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HomeMy WebLinkAbout2007-10-08 Stormwater Runoff CalculationsPrepared for: Prepared by: STORM WATER RUNOFF CALCULATIONS Best Bay Oak Park Heights, MN Project # 2007-1158 WCL Associates, Inc. 4931 West 35 Street, Suite 200 St. Louis Parks, MN 55416 Westwood Professional Services, Inc. 7699 Anagram Drive Eden Prairie, MN 55344 Phone (952) 937-5150, Fax (952) 937-5822 October 8, 2007 SUMMARY The attached storm water runoff and ponding calculations are based on The Soil Conservation Service Synthetic Unit Hydrograph Method incorporated into the software program HydroCAD Version 8.00; HydroCAD Software Solutions LLC. SITE BACKGROUND The proposed Best Buy site is located in the Brown Creek Watershed District and discharges storm water into the regional stormwater management facility adjacent and west of the proposed construction and within the site's parcel. It can be found at the intersection of 60 Street North and Krueger Lane, 3/ mile east of the County Road 5 and County Road 36 intersection in Oak Park Heights, Minnesota. The existing site is currently undeveloped with slopes of 2 to 4 percent in the main area. The slopes to the north and west, along 60 Street North and the existing pond, are roughly 3:1 and will remain during and after construction. The soils are type `B' soils, including SM, SP and SC soil classifications. The proposed infiltration will be over SM and SP soils which have infiltration rates of 0.6 inlhr and 0.8 inlhr, respectively, per the Brown Creek's Watershed District's Rules. The original conditions under which the existing regional stormwater management facility was designed required infiltration for the additional drainage volume from the 1.5 -Year (2.6 ") 24 hour storm event. The current watershed rules require infiltration for the additional drainage volume from the 2 -Year (2.8') 24 hour storm event. The proposed drainage system meets the current infiltration criteria by adding additional underground storage volume infiltration within the Best Buy parking area. RATE CONTROL AND TREATMENT The original regional stormwater management plan has been designed to infiltrate the drainage from the 1.5 -Year (2.6 ") 24 hour storm event from the site based on an impervious area of 85 percent and an overall curve number of 92. A "Revised Cooperative Agreement" has been recorded with the City of Stillwater, the City of oak Park Heights and the Brown's Creek Watershed District (BCWD). Section 4.3 of said agreement generally states that an applicant within the development area will receive compliance credit for the degree of volume control that the Trout Stream Mitigation Project (TSMP) is providing. The volume control credit has been calculated based upon the rules in affect at the time of the agreement, which is based on the volume increase from a 1.5 -year (2.6 ") 24 hour storm event. The existing site drainage is split into three areas. The North drainage flows into 60 Street North's right of way ditch which eventually drains into the existing pond. The South drainage flows into existing storm sewer and eventually into the pond while the West drainage flows directly into the existing pond. The following table describes the runoff conditions of each drainage area. * WESTWOOD PROFESSIONAL SERVICES, INC. (952) 937 -5150 Storwater Discharge Table Drainage Areas Pre - Settlement Original Post - Development Actual Post - Development 24 -Hour Event Runoff (cfs) Volume (ac -ft) Runoff (cfs) Volume (ac -ft) Runoff (cfs) Volume (ac -ft) 1.5 -Year (2.6 1 0.19 0.064 1235 0.827 N/A N/A 2 -Year (2.8 ") 0.42 0.087 N/A N/A 13.80 0.914 10 -Year (4.2 ") 3.93 0.328 22.60 1.534 22.60 1.534 100 -Year (6.0 ") 11.16 0.777 33.79 2.349 33.79 2.349 Existing Drainage Discharge Conditions (See Preliminary Drainage Map) Drainage Areas DRA -P1 (North) DRA -P2 (West) DRA -P3 (South) Total 24 -Hour Event Runoff (cfs) Volume (ac -ft) Runoff (cfs) Volume (ac-ft) Runoff (cfs) Volume (ac -ft) Runoff (cfs) Volume (ac -ft) 2 -Year (2.8h1) 0.32 0.054 0.16 0.027 0.15 0.025 0.63 0.106 10 -Year. (4.211) 3.00 0.201 1.51 0.101 1.41 0.094 5.92 0.396 100 -Year (6.0 9 8.25 0.476 4.16 0.240 3.87 0.223 16.28 0.939 SUMMARY VOLUME CALCULATIONS The current volume requirement is based on the 2 -Year (2.8') 24 hour storm event using the developed site's curve number. The discharge rates and volumes for the 1.6 -year, 2 -year, 10- year and 100 -year events are listed in the Stormwater Discharge Table for the Pre - settlement, Original and Proposed Post - development conditions. The in-depth calculations can be found in the HydroCAD reports in the Appendices. Volume Credit: (1.5 -Year Pond Post - Development Vol.) -(1.5 -Year Pre - Settlement Vol.) = 0.763 af Required: (2 -Year Actual Post - Development Vol.) -(2 -Year Pre - Settlement Vol.) = 0.827 af Difference: 0.827 ac ft need to be infiltrated under the current rules. The existing Agreement gives a credit of 0.763 ac ft. The difference is 0.064 ac ft or 2790 cf. The original volume infiltrated into the existing pond under the old rules is 0.763 ac -ft. The infiltration needed under the new rules is 0.827 ac -ft. Because 0.763 ac -ft of storage is already being infiltrated, 0.064 ac -ft or 2,790 cf is required for the proposed development. StormTech chambers have been added under the parking on the west side of the building near the pond to capture the first flush from the main rooftop drainage. A flow - splitter manhole conveys the rooftop drainage into two outflow HDPE pipes. One 12 inch HDPE pipe with a lower invert flows into the StormTech chambers until the chambers fill up to the invert of the second outflow pipe. The second pipe outfalls into the existing stormwater management facility. A detail of the splitter manhole can be found in the following page. * WESTWOOD PROFESSIONAL SERVICES, INC. (952) 937 -5150 SUMMARY SUMMARY The regional pond facility provides rate and quality control for the site. The proposed StormTech system will provide additional infiltration volume to meet the current BCWD rules. (See following pages for the StormTech details.) * WESTWOOD PROFESSIONAL SERVICES, INC. (952) 937 -5150 T CN n SUMMARY z 0 0 t N A C rl u . co w s $ 'Ai id 0 t„ id I lo 00*- WN fun ni w3mgt. (w u ) Lk gi a 0 8 3-85 in ( 981111 4 NIA 0.50 in (13 mm) 7.70 in (198 rnrn) 117-50 in (318 min)! NIA (Luw a) ui o-' v/t,€ OULU 060 ui Gel YIN (um ) iTi ao co) ur 9E'01 ( ET) u! - > E96 ui 9E"i3 VI 0 in) w acre zit, Lir uzo t (Luul 1.0 u Oal Y u U .L OI (um S)wa "o VN I (mu Crtlj ui 9Y6 I .a g 5 [(u [Le L 06'01 kwwEL£)w04r1 bum cis) U 0E•10 kunu L90 U10t 91 kw. bat) w lays [(u aas) ul OLBI ww aas) u 04.•61 b unuaLi)WG9 . 9 1 WEU t 3ZZ1S 3d €d =tuiu ost.} n! 9 (tau oce) Lit (unx ooc) u! 411121 (..1 six} ui {LULU 090 9 i• (tuul oo►) u s� onin toe) u to ��sir�ra DAL 08 09L 08 [ 00108 UM 08 00108 DM 08 Ott 08 DM CS 1390B.130trt 1Zt3d90PZ0S 1St3d30PL0S 13S1.3830#1OS 11308301 38 J 138 I3830PL3S SC74OEPE24B 1 Z 0 cf) U w 0 0 J Q 0 .416 ti 4 :i d 1 0 13' .! h 2 g n hl SUMMARY Existing Conditions * WESTWOOD PROFESSIONAL SERVICES, INC. (952) 937 -5150 L Subcat Drainage Area DRA-P1 Drainage Area DRA-P2 Drainage Area DRA-P3 Reach Pon Drainage Diagram for 07 Storm Prepared by Westwood Professional Services, Inc. 10/8/2007 HydroCAD® 8.00 s/n 003363 © 2006 HydroCAD Software Solutions LLC 07 -09 -27 Storm Prepared by Westwood Professional Services, Inc. HydroCAD® 8.00 s/n 003363 © 2006 HydroCAD Software Solutions LLC Subcatchment 7S: Drainage Area DRA -P1 Runoff = 0.14 cfs a@ 12.11 hrs, Volume= 0.039 af, Depth= 0.14" Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Type 11 24 -hr 1,5 -yr Rainfall =2.60" Area ac CN Description 3.410 3.410 57 Tc Length Slope Velocity Capacity Description min feet ftlft ) (ft/sec) Jcfs 10.0 Runoff = 0.07 cfs @ 12.11 hrs, Volume= Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type 11 24 -hr 1.5 -yr Rainfall =2.60" Area ac CN Description 1.720 1.720 57 Tc Length Slope Velocity Capacity Description min (feet) (ft/ft) (ft/sec) (cfs) 10.0 Subcatchment I I S: Drainage Area DRA -P3 Runoff -- 0.07 cfs @ 12.11 hrs, Volume= 0.018 af, Depth= 0.14" Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Type 11 24-hr 1.5 -yr Ra i nfa I I =2.60" Area (ac) CN Description 1.600 57 Pervious Area Subcatchment 105: Drainage Area DRA -P2 Pervious Area 1.600 Pervious Area Direct Entry, Direct Entry, Existing Conditions Type 11 24 1.5 - yr Rainfall=2.60" Page 2 10/8/2007 0.020 af, Depth= 0.14" Tc Length Slope Velocity Capacity Description (min) (feet) (ft /ft) (ft /sec) (cfs) 10.0 Direct Entry, 07 -09 -27 Storm Prepared by Westwood Professional Services, Inc. HydroCAD® 8.00 s/n 003363 © 2006 HydroCAD Software Solutions LLC Runoff = 0.32 cfs @ 12.09 hrs, Volume= Area ac CN Descri • tion 3.410 57 3.410 Pervious Area Runoff = 0.16 cfs @ 12.09 hrs, Volume= Area (ac) CN Description 1.720 57 1.720 Pervious Area Runoff = 0.15 cfs @ 12.09 hrs, Volume= Area (ac) CN Description 1 .600 57 1 .600 Pervious Area Subcatchment 7S: Drainage Area DRA -P1 Runoff by SCS TR-20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Type 11 24 -hr 2 -yr Rainfall =2.80" Tc Length Slope Velocity Capacity Description (min) (feet) (ft /ft) (ft /sec) (cfs) 10.0 Direct Entry, Subcatchment 19S: Drainage Area DRA -P2 Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Type 11 24-hr 2 -yr Rainfall =2.80" Tc Length Slope Velocity Capacity Description (min) (feet) (ft /ft) (ft /sec) (cfs) 10.0 Direct Entry, Subcatchment IIS: Drainage Area DRA -P3 Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Type 11 24 -hr 2 -yr Rainfal1=2.80" Tc Length Slope Velocity Capacity Description (min) (feet) (ft /ft) (ft /sec) (cfs) 10.0 Direct Entry, Existing Conditions Type 1124 - hr 2-yr Rainfall =2.84" Page 3 1 0/8/2007 0.054 af, Depth= 0.19" 0.027 af, Depth= 0.19" 0.025 af, Depth= 0.19" 07 -09 -27 Storm Prepared by Westwood Professional Services, Inc. HydroCAD® 8.00 sin 003363 © 2006 HydroCAD Software Solutions LLC Subcatchment 7S: Drainage Area DRA -P1 Runoff = 3.00 cfs @ 12.04 hrs, Volume= 0.201 af, Depth= 0.71" Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Type 11 24 -hr 10 -yr Rainfall =4.20" Area (ac) CN Description 3.410 57 3.410 Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft /ft) (ft /sec) (cfs) 10.0 Direct Entry, Runoff = 1.51 cfs @ 12.04 hrs, Volume= Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Type 11 24 -hr 10 -yr Rainfall= 4.20" Area (ac) CN Description 1.720 57 1.720 Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft /ft) (ft /sec) (cfs) 10.0 Direct Entry, Subcatchment 11S: Drainage Area DRA -P3 Runoff = 1.41 cfs a@ 12.04 hrs, Volume= 0.094 af, Depth= 0.71" Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Type 11 24 -hr 10 -yr Rainfall =4.20" Area (ac) CN Description 1.600 57 1.600 Pervious Area Subcatchment 19S: Drainage Area DRA -P2 Tc Length Slope Velocity Capacity Description (min) (feet) (ft /ft) (ft/sec) (cfs) 10.0 Direct Entry, Existing Conditions Type 1124 - hr 10 yr Rainfall =4.20" Page 4 1018/2007 0.101 af, Depth= 0.71" Existing Conditions 07 - - Storm Type 11 24-hr 100-yr Rainfall =6.00" Prepared by Westwood Professional Services, Inc. Page 5 HydroCAD® 8.00 s/n 003363 © 2006 HydroCAD Software Solutions LLC 10/8/2007 Runoff = 8.25 cfs @ 12.03 hrs, Volume= Area ac) CN Description 3.410 57 3.410 Pervious Area Runoff = 4.16 cfs @ 12.03 hrs, Volume= Area (ac) CN Description 1.720 57 1.720 Pervious Area Runoff = 3.87 cfs © 12.03 hrs, Volume= Area (ac) CN Description 1.600 57 1.600 Pervious Area Subcatchment 7S: Drainage Area DRA -Pl Tc Length Slope Velocity Capacity Description (min) (feet) (ft /ft) (ft /sec) (cfs) 10.0 Direct Entry, Tc Length Slope Velocity Capacity Description ( min) feet ) (ft/ft) ( cfs 10.0 Direct Entry, Tc Length Slope Velocity Capacity Description (min) (feet) (ft /ft) (ft /sec) (cfs) 10.0 Direct Entry, 0.476 af, Depth= 1.68" Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Type 11 24 -hr 100 -yr Rainfali=6.00" Subcatchment I0S: Drainage Area DRA -P2 0.240 af, Depth= 1.68" Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Type II 24 -hr 100 -yr Rainfall =6.00" Subcatchment 11S: Drainage Area DRA -P3 0.223 af, Depth= 1.68" Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Type 