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HomeMy WebLinkAbout2000-06-30 Supplemental Drainage Calcs Detention Basin Modification 7/22/03 • 87 Indian Rock Road Windham,NH 03087 Tel(603) 898-8516 _- Fax(603)898-8497 DK ENGINEER xG ASSOCIATES SuPPLEmENTALDMNAGECALCULATIONS FOR DETENTION BASIN MODIFICATION RECEIVED JUL 2 5 2005 NORTH ANDOVER MANNING DEPARTMENT CHATHAM CROSSING Prepared For. Cormier Andover Construction Corp. 59 Chandler Circle Andover, Massachusetts JN: 0237 CHATHAM CROSSING NORTH ANDOVER, MASSACHUSETTS SUPPLEMENTAL DRAINAGE CALCULATIONS FOR DETENTION BASIN MODIFICATION Date: July 22, 2003 PREPARED FOR: CORMIER ANDOVER CONSTRUCTION CORPORATKON' 59 Chandler Circle Andover, Massachusetts DANII.-I. �G KOHAV08 CIVIL. Np.:37752 JW 0237 DK ENGINEERING ASSOCIATES Phone: (603)898-8516 87 Indian Rock Road —Suite 7 Fax: (603)898-8497 Windham, NH 03087 a-Mail: dan@dkengineed ng.not i CHATHAM CROSSING NORTH ANDOVER, MASSACHUSETTS INTRODUCTION The purpose of this report is to design a conventional above ground detention basin as a substitute for the approved below ground concrete vault detention basin. Since the approved detention basin would require special maintenance and trained personnel to perform this maintenance, the convention detention basin would be a benefit to the Town. The variables used in this report were obtained directly from the approved "Pre- and Post Development Drainage Analysis" for Chatham Crossing, prepared by Andover Consultants, Inc. and dated January 31, 2000. These calculations will determine the Pre-Development and Post- Development peak flaw rates using the SCS-TR20 Runoff Method. Also, the peak discharge flow rates from the detention basin will be determined for all design storms. The objective is mitigate the storm drainage flows such that there will be no increase in the peak rate of runoff at any point at the parcel's boundary and the discharge from the detention basin will not increase from the original approved report. The calculations will be performed for the 2, 10 and 100-year storm events. All applicable regulations of the Town of North Andover are incorporated herein. DK ENGINEERING ASSOCIATES Page 2 Printed: July 24, 2003 e i CHATHAM CROSSING NORTH ANDOVER, MASSACHUSETTS SUMMARY The following tables summarize the pre-development vs. the post- development peak runoff flow rates and the discharge flow rates from the detention basin for the 2, 10 and 100-year storm event. As indicated, due to the detention mitigation facility located within the project, the peak flow rates are not increased and the discharge flow rates from the detention basin are less than or equal to the approved rates. Because there is no increase in the peak flow rates generated by from the site, no down stream properties should be adversely affected by this project. PRE-DEVELOPMENT VS. POST-DEVELOPMENT DRAINAGE SUMMARY TABLES Total Drainage Area Design Pre-Dev. Post-Dev. A Storm (cfs) (cfs) cs 2 5.79 4.68 1.11 10 14.42 11.87 2.55 100 23.52 18.32 5.20 APPROVED VS. PROPOSED DETENTION BASIN DISCHARGE Total Draina a Area Design Approved Proposed A Storm (cfs) (cfs) cs 2 2.32 1.78 0.54 10 5.48 5.43 0.06 100 8.29 8.30 0.01 Assumed to be zero These Storm Drainage calculations