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HomeMy WebLinkAbout20060961 Ver 1_Stormwater Info_20060612WITHERS RAVENEL 40-Wade -Phase 1 Stormwater Management Plan ~, 40-WADE Raleigh, North Carolina Prepared For: Wexford Developers, LLC P.O. Box 3557 Cary, NC 27519 Prepared By: WITHERS & RAVENEL, INC iii MacKenan Drive Cary, North Carolina 27511 V~ od ~~ ~O~o ~~ o~~'~' ems' J yaw ~~s~~~ ~~ `9 v to JuneZOO6 ,~~~ '; ;~~~ . ,, W&R Project No. Zo4467 „ • 1, ~, ri i., r ~ _ ,4 ` \~ ~~. S r~ v ~. ~~`~ t phanie A. Hal .E. 4o-WADE -Phase ~ Stormwater Management Plan Raleigh, North Carolina INTRODUCTION The purpose of this study is to document the Stormwater management plan for Phase i of the proposed development. The plan includes the design of two proposed best management practices (BMPs 1 and 2) in Phase i in order to treat Stormwater runoff. The site is located in the Neuse River Basin and is bounded on the east by Richland Creek (Basin 18, Stream 3) which is a FEMA studied stream. The proposed BMPs for Phase 1 are constructed wetlands, designed to draw down the first inch of runoff over a 2 to 5 day period and sized according to the Division of Water Quality surface area requirements in order to achieve 85%Total Suspended Solids and 4o%total nitrogen reduction. The future phases of this development will employ the use of constructed wetlands, bioretention areas, and/or wet detention basins followed by a forested filter strip in order to meet Water Quality Certification #3402 in order to manage Stormwater. These BMPs will be designed and submitted at a later date. METHODOLOGY The Stormwater study was conducted using the natural drainage features as depicted by the Wake County aerial topographic information (2-ft contours), field survey data and proposed development within the drainage areas. The scope of work included the following analyses: 4o-WADE - Phase i i W&R Project zogg67 Stormwater Management Plan )une zoo6 Figure i. Site outlined in red on zoo4 Aerial Photography _. 4o-WADE -Phase i Stormwater Management Plan ~ Raleigh, North Carolina Hydrology ^ Simulation of the 1o-year and Zoo-year rainfall events for the Raleigh area • ^ Formulation of the 1o-year, and ioo-year flood hydrographs for the proposed developed • drainage area • Hydraulic ^ Routing the 1o-year and loo-year flood hydrographs for post development runoff through the proposed stormwater BMPs The results of the hydrologic calculations are used in the hydraulic analyses. The hydraulic design requires the development of stage-storage and stage-discharge functions for the wet detention • basins. The rainfall/runoff hydrographs, stage-storage and stage-discharge functions have been compiled to create a routing computer simulation model using Haestad Methods PondPack vio.o software. This PondPack model was then used to assess the impact of the peak discharges for the design rainfall events. The PondPack modeling results are provided as appendices to this report. HYDROLOGY • The SCS Method was used to develop runoff hydrographs for the io-year and ioo-year storm events. NOAA Atlas i4 rainfall data for Raleigh-Durham International Airport was used to determine the z4- hour duration rainfall for the io-year and loo-year storm events. This method requires three basic • parameters: a curve number (CN), time of concentration (t~, and drainage area. Curve numbers were based on soil type and land use. Soil types were delineated from the