11 24 - 100 -yr Rainfall =6.00" SUMMARY Proposed Conditions + WESTWOOD PROFESSIONAL SERVICES, INC. (952) 937 -5150 P SW r „ r 4 INVIMINIMIMM %%. Site Drainage Direct o Pond (excluding rooftop drainage) < Subca ) < Reach Roof Drainage Pon < Original Conditions Proposed Conditions Link CB 5P Splitter Manhole I I I NN, 7R Total Drainage to Pond Presettlement Conditions 6P Stormtech Drainage Diagram for 07 -09-27 Storm Prepared by Westwood Professional Services, Inc. 10/8/2007 HydroCAD® 8.00 s/n 003363 © 2006 HydroCAD Software Solutions LLC 07 -09 -27 Storm Prepared by Westwood Professional Services, Inc. HydroCAD® 8.00 sin 003363 © 2006 HydroCAD Software Solutions LLC Subcatchment 15: Original Conditions Runoff = 12.55 cfs @ 12.07 hrs, Volume= 0.827 af, Depth= 1.79" Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Type 11 24 -hr 1.5 -yr Rainfall =2.60" Area (ac) CN Description 5.560 92 Urban commercial, 85% imp, HSG B 0.834 Pervious Area 4.726 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft /ft) (ft/sec) (cfs) 15.0 Direct Entry, Area (ac) CN Description 5.560 57 presettlement 5.560 Pervious Area Tc Length Slope Velocity Capacity min feet ft /ft ft /sec cfs 15.0 Subcatchment 3S: Presettlement Conditions Runoff = 0.19 cfs @ 12.21 hrs, Volume= Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt = 0.05 hrs Type 11 24 -hr 1.5 -yr Rainfall =2.60" Description 4.612 98 Paved parking & roofs 0.948 61 >75% Grass cover, Good, HSG B 5.560 92 Weighted Average 0.948 Pervious Area 4.612 impervious Area Direct Entry, Subcatchment 4S: Proposed Conditions Runoff = 12.55 cfs a@ 12.07 hrs, Volume= 0.827 af, Depth= 1.79" Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Type 11 24 -hr 1.5-yr Rainfall =2.60" ____ Area (a C N Description Proposed Conditions Type 11 24 1.5 - yr Rainfall =2.60" Page 2 10/8/2007 0.064 af, Depth= 0.14" 07 -09 -27 Storm Prepared by Westwood Professional Services, Inc. HydroCAD® 8.00 sin 003363 © 2006 HydroCAD Software Solutions LLC Tc Length Slope Velocity Capacity Description (min) (feet) (ft /ft) (ft/sec) (cfs) 15.0 Direct Entry, Runoff Subcatchment 8S: Site Drainage Directly to Pond (excluding rooftop drainage) 14.68 cfs a 12.01 hrs, Volume= 0.827 af, Depth= 1.79" Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Type 11 24 -hr 1.5 -yr Rainfall= 2.60" Area (ac) CN Description 4.612 98 impervious area not excluding main rooftop 0.948 61 >75% Grass cover, Good, HSG B 5.560 92 Weighted Average 0.948 Pervious Area 4.612 Impervious Area Tc Length Slope Velocity Capacity Description min) (feet) (ft /ft) (ft /sec) (cfs 10.0 Runoff = 2.41 cfs @ 11.98 hrs, Volume= Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Type!! 24 -hr 1.5 -yr Rainfall =2.60" Area ac CN Description 0.694 98 Area of main roof 0.694 Impervious Area Subcatchment 9S: Roof Drainage Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft /sec) (cfs) 7.0 Routing by Sim -Route method, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Proposed Conditions Type 1124 - hr 1.5 yr Rainfall =2.60" Page 3 10/8/2007 Direct Entry, area of site excluding rooftop Direct Entry, rooftop 0.137 af, Depth= 2.37" Reach 7R: Total Drainage to Pond Inflow = 14.66 cfs © 12.01 hrs, Volume= 0.910 of Outflow -- 14.66 cfs a© 12.06 hrs, Volume= 0.910 af, Atten= 0 %, Lag= 3.0 min 07 -09 -27 Storm Prepared by Westwood Professional Services, Inc. HydroCAD® 8.00 s/n 003363 © 2006 HydroCAD Software Solutions LLC Device Routing Invert Outlet Devices Device Routing #1 Primary Pond 5P: Sp litter Manhole Inflow = 5.75 cfs a@ 12.05 hrs, Volume= 3.098 of Outflow = 5.75 cfs a@ 12.10 hrs, Volume= 3.098 af, Atten= 0 %, Lag= 3.0 min Primary = 4.43 cfs © 11.95 hrs, Volume= 3.016 af Secondary = 3.60 cfs a@ 12.25 hrs, Volume= 0.082 of Routing by Sim -Route method, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Peak Elev= 921.54' a@ 12.24 hrs #1 Primary 918.00 12.0" x 4M' long Culvert RCP, sq.cut end projecting, Ke= 0.500 Outlet Invert= 91 7.98' S= 0.0050 '1' Cc= 0.900 n= 0.013 #2 Secondary 920.50' 15.0 " x 27.0' long Culvert RCP, sq.cut end projecting, Ke= 0.500 Outlet Invert= 920.00' S= 0.0185 '1' Cc= 0.900 n= 0.013 Primary OutFlow Max =4.51 cfs @ 11.95 hrs HW= 920.57' TW= 919.15' (Dynamic Tailwater) L1= Culvert (Inlet Controls 4.51 cfs © 5.75 fps) Secondary OutFlow Max =3.46 cfs @ 12.25 hrs HW= 921.48' TW =0.00' (Dynamic Tailwater) T-2= Culvert (Inlet Controls 3.46 cfs © 3.36 fps) Invert Outlet Devices Pond 6P: Stormtech Inflow = 4.43 cfs a© 11.95 hrs, Volume= 3.016 of Outflow = 4.29 cfs @ 12.20 hrs, Volume= 2.961 af, Atten= 3 %, Lag= 14.7 min Primary = 4.29 cfs @ 12.20 hrs, Volume= 2.961 af Routing by Sim -Route method, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Peak Elev = 921.51' © 12.18 hrs Surf.Area= 1 ,282 sf Storage= 3,302 cf Plug -Flow detention time 39.4 min calculated for 2.958 af (98% of inflow) Center -of -Mass det. time 19.1 min ( 1,775.0 - 1,755.9 ) Proposed Conditions Type 11 24 1.5 yr Rainfall =2.60" Page 4 1018/2007 Volume Invert Avail.Storage Storage Description #1 918.00' 1,654 cf 44.6"W x 30.0 "H x 7.12'L StormTech SC-740x 36 Inside #2 #2 917.00' 3,440 cf 20.00'W x 64.08'L x 8.00'H Prismatoid 10,253 cf Overall - 1,654 cf Embedded = 8,599 cf x 40.0% Voids 5,093 cf Total Available Storage 918.00' 12.0" x 4.0' long Culvert RCP, square edge headwall, Ke= 0.500 Outlet Invert= 917.98' S= 0.0050 '1' Cc= 0.900 n= 0.013 Primary OutFlow Max =2.88 cfs @ 12.20 hrs HW= 921.42' TW= 920.84' (Dynamic Tailwater) t- 1= Culvert (Inlet Controls 2.88 cfs © 3.67 fps) 07 -09-27 Storm Prepared by Westwood Professional Services, Inc. HydroCAD® 8.00 sin 003363 © 2006 HydroCAD Software Solutions LLC Subcatchment 1S: Original Conditions Runoff = 13.80 cfs a@ 12.07 hrs, Volume= 0.914 af, Depth= 1.97" Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Type 11 24 -hr 2 -yr Rainfall =2.80" Area (ac) CN Description 15.0 5.560 92 Urban commercial, 85% im., HSG B 0.834 4.726 Pervious Area Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft/sec) (cfs) Runoff = 0.42 cfs @ 12.16 hrs, Volume= Direct Entry, Subcatchment 3S: Presettlement Conditions 0.087 af, Depth= 0.19" Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Type 11 24 -hr 2 -yr Rainfall =2.80" Area (ac) CN Description 5.560 57 presettlement 5.560 Pervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft /ft) (ft /sec) (cfs) 15.0 Direct Entry, Subcatchment 4S: Proposed Conditions Runoff = 13.80 cfs a© 12.07 hrs, Volume= 0.914 af, Depth= 1.97" Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Type 11 24 -hr 2 -yr Rainfall =2.80" Area (ac) CN Description 4.612 98 Paved parking & roofs 0.948 61 >75% Grass cover, Good, HSG B 5.560 92 Weighted Average 0.948 Pervious Area 4.612 Impervious Area Proposed Conditions Type 1124 - hr 2 - yr Rainfall 2.80" Page 5 1 0/812007 07 -09 -27 Storm Prepared by Westwood Professional Services, Inc. HydroCAD® 8.00 sln 003363 © 2006 HydroCAD Software Solutions LLC Tc Length Slope Velocity Capacity Description (min) (feet) (ft /ft) (ft /sec) (cfs) 15.0 Direct Entry, Subcatchment 8S: Site Drainage Directly to Pond (excluding rooftop drainage) Runoff = 16.14 cfs © 12.01 hrs, Volume= 0.914 af, Depth= 1.97" Runoff by SCS TR -20 method, UH= SCS, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Type 11 24 -hr 2 -yr Rainfall =2.80" Area (ac) CN Description 4.612 98 impervious area not excluding main rooftop 0.948 61 >75% Grass cover, Good, HSG B 5.560 92 Weighted Average 0.948 Pervious Area 4.612 impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft /sec) (cfs) 10.0 Runoff = 2.60 cfs @ 11.98 hrs, Volume= Subcatchment 9S: Roof Drainage Area (ac) CN Description 0.694 98 Area of main roof 0.694 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft /ft) (ft /sec) (cfs) 7.0 Direct Entry, rooftop Direct Entry, area of site excluding rooftop 0.149 af, Depth= 2.57" Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Type 11 24 -hr 2 -yr Rainfall=2.80" Reach 7R: Total Drainage to Pond Proposed Conditions Type 1124 - hr 2 Rainfall =2.80" Page 6 1 0/8/2007 Inflow = 1 7.99 cfs a@ 12.03 hrs, Volume= 1.008 of Outflow = 17.99 cfs a@ 12.08 hrs, Volume= 1.008 af, Atten= 0 %, Lag= 3.0 min Routing by Sim -Route method, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs 07-09-27 Storm Prepared by Westwood Professional Services, Inc. HydroCAD® 8.00 sin 003363 © 2006 HydroCAD Software Solutions LLC Inflow Outflow Primary = Secondary = 6.37 cfs a@ 12.00 hrs, Volume= 6.37 cfs a@ 12.05 hrs, Volume= 4.23 cfs a@ 11.90 hrs, Volume= 4.84 cfs a@ 12.20 hrs, Volume= Pond 5P: Splitter Manhole Routing by Sim -Route method, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Peak Elev= 921.82' © 12.19 hrs Proposed Conditions Type 1124 - hr 2 Rainfall =2.80" Page 7 10/8/2007 3.119af 3.119 af, Atten= 0 %, Lag= 3.0 min 3.025 af 0.094 of Device Routing Invert Outlet Devices #1 Primary 918.00' 12.0" x 4.0' long Culvert RCP, sq.cut end projecting, Ke= 0.500 Outlet Invert= 917.98' S= 0.0050 '1' Cc= 0.900 n= 0.013 #2 Secondary 920.50' 15.0" x 27.0' long Culvert RCP, sq.cut end projecting, Ke= 0.500 Outlet Invert= 920.00' S= 0.0185 '1' Cc= 0.900 n= 0.013 Primary OutFlow Max =4.45 cfs @ 11.90 hrs HW= 920.45' TW= 919.07' (Dynamic Tailwater) t- 1= Culvert (Inlet Controls 4.45 cfs @ 5.66 fps) Secondary OutFlow Max =4.66 cfs @ 12.20 hrs HW= 921.74' TW =0.00' (Dynamic Tailwater) - 2= C ulvert (Inlet Controls 4.66 cfs @ 3.80 fps) Inflow Outflow Primary Routing by Sim -Route method, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Peak Elev= 921.83' © 12.14 hrs Surf.Area= 1,282 sf Storage= 3,467 cf Plug -Flow detention time 39.5 min calculated for 2.982 af (99% of inflow) Center -of -Mass det. time= 23.6 min ( 1,773.1 - 1,749.5 ) Volume Invert #1 918.00' #2 917.00' Device Routing #1 Primary = 4.23 cfs @ 11.90 hrs, Volume= = 4.77 cfs @ 12.15 hrs, Volume= = 4.77 cfs @ 12.15 hrs, Volume= Pond 6P: Stormtech 3.025 af 2.982 af, Atten= 0 %, Lag= 14.8 min 2.982 af Avail.Storage Storage Description 1,654 cf 44.6 "W x 30.0 "H x 7.12'L StormTech SC -740x 36 Inside #2 3,440 cf 20.00'W x 64.08'L x 8.00'H Prismatoid 10,253 cf Overall - 1,654 cf Embedded = 8,599 cf x 40.0% Voids 5,093 cf Total Available Storage Invert Outlet Devices 918.00' 12.0" x 4.0' long Culvert RCP, square edge headwall, Ke= 0.500 Outlet Invert= 917.98' 5= 0.0050 '1' Cc= 0.900 n= 0.013 Primary OutFlow Max =3.39 cfs © 12.15 hrs HW= 921.77' TW= 920.97' (Dynamic Tailwater) L1= Culvert (inlet Controls 3.39 cfs @ 4.32 fps) 07-09-27 Storm Prepared by Westwood Professional Services, Inc. HydroCAD® 8.00 s/n 003363 © 2006 HydroCAD Software Solutions LLC Subcatchment 'IS: Original Conditions Runoff = 22.60 cfs a@ 12.06 hrs, Volume= 1.534 af, Depth= 3.31" Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Type 11 24 -hr 10 -yr Rainfall= 4.20" Area (ac) CN Description 5.560 92 Urban commercial, 85% imp, HSG B 0.834 Pervious Area 4.726 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft /sec) (cfs) 15.0 Direct Entry, Subcatchment 3S: Presettlement Conditions Runoff = 3.93 cfs @ 12.10 hrs, Volume= Area (ac) CN Description 5.560 57 presettlement 5.560 Pervious Area Tc Length Slope Velocity Capacity Description Amin) (feet) (ft /ft) (ft /sec) (cfs) 15.0 Direct Entry, Proposed Conditions Type 11 24 10 - yr Rainfall=4.20" Page 8 1 0/8/2007 0.328 af, Depth= 0.71" Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Type 11 24 -hr 10 -yr Rainfall= 4.20" Subcatchment 4S: Proposed Conditions Runoff = 22.60 cfs a© 1 2.06 hrs, Volume= 1 .534 af, Depth= 3.31" Runoff by SCS TR-20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Type 11 24-hr 10 -yr Rainfall =4.20" Area (ac) CN Description 4.612 98 Paved parking & roofs 0.948 61 >75% Grass cover, Good, HSG B 5.560 92 Weighted Average 0.948 Pervious Area 4.612 Impervious Area 07 -09 -27 Storm Prepared by Westwood Professional Services, Inc. HydroCAD® 8.00 s/n 003363 © 2006 HydroCAD Software Solutions LLC Tc Length Slope Velocity Capacity Description (min) (feet) (ft /ft) (ft /sec) (cfs) 15.0 Direct Entry, Subcatchment 8S: Site Drainage Directly to Pond (excluding rooftop drainage) Runoff = 26.33 cfs ac 1 2.01 hrs, Volume= 1 .534 af, Depth= 3.31" Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt = 0.05 hrs Type II 24 -hr 10 -yr Rainfall =4.20" Area (ac) CN Description 4.612 98 impervious area not excluding main rooftop 0.948 61 >75% Grass cover, Good, HSG B 5.560 92 Weighted Average 0.948 Pervious Area 4.612 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft /ft) (ft /sec) (cfs) 10.0 Runoff = 3.94 cfs @ 11.98 hrs, Volume= Area ac CN Description Proposed Conditions Type 11 24 1O - yr Rainfa11 =4.20" Page 9 10/8/2007 Direct Entry, area of site excluding rooftop Subcatchment 9S: Roof Drainage 0.229 af, Depth= 3.96" Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt = 0.05 hrs Type 11 24 -hr 10-yr Rainfall= 4.20" 0.694 0.694 98 Area of main roof Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft /ft) (ft /sec) (cfs) 7.0 Direct Entry, rooftop Reach 7R: Total Drainage to Pond Inflow = 27.10 cfs a© 12.05 hrs, Volume = 1 .708 of Outflow = 27.10 cfs a@ 12.10 hrs, Volume= 1 .708 af, Atten= 0 %, Lag= 3.0 min Routing by Sim -Route method, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs 07 -09 -27 Storm Prepared by Westwood Professional Services, Inc. HydroCAD® 8.00 sin 003363 © 2006 HydroCAD Software Solutions LLC #1 918.00' #2 917.00' Device Routing #1 Primary Pond 5P: Splitter Manhole Inflow -- 7.27 cfs @ 11.90 hrs, Volume= 3.321 af Outflow = 7.27 cfs © 11.95 hrs, Volume= 3.321 af, Atten= 0 %, Lag= 3.0 min Primary = 3.56 cfs @ 11.80 hrs, Volume= 3.147 af Secondary = 6.58 cfs a@ 12.10 hrs, Volume= 0.174 of Routing by Sim -Route method, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Peak Elev= 922.36' a@ 12.10 hrs Device Routing Invert Outlet Devices #1 Primary 918.00' 12.0" x 4.0' long Culvert RCP, sq.cut end projecting, Ke= 0.500 Outlet Invert= 91 7.98' S= 0.0050 '1' Cc= 0.900 n= 0.013 #2 Secondary 920.50' 15.0" x 27.0' long Culvert RCP, sq.cut end projecting, Ke= 0.500 Outlet Invert= 920.00' S= 0.0185 '1' Cc= 0.900 n= 0.013 Primary OutFlow Max =4.25 cfs @ 11.80 hrs HW= 920.94' TW= 919.68' (Dynamic Tailwater) L1= Culvert (Inlet Controls 4.25 cfs @ 5.42 fps) Secondary OutFlow Max =6.36 cfs @ 12.10 hrs HW= 922.28' TW =0.00' (Dynamic Tailwater) �L2= Culvert (Inlet Controls 6.36 cfs @ 5.18 fps) Pond 6P: Stormtech Inflow = 3.56 cfs a@ 11.80 hrs, Volume= 3.147 of Outflow = 4.51 cfs a@ 12.05 hrs, Volume= 3.092 af, Atten= 0 %, Lag= 14.8 min Primary = 4.51 cfs a@ 12.05 hrs, Volume= 3.092 af Routing by Sim -Route method, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Peak Elev= 922.33' a@ 12.05 hrs Surf.Area= 1,282 sf Storage= 3,724 cf Invert Outlet Devices Proposed Conditions Type 1124 - hr 1O yr Rainfall =4.20" Page 10 1 0/8/2007 Plug -Flow detention time 39.6 min calculated for 3.088 af (98% of inflow) Center -of -Mass det. time= 19.3 min ( 1,727.4 - 1,708.1 ) Volume Invert Avail.Storage Storage Description 1,654 cf 44.6 "W x 30.0 "H x 7.12'L StormTech SC -740x 36 Inside #2 3,440 cf 20.00'W x 64.08'L x 8.00'H Prismatoid 10,253 cf Overall - 1,654 cf Embedded = 8,599 cf x 40.0% Voids 5,093 cf Total Available Storage 918.00' 12.0" x 4.0' long Culvert RCP, square edge headwall, Ke= 0.500 Outlet Invert= 917.98' S= 0.0050 '1' Cc= 0.900 n= 0.013 Primary OutFlow Max =3.75 cfs © 12.05 hrs HW= 922.33' TW= 921.35' (Dynamic Tailwater) t-1= Culvert (Inlet Controls 3.75 cfs © 4.77 fps) 07 -09 -27 Storm Prepared by Westwood Professional Services, Inc. HydroCAD® 8.00 sin 003363 © 2006 HydrocAD Software Solutions LLC Subcatchment '1 S: Original Conditions Runoff = 33.79 cfs © 12.06 hrs, Volume= 2.349 af, Depth= 5.07" Runoff by SCS TR -20 method, UH =SCS, Time Span = 0.00 -48.00 hrs, dt= 0.05 hrs Type 11 24 -hr 100 -yr Rainfall =6.00" Area (ac) CN Description 5.560 92 Urban commercial, 85% imp, HSG B 0.834 Pervious Area 4.726 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft /sec) (cfs) 15.0 Runoff Area (ac) CN Description Direct Entry, Subcatchment 3S: Presettlement Conditions 11.16 cfs a@ 12.09 hrs, Volume = 0.777 af, Depth= 1.68" Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type 11 24 -hr 100 -yr Rainfall =6.00" 5.560 57 • resettlement Proposed Conditions Type 1124 - hr 100 Rainfall =6.O0" Page 11 10/8/2007 5.560 Pervious Area Tc Length Slope Velocity