were prepared in accordance with the applicable Town of North Andover Subdivision Rules and Regulations and according to generally accepted engineering principles and in accordance with the stated regulations. DK ENGINEERING ASSOCIATES Page 3 Printed: July 24,2003 I l CHATHAM CROSSING 1 NORTH ANDOVER, MASSACHUSETTS ❑RAINAGE CALCULATIONS i PRE VS. POST DEVELOPMENT ANALYSIS DK ENGINEERING ASSOCIATES Page 4 Printed: July 24,2003 Pre Post-A Post-e Pos Pond\ Drainage Diagram for 0237-Chatham Crossing ,'Subcat;% Reach` , ond\ I Link' Prepared by DK Engineering Associates 7/24/2003 '" HydroCAD®6.00 sln 000815 © 1986 2001 Applied Microcomputer Systems 0237-Chatham Crossing 2-Year Design Storm Prepared by DK Engineering Associates H droCAD®6.00 sin 000815 OO 1986-2001 Applied Microcomputer Systems 7/24/2003 Time span=5.00-20.00 hrs, dt=0.05 hrs, 301 points Runoff by SCS TR-20 method, UH=SCS, Type III 24-hr Rainfall=3.10" Reach routing by Star-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment Post-A: Post-Development Drainage Area "A" Tc=12.6 min CN=77 Area=3.510 ac Runoff=3.61 cfs 0.305 of Subcatchment Post-B: Post-Development Drainage Area "B" Tc=13.2 min CN=82 Area=4.270 ac Runoff= 5.70 cfs 0,479 of Subcatchment Pre: "Pre-Develop Drainage Area Tc=15.0 min CN=73 Area=7.780 ac Runoff= 5.79 cfs 0.539 of Pond Pond. Detension Basin Peak Storage=7,438 of inflow= 5.70 cfs 0.479 of Primary= 1.78 cfs 0.470 of Outflow= 1.78 cfs 0,470 of Pond Pos: Summary of Post Development Inflow=4.68 cfs 0.775 of Primary=4.68 cfs 0.775 of Runoff Area = 15.560 ac Volume = 1.324 of Average Depth = 1.02" 0237-Chatham Crossing Wear Design Storm Prepared by DK Engineering Associates H droCAD®6.00 sln 000815 © 1986-2001 Applied Microcomputer Systems 7/24/2003 Time span=5.00-20.00 hrs, dt=0.05 hrs, 301 points Runoff by SCS TR-20 method, UH=SCS, Type III 24-hr Rainfall=4.80" Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment Post-A: Post-Development Drainage Area "A" Tc=12.6 min CN=77 Area=3.510 ac Runoff=8.05 cfs 0.666 of Subcatchment Past-B: Post-Development Drainage Area "B" Tc=13.2 min CN=82 Area=4.270 ac Runoff= 11.41 cfs 0.964 of Subcatchment Pre: "Pre-Develop Drainage Area Tc=15.0 min CN=73 Area=7.780 ac Runoff= 14.42 cfs 1.269 of Pond Pond: Detension Basin Peak Storage= 12,535 cf Inflow= 11.41 cfs 0.964 of Primary=5.43 cfs 0.950 of Outflow=5.43 cfs 0.950 of Pond Pos: Summary of Post Development Inflow= 11.87 cfs 1.616 of Primary= 11.87 cfs 1.616 of Runoff Area = 15.560 ac Volume = 2.899 of Average Depth = 2.24" E 0237-Chatham Crossing 100-Year Design Storm Prepared by DK Engineering Associates H droCAD®6.00 sln 000815 O 1986-2001 Applied Microcomputer Systems 7/24/2003 Time span=5.00-20.00 hrs, dt=0.05 hrs, 301 points Runoff by SCS TR-20 method, UH=SCS, Type III 24-hr Rainfall=6.40" Reach routing by Stor-Ind+Trans method - Pond routing by Stor-Ind method Subcatchment Post-A: Post-Development Drainage Area "A" Tc=12.6 min CN=77 Area=3.510 ac Runoff= 12.64 cfs 1.046 of Subcatchment Past-B: Post-Development Drainage Area "B" Tc=13.2 min CN=82 Area=4.270 ac Runoff= 16.99 cfs 1.455 of Subcatchment Pre: "Pre-Develop Drainage Area Tc=15.0 min CN=73 Area=7.780 ac Runoff=23.52 cfs 2.060 of Pond Pond: Detension Basin