond 1P: STONE TRENCH Inflow Area = 890 sf,100.00% Impervious, Inflow Depth= 4.56" for 10-Yr 24 Hr event Inflow = 0.10 cfs @ 12.08 hrs, Volume= 338 cf Outflow = 0.07 cfs @ 12.19 hrs, Volume= 338 cf, Atten=23%, Lag=6.1 min Discarded = 0.00 cfs @ 9.03 hrs, Volume= 268 cf Primary = 0.07 cfs @ 12.19 hrs, Volume= 70 cf Routed to Reach 411 :WETLAND Routing by Stor-Ind method,Time Span=0.00-30.00 hrs,dt=0.03 hrs Peak Elev=155.96' @ 12.18 hrs Surf.Area=140 sf Storage=110 cf Plug-Flow detention time= 226.7 min calculated for 338 cf(100%of inflow) Center-of-Mass det.time= 226.7 min (975.4-748.7) Volume Invert Avail.Storage Storage Description #1 154.00' 112 cf Custom Stage Data(Prismatic) Listed below(Recalc) 280 cf Overall x 40.0%Voids Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 154.00 140 0 0 156.00 140 280 280 Device Routing Invert Outlet Devices #1 Discarded 154.00' 1.020 in/hr Exfiltration over Surface area #2 Primary 155.95' 20.0'long x 1.0'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 Coef. (English) 2.69 2.72 2.75 2.85 2.98 3.08 3.20 3.28 3.31 3.30 3.31 3.32 Discarded OutFlow Max=0.00 cfs @ 9.03 hrs HW=154.02' (Free Discharge) t1=Exfiltration (Exfiltration Controls 0.00 cfs) Primary OutFlow Max=0.06 cfs @ 12.19 hrs HW=155.96' (Free Discharge) t2=Broad-Crested Rectangular Weir (Weir Controls 0.06 cfs @ 0.28 fps) 243 GREAT POND ROAD Type///24-hr 10-Yr 24 Hr Rainfall=4.80" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD°10.20-5c s/n 11576 ©2023 HydroCAD Software Solutions LLC Page 17 Pond 1P: STONE TRENCH Hydrograph Inflow 0.10 cfs QQ ..III Outflow Inflow Area-8aJO Sf Discarded ® 0.105 Primary 0.1 0.095(1 Peak Elev=155.96' 0.07 cfs °o 08 Storage=110 cf 0.075 0.0 cfs 0.07 0.065 v 0.06 "0.055 0 0.05 a 0.045 0.04 0.035 0.03 > 0.025 - 0.02 zu ! 0.015 0.0c cfs 0.01 . OOE 0..: i; 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///24-hr 100-Yr 24 Hr Rainfall=8.80" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD°10.20-5c s/n 11576 ©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 1P: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 Hydrograph 0.19 0 Runoff 0.18 0.18 cfs 0.17 j Type III 24-hr 100-Yr 24 Hr Rainfall=8.80" 0.15 - - - 0.14 Runoff Area=890 sf 0.13 0.12 j Runoff Volume=635 cf 3 0.1 j/ Runoff Depth=88.56 LL Tc=6.0 min 0.08 0.07 % CN=98 0.06 ' 0.05 0.04 i - 0.03 - 0.02 0.01 �r�r r i r ° 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///24-hr 100-Yr 24 Hr Rainfall=8.80" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD°10.20-5c s/n 11576 ©2023 HydroCAD Software Solutions LLC Page 19 Summary for Subcatchment 5S: PROP Runoff = 1.55 cfs @ 12.10 hrs, Volume= 5,229 cf, Depth= 2.52" Routed to Reach 4R :WETLAND 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 3,691 98 Paved parking, HSG A 156 76 Gravel roads, HSG A 21,061 39 >75%Grass cover,Good, HSG A 24,908 48 Weighted Average 21,217 85.18%Pervious Area 3,691 14.82%Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 6.0 Direct Entry, Subcatchment 5S: PROP Hydrograph Runoff 1.55 cfs Type III 24-hr % 100-Yr 24 Hr Rainfall=8.80" Runoff Area=24 908 sf Runoff Volume=5,229 cf- Runoff Depth=2.52" 3 Tc=6.0 min CN=48 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 Type///24-hr 100-Yr 24 Hr Rainfall=8.80" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD®10.20-5c s/n 11576 @ 2023 HydroCAD Software Solutions LLC Page 20 Summary for Reach 4R: WETLAND Inflow Area = 25,798 sf, 17.76% Impervious, Inflow Depth= 2.57" for 100-Yr 24 Hr event Inflow = 1.72 cfs @ 12.10 hrs, Volume= 5,534 cf Outflow = 1.72 cfs @ 12.10 hrs, Volume= 5,534 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 4R:WETLAND Hydrograph Inflow 1.72 cfs p Outflow 1.72 cfs Inflow Area=25,.798 sf V W 1 3 0 LL i 