Capacity Description min feet ftlft ft /sec cfs 15.0 Direct Entry, Subcatchment 45: Proposed conditions Runoff = 33.79 cfs a© 12.06 hrs, Volume= 2.349 af, Depth= 5.07" Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Type 11 24 -hr 100 -yr Rainfall= 6.00" Area (ac) CN Description 4.612 98 Paved parking & roofs 0.948 61 >75% Grass cover, Good, HSG B 5.560 92 Weighted Average 0.948 Pervious Area 4.612 Impervious Area Proposed Conditions 07 - - Storm Type 1124 -hr 100-yr Rainfall =6.00" Prepared by Westwood Professional Services, Inc. Page 12 HydroCAD® 8.00 sin 003363 © 2006 HydroCAD Software Solutions LLC 10/8/2007 Tc Length Slope Velocity Capacity Description (min) (feet) (ft/ft) (ft /sec) (cfs) 15.0 Direct Entry, Subcatchment 8S: Site Drainage Directly to Pond (excluding rooftop drainage) Runoff = 39.29 cfs a 12.01 hrs, Volume= 2.349 af, Depth= 5.07" Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Type 11 24 -hr 100 -yr Rainfall =6.00" Area (ac) CN Description 4.612 98 impervious area not excluding main rooftop 0.948 61 >75% Grass cover, Good, HSG B 5.560 92 Weighted Average 0.948 Pervious Area 4.612 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft /ft) (ft /sec) (cfs) 10.0 Direct Entry, area of site excluding rooftop Runoff = 5.65 cfs @ 11.98 hrs, Volume= Subcatchment 9S: Roof Drainage Runoff by SCS TR -20 method, UH =SCS, Time Span= 0.00-48.00 hrs, dt= 0.05 hrs Type H 24 -hr 100-yr Rainfal1=6.00" Area (ac) CN Description 0.694 98 Area of main roof 0.694 Impervious Area Tc Length Slope Velocity Capacity Description (min) (feet) (ft /ft) (ft/sec) (cfs) 7.0 Direct Entry, rooftop Reach 7R: Total Drainage to Pond Routing by Sim -Route method, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs 0.333 af, Depth= 5.76" Inflow 41.92 cfs @ 12.01 hrs, Volume= 2.627 of Outflow = 41.92 cfs a 12.06 hrs, Volume= 2.627 af, Atten= 0 %, Lag= 3.0 min 07 -09 -27 Storm Prepared by Westwood Professional Services, Inc. HydroCAD® 8.00 sin 003363 © 2006 Hyd roCAD Software Solutions LLC Inflow = 8.71 cfs a@ 11.91 hrs, Volume= 3.585 af Outflow = 8.71 cfs ac 11.96 hrs, Volume= 3.585 af, Atten= O %, Lag= 3.0 min Primary = 3.25 cfs © 10.45 hrs, Volume= 3.307 af Secondary = 7.43 cfs a@ 12.09 hrs, Volume= 0.278 of Routing by Sim -Route method, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Peak Elev= 922.68' a@ 12.09 hrs Device Routing invert Outlet Devices #1 Primary 918.00' 12.0" x 4.0' long Culvert RCP, sq.cut end projecting, Ke= 0.500 Outlet Invert= 917.98' S= 0.0050 '1' Cc= 0.900 n= 0.013 #2 Secondary 920.50' 15.0" x 27.0' long Culvert RCP, sq.cut end projecting, Ke= 0.500 Outlet Invert= 920.00' S= 0.0185 '1' Cc= 0.900 n= 0.013 Primary OutFlow Max =4.34 cfs @ 10.45 hrs HW= 920.58' TW= 919.26' (Dynamic Tailwater) L1= Culvert (Inlet Controls 4.34 cfs @ 5.52 fps) �condary OutFlow Max =6.97 cfs @ 12.09 hrs HW= 922.52' TW =0.00' (Dynamic Tailwater) 2= Culvert (Inlet Controls 6.97 cfs @ 5.68 fps) Device Routing #1 Primary Pond 5P: Splitter Manhole Invert Outlet Devices Pond 6P: Stormtech Inflow = 3.25 cfs a@ 1 0.45 hrs, Volume= 3.307 of Outflow = 4.37 cfs © 11.90 hrs, Volume= 3.252 af, Atten= 0 %, Lag= 87.0 min Primary = 4.37 cfs a@ 11.90 hrs, Volume= 3.252 af Routing by Sim -Route method, Time Span= 0.00 -48.00 hrs, dt= 0.05 hrs Peak Elev= 922.62' a@ 12.05 hrs Surf.Area= 1,282 sf Storage= 3,875 cf Plug -Flow detention time 39.5 min calculated for 3.248 af (98% of inflow) Center -of -Mass det. time= 19.2 min (1,671.0 - 1,651.8 ) Proposed Conditions Type 1124 - hr 100 Rainfall=6.00" Page 13 1 0/812007 Volume Invert Avail.Storage Storage Description #1 918.00' 1,654 cf 44.6 "W x 30.0 "H x 7.12'L StormTech SC -740x 36 Inside #2 #2 917.00' 3,440 cf 20.00'W x 64.08'L x 8.00'H Prismatold 10,253 cf Overall - 1,654 cf Embedded = 8,599 cf x 40.0% Voids 5,093 cf Total Available Storage 918.00' 12.0" x 4.0' long Culvert RCP, square edge headwall, Ke= 0.500 Outlet Invert= 917.98' 5= 0.0050 '1' Cc= 0.900 n= 0.013 Primary OutFlow Max =3.15 cfs @ 11.90 hrs HW= 921.82' TW= 921.13' (Dynamic Tailwater) L1= Culvert (Inlet Controls 3.15 cfs © 4.00 fps)