Peale Storage= 18,931 of Inflow= 16.99 cfs 1.455 of Primary=8.30 cfs 1.433 of Outflow=8.30 cfs 1.433 of Pond Pos: Summary of Post Development Inflow= 18.32 cfs 2.479 of Primary= 18.32 cfs 2.479 of Runoff Area = 15.560 ac Volume = 4.561 of Average Depth = 3.52" CHATHAM CROSSING NORTH ANDOVER, MASSACHUSETTS PRE-DEVELOPMENT DK ENGINEERING ASSOCIATES Page 5 Printed: July 24,2003 i i CHATHAM CROSSING NORTH ANDOVER, MASSACHUSETTS PRE-DEVELOPMENT 2-YEAR STORM EVENT DK ENGINEERING ASSOCIATES Page 6 Printed: July 24, 2003 0237-Chatham Crossing 2-Year Design Storm Prepared by DK Engineering Associates HydroCAD®6.00 s/n 000815 OO 1986-2001 Applied Microcomputer Systems 7/24/2003 Subcatchment Pre. "Pre-Develop Drainage Area Runoff — 5.79 cfs @ 12.23 hrs, Volume= 0.539 of Runoff by SCS TR-20 method, UH=SCS, Time Span= 5,00-20.00 hrs, dt= 0.05 hrs Type III 24-hr Rainfall=3.10" Area ac CN Description 7.780 73 From Approved Report To Length Slope Velocity Capacity Description (min) (feet) (ftlft) (ftlsec) (cfs) 15.0 Direct Entry, From Approved Report Subcatchment Pre: "Pre-Develop Drainage Area llydraguq)h Not - l� Runoff V- .......... ... ..._,..,.., - 1 I�, 1 , I 1 I I 1 I 1 , , 3 I I I I f r) 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) f CHATHAM CROSSING NORTH ANDOVER, MASSACHUSETTS PRE-DEVELOPMENT 10-YEAR STORM EVENT DK ENGINEERING ASSOG#ATES Page 7 Printed; July 24, 2003 i 4237-Chatham Crossing 10-Year Design Storm Prepared by DK Engineering Associates HydroCAD®6.00 s/n 000815 O 1986-2001 Applied Microcomputer Systems 7/24/2003 Subcatchment Pre: "Pre-Develop Drainage Area Runoff = 14.42 cfs @ 12.21 hrs, Volume= 1.269 of Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type III 24-hr Rainfall=4.80" Area (ac) CN Description 7,780 73 From Approved Report Tc Length Slope Velocity Capacity Description ----(min) (feet) (ftlft) (ftlsec) (cfs) 15.0 Direct Entry, From Approved Report Subcatchment Pre: "Pre-Develop Drainage Area Hgrs rograph Pleat f 16 15 14.42 efS Runoff I 14: f I I 13. --- ' _ .. . . . . . .. .. 12= I I I 1O- r. - -- - - - - - - - - I- -- - - - - - - - - - - - _ 8-_ ... - - - - - - - - - - - 6._ I l - 5-: 4' 01 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) CHATHAM CROSSING NORTH ANDOVER, MASSACHUSETTS PRE-DEVELOPMENT 100-YEAR STORM EVENT DK ENGINEERING ASSOCIATES Page 8 Printed: July 24,2003 0237-Chatham Crossing 100-Year Design Storm Prepared by DK Engineering Associates H droCADO 6.00 sln 000815 © 1986-2001 Applied Microcomputer Systems 7/24/2003 Subcatchment Pre: "Pre-Develop Drainage Area Runoff = 23.52 cfs @ 12.21 hrs, Volume= 2.060 of Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type III 24-hr Rainfall=6.4011 Area ac CN Description 7.780 73 From Approved Report Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ fVsec)__ (cfs) _ 15.0 Direct Entry Pp p From Approved Report Subcatchment Pre: "Pre-Develop Drainage Area 1 26 Ru�oit --- 3 23.52 cfs 22 I I I 1 20(� - 18 3 16- ` 14. ' � 1 I 0 12 iY i 1 10- r K r r `3k 1 f 1 I 1 I 42. 0.:. 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) CHATHAM CROSSING NORTH ANDOVER, MASSACHUSETTS POST-DEVELOPMENT DK ENGINEERING ASSOCIATES Page 9 Printed: July 24,2003 CHATHAM CROSSING NORTH ANDOVER, MASSACHUSETTS POST-DEVELOPMENT 2-YEAR STORM EVENT DK ENGINEERING ASSOCIATES Page 10 Printed: July 24, 2003 3 0237-Chatham Crossing 2-Year Design Storm Prepared by DK Engineering Associates HydroCAD®6.00 sh 000815 © 1986-2001 Applied Microcomputer Systems 7124/2003 Subcatchment Post-A: Post-Development Drainage Area "A" Runoff _ 3.61 cfs @ 12.19 hrs, Volume= 0.305 of Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type III 24-hr Rainfall=3.10" Area (ac) CN Description 3.510 77 From Approved Report Tc Length Slope Velocity Capacity Description min feet ft/ft fttsec cfs 12.6 Direct Entry, From Approved Report Subcatchment Post-A: Post-Development Drainage Area "A" E (j- - - 31 RunoFf ( 36icfs - I I � I I 4 3- LL N I t I �T fy�'.• I - - t --- --- - - - - - - - 1 t 1 { 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) 0237-Chatham Crossing 2-Year Design Storm Prepared by DK Engineering Associates N droCAD®6.00 s/n 000815 © 1986-2001 Applied Microcomputer Systems 7/24 2003 Subcatchment Post-B: Post-Development Drainage Area "B" Runoff = 5.70 cfs @ 12.19 hrs, Volume= 0.479 of Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt=0.05 hrs Type III 24-hr Rainfall=3.10" Area ac CN Description 4.270 82 From Approved Report Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (fVsec) ( sl_-_ 13.2 Direct n E #rtr y, From Approved Report Subcatchment Post-B: Post-Development Drainage Area "B" 3 3 w o , 2- 0- ' ' , i , . . , i" S 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) 0237-Chatham Crossing 2-Year Design Storm Prepared by DK Engineering Associates H droCAD®6.00 sln 000815 © 1986-2001 Applied Microcom uter Systems 7/24/2003 Pond Pond; Detension Basin Inflow = 5,70 cfs @ 12,19 hrs, Volume= 0.479 of Outflow = 1.78 cfs @ 12.63 hrs, Volume= 0A70 af, Atten= 69%, Lag= 26,1 min Primary - 1.78 cfs @ 12.63 hrs, Volume= 0.470 of Routing by Stor-Ind method, Time Span= 5,00-20,00 hrs, dt= 0.05 hrs Peak Elev= 218.76' Storage= 7,438 cf Plug-Flow detention time= 61,3 min calculated for 0.470 of(98% of inflow) Storage and wetted areas determined by Prismatic sections Elevation Surf.Area Inc.Store Cum.Store (feet) s -ft cubic-feet cubic-feet 216.00 1,675 0 0 218.00 2,961 4,636 4,636 220.00 4,456 7,417 12,053 222.00 6,177 10,633 22,686 rimary OutFlow (Free Discharge) =Culvert 2=Orifice/Grate 3=Orifice/Grate =Orifice/Grate # Routing Invert Outlet Devices 1 Primary 215.95' 15.0" x 28.0' long Culvert RCP, square edge headwaii, Ke= 0.500 Outlet Invert= 215.10' S= 0.0304 '1' n= 0.013 Cc= 0.900 2 Device 1 216.00' 4.0" Vert. Orifice/Grate X 2.00 C= 0.600 3 Device 1 218.50' 8.0" Vert. Orifice/Grate X 2.00 C= 0.600 4 Device 1 221.15' 24.0" Horiz. Orifice/Grate Limited to weir flow C= 0.600 i 0237WChatham Crossing 2-Year Design Storm Prepared by DK Engineering Associates HydroCAD®6.00 sh 000815 O 1986-2001 Applied Microcomputer Systems 7/24/2003 Pond Pond: Detension Basin 1 1 I 3 0 In 5.70 cfs II Mary ' a Pri 6- ' [ 1 I f 1 1 I 5- 1 I i Alf - f - 4- 1 N I I F IfA., 3 2 1.78 cfs 1 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) i 0237=Chatham Crossing 2-Year Design Storm Prepared by DK Engineering Associates HydroCA©®6.00 s/n 000815 O 1986-2001 Applied Microcomputer Systems 7/24/2003 Pond Pos: Summary of Post Development Inflow - 4.68 cfs @ 12.20 hrs, Volume= 0.775 of Primary = 4.68 cfs @ 12.20 hrs, Volume= 0.775 af, Atten= 0%, Lag= 0.0 ruin Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Pond Pos: Summary of Post Development Hydcc.)