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///24-hr 100-Yr 24 Hr Rainfall=8.80" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD°10.20-5c s/n 11576 ©2023 HydroCAD Software Solutions LLC Page 21 Summary for Pond 1P: STONE TRENCH Inflow Area = 890 sf,100.00% Impervious, Inflow Depth= 8.56" for 100-Yr 24 Hr event Inflow = 0.18 cfs @ 12.08 hrs, Volume= 635 cf Outflow = 0.18 cfs @ 12.09 hrs, Volume= 621 cf, Atten=0%, Lag=0.2 min Discarded = 0.00 cfs @ 6.84 hrs, Volume= 316 cf Primary = 0.18 cfs @ 12.09 hrs, Volume= 305 cf Routed to Reach 411 :WETLAND Routing by Stor-Ind method,Time Span=0.00-30.00 hrs,dt=0.03 hrs Peak Elev=155.97' @ 12.09 hrs Surf.Area=140 sf Storage=110 cf Plug-Flow detention time= 154.9 min calculated for 621 cf(98%of inflow) Center-of-Mass det.time= 140.5 min (880.6-740.1) Volume Invert Avail.Storage Storage Description #1 154.00' 112 cf Custom Stage Data(Prismatic) Listed below(Recalc) 280 cf Overall x 40.0%Voids Elevation Surf.Area Inc.Store Cum.Store (feet) (sq-ft) (cubic-feet) (cubic-feet) 154.00 140 0 0 156.00 140 280 280 Device Routing Invert Outlet Devices #1 Discarded 154.00' 1.020 in/hr Exfiltration over Surface area #2 Primary 155.95' 20.0'long x 1.0'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 Coef. (English) 2.69 2.72 2.75 2.85 2.98 3.08 3.20 3.28 3.31 3.30 3.31 3.32 Discarded OutFlow Max=0.00 cfs @ 6.84 hrs HW=154.02' (Free Discharge) t1=Exfiltration (Exfiltration Controls 0.00 cfs) Primary OutFlow Max=0.16 cfs @ 12.09 hrs HW=155.97' (Free Discharge) t2=Broad-Crested Rectangular Weir (Weir Controls 0.16 cfs @ 0.39 fps) 243 GREAT POND ROAD Type///24-hr 100-Yr 24 Hr Rainfall=8.80" Prepared by Patriot Engineering Printed 10/29/2025 HydroCAD°10.20-5c s/n 11576 ©2023 HydroCAD Software Solutions LLC Page 22 Pond 1P: STONE TRENCH Hydrograph Inflow 0,18 cfs ill Outflow 0.18 cfs -- Discarded El Primary 0.2 Inflow Area=890 sf 0.19 0.17 °.,8 Peak Elev=155.97' 0.16 0.15 Storage=1-10 cf 0.14 0.13 a 0.12 0.11 3 0.1 0.09 a 0.08 0.07 �i 0.06 i 0.05 0.04 i 0.03 0.02 � 0.00as 0.01 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 Control Measures during Construction 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 '/4 to '/2 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 g. 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 Lexington, all physical sediment and erosion controls shall be removed from the site. Long-Term Inspection and Maintenance Measures after Construction Erosion Control Eroded sediments can adversely affect the performance of the stormwater management system. Eroding or barren areas should be immediately re-vegetated. Debris and Litter Removal Trash may collect in the BMP's, potentially causing clogging of the facilities. All debris and litter shall be removed when necessary, and after each 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 1/2 inch of stone can be removed and replaced if the edge becomes clogged Debris and Litter Removal Trash may collect in the BMP's, potentially causing clogging of the facilities. All debris and litter shall be removed when necessary, and after each 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 CONSTRUCTION PHASE INSPECTION SCHEDULE AND EVALUATION CHECKLIST PROJECT LOCATION: 243 Great Pond Road WEATHER: Inspecti Required Follow-up Inspect Area Comments Recommendat Inspection on Inspection Required Date or Inspected Frequency if ion (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: STORMWATER MANAGEMENT AFTER CONSTRUCTION INSPECTION SCHEDULE AND EVALUATION CHECKLIST PROJECT LOCATION: 243 Great Pond Road WEATHER: Inspecti Required Follow-up Inspect Area Inspected Ins ection Comments Recommenda Inspection on or p ion Required Date Frequency if (yes/no) 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: