Loading...
HomeMy WebLinkAboutStormwater Report - 498 CHICKERING ROAD 5/23/2012 OSED BAND FACILITY NORTHANDOVER, MASSACHUSETTS PROJECT DRAINAGE REPORT DATE: APRIL 12 , 2012 SUPPLEMENTAL CALCULATIONS DATE: MAY 23, 2012 PREPARED FOR DEVELOPER: LOWELLFIVE, LLC �p.�-�N QFMgss One Merrimack Plaza Lowell, MA 01 852 ° VLADIAMIR L goyG NEMCHENOK fN„ v L y ss�ohAL Merrimack Engineering Services, Inc. Email: merreng @aol.com 66 Park Street Phone: (978)-475-3555 Andover,MA 01810 Fax: (978)-475-7448 p OSED BANK FACILITY NORTHANDOVER, MASSACHUSETTS < TABLE OF CONTENTS > SECTION 1.0 INTRODUCTION SECTION 2.0 LOCUS MAPS SECTION 3.0 SUMMARY 3.1 Pre vs. Post-Subcatchment Areas SECTION 4.0 STORM DRAINAGE CALCULATIONS Description of Drainage System &Design Calculations 4.1 Pre vs. Post-Development Analysis 4.2.1 Pre-Development —2, 10 & 100-Year Storm Event 4.2.2 Post-Development—2, 10 & 100-Year Storm Event SECTION 5.0 APPENDIX 5.1 Rainfall Data Maps 5.2 National Resources Conservation Service(MRCS)— Soil Description with Classification SECTION 6.0 DRAINAGE AREA MAPS Merrimack Engineering Services, Inc. 66 Park Street Phone: (978)475-3555 Andover,MA 0 1810_ Fax: (978)475-7448 PROPOSED BANK FACILITY NORTHANDOVER, MASSACHUSETTS < SECTION 1.0 > INTRODUCTION The project consists of a proposed bank facility(total foot print- 3,159 S.F.)with appurtenant parking lot and grading,on a 0.72 acre parcel located at 498 Chickering Road(Rte 125),North Andover,MA. The subject parcel is mostly paved with some grass and shrubs areas along the south(Park Street),west and north(Franklin Street)sides of the site.The site is a former gas station and contains a building and canopy to be removed.A new building(retail facility)will be built approximately at the center of the lot,to the east of the existing building.There are no wetlands on the site or within 100' of the site. Topographic elevations at the site range from a high of 138±at the southwest corner of the at Park Street to a low of 123±at northeast corner of the parcel toward Franklin Street,a difference of 15f feet. The parcel is above the 100-year flood elevation of 95.0 (Zone AE)as depicted on Flood Insurance Rate Map,Community Panel 250098 0003C,dated June 02, 1993. Soils within the vicinity of the project have been mapped by USDA-NRCS (formerly SCS) and consist of Udorthents smoothed soils(68.5%)and Woodbridge fine sandy loam,which is classified within the SCS Hydrological Soils Group C. For a more detailed description of the soils at this site see Section 5.2 of this report. These calculations will determine Pre-Development and Post-Development runoff rates using the SCS-TR20 Runoff Method,as implemented by the HydroCad computer model.The calculations will be performed for the 2, 10 and 100-year storm event. Merrimack Engineering Services, Inc. Section 1 -Page 1 Printed; April 12,2012 PROPOSED BANK FA CILI T Y NORTHANDOVER, MASSACHUSETTS < SECTION 2.0 > LOCUS MAPS Merrimack Engineering Services,Inc. Section 2—Page 1 Printed: April 12,2012 � 1 � r si r Mttltt Si£e�t '� t t s�r a���l = ,�Etnage Ms�st,I$ Commomv aifh of PAes,acbuset4e E ErA ✓ 20D7 Enra�a fieohnofagl�es R 01iit,42,i1`'39.48.N '7i D7 41:74 W ti eisq�127,ft Site m{e4 llll111111 104 OSED BANIC FACILITY NORTHANDOVER, MASSACHUSETTS < SECTION 2.0 > Site Soils Map esSr-x COUNTY, MASSACHUSETTS, N ,.._._... _1 i•loirta shrr f 33} S i t ftrrt 1 orr< � t>aH X44 u Pua PaD t Ur PaG 2 Us9ood 1 t�rtq W F3 W1E3 GrnF3 PJCi \\ F?tin SITE Cali ur.) shy �' �o NOR T W5B �. p� r�,�f Pao 4'� f1F3 .1 n 17 Witl Pa Zt Pact 0r idw ;t i li lt. s ' 'UIS. C �fBLC'Y£S U t�rrtrd ; q fi u 0 Mon i Pa[3 Stt3 tµuttr r IaC c O O .4Jtt ♦ cS�L� L; 13', t° Sa 46.: y < itdn �Wg:. Witt J f� YaCf MA .RdA �,,.J macs ors lci %'-. . <� srt c :>tFJ Wg tic) ti tin ! 1 F'}U � L 5 5p ~ Witt U S UD—Udorthents, smoothed. WrB—Woodbridge fine sandy loam, 0 to 8 percent slopes. Merrimack Engineering Services,Inc. Section 2—Page 4 Printed: April 12,2012 z P-4 0 N a _ t d a: 3 2. o i� I Ai 0 Y r �* _C � w TRI H y C N d li w i � a U cn V c 0. O C7 � F4 �g N r W 2 o Io o S rn w ru I°n o u 0 u g Z (Mf) w e o O N o0 G 7 ++ m o 0) U) v L a Y � 0 N � 0 V Z C 7 N L i Q y a 'O y C rn o i G M ,_, N �p c O 10 o a OI a+ m . o v E aI ......._ �.., J 7 Ill O y,r Op.N_ in u fu m a s y g T m in V V) W N w 0 D D OPOSED BANK FACILITY NORTHANDOVER, MASSACHUSETTS < SECTION 3.0 > Summary As indicated in the Introduction,the objective of the project design is to mitigate any increase in storm drainage flow rate as the result of the site modifications. The procedure utilized as follows: 1) The area to be modified is currently paved and was used for gas station in the past.It was determined 36,759 square feet and will be modified with the demolition of the old building,construction with the new bank facility,and re- paving of the site.The runoff rate was calculated during the 2, 10,and 100-year storm and the runoff hydrograph was developed. 2) There are catch basins that will collect the proposed site runoff and convey it the proposed grass swale and further to the system that currently receives the existing site runoff. The following chart is a summary of pre and post-development peak flow rates for 2, 10 and 100-year storm events of the accumulative design point(Catch Basin RI —Pre-development,End of 15'-12"RCP(Core to existing Catch Basin RI — Post-development),as shown on the accompanying drainage plans. Rainfall /Storm Event Structure/ Design Point 2—YR cfs 1 10—YR (cfs) 100—YR(c S) Pre Post Change Pre Post Change Pre Post Change R1 -Pre 2.02 1.80 T -0.22 3.09 2.95 -0.14 4.53 4.52 -0.01 PRP -Post Merrimack Engineering Services, Inc. Section 3 —Page 1 Printed: April 12,2012 PROPOSED BANK FACILITY NORTHANDOVER, MASSACHUSETTS < SECTION 4.0 > Storm drainage calculations The proposed drainage system is a combination of closed and open system. Catch basins will be constructed at low points of proposed parking area with discharge via flared end section to the proposed grass swale to transfer the runoff via rip-rap forebay to the existing stormwater drainage system. Decreases in peak flow will be obtained through the reduction of impervious area on site. Velocity Summary Soils on site consist of Woodbridge fine sandy loam,which is classified within the SCS Hydrological Soils Group C and have high erosion resistance(Erosion Factor K= 17). According to"Design Charts for Open Channel Flow",Kentucky Bluegrass,which is most common vegetation for grass swales,has permissible velocity 7.0 fps for soils with high erosion resistance. Because maximum 100-yr stormwater velocity at the swale entrance is 6.1 fps(<7.0 fps),the drainage system design is adequate. Pre and Post-Development Drainage Area Maps accompany these calculations. Merrimack Engineering Services, Inc. Section 4—Page 1 Printed: April 12,2012 PROPOSED AN FACILITY NORTHANDOVER, MASSACHUSETTS < SECTION 4.1 > Pre vs. Post Development Hydrologic Analysis & Design 2, 10 & 100—Year Storm Event Merrimack Engineering Services, Inc. Section 4—Page 2 Printed: April 12,2012 OPOSED BANK ACIY NORTHANDOVER, MASSACHUSETTS < SECTION 4.2.1 > PRE - DEVELOPMENT— 2, 10, & 100 — Year STORM EVENT Merrimack Engineering Services, Inc. Section 4—Page 3 Printed: April 12,2012 S1 = CB1 (Subcatchment 1 - (Catch asin #1 ) Existing Conditions) ca = S2, ....... CB2 ; (Subcatchment 2 - (Catch lka sin #2) Existing Conditions) cg , S3 = CB3 (Subcatchment 3 - (Catch Basin #3) Existing Conditions) SUbCa#' Reaeh .POnLjtl Drainage Diagram for 498 Chickering Road Pre-Dyn 2012 Prepared by Merrimack Engineering Services 5115/2012 HydroCAD®7.00 s/n 000899 0 1986-2003 Applied Microcomputer Systems 498 Chickering Road Pre-Dyn 2012 Type ///24-hr 2-yr Rainfall=3.10" Prepared by Merrimack Engineering Services Page 2 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/15/2012 Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Subcatchment SI: (Subcatchment 1 - Existing Conditions) Runoff Area=20,645 sf Runoff Depth=2.65" Flow Length=377' Tc=9.7 min CN=96 Runoff=1.20 cfs 0.105 of Subcatchment S2: (Subcatchment 2 - Existing Conditions) Runoff Area=2,920 sf Runoff Depth=2.76" Flow Length=212' Tc=5.0 min CN=97 Runoff=0.20 cfs 0.015 of Subcatchment S3: (Subcatchment 3 - Existing Conditions) Runoff Area=13,215 sf Runoff Depth=1.99" Flow Length=400' Tc=7.8 min CN=89 Runoff=0.65 cfs 0.050 of Pond CBI: (Catch Basin #1) Inflow=2.02 cfs 0.170 of Primary=2.02 cfs 0.170 of Pond CB2: (Catch Basin #2) Peak Elev=116.50' Inflow=0.84 cfs 0.066 of 12.0"x 20.0' Culvert Outflow=0.84 cfs 0.066 of Pond CB3: (Catch Basin #3) Peak Elev=117.39' Inflow=0.65 cfs 0.050 of 12.0"x 56.0' Culvert Outflow=0.65 cfs 0.050 of Total Runoff Area= 0.844 ac Runoff Volume= 0.170 of Average Runoff Depth = 2.42" 498 Chickering Road Pre-Dyn 2012 Type 111 24-hr 2-yr Rainfall=3.10" Prepared by Merrimack Engineering Services Page 3 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/15/2012 Subcatchment S1: (Subcatchment 1 - Existing Conditions) Runoff = 1.20 cfs @ 12.13 hrs, Volume= 0.105 af, Depth= 2.65" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2-yr Rainfall=3.10" Area (sf) CN Description 2,041 79 50-75% Grass cover, Fair, HSG C _ 18,604 98 Paved parking & roofs 20,645 96 Weighted Average Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 8.1 50 0.0600 0.1 Sheet Flow, Subcatchment- 1 Woods: Light underbrush n= 0.400 P2= 3.10" 0.2 50 0.0650 5.2 Shallow Concentrated Flow, Subcatchment- 1 Paved Kv= 20.3 fps 0.7 150 0.0337 3.7 Shallow Concentrated Flow, Subcatchment- 1 Paved Kv= 20.3 fps 0.5 57 0.0700 1.9 Shallow Concentrated Flow, Subcatchment- 1 Short Grass Pasture Kv= 7.0 fps 0.2 70 0.0681 5.3 Shallow Concentrated Flow, Subcatchment- 1 Paved Kv= 20.3 fps 9.7 377 Total Subcatchment S1: (Subcatchment 1 - Existing Conditions) Hydrograph 1 .20 cfs D Runoff Type 11124 he 2-yr. _Rainfall.=11.0'_ i. 1 Runoff Area--'20,645 sf. ^, Runoff Volume=0'.105 of Runoff Depth=2.65" 3 Flow Length, =377' min . Tc=9 u_ q- CN-96 0 , 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Pre-Dyn 2012 Type 111 24-hr 2-yr Rainfall=3.10" Prepared by Merrimack Engineering Services Page 4 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/15/2012 Subcatchment S2: (Subcatchment 2 - Existing Conditions) Runoff = 0.20 cfs @ 12.07 hrs, Volume= 0.015 af, Depth= 2.76" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2-yr Rainfall=3.10" Area (sf) CN Description 197 79 50-75% Grass cover, Fair, HSG C 2,723 98 Paved parking & roofs 2,920 97 Weighted Average Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.5 50 0.0420 1.6 Sheet Flow, Subcatchment- 2 Smooth surfaces n= 0.011 P2= 3.10" 0.1 34 0.0588 4.9 Shallow Concentrated Flow, Subcatchment-2 Paved Kv= 20.3 fps 0.5 60 0.0750 1.9 Shallow Concentrated Flow, Subcatchment-2 Short Grass Pasture Kv= 7.0 fps 0.2 68 0.0555 4.8 Shallow Concentrated Flow, Subcatchment-2 Paved Kv= 20.3 fps 3.7 Direct Entry, (Adjust for min. 5minute Tc) 5.0 212 Total Subcatchment S2: (Subcatchment 2 - Existing Conditions) Hydrograph 0.22_ 0 Runoff 0.20 Cfs 0.2 Type III 24-hr 2-yr 0.18--_ Rainfall.3.10" 0.16 Runoff Area= sf -- 0.14- Runoff Volume=0:01v of N -- 0.12- Runoff-Depth=2.76" 3 = Flow Length=212' - 0 0.1 - -Tc=5A min- - - 0.08_. =. C.N: .97 0.06 0.04 0.02-- , 0 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Pre-Dyn 2012 Type 111 24-hr 2-yr Rainfall=3.10" Prepared by Merrimack Engineering Services Page 5 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/15/2012 Subcatchment S3: (Subcatchment 3 - Existing Conditions) Runoff = 0.65 cfs @ 12.11 hrs, Volume= 0.050 af, Depth= 1.99" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 2-yr Rainfall=3.10" Area (sf) CN Description 6,086 79 50-75% Grass cover, Fair, HSG C 7,129 98 Paved parking & roofs 13,215 89 Weighted Average Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 4.3 50 0.0400 0.2 Sheet Flow, Subcatchment-3 Grass: Short n= 0.150 P2= 3.10" 0.9 72 0.0332 1.3 Shallow Concentrated Flow, Subcatchment-3 Short Grass Pasture Kv= 7.0 fps 0.8 59 0.0305 1.2 Shallow Concentrated Flow, Subcatchment- 3 Short Grass Pasture Kv= 7.0 fps 1.0 81 0.0386 1.4 Shallow Concentrated Flow, Subcatchment- 3 Short Grass Pasture Kv= 7.0 fps 0.4 42 0.0564 1.7 Shallow Concentrated Flow, Subcatchment- 3 Short Grass Pasture Kv= 7.0 fps 0.4 96 0.0428 4.2 Shallow Concentrated Flow, Subcatchment-3 Paved Kv= 20.3 fps 7.8 400 Total 498 Chickering Road Pre-Dyn 2012 Type 111 24-hr 2-yr Rainfall=3.10" Prepared by Merrimack Engineering Services Page 6 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/15/2012 Subcatchment S3: (Subcatchment 3 - Existing Conditions) Hyd rog raph 0.7 0.65 cfs Runoff Type III 24-hr 2-yr. 0.6- Rainfall=3.10" Runoff Arewl 3;245 sf 0.5 Runoff Volume=0.050'af N e 0.4 3 - Flow Length=400' —° 0.3-- Tc=7.8 min CN:=89 0.2 0.1 _ y 0 . , 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Pre-Dyn 2012 Type 111 24-hr 2-yr Rainfall=3.10" Prepared by Merrimack Engineering Services Page 7 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/15/2012 Pond CB1: (Catch Basin #1) Inflow Area = 0.844 ac, Inflow Depth = 2.42" for 2-yr event Inflow = 2.02 cfs @ 12.12 hrs, Volume= 0.170 of Primary = 2.02 cfs @ 12.12 hrs, Volume= 0.170 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Pond CB1: (Catch Basin #1) Hydrograph Inflow 2 Inflow'Area=j, 2.02 Cfs Primary 0 1 FZ ;u w 0 , 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Pre-Dyn 2012 Type ///24-hr 2-yr Rainfall=3.10" Prepared by Merrimack Engineering Services Page 8 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/15/2012 Pond C132: (Catch Basin #2) Inflow Area = 0.370 ac, Inflow Depth = 2.13" for 2-yr event Inflow = 0.84 cfs @ 12.10 hrs, Volume= 0.066 of Outflow = 0.84 cfs @ 12.10 hrs, Volume= 0.066 af, Atten= 0%, Lag= 0.0 min Primary = 0.84 cfs @ 12.10 hrs, Volume= 0.066 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 116.50' @ 12.10 hrs Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 115.97' 12.0" x 20.0' long Culvert CPP, projecting, no headwall, Ke= 0.900 Outlet Invert= 115.23' S= 0.0370 '/' n= 0.011 Cc= 0.900 Primary OutFlow Max=0.83 cfs @ 12.10 hrs HW=116.50' TW=0.00' (Dynamic Tailwater) L1=Culvert (Inlet Controls 0.83 cfs @ 2.0 fps) Pond CB2: (Catch Basin #2) Hydrograph Inflow 0.9 0.84 CfS _- -._ _ Primary -i nflow Area=Q. 0.8- -Peak Elev 1116 .50' 0.7 12:0"x 20 Culvert 0.6 ; V -- 0.5 C 0.4 v. 0.3= a 0.2 - 0.1 0- _ 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Pre-Dyn 2012 Type Ill 24-hr 2-yr Rainfall=3.10" Prepared by Merrimack Engineering Services Page 9 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/15/2012 Pond CB3: (Catch Basin #3) Inflow Area = 0.303 ac, Inflow Depth = 1.99" for 2-yr event Inflow = 0.65 cfs @ 12.11 hrs, Volume= 0.050 of Outflow = 0.65 cfs @ 12.11 hrs, Volume= 0.050 af, Atten= 0%, Lag= 0.0 min Primary = 0.65 cfs @ 12.11 hrs, Volume= 0.050 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 117.39' @ 12.12 hrs Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 116.89' 12.0" x 56.0' long Culvert CMP, projecting, no headwall, Ke= 0.900 Outlet Invert= 116.02' S= 0.01557' n= 0.024 Cc= 0.900 Primary OutFlow Max=0.63 cfs @ 12.11 hrs HW=117.38' TW=116.50' (Dynamic Tailwater) L1=Culvert (Barrel Controls 0.63 cfs @ 2.4 fps) Pond CB3: (Catch Basin #3) Hydrograph Inflow 0.7 0.65 cfs Primary Inflow Area=O. 0.6- Peak E1ev-117:39' 120" x 56.0' Culvert 0.5_ w 0.4 �° 0.3- 0.2 0.1 0 e , 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Pre-Dyn 2012 Type 111 24-hr 10-yr Rainfall=4.50" Prepared by Merrimack Engineering Services Page 10 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/15/2012 Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Subcatchment S1: (Subcatchment 1 -Existing Conditions) Runoff Area=20,645 sf Runoff Depth=4.03" Flow Length=377' Tc=9.7 min CN=96 Runoff=1.78 cfs 0.159 of Subcatchment S2: (Subcatchment 2 -Existing Conditions) Runoff Area=2,920 sf Runoff Depth=4.15" Flow Length=212' Tc=5.0 min CN=97 Runoff=0.29 cfs 0.023 of Subcatchment S3: (Subcatchment 3 -Existing Conditions) Runoff Area=13,215 sf Runoff Depth=3.29" Flow Length=400' Tc=7.8 min CN=89 Runoff=1.06 cfs 0.083 of Pond CB1: (Catch Basin #1) Inflow=3.09 cfs 0.266 of Primary=3.09 cfs 0.266 of Pond CB2: (Catch Basin #2) Peak Elev=116.68' Inflow=1.34 cfs 0.106 of 12.0"x 20.0' Culvert Outflow=1.34 cfs 0.106 of Pond CB3: (Catch Basin #3) Peak Elev=117.55' Inflow=1.06 cfs 0.083 of 12.0"x 56.0' Culvert Outflow=1.06 cfs 0.083 of Total Runoff Area = 0.844 ac Runoff Volume= 0.266 of Average Runoff Depth = 3.77" 498 Chickering Road Pre-Dyn 2012 Type ///24-hr 10-yr Rainfall=4.50" Prepared by Merrimack Engineering Services Page 11 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/15/2012 Subcatchment S1: (Subcatchment 1 - Existing Conditions) Runoff = 1.78 cfs @ 12.13 hrs, Volume= 0.159 af, Depth= 4.03" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10-yr Rainfall=4.50° Area (sf) CN Description 2,041 79 50-75% Grass cover, Fair, HSG C 18,604 98 Paved parking & roofs 20,645 96 Weighted Average Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 8.1 50 0.0600 0.1 Sheet Flow, Subcatchment- 1 Woods: Light underbrush n= 0.400 P2= 3.10° 0.2 50 0.0650 5.2 Shallow Concentrated Flow, Subcatchment- 1 Paved Kv= 20.3 fps 0.7 150 0.0337 3.7 Shallow Concentrated Flow, Subcatchment- 1 Paved Kv= 20.3 fps 0.5 57 0.0700 1.9 Shallow Concentrated Flow, Subcatchment- 1 Short Grass Pasture Kv= 7.0 fps 0.2 70 0.0681 5.3 Shallow Concentrated Flow, Subcatchment- 1 Paved Kv= 20.3 fps 9.7 377 Total Subcatchment S1: (Subcatchment 1 - Existing Conditions) Hydrograph 1 '78 cfs Runoff Type III 24-hr 10-yr Rainfall, 4.50" Runoff Area=20,645 sf Runoff Volume=0:159 of N y, ....Runoff.Depth=4.03" 3 1 Flow Length=377' —° - Tc=9.7 min v_ CN=96 0 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Pre-Dyn 2012 Type Ill 24-hr 10-yr Rainfall=4.50" Prepared by Merrimack Engineering Services Page 12 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/15/2012 Subcatchment S2: (Subcatchment 2 - Existing Conditions) Runoff = 0.29 cfs @ 12.07 hrs, Volume= 0.023 af, Depth= 4.15" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10-yr Rainfall=4.50" Area (sf) CN Description 197 79 50-75% Grass cover, Fair, HSG C 2,723 98 Paved parking & roofs 2,920 97 Weighted Average Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.5 50 0.0420 1.6 Sheet Flow, Subcatchment-2 Smooth surfaces n= 0.011 P2= 3.10" 0.1 34 0.0588 4.9 Shallow Concentrated Flow, Subcatchment-2 Paved Kv= 20.3 fps 0.5 60 0.0750 1.9 Shallow Concentrated Flow, Subcatchment-2 Short Grass Pasture Kv= 7.0 fps 0.2 68 0.0555 4.8 Shallow Concentrated Flow, Subcatchment- 2 Paved Kv= 20.3 fps 3.7 Direct Entry, (Adjust for min. 5minute Tc) 5.0 212 Total Subcatchment S2: (Subcatchment 2 - Existing Conditions) Hyd rog raph 0.29 cfs . Runo 0.3 Type III 24-hr 10-yr -Rainfa11=4:50" 0.25- Runoff Area 2,920 sf --Runoff-Volume=0:023 of. 0.2- Runoff Depth=4.15" Flow Length=212' c 0.15- Tc '5.0 min 0.1 CN-97 0.05 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Pre-Dyn 2012 Type 11124-hr 10-yr Rainfall=4.50" Prepared by Merrimack Engineering Services Page 13 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/15/2012 Subcatchment S3: (Subcatchment 3 - Existing Conditions) Runoff = 1.06 cfs @ 12.11 hrs, Volume= 0.083 af, Depth= 3.29" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 10-yr Rainfall=4.50° Area (sf) CN Description 6,086 79 50-75% Grass cover, Fair, HSG C 7,129 98 Paved parking & roofs 13,215 89 Weighted Average Tc Length Slope Velocity Capacity Description -- (min) (feet) (ft/ft) (ft/sec) (cfs) 4.3 50 0.0400 0.2 Sheet Flow, Subcatchment-3 Grass: Short n= 0.150 P2= 3.10" 0.9 72 0.0332 1.3 Shallow Concentrated Flow, Subcatchment-3 Short Grass Pasture Kv= 7.0 fps 0.8 59 0.0305 1.2 Shallow Concentrated Flow, Subcatchment-3 Short Grass Pasture Kv= 7.0 fps 1.0 81 0.0386 1.4 Shallow Concentrated Flow, Subcatchment-3 Short Grass Pasture Kv= 7.0 fps 0.4 42 0.0564 1.7 Shallow Concentrated Flow, Subcatchment-3 Short Grass Pasture Kv= 7.0 fps 0.4 96 0.0428 4.2 Shallow Concentrated Flow, Subcatchment-3 Paved Kv= 20.3 fps 7.8 400 Total 498 Chickering Road Pre-Dyn 2012 Type 11124-hr 10-yr Rainfall=4.50" Prepared by Merrimack Engineering Services Page 14 HydroCADO 7.00 s/n 000899 ©1986-2003 Applied Microcomputer Systems 5/15/2012 Subcatchment S3: (Subcatchment 3 - Existing Conditions) Hydrograph 1 .06 Cfs Runoff Type III 24 hr 10-yr 1 Rainfall=4.50" Runoff Area--1 3,215 sf ,^ Runoff Volutbte=0:083 of Runoff Depth=3.29" 3 - Flow Length-"400' -° Tc=7.8 min u_ CN=89 ?y 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Pre-Dyn 2012 Type 111 24-hr 10-yr Rainfall=4.50" Prepared by Merrimack Engineering Services Page 15 HydroCADO 7.00 s/n 000899 ©1986-2003 Applied Microcomputer Systems 5/15/2012 Pond CB1: (Catch Basin #1) Inflow Area = 0.844 ac, Inflow Depth = 3.77" for 10-yr event Inflow - 3.09 cfs @ 12.12 hrs, Volume= 0.266 of Primary = 3.09 cfs @ 12.12 hrs, Volume= 0.266 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Pond CB1: (Catch Basin #1) Hydrograph EM Inflow _ 3.09 cfs 0 Primary inflow Area= 3 : 2 0 1 0 O'"2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Pre-Dyn 2012 Type 111 24-hr 10-yr Rainfall=4.50" Prepared by Merrimack Engineering Services Page 16 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/15/2012 Pond CB2: (Catch Basin #2) Inflow Area = 0.370 ac, Inflow Depth = 3.45" for 10-yr event Inflow = 1.34 cfs @ 12.10 hrs, Volume= 0.106 of Outflow = 1.34 cfs @ 12.10 hrs, Volume= 0.106 af, Atten= 0%, Lag= 0.0 min Primary = 1.34 cfs @ 12.10 hrs, Volume= 0.106 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 116.68' @ 12.10 hrs Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 115.97' 12.0" x 20.0' long Culvert CPP, projecting, no headwall, Ke= 0.900 Outlet Invert= 115.23' S= 0.03707' n= 0.011 Cc= 0.900 Primary OutFlow Max=1.33 cfs @ 12.10 hrs HW=116.67' TW=0.00' (Dynamic Tailwater) L1=Culvert (Inlet Controls 1.33 cfs @ 2.3 fps) Pond CB2: (Catch Basin #2) Hydrograph Inflow Inflow Area= 1 .34 Cfs 01 Primary Peak Elev=116.68 _12:0" x 20:0' Culve 3 0 0 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Pre-Dyn 2012 Type /// 24-hr 10-yr Rainfall=4.50" Prepared by Merrimack Engineering Services Page 17 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/15/2012 Pond CB3: (Catch Basin #3) Inflow Area = 0.303 ac, Inflow Depth = 3.29" for 10-yr event Inflow = 1.06 cfs @ 12.11 hrs, Volume= 0.083 of Outflow = 1.06 cfs @ 12.11 hrs, Volume= 0.083 af, Atten= 0%, Lag= 0.0 min Primary = 1.06 cfs @ 12.11 hrs, Volume= 0.083 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 117.55' @ 12.12 hrs Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 116.89' 12.0" x 56.0' long Culvert CMP, projecting, no headwall, Ke= 0.900 Outlet Invert= 116.02' S= 0.0155 '/' n= 0.024 Cc= 0.900 Primary OutFlow Max=1.02 cfs @ 12.11 hrs HW=117.54' TW=116.67' (Dynamic Tailwater) L1=Culvert (Barrel Controls 1.02 cfs @ 2.7 fps) Pond CB3: (Catch Basin #3) Hydrograph A A^ Inflow Inflow Area= 1 .06 cfs Primary 1 Peak Elev=117.55` 12.0" x W10' Culve J02 3 0 u., 0 i 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Pre-Dyn 2012 Type Ill 24-hr 900-yr Rainfall=6.40" Prepared by Merrimack Engineering Services Page 18 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/15/2012 Time span=0.00-24.00 hrs, dt=0.05 hrs, 481 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Subcatchment SI: (Subcatchment 1 -Existing Conditions) Runoff Area=20,645 sf Runoff Depth=5.92" Flow Length=377' Tc=9.7 min CN=96 Runoff=2.57 cfs 0.234 of Subcatchment S2: (Subcatchment 2 -Existing Conditions) Runoff Area=2,920 sf Runoff Depth=6.04" Flow Length=212' Tc=5.0 min CN=97 Runoff=0.42 cfs 0.034 of Subcatchment S3: (Subcatchment 3 -Existing Conditions) Runoff Area=13,215 sf Runoff Depth=5.12" Flow Length=400' Tc=7.8 min CN=89 Runoff=1.62 cfs 0.129 of Pond CBI: (Catch Basin #1) Inflow=4.53 cfs 0.397 of Primary=4.53 cfs 0.397 of Pond CB2: (Catch Basin #2) Peak Elev=116.92' Inflow=2.01 cfs 0.163 of 12.0"x 20.0' Culvert Outflow=2.01 cfs 0.163 of Pond CB3: (Catch Basin #3) Peak Elev=117.77' Inflow=1.62 cfs 0.129 of 12.0"x 56.0' Culvert Outflow=1.62 cfs 0.129 of Total Runoff Area =0.844 ac Runoff Volume=0.397 of Average Runoff Depth =5.64" 498 Chickering Road Pre-Dyn 2012 Type Ill 24-hr 100-yr Rainfall=6.40" Prepared by Merrimack Engineering Services Page 19 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/15/2012 Subcatchment S1: (Subcatchment 1 - Existing Conditions) Runoff = 2.57 cfs @ 12.13 hrs, Volume= 0.234 af, Depth= 5.92" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100-yr Rainfall=6.40" Area (sf) CN Description 2,041 79 50-75% Grass cover, Fair, HSG C 18,604 98 Paved parking & roofs 20,645 96 Weighted Average Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 8.1 50 0.0600 0.1 Sheet Flow, Subcatchment- 1 Woods: Light underbrush n= 0.400 P2= 3.10" 0.2 50 0.0650 5.2 Shallow Concentrated Flow, Subcatchment- 1 Paved Kv= 20.3 fps 0.7 150 0.0337 3.7 Shallow Concentrated Flow, Subcatchment- 1 Paved Kv= 20.3 fps 0.5 57 0.0700 1.9 Shallow Concentrated Flow, Subcatchment- 1 Short Grass Pasture Kv= 7.0 fps 0.2 70 0.0681 5.3 Shallow Concentrated Flow, Subcatchment- 1 Paved Kv= 20.3 fps 9.7 377 Total Subcatchment S1: (Subcatchment 1 - Existing Conditions) Hydrograph 2.57 Cfs Runoff Type III 24-hr 100 1 r Rainfall=6.40" 2 -Runoff-Area=20;645 sf Runoff Volume=0:234 of N Runoff Depth=5.92" 3 Flow Length=377' ° _.Tc.=9 7-min_... 1 CN=96 x 0- Is ' 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Pre-Dyn 2012 Type 111 24-hr 100-yr Rainfall=6.40" Prepared by Merrimack Engineering Services Page 20 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/15/2012 Subcatchment S2: (Subcatchment 2 - Existing Conditions) Runoff = 0.42 cfs @ 12.07 hrs, Volume= 0.034 af, Depth= 6.04" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100-yr Rainfall=6.40" Area (sf) CN Description 197 79 50-75% Grass cover, Fair, HSG C 2,723 98 Paved parking & roofs 2,920 97 Weighted Average Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 0.5 50 0.0420 1.6 Sheet Flow, Subcatchment-2 Smooth surfaces n= 0.011 P2= 3.10" 0.1 34 0.0588 4.9 Shallow Concentrated Flow, Subcatchment-2 Paved Kv= 20.3 fps 0.5 60 0.0750 1.9 Shallow Concentrated Flow, Subcatchment-2 Short Grass Pasture Kv= 7.0 fps 0.2 68 0.0555 4.8 Shallow Concentrated Flow, Subcatchment-2 Paved Kv= 20.3 fps 3.7 Direct Entry, (Adjust for min. 5minute Tc) 5.0 212 Total Subcatchment S2: (Subcatchment 2 - Existing Conditions) Hydrograph Runoff 0.45 0.42 cfs - Type i 1 124--h r 100 y 0.4- , Rainfall=6.40". _:_ _ 0.35- Runoff Area 2,920 sf 0.3_ Runoff Volume=0.034 of -- 0.25 Runoff-Depth=6.04" 3 Flow Length-212' �° 0.2 Tc ':-5.0 min 0.15_ ' CN 97 .. - 0.1 _ .......... 0.05- 0- ; 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Pre-Dyn 2012 Type 111 24-hr 100-yr Rainfall=6.40" Prepared by Merrimack Engineering Services Page 21 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/15/2012 Subcatchment S3: (Subcatchment 3 - Existing Conditions) Runoff = 1.62 cfs @ 12.11 hrs, Volume= 0.129 af, Depth= 5.12" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Type III 24-hr 100-yr Rainfall=6.40° Area (sf) CN Description 6,086 79 50-75% Grass cover, Fair, HSG C 7,129 98 Paved parking & roofs 13,215 89 Weighted Average Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 4.3 50 0.0400 0.2 Sheet Flow, Subcatchment-3 Grass: Short n= 0.150 P2= 3.10" 0.9 72 0.0332 1.3 Shallow Concentrated Flow, Subcatchment-3 Short Grass Pasture Kv= 7.0 fps 0.8 59 0.0305 1.2 Shallow Concentrated Flow, Subcatchment-3 Short Grass Pasture Kv= 7.0 fps 1.0 81 0.0386 1.4 Shallow Concentrated Flow, Subcatchment-3 Short Grass Pasture Kv= 7.0 fps 0.4 42 0.0564 1.7 Shallow Concentrated Flow, Subcatchment-3 Short Grass Pasture Kv= 7.0 fps 0.4 96 0.0428 4.2 Shallow Concentrated Flow, Subcatchment-3 Paved Kv= 20.3 fps 7.8 400 Total 498 Chickering Road Pre-Dyn 2012 Type ///24-hr 100-yr Rainfall=6.40" Prepared by Merrimack Engineering Services Page 22 HydroCADO 7.00 s/n 000899 @ 1986-2003 Applied Microcomputer Systems 5/15/2012 Subcatchment S3: (Subcatchment 3 - Existing Conditions) Hydrograph J 1 .62 Cfs oRunol Type III 24-hr 100-qr Rainfall=6.40" Runoff Area 13,215 Sf. Runoff Volurne=0'.129 of RU n-dff Dept h-5*.12" Flow Len gth 400' 0 Tc min n CN 89 0� 0 2 4 6 8 10 12 14 1'6* '1' 2 8. . . . '0' 22 24 Time (hours) 498 Chickering Road Pre-Dyn 2012 Type 111 24-hr 100-yr Rainfall=6.40° Prepared by Merrimack Engineering Services Page 23 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/15/2012 Pond CB1: (Catch Basin #1) Inflow Area = 0.844 ac, Inflow Depth = 5.64" for 100-yr event Inflow = 4.53 cfs @ 12.12 hrs, Volume= 0.397 of Primary = 4.53 cfs @ 12.12 hrs, Volume= 0.397 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Pond CB1: (Catch Basin #1) Hydrograph 5 4.53 CfS Inflow Inflow Area= Primary 4 _-.. ...._.... 3 v 2 1- 0 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Pre-Dyn 2012 Type 11124-hr 100-yr Rainfall=6.40" Prepared by Merrimack Engineering Services Page 24 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/15/2012 Pond C132: (Catch Basin #2) Inflow Area = 0.370 ac, Inflow Depth = 5.29" for 100-yr event Inflow = 2.01 cfs @ 12.10 hrs, Volume= 0.163 of Outflow = 2.01 cfs @ 12.10 hrs, Volume= 0.163 af, Atten= 0%, Lag= 0.0 min Primary = 2.01 cfs @ 12.10 hrs, Volume= 0.163 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 116.92' @ 12.10 hrs Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 115.97' 12.0" x 20.0' long Culvert CPP, projecting, no headwall, Ke= 0.900 Outlet Invert= 115.23' S= 0.0370 '/' n= 0.011 Cc= 0.900 Primary OutFlow Max=2.01 cfs @ 12.10 hrs HW=116.91' TW=0.00' (Dynamic Tailwater) t1=Culvert (Inlet Controls 2.01 cfs @ 2.6 fps) Pond CB2: (Catch Basin #2) Hydrograph Inflow 2 Inflow.Area= . 2.01 Cfs M Primary Peak Elev=116.92E 12.0" x 20;0' Culve f 0 1 LL 0 . , 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Pre-Dyn 2012 Type Ill 24-hr 100-yr Rainfall=6.40" Prepared by Merrimack Engineering Services Page 25 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/15/2012 Pond CB3: (Catch Basin #3) Inflow Area = 0.303 ac, Inflow Depth = 5.12" for 100-yr event Inflow = 1.62 cfs @ 12.11 hrs, Volume= 0.129 of Outflow = 1.62 cfs @ 12.11 hrs, Volume= 0.129 af, Atten= 0%, Lag= 0.0 min Primary = 1.62 cfs @ 12.11 hrs, Volume= 0.129 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.05 hrs Peak Elev= 117.77' @ 12.12 hrs Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 116.89' 12.0" x 56.0' long Culvert CMP, projecting, no headwall, Ke= 0.900 Outlet Invert= 116.02' S= 0.01557' n= 0.024 Cc= 0.900 Primary OutFlow Max=1.53 cfs @ 12.11 hrs HW=117.76' TW=116.90' (Dynamic Tailwater) t-1=Culvert (Barrel Controls 1.53 cfs @ 2.8 fps) Pond CB3: (Catch Basin #3) Hydrograph EM Inflow Inflow Area= . 1 .62 Cf.S Primary Peak Elev=117.77' "* 12.0" x 5&0' CUIV6 � 1 o u. 0 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) AI FACILITY NORTHANDOVER, MASSACHUSETTS < SECTION 4.2.2 > POST - DEVELOPMENT—2, 10, & 100 — Year STORM EVENT Merrimack Engineering Services, Inc. Section 4--Page 4 Printed: April 12,2012 (Subcatchment 3- (Catch Basin#3) Proposed Conditions) ca (Drain ME nhole#2) (Subcatchment 4- (Catch Basin#4) Proposed Conditions) ca X51-: -cs oMri1; (Subcatchment 1- (Catch Basin#1) Proposed Conditions) (Drain Manhole#1) (Design int-Flared Grass Swale (Catch Basin#5) (15'-12"RCP Core to End Iection) Exist CB) SP2 _G82 SP1-G` (Subcatchment 2- (Catch Basin#2) Proposed Conditions) (Subcatchment 1- Proposed Conditions-Grass& Shrubs) SubCat' Reach �POIl` : l.li Ike Drainage Diagram for 498 Chickering Road Post-Dyn Prepared by Merrimack Engineering Services 5/23/2012 HydroCAD®7.00 s/n 000899 ©1986-2003 Applied Microcomputer Systems 498 Chickering Road Post-Dyn Type 111 24-hr 2-yr Rainfall=3.10" Prepared by Merrimack Engineering Services Page 27 H droCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Time span=0.00-24.00 hrs, dt=0.02 hrs, 1201 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Subcatchment SP1: (Subcatchment 1 - Proposed Conditions) Runoff Area=9,481 sf Runoff Depth=2.35" Flow Length=144' Tc=6.4 min CN=93 Runoff=0.57 cfs 0.043 of Subcatchment SP1-G: (Subcatchment 1 -Proposed Conditions Runoff Area=4,305 sf Runoff Depth=0.87" Flow Length=86' Tc=8.2 min CN=72 Runoff=0.08 cfs 0.007 of Subcatchment SP2: (Subcatchment 2- Proposed Conditions) Runoff Area=1,134 sf Runoff Depth=2.87" Tc=5.0 min CN=98 Runoff=0.08 cfs 0.006 of Subcatchment SP3: (Subcatchment 3 - Proposed Conditions) Runoff Area=8,552 sf Runoff Depth=2.16" Flow Length=102' Tc=5.0 min CN=91 Runoff=0.51 cfs 0.035 of Subcatchment SP4: (Subcatchment 4- Proposed Conditions) Runoff Area=13.287 sf Runoff Depth=1.75" Flow Length=76' Tc=7.4 min CN=86 Runoff=0.59 cfs 0.044 of Reach FES: (Design Point-Flared End Section) Inflow=1.81 cfs 0.136 of Outflow=1.81 cfs 0.136 of Reach GS: Grass Swale Peak Depth=0.34' Max Vet=1.8 fps Inflow=1.81 cfs 0.136 of n=0.030 L=58.0' S=0.0100 '/' Capacity=5.90 cfs Outflow=1.80 cfs 0.136 of Reach PRP: (15'-12" RCP Core to Exist CB) Peak Depth=0.31' Max Vet=8.7 fps Inflow=1.80 cfs 0.136 of D=12.0" n=0.011 L=15.0' S=0.0427 '/' Capacity=8.70 cfs Outflow=1.80 cfs 0.136 of Pond CB1: (Catch Basin #1) Peak Elev=124.62' Inflow=0.57 cfs 0.043 of 12.0" x 10.0' Culvert Outflow=0.57 cfs 0.043 of Pond CB2: (Catch Basin #2) Peak Elev=124.57' Inflow=0.08 cfs 0.006 of 12.0"x 34.0' Culvert Outflow=0.08 cfs 0.006 of Pond CB3: (Catch Basin #3) Peak EIev=125.80' Inflow=0.51 cfs 0.035 of 12.0"x 125.0' Culvert Outflow=0.51 cfs 0.035 of Pond CB4: (Catch Basin#4) Peak Elev=125.92' Inflow=0.59 cfs 0.044 of 12.0"x 133.0' Culvert Outflow=0.59 cfs 0.044 of Pond CB5: (Catch Basin #5) Peak EIev=122.70' Inflow=1.80 cfs 0.136 of Outflow=1.80 cfs 0.136 of Pond DMH1: (Drain Manhole#1) Peak Elev=124.57' Inflow=1.73 cfs 0.129 of 12.0"x 12.0' Culvert Outflow=1.73 cfs 0.129 of Pond DMH2: (Drain Manhole#2) Peak Elev=124.78' Inflow=1.08 cfs 0.080 of 12.0" x 25.0' Culvert Outflow=1.08 cfs 0.080 of 498 Chickering Road Post-Dyn Type 11124-hr 2-yr Rainfall=3.10" Prepared by Merrimack Engineering Services Page 28 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Total Runoff Area = 0.844 ac Runoff Volume= 0.136 of Average Runoff Depth = 1.93" 498 Chickering Road Post-Dyn Type 11124-hr 2-yr Rainfall=3.10" Prepared by Merrimack Engineering Services Page 29 HydroCAD®7 00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Subcatchment SP1: (Subcatchment 1 - Proposed Conditions) Runoff = 0.57 cfs @ 12.09 hrs, Volume= 0.043 af, Depth= 2.35" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Type III 24-hr 2-yr Rainfall=3.10" Area (sf) CN Description 1,967 72 Woods/grass comb., Good, HSG C 7,514 98 Paved parking & roofs 9,481 93 Weighted Average Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.7 50 0.0200 0.1 Sheet Flow, Subcatchment- 1 Grass: Short n= 0.150 P2= 3.10" 0.4 35 0.0340 1.4 Sheet Flow, Subcatchment- 1 Smooth surfaces n= 0.011 P2= 3.10" 0.3 59 0.0340 3.7 Shallow Concentrated Flow, Subcatchment- 1 Paved Kv= 20.3 fps 6.4 144 Total Subcatchment SP1: (Subcatchment 1 - Proposed Conditions) Hydrograph 0.57 cfs IE] Runoff' 0.6 0.55_ TYpe I1f 24-hr 2-)(t Rainfall.=3.10" 0.5- _ 0.45 Runoff Area=9;481-sf 0.4- Runoff Volume=0:043 of , v 0.35- Runoff Depth-2.35" Flow Length-144' 3 0.3 M 0.25 Tc-6�4 min CN=93 0.2= 0.15" 0.1= 0.05- 4 0= 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type /// 24-hr 2-yr Rainfall=3.10" Prepared by Merrimack Engineering Services Page 30 HydroCAD®7 00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Subcatchment SP1-G: (Subcatchment 1 - Proposed Conditions-Grass & Shrubs) Runoff = 0.08 cfs @ 12.13 hrs, Volume= 0.007 af, Depth= 0.87" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Type III 24-hr 2-yr Rainfall=3.10" Area (sf) CN Description 4,305 72 Woods/grass comb., Good, HSG C Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.9 50 0.0640 0.1 Sheet Flow, Subcatchment- 2 -Landscaping Woods: Light underbrush n= 0.400 P2= 3.10" 0.3 36 0.0630 1.8 Shallow Concentrated Flow, Subcatchment- 2- Landscaping Short Grass Pasture Kv= 7.0 fps 8.2 86 Total Subcatchment SP1-G: (Subcatchment 1 - Proposed Conditions-Grass & Shrubs) Hydrog raph 0.08 El Runoff 0.09 0.08_ Type HI,24-hr 2-yr.- - RaWall.3.10" ; 0.07 _ Runoff Area=4,305 sf -- 0.06 Runoff Volume-0.00 of --Runoff-Depth=0.87" Yr -- 0.05 3 Flow_Len_gt-=06' _° 0.04= Tc=8.2 min 0.03_ CN'=72. 0.02 0.01 0- 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type /// 24-hr 2-yr Rainfall=3.10" Prepared by Merrimack Engineering Services Page 31 HvdroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Subcatchment SP2: (Subcatchment 2 - Proposed Conditions) Runoff = 0.08 cfs @ 12.07 hrs, Volume= 0.006 af, Depth= 2.87" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Type III 24-hr 2-yr Rainfall=3.10" Area (sf) CN Description 1,134 98 Paved parking & roofs Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, (5.0 minutes - Minimum Tc) Subcatchment SP2: (Subcatchment 2 - Proposed Conditions) Hydrograph 0.09- 0.08 CfS Runoff 0.08 Type III 24-h'r 2-yr 0.07 --Rainfall'=110 -Runoff Area=1,134.sf - - - -- 0.06 Runoff Voluhie=0.006 a 0.05 Runoff Depth=2.87" Tc=5-O min 0 0.04 CN=98 . 0.03- 0.02= , 0.01 0 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type ///24-hr 2-yr Rainfall=3.10" Prepared by Merrimack Engineering Services Page 32 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Subcatchment SP3: (Subcatchment 3 - Proposed Conditions) Runoff = 0.51 cfs @ 12.07 hrs, Volume= 0.035 af, Depth= 2.16" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Type III 24-hr 2-yr Rainfall=3.10" Area (sf) CN Description 2,525 74 >75% Grass cover, Good, HSG C 6,027 98 Paved parking & roofs 8,552 91 Weighted Average Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 4.2 25 0.0765 0.1 Sheet Flow, Subcatchment 3 Woods: Light underbrush n= 0.400 P2= 3.10" 0.2 25 0.0765 1.8 Sheet Flow, Subcatchment 3 Smooth surfaces n= 0.011 P2= 3.10" 0.2 52 0.0765 5.6 Shallow Concentrated Flow, Subcatchment 3 Paved Kv= 20.3 fps 0.4 Direct Entry, Adjust for min. 5 minute Tc 5.0 102 Total Subcatchment SP3: (Subcatchment 3 - Proposed Conditions) Hydrograph 0.55- 0.51 CfS Runoff _ - .. _ _. . 0.5_ Type III 24-hr 2-yr:: 0.45 Rainfall=3.10" 0.4 Runoff Area-8,552 sf N 0.35 _Runoff Volume=0.03-5 of 0.3 Runoff-Depth=2.16" 3 - -Flow-Length-102' _. 0 0.25- Tc=5.0 min 0.2 CN`91 0.15 0.1 0.05- ke ,r , ia 0 2 4 6 8 10 12 14 ­ 116 ' 1'8 ­ 2'0 22 24 Time (hours) 498 Chickering Road Post-Dyn Type /// 24-hr 2-yr Rainfall=3.10" Prepared by Merrimack Engineering Services Page 33 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Subcatchment SP4: (Subcatchment 4 - Proposed Conditions) Runoff = 0.59 cfs @ 12.11 hrs, Volume= 0.044 af, Depth= 1.75" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Type III 24-hr 2-yr Rainfall=3.10" Area (sf) CN Description 6,107 72 Woods/grass comb., Good, HSG C 7,180 98 Paved parking & roofs 13,287 86 Weighted Average Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.2 50 0.0800 0.1 Sheet Flow, Subcatchment-4 Woods: Light underbrush n= 0.400 P2= 3.10" 0.2 26 0.1150 2.4 Shallow Concentrated Flow, Subcatchment- 1 Short Grass Pasture Kv= 7.0 fps 7.4 76 Total Subcatchment SP4: (Subcatchment 4 - Proposed Conditions) Hydrograph 0.65- 0.59 CfS D Runoff _..._ 0.6 —Type Ill.-24-hr 2.yr 0.55- - _Rainfal1=11.0"... 0.5 Runoff-Area=13,287 sf 0.45- Runoff Volume=0.044 of OA: -Runoff Depth=11-511 0.35- 3 Flow Length=7-W- 0 0.3 FL 0.25 Tc=7.4 min _ 0.2- CW86 . 0.15 0.1 _ 0.05 0- 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type ///24-hr 2-yr Rainfall=3.10" Prepared by Merrimack Engineering Services Page 34 HydroCAD®7.00 s/n 000899 ©1986-2003 Applied Microcomputer Systems 5/23/2012 Reach FES: (Design Point - Flared End Section) Inflow Area = 0.844 ac, Inflow Depth = 1.93" for 2-yr event Inflow = 1.81 cfs @ 12.09 hrs, Volume= 0.136 of Outflow = 1.81 cfs @ 12.09 hrs, Volume= 0.136 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Reach FES: (Design Point - Flared End Section) Hydrograph ® Inflow 2 1 .8'I cfs E3 outflow Inflow Area=O. e 1 >, 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 111 24-hr 2-yr Rainfall=3.10" Prepared by Merrimack Engineering Services Page 35 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Reach GS: Grass Swale Inflow Area = 0.844 ac, Inflow Depth = 1.93" for 2-yr event Inflow = 1.81 cfs @ 12.09 hrs, Volume= 0.136 of Outflow = 1.80 cfs @ 12.10 hrs, Volume= 0.136 af, Atten= 0%, Lag= 0.4 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Max. Velocity= 1.8 fps, Min. Travel Time= 0.5 min Avg. Velocity = 0.5 fps, Avg. Travel Time= 1.8 min Peak Depth= 0.34' @ 12.10 hrs Capacity at bank full= 5.90 cfs Inlet Invert= 123.58', Outlet Invert= 123.00' 1.50' x 0.60' deep channel, n= 0.030 Length= 58.0' Slope= 0.01007' Side Slope Z-value= 4.0'/' Reach GS: Grass Swale Hydrograph cfs El 2 1 .80 Inflow Area=O. Outflow Peak Depth=0.34' t Max Vel=1.8 fps h n=0.030 ~ r L=58.0' 0 1 S-0.0100 '/' Capacity=5.90° cfs f, 0 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type /// 24-hr 2-yr Rainfall=3.10" Prepared by Merrimack Engineering Services Page 36 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Reach PRP: (15'-12" RCP Core to Exist CB) Inflow Area = 0.844 ac, Inflow Depth = 1.93" for 2-yr event Inflow = 1.80 cfs @ 12.10 hrs, Volume= 0.136 of Outflow = 1.80 cfs @ 12.10 hrs, Volume= 0.136 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Max. Velocity= 8.7 fps, Min. Travel Time= 0.0 min Avg. Velocity= 2.7 fps, Avg. Travel Time= 0.1 min Peak Depth= 0.31' @ 12.10 hrs Capacity at bank full= 8.70 cfs Inlet Invert= 119.50', Outlet Invert= 118.86' 12.0" Diameter Pipe n= 0.011 Length= 15.0' Slope= 0.0427 '/' Reach PRP: (15'-12" RCP Core to Exist CB) Hydrograph Inflow 2 1 .80 Cfs p Outflow Inflow Area=O. . Peak Depth=0.31' Max Vet=8.7 fps D=12.0" n=0.011 c 1 L=1 5.0' LL S=0.0427 T: Capacity=8.70 cfs 0 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 111 24-hr 2-yr Rainfall=3.10" Prepared by Merrimack Engineering Services Page 37 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Pond CB1: (Catch Basin #1) Inflow Area = 0.218 ac, Inflow Depth = 2.35" for 2-yr event Inflow = 0.57 cfs @ 12.09 hrs, Volume= 0.043 of Outflow = 0.57 cfs @ 12.09 hrs, Volume= 0.043 af, Atten= 0%, Lag= 0.0 min Primary = 0.57 cfs @ 12.09 hrs, Volume= 0.043 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Peak Elev= 124.62' @ 12.11 hrs Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 123.85' 12.0" x 10.0' long Culvert CPP, projecting, no headwall, Ke= 0.900 Outlet Invert= 123.80' S= 0.0050 '/' n= 0.011 Cc= 0.900 Primary OutFlow Max=0.49 cfs @ 12.09 hrs HW=124.61' TW=124.56' (Dynamic Tailwater) L1=Culvert (Inlet Controls 0.49 cfs @ 0.8 fps) Pond CB1: (Catch Basin #1) Hydrograph � Inflow _ 0.57 cfs _ Primary 0.6= Inflow Area=O. 0.55 Peak Elev 124.62' 0.5 1ZO x_10.0' Culvert 0.45 0.4-_ N _ 0.35- c 0.3- u. 0.25 0.2 - 0.15 _ .... - r 0.05 0 , 1 14 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 111 24-hr 2-yr Rainfall=3.10" Prepared by Merrimack Engineering Services Page 38 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Pond CB2: (Catch Basin #2) Inflow Area = 0.026 ac, Inflow Depth = 2.87" for 2-yr event Inflow = 0.08 cfs @ 12.07 hrs, Volume= 0.006 of Outflow = 0.08 cfs @ 12.07 hrs, Volume= 0.006 af, Atten= 0%, Lag= 0.0 min Primary = 0.08 cfs @ 12.07 hrs, Volume= 0.006 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Peak Elev= 124.57' @ 12.11 hrs Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 123.97' 12.0" x 34.0' long Culvert CPP, projecting, no headwall, Ke= 0.900 Outlet Invert= 123.80' S= 0.0050 '/' n= 0.011 Cc= 0.900 Primary OutFlow Max=0.00 cfs @ 12.07 hrs HW=124.51' TW=124.55' (Dynamic Tailwater) L1=Culvert ( Controls 0.00 cfs) Pond CB2: (Catch Basin #2) Hydrograph Inflow 0.09 _ 0.08 cfs 0.08 Inflow:Area= _� Primary Peak Elev=124.57' 0.07= 12.0" x340` C; W 0.06- 0.05 - _6 0.04 y. 0.03 0.02 0.01 Q � , < l; i 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type ///24-hr 2-yr Rainfall=3.10" Prepared by Merrimack Engineering Services Page 39 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Pond CB3: (Catch Basin #3) Inflow Area = 0.196 ac, Inflow Depth = 2.16" for 2-yr event Inflow = 0.51 cfs @ 12.07 hrs, Volume= 0.035 of Outflow = 0.51 cfs @ 12.07 hrs, Volume= 0.035 af, Atten= 0%, Lag= 0.0 min Primary = 0.51 cfs @ 12.07 hrs, Volume= 0.035 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Peak Elev= 125.80' @ 12.07 hrs Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 125.40' 12.0" x 125.0' long Culvert CPP, projecting, no headwall, Ke= 0.900 Outlet Invert= 124.15' S= 0.0100 '/' n= 0.011 Cc= 0.900 Primary OutFlow Max=0.50 cfs @ 12.07 hrs HW=125.80' TW=124.75' (Dynamic Tailwater) L-1=Culvert (Inlet Controls 0.50 cfs @ 1.7 fps) Pond CB3: (Catch Basin #3) Hydrograph Inflow 0.55 -- _ 0.51 CfS D Primary Inflow Area=O. 0.5 _. . . _.. . . 0.45 Peak Elev-125:80' 12:0" x 125.0' Culve_ 0.35= - 0.3- o 0.25 u. - 0.2 ;f 0.15 0.1 0.05 0 . 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 111 24-hr 2-yr Rainfall=3.10" Prepared by Merrimack Engineering Services Page 40 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Pond CB4: (Catch Basin #4) Inflow Area = 0.305 ac, Inflow Depth = 1.75" for 2-yr event Inflow = 0.59 cfs @ 12.11 hrs, Volume= 0.044 of Outflow = 0.59 cfs @ 12.11 hrs, Volume= 0.044 af, Atten= 0%, Lag= 0.0 min Primary = 0.59 cfs @ 12.11 hrs, Volume= 0.044 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Peak Elev= 125.92' @ 12.11 hrs Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 125.48' 12.0" x 133.0' long Culvert CPP, projecting, no headwall, Ke= 0.900 Outlet Invert= 124.15' S= 0.0100 '/' n= 0.011 Cc= 0.900 Primary OutFlow Max=0.59 cfs @ 12.11 hrs HW=125.92' TW=124.78' (Dynamic Tailwater) L1=Culvert (Inlet Controls 0.59 cfs @ 1.8 fps) Pond CB4: (Catch Basin #4) Hydrograph rffl Inflow 0.65 Area=O, 0.59 cfs Primary 0.6 0.55 --P-eak- E1ev=1-25:92' 11 0.5 _12.+0" x 1.33.0' CuIV 0.45 0.4- .. 0.35_ c 0.3 �- 0.25- 0.2 0.15 0.05 a. Q 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type /// 24-hr 2-yr Rainfall=3.10" Prepared by Merrimack Engineering Services Page 41 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Pond CBS: (Catch Basin #5) Inflow Area = 0.844 ac, Inflow Depth = 1.93" for 2-yr event Inflow = 1.80 cfs @ 12.10 hrs, Volume= 0.136 of Outflow = 1.80 cfs @ 12.10 hrs, Volume= 0.136 af, Atten= 0%, Lag= 0.0 min Primary = 1.80 cfs @ 12.10 hrs, Volume= 0.136 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Peak Elev= 122.70' @ 12.10 hrs Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 122.23' 2.0' long x 0.9' 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) 2.71 2.75 2.81 2.93 3.04 3.13 3.22 3.28 3.31 3.30 3.31 3.32 Primary OutFlow Max=1.80 cfs @ 12.10 hrs HW=122.70' TW=119.81' (Dynamic Tailwater) t-1=Broad-Crested Rectangular Weir (Weir Controls 1.80 cfs @ 1.9 fps) Pond CBS: (Catch Basin #5) Hydrograph ® Inflow 2 1 .80 Cfs El Primary Inflow Area= Peak Bev' u. y% 0 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 111 24-hr 2-yr Rainfall=3.10" Prepared by Merrimack Engineering Services Page 42 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Pond DMH1: (Drain Manhole #1) Inflow Area = 0.745 ac, Inflow Depth = 2.07" for 2-yr event Inflow = 1.73 cfs @ 12.09 hrs, Volume= 0.129 of Outflow = 1.73 cfs @ 12.09 hrs, Volume= 0.129 af, Atten= 0%, Lag= 0.0 min Primary = 1.73 cfs @ 12.09 hrs, Volume= 0.129 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Peak Elev= 124.57' @ 12.09 hrs Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 123.70' 12.0" x 12.0' long Culvert CPP, projecting, no headwall, Ke= 0.900 Outlet Invert= 123.58' S= 0.0100 '/' n= 0.011 Cc= 0.900 Primary OutFlow Max=1.72 cfs @ 12.09 hrs HW=124.56' TW=0.00' (Dynamic Tailwater) L1=Culvert (Barrel Controls 1.72 cfs @ 3.2 fps) Pond DMH1: (Drain Manhole #1) Hydrograph EM Inflow Inflow Area= 1 .73 Gfs El Primary Peak Elev=124.57` 12:.0" X.1110, Ulm lve 40 - v o Y, . y 0 e i . 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 111 24-hr 2-yr Rainfall=3.10" Prepared by Merrimack Engineering Services Page 43 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Pond DMH2: (Drain Manhole #2) Inflow Area = 0.501 ac, Inflow Depth = 1.91" for 2-yr event Inflow = 1.08 cfs @ 12.09 hrs, Volume= 0.080 of Outflow = 1.08 cfs @ 12.09 hrs, Volume= 0.080 af, Atten= 0%, Lag= 0.0 min Primary = 1.08 cfs @ 12.09 hrs, Volume= 0.080 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Peak Elev= 124.78' @ 12.10 hrs Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 124.05' 12.0" x 25.0' long Culvert CPP, projecting, no headwall, Ke= 0.900 Outlet Invert= 123.80' S= 0.0100 '/' n= 0.011 Cc= 0.900 Primary OutFlow Max=1.04 cfs @ 12.09 hrs HW=124.78' TW=124.56' (Dynamic Tailwater) t1=Culvert (Barrel Controls 1.04 cfs @ 2.4 fps) Pond DMH2: (Drain Manhole #2) Hydrograph Am 1 .08 cfs M Inflow Inflow Aa= Primary if Peak Elev=124.78` 12.0" x 25:0' Culve k 3 o rt PER 11 0 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type ///24-hr 10-yr Rainfall=4.50" Prepared by Merrimack Engineering Services Page 44 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Time span=0.00-24.00 hrs, dt=0.02 hrs, 1201 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Subcatchment SP1: (Subcatchment 1 - Proposed Conditions) Runoff Area=9,481 sf Runoff Depth=3.70" Flow Length=144' Tc=6.4 min CN=93 Runoff=0.88 cfs 0.067 of Subcatchment SP1-G: (Subcatchment 1 - Proposed Conditions Runoff Area=4,305 sf Runoff Depth=1.82" Flow Length=86' Tc=8.2 min CN=72 Runoff=0.19 cfs 0.015 of Subcatchment SP2: (Subcatchment 2- Proposed Conditions) Runoff Area=1,134 sf Runoff Depth=4.26" Tc=5.0 min CN=98 Runoff=0.12 cfs 0.009 of Subcatchment SP3: (Subcatchment 3 - Proposed Conditions) Runoff Area=8,552 sf Runoff Depth=3.50" Flow Length=102' Tc=5.0 min CN=91 Runoff=0.80 cfs 0.057 of Subcatchment SP4: (Subcatchment 4- Proposed Conditions) Runoff Area=13.287 sf Runoff Depth=3.00" Flow Length=76' Tc=7.4 min CN=86 Runoff=1.01 cfs 0.076 of Reach FES: (Design Point-Flared End Section) Inflow=2.95 cfs 0.225 of Outflow=2.95 cfs 0.225 of Reach GS: Grass Swale Peak Depth=0.43' Max Vet=2.1 fps Inflow=2.95 cfs 0.225 of n=0.030 L=58.0' S=0.0100 T Capacity=5.90 cfs Outflow=2.95 cfs 0.225 of Reach PRP: (15'-12" RCP Core to Exist CB) Peak Depth=0.40' Max Vet=10.0 fps Inflow=2.95 cfs 0.225 of D=12.0" n=0.011 L=15.0' S=0.0427 '/' Capacity=8.70 cfs Outflow=2.95 cfs 0.225 of Pond CB1: (Catch Basin#1) Peak Elev=125.15' Inflow=0.88 cfs 0.067 of 12.0" x 10.0' Culvert Outflow=0.88 cfs 0.067 of Pond CB2: (Catch Basin #2) Peak EIev=125.07' Inflow=0.12 cfs 0.009 of 12.0"x 34.0' Culvert Outflow=0.12 cfs 0.009 of Pond CB3: (Catch Basin#3) Peak Elev=125.92' Inflow=0.80 cfs 0.057 of 12.0"x 125.0' Culvert Outflow=0.80 cfs 0.057 of Pond CB4: (Catch Basin#4) Peak EIev=126.08' Inflow=1.01 cfs 0.076 of 12.0"x 133.0' Culvert Outflow=1.01 cfs 0.076 of Pond CB5: (Catch Basin#5) Peak Elev=122.88' Inflow=2.95 cfs 0.225 of Outflow=2.95 cfs 0.225 of Pond DMH1: (Drain Manhole#1) Peak EIev=125.06' Inflow=2.78 cfs 0.210 of 12.0"x 12.0' Culvert Outflow=2.78 cfs 0.210 of Pond DMH2: (Drain Manhole#2) Peak Elev=125.41' Inflow=1.78 cfs 0.133 of 12.0"x 25.0' Culvert Outflow=1.78 cfs 0.133 of 498 Chickering Road Post-Dyn Type ///24-hr 90-yr Rainfall=4.50" Prepared by Merrimack Engineering Services Page 45 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Total Runoff Area = 0.844 ac Runoff Volume = 0.225 of Average Runoff Depth = 3.20" 498 Chickering Road Post-Dyn Type 111 24-hr 10-yr Rainfall=4.50" Prepared by Merrimack Engineering Services Page 46 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Subcatchment SP1: (Subcatchment 1 - Proposed Conditions) Runoff = 0.88 cfs @ 12.09 hrs, Volume= 0.067 af, Depth= 3.70" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Type III 24-hr 10-yr Rainfall=4.50" Area (sf) CN Description 1,967 72 Woods/grass comb., Good, HSG C 7,514 98 Paved parking & roofs 9,481 93 Weighted Average Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.7 50 0.0200 0.1 Sheet Flow, Subcatchment- 1 Grass: Short n= 0.150 P2= 3.10" 0.4 35 0.0340 1.4 Sheet Flow, Subcatchment- 1 Smooth surfaces n= 0.011 P2= 3.10" 0.3 59 0.0340 3.7 Shallow Concentrated Flow, Subcatchment- 1 Paved Kv= 20.3 fps 6.4 144 Total Subcatchment SP1: (Subcatchment 1 - Proposed Conditions) Hydrograph 0.88 Cfs D Runoff 0.9 Type III 24-hr 10-yr x 0.8- Rainfall=4.50" 0 7_ Runoff Area=9,481 s- - n 0.6 Runoff-Volume=0.067 of 0 .._Run_o_ff._D.epth 3 70" 0.5 -- 3 Flow Length 144' ,° 0.4- Tc 6.4 min 0.3= -CN 793 0.1 0 MW 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 111 24-hr 10-yr Rainfall=4.50" Prepared by Merrimack Engineering Services Page 47 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Subcatchment SP1-G: (Subcatchment 1 - Proposed Conditions-Grass & Shrubs) Runoff = 0.19 cfs @ 12.12 hrs, Volume= 0.015 af, Depth= 1.82" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Type III 24-hr 10-yr Rainfall=4.50" Area (sf) CN Description 4,305 72 Woods/grass comb., Good, HSG C Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.9 50 0.0640 0.1 Sheet Flow, Subcatchment-2 -Landscaping Woods: Light underbrush n= 0.400 P2= 3.10" 0.3 36 0.0630 1.8 Shallow Concentrated Flow, Subcatchment-2 - Landscaping Short Grass Pasture Kv= 7.0 fps 8.2 86 Total Subcatchment SP1-G: (Subcatchment 1 - Proposed Conditions-Grass & Shrubs) Hydrograph 0.2- 0.19 Cfs D Runoff -Type-III 2- 4-hr 1-0 yr - 0.18 ...Rainfall=4.5.0" 0.16 Runoff Area=4,305 sf 0.14 Runoff Volume=0.015 of 0.12 Runoff Depth=1.82" - oLeigth 8Flw 60.1c �- 0.08 Tc 82 min _ CN=72 ,. 0.06- T. , 0.04 0.02 0 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 111 24-hr 10-yr Rainfall=4.50" Prepared by Merrimack Engineering Services Page 48 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Subcatchment SP2: (Subcatchment 2 - Proposed Conditions) Runoff = 0.12 cfs @ 12.07 hrs, Volume= 0.009 af, Depth= 4.26" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Type III 24-hr 10-yr Rainfall=4.50" Area (sf) CN Description 1,134 98 Paved parking & roofs Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, (5.0 minutes -Minimum Tc) Subcatchment SP2: (Subcatchment 2 - Proposed Conditions) Hydrograph 0.13 0.12 Cf5 Runoff 0.12- Type-III.24-hr 10_Yr_ ._ 0.11 -Ra(nfal1=4.50" 0.1 -Runoff-Area=1,134 sf 0.09- -Runoff Volume=0 009 of _ n 0.08_ 0.07 Runoff-Depth-4.26" - - c 0.06 -Tc=5.0 min _ iL 0.05 CN=98 0.04 0.03 _ .... _ - 0.02 0.01 0 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 11124-hr 10-yr Rainfall=4.50" Prepared by Merrimack Engineering Services Page 49 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Subcatchment SP3: (Subcatchment 3 - Proposed Conditions) Runoff = 0.80 cfs @ 12.07 hrs, Volume= 0.057 af, Depth= 3.50" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Type III 24-hr 10-yr Rainfall=4.50" Area (sf CN Description 2,525 74 >75% Grass cover, Good, HSG C 6,027 98 Paved parking & roofs 8,552 91 Weighted Average Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 4.2 25 0.0765 0.1 Sheet Flow, Subcatchment 3 Woods: Light underbrush n= 0.400 P2= 3.10" 0.2 25 0.0765 1.8 Sheet Flow, Subcatchment 3 Smooth surfaces n= 0.011 P2= 3.10" 0.2 52 0.0765 5.6 Shallow Concentrated Flow, Subcatchment 3 Paved Kv= 20.3 fps 0.4 Direct Entry,Adjust for min. 5 minute Tc 5.0 102 Total Subcatchment SP3: (Subcatchment 3 - Proposed Conditions) Hydrograph 0.80 cfs El Runoff 0.8- Type III 24-hr 10-yr ; 0.7- Rainfall 4.50 .-Rugoff Area=8,552 sf _ 0.6 Runoff Volume 0 057 of 0.5 Runoff Depth=3.50" 3 - Flow-Length;=102' . .. -- 0 0.4_ Tc=5.0 min u. 0.3_ CN=91 0.1- Q s 10 12� , 0 2 4 6 8 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 111 24-hr 10-yr Rainfall=4.50" Prepared by Merrimack Engineering Services Page 50 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Subcatchment SP4: (Subcatchment 4 - Proposed Conditions) Runoff = 1.01 cfs @ 12.10 hrs, Volume= 0.076 af, Depth= 3.00" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Type III 24-hr 10-yr Rainfall=4.50" Area (sD CN Description 6,107 72 Woods/grass comb., Good, HSG C 7,180 98 Paved parking & roofs 13,287 86 Weighted Average Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.2 50 0.0800 0.1 Sheet Flow, Subcatchment-4 Woods: Light underbrush n= 0.400 P2= 3.10" 0.2 26 0.1150 2.4 Shallow Concentrated Flow, Subcatchment- 1 Short Grass Pasture Kv= 7.0 fps 7.4 76 Total Subcatchment SP4: (Subcatchment 4 - Proposed Conditions) Hydrograph 1 .01 cfs Runoff 1 Type III 24-hr 10-yr Rainfall=4.50" Runoff Area'13,287 sf Runoff Volume=0.076 of N Runoff Depth=3.00" 3 Flow Length=76' o Tc=7.4 min CN=86 f- 0 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 11124-hr 10-yr Rainfall=4.50" Prepared by Merrimack Engineering Services Page 51 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Reach FES: (Design Point - Flared End Section) Inflow Area = 0.844 ac, Inflow Depth = 3.20" for 10-yr event Inflow = 2.95 cfs @ 12.09 hrs, Volume= 0.225 of Outflow = 2.95 cfs @ 12.09 hrs, Volume= 0.225 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs . Reach FES: (Design Point - Flared End Section) Hydrograph Inflow 2.95 Cfs _ _ _ El Outflow 3 Inflow Area=O. 2 3 0 F 1 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 11124-hr 10-yr Rainfall=4.50" Prepared by Merrimack Engineering Services Page 52 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Reach GS: Grass Swale Inflow Area = 0.844 ac, Inflow Depth = 3.20" for 10-yr event Inflow = 2.95 cfs @ 12.09 hrs, Volume= 0.225 of Outflow = 2.95 cfs @ 12.10 hrs, Volume= 0.225 af, Atten= 0%, Lag= 0.4 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Max. Velocity= 2.1 fps, Min. Travel Time= 0.5 min Avg. Velocity = 0.6 fps, Avg. Travel Time= 1.6 min Peak Depth= 0.43' @ 12.10 hrs Capacity at bank full= 5.90 cfs Inlet Invert= 123.58', Outlet Invert= 123.00' 1.50' x 0.60' deep channel, n= 0.030 Length= 58.0' Slope= 0.0100 ? Side Slope Z-value=4.07' Reach GS: Grass Swale Hydrograph M Inflow 2.95 cfs outflow 3 Inflow..Area=O: Peak Depth=0:43' ry .._Max Vet=2.1 _fps 2_ n=0.030 L o S=0.0100 1 Capacity=5.90 cfs 0 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 111 24-hr 10-yr Rainfall=4.50" Prepared by Merrimack Engineering Services Page 53 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Reach PRP: (15'-12" RCP Core to Exist CB) Inflow Area = 0.844 ac, Inflow Depth = 3.20" for 10-yr event Inflow = 2.95 cfs @ 12.10 hrs, Volume= 0.225 of Outflow = 2.95 cfs @ 12.10 hrs, Volume= 0.225 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Max. Velocity= 10.0 fps, Min. Travel Time= 0.0 min Avg. Velocity= 3.1 fps, Avg. Travel Time= 0.1 min Peak Depth= 0.40' @ 12.10 hrs Capacity at bank full= 8.70 cfs Inlet Invert= 119.50', Outlet Invert= 118.86' 12.0" Diameter Pipe n= 0.011 Length= 15.0' Slope= 0.0427 '/' Reach PRP: (15'-12" RCP Core to Exist CB) Hydrograph Inflow _ cfs 2.95 Outflow 3 Inflow Area=O. Peak Depth=0.40' Max Ve1=10.0 fps D=12.0 2 n=0.011 c L=15.0 v_ S=00427 1 Capacity=8.70 cfs J 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type ///24-hr 10-yr Rainfall=4.50" Prepared by Merrimack Engineering Services Page 54 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Pond CB1: (Catch Basin #1) Inflow Area = 0.218 ac, Inflow Depth = 3.70" for 10-yr event Inflow = 0.88 cfs @ 12.09 hrs, Volume= 0.067 of Outflow = 0.88 cfs @ 12.09 hrs, Volume= 0.067 af, Atten= 0%, Lag= 0.0 min Primary = 0.88 cfs @ 12.09 hrs, Volume= 0.067 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Peak Elev= 125.15' @ 12.11 hrs Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 123.85' 12.0" x 10.0' long Culvert CPP, projecting, no headwall, Ke= 0.900 Outlet Invert= 123.80' S= 0.0050 ? n= 0.011 Cc= 0.900 Primary OutFlow Max=0.64 cfs @ 12.09 hrs HW=125.10' TW=125.05' (Dynamic Tailwater) t-1=Culvert (Inlet Controls 0.64 cfs @ 0.8 fps) Pond CB1: (Catch Basin #1) Hydrograph Inflow 0.9- Anf(_ow Area=O. 0.88 Cfs Primary _ 4r 0.8 Peak Elev-125'15' 11011 x100' Culvert 0.7 =- -v 0.5- - ,° 0.4 0.3= 0.2- 0.1 f Q � � 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 111 24-hr 10-yr Rainfall=4.50" Prepared by Merrimack Engineering Services Page 55 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Pond CB2: (Catch Basin #2) Inflow Area = 0.026 ac, Inflow Depth = 4.26" for 10-yr event Inflow = 0.12 cfs @ 12.07 hrs, Volume= 0.009 of Outflow = 0.12 cfs @ 12.07 hrs, Volume= 0.009 af, Atten= 0%, Lag= 0.0 min Primary = 0.12 cfs @ 12.07 hrs, Volume= 0.009 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Peak Elev= 125.07' @ 12.11 hrs Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 123.97' 12.0" x 34.0' long Culvert CPP, projecting, no headwall, Ke= 0.900 Outlet Invert= 123.80' S= 0.00507' n= 0.011 Cc= 0.900 Primary OutFlow Max=0.00 cfs @ 12.07 hrs HW=124.90' TW=125.01' (Dynamic Tailwater) L1=Culvert ( Controls 0.00 cfs) Pond CB2: (Catch Basin #2) Hydrograph Inflow 0.13 0.12 d8 _ 0 Primary 0.12 - Inflow Area=O. 0.11 Peak Elev=125 07' 0.1 - A-120" x 34.0' Culvert 0.09 _ { 0.08; 0.07- c 0.06 -. 0.05 0.04 0.03_ 0.02_.,', ig 0.013 r; 1 14 0 o r 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 1//24-hr 10-yr Rainfall=4.50" Prepared by Merrimack Engineering Services Page 56 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Pond CB3: (Catch Basin #3) Inflow Area = 0.196 ac, Inflow Depth = 3.50" for 10-yr event Inflow = 0.80 cfs @ 12.07 hrs, Volume= 0.057 of Outflow = 0.80 cfs @ 12.07 hrs, Volume= 0.057 af, Atten= 0%, Lag= 0.0 min Primary = 0.80 cfs @ 12.07 hrs, Volume= 0.057 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Peak Elev= 125.92' @ 12.10 hrs Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 125.40' 12.0" x 125.0' long Culvert CPP, projecting, no headwall, Ke= 0.900 Outlet Invert= 124.15' S= 0.0100 '/' n= 0.011 Cc= 0.900 Primary OutFlow Max=0.80 cfs @ 12.07 hrs HW=125.92' TW=125.25' (Dynamic Tailwater) t1=Culvert (Inlet Controls 0.80 cfs @ 1.9 fps) Pond CB3: (Catch Basin #3) Hydrograph Inflow . 080 Cfs _ Primary Inflow Area=O. 0.8 _ . = Peak Elev=125:92' 0.7 -1 Z0" x�1-25:0' Culve 0.6- "" 0.5 3 0.4- 0.3' -0.2- 0.1. 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type ///24-hr 10-yr Rainfall=4.50" Prepared by Merrimack Engineering Services Page 57 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Pond CB4: (Catch Basin #4) Inflow Area = 0.305 ac, Inflow Depth = 3.00" for 10-yr event Inflow = 1.01 cfs @ 12.10 hrs, Volume= 0.076 of Outflow = 1.01 cfs @ 12.10 hrs, Volume= 0.076 af, Atten= 0%, Lag= 0.0 min Primary = 1.01 cfs @ 12.10 hrs, Volume= 0.076 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Peak Elev= 126.08' @ 12.11 hrs Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 125.48' 12.0" x 133.0' long Culvert CPP, projecting, no headwall, Ke= 0.900 Outlet Invert= 124.15' S= 0.0100 '/' n= 0.011 Cc= 0.900 Primary OutFlow Max=0.99 cfs @ 12.10 hrs HW=126.08' TW=125.39' (Dynamic Tailwater) t--1=Culvert (Barrel Controls 0.99 cfs @ 2.9 fps) Pond C134: (Catch Basin #4) Hydrograph Inflow --.. _.. . 1 .01 Cfs - __ _ _ __ __ _ _ _ Primary 1- Inflow.Area= . Peak Bev'126.08` 12.0" x133.0' Culy f : 0 0 t" 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 111 24-hr 10-yr Rainfall=4.50" Prepared by Merrimack Engineering Services Page 58 HydroCAD®7 00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Pond CBS: (Catch Basin #5) Inflow Area = 0.844 ac, Inflow Depth = 3.20" for 10-yr event Inflow = 2.95 cfs @ 12.10 hrs, Volume= 0.225 of Outflow = 2.95 cfs @ 12.10 hrs, Volume= 0.225 af, Atten= 0%, Lag= 0.0 min Primary = 2.95 cfs @ 12.10 hrs, Volume= 0.225 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Peak Elev= 122.88' @ 12.10 hrs Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 122.23' 2.0' long x 0.9' 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) 2.71 2.75 2.81 2.93 3.04 3.13 3.22 3.28 3.31 3.30 3.31 3.32 Primary OutFlow Max=2.94 cfs @ 12.10 hrs HW=122.87' TW=119.90' (Dynamic Tai[water) t--1=Broad-Crested Rectangular Weir (Weir Controls 2.94 cfs @ 2.3 fps) Pond C135: (Catch Basin #5) Hydrograph ----- Inflow 2.95 Cfs __ [3 Primary 3_ Inflow Area= Peak Elev=122.88' 4 2 v 3 0 1- 0 2 4 6 8 1'0­ 12 14 1'6 ' 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 11124-hr 10-yr Rainfall=4.50" Prepared by Merrimack Engineering Services Page 59 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Pond DMH1: (Drain Manhole #1) Inflow Area = 0.745 ac, Inflow Depth = 3.38" for 10-yr event Inflow = 2.78 cfs @ 12.09 hrs, Volume= 0.210 of Outflow = 2.78 cfs @ 12.09 hrs, Volume= 0.210 af, Atten= 0%, Lag= 0.0 min Primary = 2.78 cfs @ 12.09 hrs, Volume= 0.210 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Peak Elev= 125.06' @ 12.09 hrs Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 123.70' 12.0" x 12.0' long Culvert CPP, projecting, no headwall, Ke= 0.900 Outlet Invert= 123.58' S= 0.0100 '/' n= 0.011 Cc= 0.900 Primary OutFlow Max=2.76 cfs @ 12.09 hrs HW=125.05' TW=0.00' (Dynamic Tailwater) t-1=Culvert (Inlet Controls 2.76 cfs @ 3.5 fps) Pond DMH1: (Drain Manhole #1) Hydrograph Inflow 3 2.78 cfs El Primary Inflow Area= Peak Elev=125.06` 12.0''-x 12:0' Culve _ 2 3 o 1 , i � ._ r 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type ///24-hr 10-yr Rainfall=4.50" Prepared by Merrimack Engineering Services Page 60 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Pond DMH2: (Drain Manhole #2) Inflow Area = 0.501 ac, Inflow Depth = 3.19" for 10-yr event Inflow = 1.78 cfs @ 12.09 hrs, Volume= 0.133 of Outflow = 1.78 cfs @ 12.09 hrs, Volume= 0.133 af, Atten= 0%, Lag= 0.0 min Primary = 1.78 cfs @ 12.09 hrs, Volume= 0.133 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Peak Elev= 125.41' @ 12.10 hrs Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 124.05' 12.0" x 25.0' long Culvert CPP, projecting, no headwall, Ke= 0.900 Outlet Invert= 123.80' S= 0.0100 '/' n= 0.011 Cc= 0.900 Primary OutFlow Max=1.65 cfs @ 12.09 hrs HW=125.36' TW=125.05' (Dynamic Tailwater) L1=Culvert (Inlet Controls 1.65 cfs @ 2.1 fps) Pond DMH2: (Drain Manhole #2) Hydrograph 01 Inflow Inflow`Area= 1 .78 cfs 0 Primary Peak Bev'125.41 12.0" x2510 Culve 0 0-AMR 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 111 24-hr 100-yr Rainfall=6.40" Prepared by Merrimack Engineering Services Page 61 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Time span=0.00-24.00 hrs, dt=0.02 hrs, 1201 points Runoff by SCS TR-20 method, UH=SCS Reach routing by Dyn-Stor-Ind method - Pond routing by Dyn-Stor-Ind method Subcatchment SP1: (Subcatchment 1 - Proposed Conditions) Runoff Area=9,481 sf Runoff Depth=5.57" Flow Length=144' Tc=6.4 min CN=93 Runoff=1.30 cfs 0.101 of Subcatchment SP1-G: (Subcatchment 1 - Proposed Conditions Runoff Area=4,305 sf Runoff Depth=3.32" Flow Length=86' Tc=8.2 min CN=72 Runoff=0.36 cfs 0.027 of Subcatchment SP2: (Subcatchment 2 - Proposed Conditions) Runoff Area=1,134 sf Runoff Depth=6.16" Tc=5.0 min CN=98 Runoff=0.17 cfs 0.013 of Subcatchment SP3: (Subcatchment 3 - Proposed Conditions) Runoff Area=8,552 sf Runoff Depth=5.35" Flow Length=102' Tc=5.0 min CN=91 Runoff=1.20 cfs 0.087 of Subcatchment SP4: (Subcatchment 4- Proposed Conditions) Runoff Area=13.287 sf Runoff Depth=4.79" Flow Length=76' Tc=7.4 min CN=86 Runoff=1.59 cfs 0.122 of Reach FES: (Design Point-Flared End Section) Inflow=4.53 cfs 0.351 of Outflow=4.53 cfs 0.351 of Reach GS: Grass Swale Peak Depth=0.53' Max Vet=2.4 fps Inflow=4.53 cfs 0.351 of n=0.030 L=58.0' S=0.0100 '/' Capacity=5.90 cfs Outflow=4.52 cfs 0.351 of Reach PRP: (15'-12" RCP Core to Exist CB) Peak Depth=0.51' Max Vet=11.2 fps Inflow=4.52 cfs 0.351 of D=12.0" n=0.011 L=15.0' S=0.0427 '/' Capacity=8.70 cfs Outflow=4.52 cfs 0.351 of Pond CB1: (Catch Basin#1) Peak Elev=126.35' Inflow=1.30 cfs 0.101 of 12.0"x 10.0' Culvert Outflow=1.30 cfs 0.101 of Pond CB2: (Catch Basin #2) Peak Elev=126.17' Inflow=0.17 cfs 0.013 of 12.0"x 34.0' Culvert Outflow=0.17 cfs 0.013 of Pond CB3: (Catch Basin #3) Peak EIev=127.10' Inflow=1.20 cfs 0.087 of 12.0"x 125.0' Culvert Outflow=1.20 cfs 0.087 of Pond CB4: (Catch Basin #4) Peak EIev=127.28' Inflow=1.59 cfs 0.122 of 12.0"x 133.0' Culvert Outflow=1.59 cfs 0.122 of Pond CB5: (Catch Basin #5) Peak EIev=123.07' Inflow=4.52 cfs 0.351 of Outflow=4.52 cfs 0.351 of Pond DMH1: (Drain Manhole#1) Peak Elev=126.17' Inflow=4.19 cfs 0.324 of 12.0"x 12.0' Culvert Outflow=4.19 cfs 0.324 of Pond DMH2: (Drain Manhole#2) Peak Elev=126.98' Inflow=2.73 cfs 0.209 of 12.0"x 25.0' Culvert Outflow=2.73 cfs 0.209 of 498 Chickering Road Post-Dyn Type 11124-hr 100-yr Rainfall=6.40" Prepared by Merrimack Engineering Services Page 62 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/2312012 Total Runoff Area = 0.844 ac Runoff Volume = 0.351 of Average Runoff Depth = 4.99" 498 Chickering Road Post-Dyn Type 111 24-hr 100-yr Rainfall=6.40" Prepared by Merrimack Engineering Services Page 63 HydroCADO 7.00 s/n 000899 ©1986-2003 Applied Microcomputer Systems 5/23/2012 Subcatchment SP1: (Subcatchment 1 - Proposed Conditions) Runoff = 1.30 cfs @ 12.09 hrs, Volume= 0.101 af, Depth= 5.57" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Type III 24-hr 100-yr Rainfall=6.40" Area (sf) CN Description 1,967 72 Woods/grass comb., Good, HSG C 7,514 98 Paved parking & roofs 9,481 93 Weighted Average Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.7 50 0.0200 0.1 Sheet Flow, Subcatchment- 1 Grass: Short n= 0.150 P2= 3.10" 0.4 35 0.0340 1.4 Sheet Flow, Subcatchment- 1 Smooth surfaces n= 0.011 P2= 3.10" 0.3 59 0.0340 3.7 Shallow Concentrated Flow, Subcatchment- 1 Paved Kv= 20.3 fps 6.4 144 Total Subcatchment SP1: (Subcatchment 1 - Proposed Conditions) Hydrograph 1 .30 cfs D Runoff Type III 24-hr 100=yr5. Rainfall=6.40" 1 Runoff_Area=9;481 sf _ Runoff Volume=0101 of v Runoff Depth=5.57" 3 Flow Length=144' ° Tc=6.4 min ° CN=93 r 0 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 111 24-hr 100-yr Rainfall=6.40" Prepared by Merrimack Engineering Services Page 64 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Subcatchment SP1-G: (Subcatchment 1 - Proposed Conditions-Grass & Shrubs) Runoff = 0.36 cfs @ 12.12 hrs, Volume= 0.027 af, Depth= 3.32" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Type III 24-hr 100-yr Rainfall=6.40" Area (sf) CN Description 4,305 72 Woods/grass comb., Good, HSG C Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.9 50 0.0640 0.1 Sheet Flow, Subcatchment-2 - Landscaping Woods: Light underbrush n= 0.400 P2= 3.10" 0.3 36 0.0630 1.8 Shallow Concentrated Flow, Subcatchment- 2- Landscaping Short Grass Pasture Kv= 7.0 fps 8.2 86 Total Subcatchment SP1-G: (Subcatchment 1 - Proposed Conditions-Grass & Shrubs) Hydrograph 0.36 cfs El Runoff 0.35 Type III 24-hr 1002 r _Rainfall;=6,40"- _ 0.3 Runoff Area 4,305 sf N 0.25 Runoff Volume=0.027 of 0 - _Runoff_Depth=3.32" 3 0.2--- Flo:.w Length=86' o �- 0.15- -Tc=8.2 min , CU 72 0.05 0 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type /// 24-hr 100-yr Rainfall=6.40" Prepared by Merrimack Engineering Services Page 65 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Subcatchment SP2: (Subcatchment 2 - Proposed Conditions) Runoff = 0.17 cfs @ 12.07 hrs, Volume= 0.013 af, Depth= 6.16" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Type III 24-hr 100-yr Rainfall=6.40" Area (so CN Description 1,134 98 Paved parking & roofs Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 5.0 Direct Entry, (5.0 minutes - Minimum Tc) Subcatchment SP2: (Subcatchment 2 - Proposed Conditions) Hydrograph 0.18 0.17 cfs Runoff 0.16_ —Type-111-24-hr 100;�r _ Rainfall=6.40" 0.14_ Runoff Area=1,134 sf N 0.12 Runoff Volume=0.013 of 0.1 Runoff-Depth=6:1-6"__ 3 Tc=5.0 min_ _ �° 0.08- CN=98 0.06 0.04- , 0.02- 0_ r, 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 11124-hr 100-yr Rainfall=6.40" Prepared by Merrimack Engineering Services Page 66 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Subcatchment SP3: (Subcatchment 3 - Proposed Conditions) Runoff = 1.20 cfs @ 12.07 hrs, Volume= 0.087 af, Depth= 5.35" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Type III 24-hr 100-yr Rainfall=6.40" Area (sf) CN Description 2,525 74 >75% Grass cover, Good, HSG C 6,027 98 Paved parking & roofs 8,552 91 Weighted Average Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 4.2 25 0.0765 0.1 Sheet Flow, Subcatchment 3 Woods: Light underbrush n= 0.400 P2= 3.10" 0.2 25 0.0765 1.8 Sheet Flow, Subcatchment 3 Smooth surfaces n= 0.011 P2= 3.10" 0.2 52 0.0765 5.6 Shallow Concentrated Flow, Subcatchment 3 Paved Kv= 20.3 fps 0.4 Direct Entry,Adjust for min. 5 minute Tc 5.0 102 Total Subcatchment SP3: (Subcatchment 3 - Proposed Conditions) Hydrograph 1 .20 cfs Runoff Type III 24-hr 100=yr Rainfall=6.40:" -- 1 Runoff Area=* 8,552 sf Runoff Volume=0:087 of 0 Runoff Depth=5.3:5" 3 Flow Length=102' -° Tc-5.0 min LL CN=91 jili 0 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type ///24-hr 100-yr Rainfall=6.40" Prepared by Merrimack Engineering Services Page 67 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Subcatchment SP4: (Subcatchment 4 - Proposed Conditions) Runoff = 1.59 cfs @ 12.10 hrs, Volume= 0.122 af, Depth= 4.79" Runoff by SCS TR-20 method, UH=SCS, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Type III 24-hr 100-yr Rainfall=6.40" Area (sf) CN Description 6,107 72 Woods/grass comb., Good, HSG C 7,180 98 Paved parking & roofs 13,287 86 Weighted Average Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 7.2 50 0.0800 0.1 Sheet Flow, Subcatchment-4 Woods: Light underbrush n= 0.400 P2= 3.10" 0.2 26 0.1150 2.4 Shallow Concentrated Flow, Subcatchment- 1 Short Grass Pasture Kv= 7.0 fps 7.4 76 Total Subcatchment SP4: (Subcatchment 4 - Proposed Conditions) Hydrograph 1 .59 cfs Runoff Type III 24-he 100=yr Rainfall=6.40" Runoff Area=13,287 sf. ^, Runoff Volume=0:122 of 1- Runoff Depth=4.79" 3 Flow Length=76' ° Tc=7.4 min M 86 0 f 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type ///24-hr 100-yr Rainfall=6.40" Prepared by Merrimack Engineering Services Page 68 HydroCAD®7 00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Reach FES: (Design Point - Flared End Section) Inflow Area = 0.844 ac, Inflow Depth = 4.99" for 100-yr event Inflow = 4.53 cfs @ 12.09 hrs, Volume= 0.351 of Outflow = 4.53 cfs @ 12.09 hrs, Volume= 0.351 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Reach FES: (Design Point - Flared End Section) Hydrograph - - Inflow 5 4.53 cfs D Outflow Inflow: 4 3- 3 ... ... -- - - - - LL 2 fi 0 41 1- 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) i 498 Chickering Road Post-Dyn Type 111 24-hr 100-yr Rainfall=6.40" Prepared by Merrimack Engineering Services Page 69 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Reach GS: Grass Swale Inflow Area = 0.844 ac, Inflow Depth = 4.99" for 100-yr event Inflow = 4.53 cfs @ 12.09 hrs, Volume= 0.351 of Outflow = 4.52 cfs @ 12.10 hrs, Volume= 0.351 af, Atten= 0%, Lag= 0.3 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Max. Velocity= 2.4 fps, Min. Travel Time= 0.4 min Avg. Velocity= 0.7 fps, Avg. Travel Time= 1.3 min Peak Depth= 0.53' @ 12.10 hrs Capacity at bank full= 5.90 cfs Inlet Invert= 123.58', Outlet Invert= 123.00' 1.50' x 0.60' deep channel, n= 0.030 Length= 58.0' Slope= 0.0100T Side Slope Z-value= 4.07' Reach GS: Grass Swale Hydrograph Inflow 5 4.52 Cfs outflow Inflow'Area=O. 4 Peak Depth=0 53' Max Vet=2.4 fps 3 n=0.030 L=58.0' �° 2 S-0.0100 '/' Capacity=5.90; cfs:,r 1 0 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 11124-hr 100-yr Rainfal1=640" Prepared by Merrimack Engineering Services Page 70 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Reach PRP: (15'-12" RCP Core to Exist CB) Inflow Area = 0.844 ac, Inflow Depth = 4.99" for 100-yr event Inflow = 4.52 cfs @ 12.10 hrs, Volume= 0.351 of Outflow = 4.52 cfs @ 12.10 hrs, Volume= 0.351 af, Atten= 0%, Lag= 0.0 min Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Max. Velocity= 11.2 fps, Min. Travel Time= 0.0 min Avg. Velocity = 3.5 fps, Avg. Travel Time= 0.1 min Peak Depth= 0.51' @ 12.10 hrs Capacity at bank full= 8.70 cfs Inlet Invert= 119.50', Outlet Invert= 118.86' 12.0" Diameter Pipe n= 0.011 Length= 15.0' Slope= 0.0427 '/' Reach PRP: (15'-12" RCP Core to Exist CB) Hydrograph 5 Inflow 452 cfs outflow Inflow Area=O. . 4 Peak Depth=0.51' Max Vet=11.2 fps .. D=12.0" 3 n=0.011 c L=15-.0' u. 2- S=0.0427 /' Capacity=8°.70-cfs 1 NNE 0 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 111 24-hr 100-yr Rainfall=6.40" Prepared by Merrimack Engineering Services Page 71 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Pond CB1: (Catch Basin #1) Inflow Area = 0.218 ac, Inflow Depth = 5.57" for 100-yr event Inflow = 1.30 cfs @ 12.09 hrs, Volume= 0.101 of Outflow = 1.30 cfs @ 12.09 hrs, Volume= 0.101 af, Atten= 0%, Lag= 0.0 min Primary = 1.30 cfs @ 12.09 hrs, Volume= 0.101 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Peak Elev= 126.35' @ 12.11 hrs Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 123.85' 12.0" x 10.0' long Culvert CPP, projecting, no headwall, Ke= 0.900 Outlet Invert= 123.80' S= 0.0050 '/' n= 0.011 Cc= 0.900 Primary OutFlow Max=0.92 cfs @ 12.09 hrs HW=126.24' TW=126.14' (Dynamic Tailwater) L1=Culvert (Inlet Controls 0.92 cfs @ 1.2 fps) Pond CB1: (Catch Basin #1) Hydrograph IM Inflow Inflow.Area= 1 .30 Cfs p Primary Peak Elev=126.35` 1 12.0" x100' Culve 3 0 0 2 4 6 8 10 12 14 1I 6 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 11124-hr 100-yr Rainfall=6.40" Prepared by Merrimack Engineering Services Page 72 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Pond CB2: (Catch Basin #2) Inflow Area = 0.026 ac, Inflow Depth = 6.16" for 100-yr event Inflow = 0.17 cfs @ 12.07 hrs, Volume= 0.013 of Outflow = 0.17 cfs @ 12.07 hrs, Volume= 0.013 af, Atten= 0%, Lag= 0.0 min Primary = 0.17 cfs @ 12.07 hrs, Volume= 0.013 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Peak Elev= 126.17' @ 12.11 hrs Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 123.97' 12.0" x 34.0' long Culvert CPP, projecting, no headwall, Ke= 0.900 Outlet Invert= 123.80' S= 0.0050 '/' n= 0.011 Cc= 0.900 Primary OutFlow Max=0.00 cfs @ 12.07 hrs HW=125.80' TW=126.06' (Dynamic Tailwater) t--1=Culvert ( Controls 0.00 cfs) Pond CB2: (Catch Basin #2) Hydrograph Inflow 0.18-, 0.17 CfS El Primary Inflow Area=O. 0.16 Peak-Elev=426:1-7' 0.14--- 12wff x 34.0. y 0.12- .02 " 0.1 c 0.08- 0.06: - _ - - - - _ r , 0.04- " 0.02- 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 111 24-hr 100-yr Rainfall=6.40" Prepared by Merrimack Engineering Services Page 73 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Pond C133: (Catch Basin #3) Inflow Area = 0.196 ac, Inflow Depth = 5.35" for 100-yr event Inflow = 1.20 cfs @ 12.07 hrs, Volume= 0.087 of Outflow = 1.20 cfs @ 12.07 hrs, Volume= 0.087 af, Atten= 0%, Lag= 0.0 min Primary = 1.20 cfs @ 12.07 hrs, Volume= 0.087 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Peak Elev= 127.10' @ 12.12 hrs Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 125.40' 12.0" x 125.0' long Culvert CPP, projecting, no headwall, Ke= 0.900 Outlet Invert= 124.15' S= 0.0100 '/' n= 0.011 Cc= 0.900 Primary OutFlow Max=0.00 cfs @ 12.07 hrs HW=126.40' TW=126.61' (Dynamic Tailwater) t1=Culvert (Controls 0.00 cfs) Pond CB3: (Catch Basin #3) Hydrograph --- Inflow Inflow:Area= . 1 .20 cfs � Primary Peak Etev=127.10` 1 12:.0" x125.0' Culy 3 0 I i'510111 k gx>/ - j 0 ' 1 . 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 111 24-hr 100-yr Rainfall=6.40" Prepared by Merrimack Engineering Services Page 74 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Pond CB4: (Catch Basin #4) Inflow Area = 0.305 ac, Inflow Depth = 4.79" for 100-yr event Inflow = 1.59 cfs @ 12.10 hrs, Volume= 0.122 of Outflow = 1.59 cfs @ 12.10 hrs, Volume= 0.122 af, Atten= 0%, Lag= 0.0 min Primary = 1.59 cfs @ 12.10 hrs, Volume= 0.122 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Peak Elev= 127.28' @ 12.12 hrs Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 125.48' 12.0" x 133.0' long Culvert CPP, projecting, no headwall, Ke= 0.900 Outlet Invert= 124.15' S= 0.0100 '/' n= 0.011 Cc= 0.900 Primary OutFlow Max=1.21 cfs @ 12.10 hrs HW=127.14' TW=126.96' (Dynamic Tailwater) L1=Culvert (Barrel Controls 1.21 cfs @ 1.5 fps) Pond CB4: (Catch Basin #4) Hydrograph Inflow Inflow Area= . 1 .59 Cfs p Primary Peak Elev=127.28` 120" x133.0' CUM W WAMMEWO 1 3 �f o- � 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 111 24-hr 100-yr Rainfall=6.40" Prepared by Merrimack Engineering Services Page 75 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Pond CB5: (Catch Basin #5) Inflow Area = 0.844 ac, Inflow Depth = 4.99" for 100-yr event Inflow = 4.52 cfs @ 12.10 hrs, Volume= 0.351 of Outflow = 4.52 cfs @ 12.10 hrs, Volume= 0.351 af, Atten= 0%, Lag= 0.0 min Primary = 4.52 cfs @ 12.10 hrs, Volume= 0.351 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Peak Elev= 123.07' @ 12.10 hrs Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 122.23' 2.0' long x 0.9' 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) 2.71 2.75 2.81 2.93 3.04 3.13 3.22 3.28 3.31 3.30 3.31 3.32 Primary OutFlow Max=4.50 cfs @ 12.10 hrs HW=123.06' TW=120.01' (Dynamic Tailwater) t-1=Broad-Crested Rectangular Weir (Weir Controls 4.50 cfs @ 2.7 fps) Pond CB5: (Catch Basin #5) Hydrograph IM 5 Inflow Inflow Area= 4.52 Cfs �� Primary 4 Peak Bev' o u. 2 0 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 111 24-hr 100-yr Rainfall=6.40" Prepared by Merrimack Engineering Services Page 76 HydroCADO 7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Pond DMH1: (Drain Manhole #1) Inflow Area = 0.745 ac, Inflow Depth = 5.21" for 100-yr event Inflow = 4.19 cfs @ 12.09 hrs, Volume= 0.324 of Outflow = 4.19 cfs @ 12.09 hrs, Volume= 0.324 af, Atten= 0%, Lag= 0.0 min Primary = 4.19 cfs @ 12.09 hrs, Volume= 0.324 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Peak Elev= 126.17' @ 12.09 hrs Plug=Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 123.70' 12.0" x 12.0' long Culvert CPP, projecting, no headwall, Ke= 0.900 Outlet Invert= 123.58' S= 0.01007' n= 0.011 Cc= 0.900 Primary OutFlow Max=4.16 cfs @ 12.09 hrs HW=126.15' TW=0.00' (Dynamic Tailwater) L1=Culvert (Inlet Controls 4.16 cfs @ 5.3 fps) Pond DMH1: (Drain Manhole #1) Hydrograph Em Inflow -Inflow Area= 4.19 cfs _ EJ Primary 4 Peak Elev=126.17` 12.0"--X 12 0! Culve - 3 v 0 2 : u_ 1- 0 2 4 6 '8­­10 12 14 16 18 20 22 24 Time (hours) 498 Chickering Road Post-Dyn Type 111 24-hr 100-yr Rainfall=6.40" Prepared by Merrimack Engineering Services Page 77 HydroCAD®7.00 s/n 000899 © 1986-2003 Applied Microcomputer Systems 5/23/2012 Pond DMH2: (Drain Manhole #2) Inflow Area = 0.501 ac, Inflow Depth = 5.00" for 100-yr event Inflow = 2.73 cfs @ 12.09 hrs, Volume= 0.209 of Outflow = 2.73 cfs @ 12.09 hrs, Volume= 0.209 af, Atten= 0%, Lag= 0.0 min Primary = 2.73 cfs @ 12.09 hrs, Volume= 0.209 of Routing by Dyn-Stor-Ind method, Time Span= 0.00-24.00 hrs, dt= 0.02 hrs Peak Elev= 126.98' @ 12.10 hrs Plug-Flow detention time= (not calculated: outflow precedes inflow) Center-of-Mass det. time= (not calculated) # Routing Invert Outlet Devices 1 Primary 124.05' 12.0" x 25.0' long Culvert CPP, projecting, no headwall, Ke= 0.900 Outlet Invert= 123.80' S= 0.0100 '/' n= 0.011 Cc= 0.900 Primary OutFlow Max=2.54 cfs @ 12.09 hrs HW=126.87' TW=126.15' (Dynamic Tailwater) L1=Culvert (Inlet Controls 2.54 cfs @ 3.2 fps) Pond DMH2: (Drain Manhole #2) Hydrograph M Inflow 3 2.73 Cfs El Primary Inflow:Area- Peak Elev=126.98 120 Cve. _ .. 2 v 3 o ... ..._.._... ._ .._ : .. 1 . .r�y 0 0 2 4 6 8 10 12 14 16 18 20 22 24 Time (hours) PROPOSED BANK FACILITY NORTHANDOVER, MASSACHUSETTS < SECTION 5.0 > APPENDIX Merrimack Engineering Services, Inc. Section 5—Page 1 Printed: April 12,2012 PROPOSED BANK FACILITY NORTHANDOVER, MASSACHUSETTS < SECTION 5.1 > RAINFALL DATA MAPS Merrimack Engineering Services,Inc. Section 5—Page 2 Printed: April 12,2012 PROPOSED AK FACILITY NORTHANDOVER, MASSACHUSETTS < SECTION 5.1 > Rainfall Data Map Qur £SSE_X" FRANKLIN = _ ¢ = itt00LE5EX �±2 SUFFOt K HA#iPSHI.R� V�OitCES7ER n RA3NFALL DATA : MAP �� _ _ N57 L£ Ti � YEAR,' 24 Hg11R PRfCIP17ATiON-(iN'�HES) - = tVANIUCKE7 2 ESSEX - ;; FRANKi;lN - :s- - SUiOLK a'' _HApPSHIRE j yr4RCE5TER Y HAiAPOEN:' - - �q 9 _ to 8. 2 - < N57- L . BAR _ E 1•fy YEAR,; 24,H4lIR PRECIPITATION T i- _ JUKES . "NANTUCKET Merrimack Engineering Services,Inc. Section 5-Page.3 Printed: April 12,2012 BANK FACILITY -P-R- OPOSED NORTHANDOVER, MASSACHUSETTS < SECTION 5.1 > Rainfall Data Map a S Merrimack Engineering Services, Inc. Section 5-Page 4 Printed: April 12,2012 PROPOSED BANK FA C T NORTHANDOVER, MASSACHUSETTS < SECTION 5.2 > NATIONAL RESOURCES CONSERVATION SERVICE - SOIL DESCRIPTION WITH CLASSIFICATION Merrimack Engineering Services, Inc. Section 5—Page 5 Printed: April 12,2012 PR OSED BANK FA CILI T Y NORTHANDOVER, MASSACHUSETTS Soils description: Woodbridge series soils The Woodbridge series consists of coarse-loamy,mixed,mesic Typic Fragiochrepts.These deep and moderately well drained soils are on uplands. The soils formed in compact glacial till derived mainly from schist and granite. Slopes range from 0 to 25 percent. Woodbridge soils formed in the same kind of material as well drained Paxton soils,poorly drained Ridgebury soils,and very poorly drained Whitman soils.They are similar to the Scituate,and Sutton soils. Woodbridge soils have less sand in the substratum than the Scituate soils.They have a fragipan,which the Sutton soils do not have. Typical pedon of Woodbridge fine sandy loam,3 to 8 percent slopes,in the town of Georgetown,in a field 700 feet southwest of the junction of Andover and West Streets: Ap-0 to 9 inches;very dark grayish brown(10YR 3/2)fine sandy loam;very weak fine and medium granular structure; friable;many fine roots; 10 percent angular coarse fragments 2 to 20 millimeters in diameter;medium acid;abrupt smooth boundary. B21-9 to 16 inches;yellowish brown(1 OYR 5/4)fine sandy loam that fades to light olive brown(2.5Y 5/4)with depth; very weak fine and medium granular structure; friable;common fine roots;many small worm holes filled with very dark grayish brown material from Ap horizon; 10 percent angular gravel;medium acid;clear wavy boundary. B22-16 to 23 inches;olive brown(2.5Y 4/4)fine sandy loam; common fine distinct gray to light gray(5Y 6/1)and yellowish brown(1 OYR 5/6)mottles;weak medium subangular blocky structure;friable;few fine herbaceous roots; 10 percent angular gravel,3 percent stones;medium acid;abrupt wavy boundary. A'2-23 to 26 inches;light olive gray(5Y 6/2)fine sandy loam;common fine distinct strong brown(7.5YR 5/6)and yellowish red(5YR 5/6)mottles;weak medium subangular blocky structure;firm;few fine roots; 15 percent angular and subrounded gravel,3 percent stones;strongly acid;abrupt wavy boundary. Cx-26 to 60 inches; light olive brown(2.5Y 5/4)fine sandy loam;common fine distinct strong brown(7.5YR 5/6) mottles;moderate to strong thick platy structure;very firm; 10 percent angular gravel,3 percent stones;strongly acid. The depth to the firm or very firm fragipan ranges from 21 to 29 inches. The depth to mottling ranges 16 to 29 inches. The content of coarse fragments in the solum and substratum ranges from 5 to 30 percent.The reaction ranges from strongly acid to medium acid.The surface layer is slightly acid to neutral where limed. i The Ap horizon has hue of l OYR,value of 3 or 4,and cbroma of 2 or 3.The A 1 horizon is 1 unit lower in value or chroma or both.The texture of the A horizon is fine sandy loam or loam. The B21 horizon has hue of 7.5YR or l OYR,value of 4 or 5,and chroma of 4 to 6. It is fine sandy loam or loam. The B22 horizon has hue of l OYR or 2.5Y with value and chroma of 4 to 6 and is distinctly mottled. It is sandy loam,fine sandy loam,or loam.Some pedons do not have an A'2 horizon. The Cx horizon has hue of 2.5Y or 5Y,value of 4 or 5,and chroma of 3 or 4.It is sandy loam,fine sandy loam,or loam or thin gravely analogues. Merrimack Engineering Services,Inc. Section 5—Page 6 Printed: April 12,2012 PROPOSED -BANK FACILITY NORTHANDOVER, MASSACHUSETTS < SECTION 6.0 > DRAINAGE AREA MAPS Merrimack Engineering Services,Inc. Section 6—Page 1 Printed: April 12,2012 DRAINAGE FACILITIES OPERATIONAL AND MAINTENANCE PLAN MAY 15, 2012 498 CHICKERING ROAD LOWELL FIVE BANK NORTH ANDOVER, MASSACHUSETTS OWNER: PARK STREET REDEVELOPMENT,LLC 231 SUTTON STREET, SUITE 1B NORTH ANDOVER,MA 01845 PARTY RESPONSIBLE FOR O &M: PARK STREET REDEVELOPMENT,LLC 231 SUTTON STREET, SUITE 1B NORTH ANDOVER,MA 01845 SHORT TERM MAINTENANCE PROGRAM DURING CONSTRUCTION 1. A site inspection shall be performed by a P.E. during the construction of the grading and drainage facilities and those improvements shown on the Site Development Plans. These inspections shall be done at least once every week during the applicable construction period. Inspections shall not be required during periods of inactivity to these facilities. A report shall be generated and forwarded to the North Andover Planning Board and DPW after each inspection. M 2. Care shall be taken at all times to control erosion and sediment movement by compaction of disturbed areas and by the use and maintenance of hay bale/silt fences at each drainage structure and at limits of work as shown on the Site Plans. Attention is called to the Sensitive Use Restriction recorded in Essex No. District Registry of Deeds Book 11072, Page 215 and all work shall be done as specified therein. An LSP shall be on site during excavation and earth moving operations to test soils and direct earthworks handling methods and procedures. The contractor shall take direction from the LSP and carry out all directives. All exposed soil finish surfaces shall be paved or immediately landscaped and stabilized; or loamed, seeded and mulched with a layer of mulch hay. Outside of the growing season, surfaces shall be covered with a layer of mulch hay until climate conditions allow for seeding. SHORT TERM MAINTENANCE PROGRAM DURING CONSTRUCTION (Cont'd) 3. The contractor shall ensure that all runoff is collected in the appropriate structures as they are constructed and that uncontrolled runoff is kept to a minimum. The contractor shall protect the safety of the personnel on site by installing grates or covers on each drainage structure when it is built. The site contractor for the project will be responsible for the operation and maintenance of the stormwater management systems during construction. 4. During construction, all drainage structures will be cleaned on an as needed basis and/or after heavy rainfalls. Prior to the placement of any impervious materials on site, all drainage structures shall be properly installed and functional. After construction, the inspection of catch basins, including the oil and grease traps other facilities such as roof drainage, grass swale, forebay and rip-rap areas shall be performed on a two (2)times per year basis. The basins are to be cleaned at least once per year (after spring street sweeping) to prevent blockage. If it is found at the time of cleaning that the depth of the accumulated sediment is greater than 50% of the depth of the sump, the maintenance schedule will be adjusted to include more frequent cleanings. Disposal of the accumulated sediment and hydrocarbons must be in accordance with applicable local, state, and federal guidelines and regulations. Structural repairs will be performed as needed. 5. The deep sump catch basins will also be inspected on a weekly basis during construction to insure that no appreciable amount of sediment remains in the sump for prolonged periods of time. Sediment can be removed by shovel for catch basins with installed oil separator hoods or grease traps. Any sediment overflowing into the discharge pipes from the catch basins is to be flushed to either the next downstream manhole or to the sediment forebay and then removed by machine or shovel. However, approval of the LSP must be obtained to assure that sediments not contaminated. 6. . To reduce the amount of sediment entering the catch basins, and the drainage system during the construction of each phase of the project, the catch basins will be surrounded by haybales and a crushed stone berm. This will prevent some of the sediment from entering the catch basins during storm events. In addition, being discharged from the construction site, sediment contaminated storm water will be processed in the storm water treatment system. Clean water bypassing the site will be routed directly to the receiving stream. Sediment ponds and traps, vegetated buffer strips, sediment barriers or filters, dikes, and other BMP's intended to trap sediment on site will be constructed as one of the first steps in grading. These BMP's will be installed before other land-disturbing activities take place, if so directed by the Engineer. This is especially required in the grass swale,where mulch or other surface cover must be put over the seeded area until the grass germinates and reaches a stand of 2". • Selected BMP • Straw Bale Barrier • Brush Barrier • Silt Fence • Vegetative Strip • Sediment Trap • Stone Check Dams All excavated materials shall be properly handled and disposed during and after construction. SHORT TERM MAINTENANCE PROGRAM DURING CONSTRUCTION (Cont'd) 7. During the first year of operation the drainage structures and facilities including the forebay and drainage swale shall be inspected shortly after each storm event greater than 1.5 inches and again 2 to 3 days later to ensure that the systems are functioning properly and infiltration structures and detention ponds are emptied within three days. Any evidence of erosion in the swale or forebay, evidence of sediment in the roof drains and catch basins structures shall be repaired as outlined above. Any built-up sediment within the basin, and inlet pipes shall be removed and monitored for any additional built up sediment. Any extraneous shrub or brush from embankment areas shall be removed; any burrow holes or barren spots shall be filled with compacted loam and seeded. In the event that any drainage device is observed not functioning properly or excess sediment built-up is observed, the responsible party shall contact the P.E. within 72hours. 8. The above referenced maintenance sequence shall also be performed when the drainage system is complete and online after its initial 30 and 60 days. 9. Upon substantial completion of the drainage facilities an inspection shall be performed by the P.E. and report issued to the North Andover Planning Board. 10. Upon completion of and the successful establishment and stabilization of the site and the landscaped areas, the P.E. shall perform an inspection with an agent of the North Andover Planning Board/and or DPW. At the appropriate time, a report indicating that the construction, establishment, and stabilization of these areas are in substantial conformance to the plans and Conditions of Approval shall be provided to the Board. LONG TERM MAINTENANCE PROGRAM 1. Upon completion of the project, the owner shall be responsible for the operation and maintenance of the stromwater management system. The responsibilities shall extend to the grass swale, rip-rap forebay,piping and catch basins and manholes. 2. On or about every May 1 and November 1 of each year a site inspection shall be performed by a Registered Professional Engineer (P.E.) of the Commonwealth of Massachusetts to report on the status of the drainage system. The inspector will schedule the inspection with the responsible parties 48 hours prior to the inspection so arrangements can be made to access all drainage system components, including if necessary, roping off of the immediate areas within the site to assure appropriate and safe access. This report shall include the name, address and telephone number of the owner of the drainage facilities, the names, address and telephone numbers of parties responsible for the operation and maintenance of the drainage facilities, and an outline of remaining funds in the line item of the budget for drainage maintenance. The report shall also identify the current status of the drainage facility. The inspection shall include a visual inspection of each drainage structure including the catch basins,manholes, swale, forebay, roof drains,plantings, BMP"s and any other structure or condition relating to the long term operation of the drainage facilities. The report shall outline any observed pollution, if observed. The report shall be provided to the No Andover Planning Board and DPW and owner. LONG TERM MAINTENANCE PROGRAM(Cont'd.) 3. On or about May 1 and November 1 of each year, for two years, and then once a year thereafter, a Landscape Contractor that owns or has access to a vacuum truck or catch basin cleaner or by shovel shall complete the cleaning out of any debris in the drainage system and ancillary components. A short written report shall be prepared of the work performed, and to be submitted to the inspection(P.E.) for inclusion in this report. 4. If the inspector reports that work needs to be done to maintain any facility then the work must be completed within the next 4 weeks,unless otherwise specified, the condition of which shall be reported in the inspector's next report. The owner shall become the responsible party of scheduling and bearing all costs associated with the maintenance requirements of the proposed drainage facilities. 5. On or about November 15 of each year a Landscape Contractor shall perform the service of cleaning out of any debris in the non-catchbasin drainage structures or drainage pipes. He shall prepare a short written report of the work performed and submit to the inspector(P.E.) for inclusion in this report. He shall report the status to the North Andover Planning Board,No Andover DPW and the P.E. 6. Once every year from the date of commencement, on or about November 15, the catch basins shall be thoroughly cleaned by mechanical and/or manual means to remove any debris and sediment,more frequently if sediment buildup is within 2' of the outlet invert pipe. . Periodic power sweeping may be increased or decreased, as a result of debris accumulation quantities observed within the drainage facilities. 7. Once every year from the date of commencement, usually in the spring, a Landscape Contractor shall reseed or stabilize any areas which have eroded or developed sediment or which have developed conditions not shown on the plans. A written report of such activities shall be presented to the inspector for inclusion in his report. 8. Snow removal and disposal practices of street sweepings shall not be disposed of in M any of the drainage structures. 9. The sweeping program is composed of two segments; Spring and Summer. The Spring program starts in April as early as possible and/or as the road and weather conditions cooperate. The Summer sweeping shall be done between the end of August to end of September, in advance of the Fall and Winter months. The contractor shall utilize vacuum or regenerative air sweepers. These types of sweepers are more effective and powerful in picking up the relatively heavier/coarser sediment/sand leftover from the Winter season/operations, and accumulated soil present in the late spring and summer months. 10. If the inspector reports that work needs to be done to maintain any facility then the work must be completed within the next four weeks,unless otherwise specified, and the condition of which shall be reported in the inspector's next report.