(jr;.,)p`a Plot --i-- . ._ .............. [I k - Inflow 1 I ILA PJ3 � Primary 5 4.68 cfs ! 1 I f � 1 4- 3 yw - - D - a . 2"" .& ! I I I I "' r n 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) e I I i CHATHAM CROSSING NORTH ANDOVER, MASSACHUSETTS POST-DEVELOPMENT 14-YEAR STORM EVENT DK ENGINEERING ASSOCIATES Page 11 Prinked: Juiy24,2003 0237-Chatham Crossing 10-Year Design Storm Prepared by DK Engineering Associates H droCADO 6.00 s/n 000815 © 1986-2001 Applied Microcomputer Systems 7/24/2003 Subcatchment Post-A: Post-Development Drainage Area "A" Runoff = 8.05 cfs @ 12.18 hrs, Volume= 0.666 of Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type III 24-hr Rainfall=4.80" Area ac CN Description 3.610 77 From Approved Report Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) 12.6 Direct Entry, From Approved Report Subcatchment Post-A: Post-Development Drainage Area "A" Hydrograph Plot 9 —----- E L Runoff - - - - - - - --'- - - ; - 8.05cfs -�- - f I 1 1 1 7" f I 1 1 I 0 _IL . I I 1 { I 1 3- 1 1 'yyYY'33� 1 f f 0 . WI 5 6 7 8 9 1q 11 12 13 14 15 16 17 18 19 20 Time (hours) 0237-Chatham Crossing 10-Year Design Storm Prepared by DK Engineering Associates HydroCADO 6.00 s/n 000815 O 1986-2001 Applied Microcomputer Systems 7/24/2003 Subcatchment Post-B: Post-Development Drainage Area "B" Runoff - 11.41 cfs @ 12.18 hrs, Volume= 0,964 of Runoff by SOS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt= 0,05 hrs Type III 24-hr Rainfall=4.80" Area ac ON Description 4.270 82 From Approved Report Tc Length Slope Velocity Capacity Description (min) (feet) (ftlft) (ftlsec) (cfs) 13.2 Direct Entry, From Approved Report Subcatchment Post-B: Post-Development Drainage Area "B" Hydrog raph Plot I I I ! f 12- ' , 1 41 cfs.. 7 I I f 7 y LL 4: 3; 1 I f 1 , 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 2€3 Time (hours) 0237-Chatham Crossing 10-Year Design Storm Prepared by DK Engineering Associates HydroCADO 6.00 s/n 000815 O 1986-2001 Applied Microcomputer Systems 7/24/2003 Pond Pond; Detension Basin Inflow - 11.41 cfs @ 12.18 hrs, Volume= 0.964 of Outflow - 5.43 cfs @ 12.48 hrs, Volume= 0.950 af, Atten= 52%, Lag= 17.6 min Primary = 5.43 cfs @ 12.48 hrs, Volume= 0.950 of Routing by Star-Ind method, Time Span= 5.00-20.00 hrs, dt=0.05 hrs Peak Elev= 220.09' Storage= 12,535 cf Plug-Flow detention time= 52.5 min calculated for 0.946 of(98% of inflow) Storage and wetted areas determined by Prismatic sections Elevation Surf.Area Inc.Store Cum.Store feet s -ft cubic-feet cubic-feet 216.00 1,675 0 0 218.00 2,961 4,636 4,636 220.00 4,456 7,417 12,053 222.00 6,177 10,633 22,686 primary OutFlow (Free Discharge) —E32=Orifice/G ulvert rate =Orifice/Grate =Orifice/Grate # Routing Invert Outlet Devices 1 Primary 215.95' 15.0" x 28.0' long Culvert RCP, square edge headwall, Ke= 0.500 Outlet Invert= 215.10' S= 0.0304 T n= 0.013 Cc= 0.900 2 Device 1 216.00' 4.0"Vert. Orifice/Grate X 2.00 C= 0.600 3 Device 1 218.50' 8.0"Vert. Orifice/Grate X 2.00 C= 0.600 4 Device 1 221.15' 24.0" Horiz. Orifice/Grate Limited to weir flow C= 0.600 0237-Chatham Crossing 90-Year Design Storm Prepared by DK Engineering Associates H droCADO 6.00 sln 000815 © 1986-2001 Applied Microcomputer Systems 7/24/2003 Pond Pond: Detension Basin Hydrograph Plot i Inflow E 11.41 1 E[I • 1 cf`�fs f �i II IIII Primary ... 92= 10. ' S- 7- ...�.,i 1 �-r 6: 5 43 cfs EtF - { I ! 1 4-- 2- NO L 1- � 0" f F I E. 1 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) 0237-Chatham Crossing 10-Year Design Storm Prepared by DK Engineering Associates H droCAD®6.00 s/n 000815 O 1986-2001 Applied Microcomputer S sterns 7/24/2003 Pond Pos: Summary of Post Development Inflow = 11.87 cfs @ 12.22 hrs, Volume= 1.616 of Primary = 11.87 cfs @ 12.22 hrs, Volume= 1.616 af, Atten= 0%, Lag= 0.0 min Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Pond Pos: Summary of Post Development HOF(4Ar IVIII P l(A Inflow Primary �i�i /+ I 3 - t 1 VQ 7 cfs 12-. iT i 10: i 3 1. a 6= • I I I d �y„�"A 3i I I I ' 4_ r 3-- 2- ^" 0.:. I 5 6 7 8 9 10 11 1 12 1 1 13 14 15 16 17 18 19 20 Time (hours) CHATHAM CROSSING NORTH ANDOVER, MASSACHUSETTS POST-DEVELOPMENT 1 QQ-YEAR STORM EVENT DK ENGINEERING AsSOCIATEs Page 12 Printed: July 24, 2003 0237-Chatham Crossing 100-Year Design Storm Prepared by DK Engineering Associates HydroCAD®6.00. sln 000815 O 198.6-2001 Applied Microcomputer Systems 7/24/2003 Subcatchment Post-A: Post-Development Drainage Area "A" Runoff = 12.64 cfs @ 12.17 hrs, Volume= 1.046 of Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type III 24-hr Rainfall=6.40" Area (ac) CN Description 3.510 77 From Approved Report Tc Length Slope Velocity Capacity Description min feet ftlft ftlsec cfs 12.6 Direct Entry, From Approved Report Subcatchment Post-A: Post-Development Drainage Area "A" Fiydro�p'ap'h Not 14- W 11 Runoff - - -13- 12 64 cfs _ 1 i 12 N 8 � I u 6- 5 4{- 2-: r .. I I f w 0: r 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) i 0237-Chatham Crossing 100-Year Design Storm Prepared by DK Engineering Associates HdroCADV 6.00 s/n 000815 O 1986-2001 Applied Microcomputer Systems 7/24/2003 Subcatchment Post-B: Post-Development Drainage Area "B" i Runoff - 16.99 cfs @ 12.18 hrs, Volume= 1.465 of Runoff by SCS TR-20 method, UH=SCS, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs Type III 24-hr Rainfall=6.40" Area ac CN Description 4.270 82 From Approved Report Tc Length Slope Velocity Capacity Description min feet ft/ft ft/sec cfs 13.2 Direct Entry, From Approved Report Subcatchment Post-B: Post-Development Drainage Area "B" Hydrograph Plot N unoff M; 16 99 cfs 16 15= - - - - 14 12- r I 1 I , 6` 4. 3 3- " r 1 , 5 6 7 a 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) 0237-Chatham Crossing140-Year Design Storm 9 Prepared by DK Engineering Associates hl droCAD®6.00 s/n 000815 O 1986-2001 Applied Microcom uter stems 7/24/2003 Pond Pond; Detension Basin Inflow - 16,99 cfs @ 12.18 hrs, Volume= 1 A55 of Outflow - 8.30 cfs @ 12.46 hrs, Volume= 1.433 af, Atten= 51%, Lag= 16.9 min Primary - 8,30 cfs @ 12.46 hrs, Volume= 1.433 of Routing by Star Ind method, Time Span= 5.00-20.00 hrs, dt= 0.05 hrs i Peak Elev= 221.29' Storage= 18,931 cf Plug-Flow detention time= 50.9 min calculated for 1.429 of(98% of inflow) Storage and wetted areas determined by Prismatic sections Elevation Surf.Area 1nc.Store Cum.Store (feet) _ (sq-ft) (cubic-feet) (cubic-feet) 216.00 1,675 0 0 218.00 2,961 4,636 4,636 220.00 4,456 7,417 12,053 222.00 6,177 10,633 22,686 rimary OutFlow (Free Discharge) 1=Culvert 2=Orifice/Grate 3=Orifice/Grate =Orifice/Grate _ # Routing Invert Outlet Devices 1 Prima ry215.95 15.0 x 28.0 long Culvert RCP square edge headwall, Ke= 0.500 Outlet Invert= 215.10' S= 0.0304 7' n= 0.013 Cc= 0.900 2 Device 1 216.00' 4.0"Vert. Orifice/Grate X 2.00 C= 0.600 3 Device 1 218.50' 8.0"Vert. Orifice/Grate X 2.00 C= 0.600 4 Device 1 221.15' 24.0" Horiz. Orifice/Grate Limited to weir flow C= 0.600 0237-Chatham Crossing 100-Year Design Storm Prepared by DK Engineering Associates N droCAD®6.00 s/n 000815 © 1986-2001 Applied Microcomputer Systems 7/24/2003 Pond Pond: Detension Basin 3--Iy€feogm kiph Plot [ I I I _?Inflow 19, 9 6.99 Cfs ) JEf Primary 17i 16- r I 15 I I [ I I [ 14- 13•'� � I r I 12' 1 3 9- ' 8.30 cfs B - f „�� 1 l t J3 € I 4 iL 7: � 1 6 ` - r 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Time (hours) 0237-Chatham Crossing 100-Year Design Storm Prepared by DK Engineering Associates H droCAM 6.00 s/n 000815 © 1986-2001 Applied Microcomputer Systems 7/24/2003 Pond Pos: Summary of Post Development Inflow = 18.32 cfs @ 12.19 hrs, Volume= 2.479 of Primary = 18.32 cfs @ 12.19 hrs, Volume= 2.479 af, Men= 0%, Lag= 0.0 min Routing by Stor-Ind method, Time Span= 5.00-20.00 hrs, dt=0.05 hrs Pond Pos: Summary of Post Development Inflow 20 - - - ":1 Prtrnary 18 32 cfs 1 4 1 - 18'; 16 ; E 1. 15- x 13- 3 1 I I 1 I I 3A. 10 ' I I 5- 4 2 e y . 0.6 6 7 8 9 10 11 112 13 14 15 16 17 18 19 20 Time (hours) i i O� �C ro / RIM = 221.27 1 PEX. DMH Vg� �� �, ��P ��, INV. IN = 217.97 (12") 1 l / `ti r' r'� INV. IN = 217.91 (15") 1 INV. OUT = 217.77 (15") 1 INv. 4 0 �2a a 37 L.F. - 15" RCP S = 0.030 kP 01, ��O cry fCO 0 \\ 0 0 J \ Di JJ J O LOT 2 Ov 1 LOT 3 CHATHAM CROSSING North Andover, Massachusetts 1 Detention Basin Design Plan ' PREPARED FOR Cormier Andover Construction Corp. SCALE: 59 Chandler Circle I Andover,h4assachusetls 1"= 20' { ASSESSORS MAP N LOT 4 I� DKEngtueelhlgAssaetates SCALE: DATES:a6113/G/13103 ,"Indian Rock'Road Suite 7 DR,BY:Dr: Whrdham,Nil 03087-1656 JOB NO.:0237 IM Tc1(603)899.8516—Fat(603)898.8497 si FEET:i"r l NEENAHR-4351-D BEEHIVE GRATE OR APPROVED EQUAJ, RIM=221.15 CONC.OR MORTAR 3"(MIN-) 24"+I SQ, MORTAR ALL JOINTS 8"MIN. OPENING , Lyf � 2-8"DIA.VERTICAL ORIFICE 4'-0"DIA. INV.IN=218.50 > No-4 REINFORCING BARS SET O 4"(MIN.)INTO STRUCTURE w (MAX.2"OPENING TYP.) 15"RCP I 2-4"DIA.VERTICAL ORIFICE INV.IN 216.00 DISCHARGE PIPE INV.OUT=215.95 DISCHARGE ACCEPTABLE SUB-GRADE DETENTION BASIN OUTLET STRUCTURE CHATHAM CROSSING N.T.S. North Andover,Massachusetts Detention Basin Outlet Structure PREPARED FOR Cormier Andover Constmorion Corp. 59 Chandler Circle Andover,M=achuscvs ASSESSORS MAP# LOT# DK Engineering Associates SCALZNZ.S. DATE:07t-12103 STladiaa Rock Road—Suite 7.. DR.BY:D.K. Wwdb2m.NH 03087-1556 JOB NO,0237 � � 7ef(603)S98-S516-FmT(693)89S— 497 I SHEET:I of I ..................... .............................. ......................... ................................. --------------------...................