Soil Survey of Wake County, North Carolina (November 1970). Land use data was determined using aerial • photography and the most recent site plans for the proposed site. The curve numbers used in this study are listed in the appendix of this report. • • Times of concentration were estimated to have a time of concentration of 5 minutes to account for shallow paved flow, and piping. HYDRAULICS Computer simulated reservoir routing ofthe io-year, and loo-year design storms utilized stage- storage and stage-discharge functions. Stage-storage functions were derived from the proposed contours for the wet detention basins. Anon-linear regression relation for surface area versus elevation was derived for the BMPs. This relation estimates the incremental volume of the basin to the stage or elevation of the basins. Stage-discharge functions were developed to size the outlet structures forthe wetlands. CONCLUSIONS Based on the routing study, the outlet proposed for each constructed wetland passes the loo-year storm. The results for both runs are included in the appendix of this report. Table 1 and Table 2 summarize the design for the outlets of the BMPs. Planting schedules and more detailed design information is included on Sheets 3 and 4 of the Stormwater Management Plan drawings submitted with this report. Sheet 2 of the Stormwater Management Plan drawings show the locations of future BMPs to be incorporated in the overall stormwater plan. 4o-WADE -Phase i Stormwater Management Plan W&R Project zo4467 lunezoo6 4o-WADE -Phase 1 Stormwater Management Plan Raleigh, North Carolina TABLE 1. BMP 1 CONSTRUCTED WETLAND DESIGN SUMMARY Bottom of Pond 379.00' Top of Dam 385.00' Drawdown Orifice 3" Diameter at 382.00' Spillway 5o ft - Crest at 384.00' loo-year WSEL 384.84' TABLE 2. BMP 2 CONSTRUCTED WETLAND DESIGN SUMMARY Bottom of Pond 379.00' Top of Dam 385.00' Drawdown Orifice 2.5" Diameter at 382.00' Riser 4' x 4' -Crest at 383.20' Outlet Barrel 30" RCP - 9o LF at 5.6% loo-year WSEL 384.19' 4o-WADE - Phase i 3 W&R Project zo4467 Stormwater Management Plan lune zoo6 ~ ,~ - r ~a .:~ ~ w ~ , ~ . =" dVCI'•9vi,-Y.Ybla .. ...Mf i~ BV Designer ._ snn r-zao' Drawn B} Date sax oe/oe/oa Checked By lob Nei -- wee saaae~ 40-WADE -Phase 1 DRAINAGE AREA MAP !``~: rh ~4 ;V ~ ~~: ~~ p6r {~ ~~ '' ~ ~~~ ~ ~ ~~ ~: ~,. ~ 5 ' ~' '^ t ~~ t`~ ~~ ~. ~ ~ ~ ~ ~ d ~~ ~~ WITHERS ~ RAVENEL s^eeLN° ENGINEERS I PLANNERS I SURVEYORS 1 I i l Mei Kendn Drive (an, vunh Gimlina'_i I teP. 919-369-3340 v,v<w.wi~henraveneirom lae. 919-J67-6008 ROUTING CALC U LATI 0 N S To B 1 ~a o. ~F 'o BMP 1 0 ~~ /moo Out BMP1 Out BMP2 o BMP ryo C as BMPZ • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Table of Contents Table of Contents **************t****;r** MASTER SUMMARY **t******t************ Watershed....... Master Network Summary ............. 1..01 ****************** DESIGN STORMS SUMMARY ******************* RDU NOAA 14 Desi Design. Storms ...................... 2.01 *t******************** TC CALCULATIONS *************t******* TO BMP 1........ Tc Calcs ........................... 3.01 TO BMP 2........ Tc Calcs ........................... 3.03 ******************t*** CN CALCULATIONS ****rrt*******:t****** TO BMP 1........ Runoff CN-Area ..................... 4.01 TO BMP 2........ Runoff CN-Area ..................... 4.02 *********************** POND VOLUMES ******t**************** BMP 1........... Vol: Elev-Area ..................... 5.01 BMP2............ Vol: E1ev-Area ..................... 5.02 ******************** OUTLET STRUCTURES ********************* BMP 1 Outlet.... Outlet Input Data .................. 6.01 i S/N: DOYXYWH3NLBE PondPack (10.00.015.00) 10:27 AM Withers & Ravenel 6/6/2006 Table of Contents 11 Composite Rating Curve ............. 6.03 BMP 2 Outlet.... Outlet Input Data .................. 6.11 Composite Rating Curve ............. 6.14 S/N: DOYXYWH3NLBE Withers & Ravenel PondPack (10.00.015.00) 10:27 AM 6/6/2006 • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Type.... Master Network Summary Page 1.01 Name.... Watershed File.... K:\04\04-460\04467\H&H\pondpack\40wade_BMP1.ppw MASTER DESIGN STORM SUMMARY Network Storm Collection: RDU NOAA 14 Desi Total Depth Rainfall Return Event in Type RNF ID ------------ ------ ---------------- ---------------- 10 4.9800 Time-Depth Curve RDU NOAA 10yr 100 7.3700 Time-Depth Curve RDU NOAA 100yr MASTER NETWORK SUMMARY SCS Unit Hydrograph Method (*Node=Outfall; +Node=Diversion;) (T run= HYG Truncation: Blank=None; L=Left; R=Rt; LR=Left&Rt) Return HYG Vol Node ID Type Event cu.ft Trun BMP 1 IN POND 10 239304 BMP 1 IN POND 100 383806 BMP 1 OUT POND 10 235574 R BMP 1 OUT POND 100 379950 R BMP2 IN POND 10 138421 BMP2 IN POND 100 223874 BMP2 OUT POND 10 136926 BMP2 OUT POND 100 222335 *OUT BMP1 JCT 10 235573 R *OUT BMP1 JCT 100 379949 R *OUT BMP2 JCT 10 136924 *OUT BMP2 JCT 100 222334 TO BMP 1 AREA 10 239304 TO BMP 1 AREA 100 383806 Max Qpeak Qpeak Max WSEL Pond Storage hrs cfs ft cu.ft 12.1000 99.98 12.1000 128.42 1.2.1500 84.67 384.68 73788 12,1500 110.79 384.82 77764 1.2.1.000 58.29 12.1000 75.49 12.1500 44.00 384.01. 41250 12.1.500 59.58 384.1.9 45363 12.1500 84.67 12.1500 110.79 12.1500 44.00 12.1500 59.58 12.1000 99.98 1.2.1000 128.42 S/N: DOYXYWH3NLBE PondPack (10.00.015.00) 10:27 AM Withers & Ravenel 6/6/2006 Type.... Master Network Summary Page 1.02 Name.... Watershed File.... K:\04\04-460\04467\H&H\pondpack\40wade_BMPl.ppw MASTER NETWORK SUMMARY SCS Unit Hydrograph Method (*Node=Outfall; +Node=Diversion;) (T run= HYG Truncation: Blank=None; L=Left; R=Rt; LR=Left&Rt) Return HYG Vol Qpeak Qpeak Max WSEL Node ID Type Event cu.ft Trun hrs cfs ft TO BMP 2 AREA 10 138421 12.1000 58.29 TO BMP 2 AREA 100 223874 12.1000 75.49 Max Pond Storage cu.ft S/N: DOYXYWH3NLBE Withers & Ravenel PondPack (10.00.015.00) 10:27 AM 6/6/2006 • • • • • • • • • • • • • • • • • • • Type.... Design Storms Page 2.01 Name.... RDU NOAA 14 Desi File.... K:\04\04-460\04467\H&H\pondpack\40wade_BMPl.ppw Title... Project Date: 4/11/2006 Project Engineer: Project Title: Watershed Project Comments: DESIGN STORMS SUMMARY Design Storm Fi1e,ID = RDU NOAA 14 Desi Storm Tag Name = 10 Data Type, File, ID Storm Frequency Total Rainfall. Depth Duration Multiplier Resulting Duration Resulting Start Time Storm Tag Name = 100 Data Type, File, ID = Time-Depth Curve RDU NOAA 100yr Storm Frequency = 100 yr Total Rainfall. Depth= 7.3700 in Duration Multiplier = 1 Resulting Duration = 23.9990 hrs Resulting Start Time= .0000 hrs Step= .0833 hrs End= 23.9990 hrs Time-Depth Curve RDU NOAA 10yr 10 yr 4.9800 in 1 23.9904 hrs .0000 hrs Step= .0833 hrs End= 23.9904 hrs S/N: DOYXYWH3NLBE PondPack (10.00.015.00) 10:27 AM Withers & Ravenel 6/6/2006 • • • • • • • • • • • • • • • • • • • • • • • Type.... Tc Calcs Name.... TO BMP l File.... K:\04\04-460\04467\H&H\pondpack\40wade_BMPl.ppw TIME OF CONCENTRATION CALCULATOR Segment #1: Tc: User Defined Segment #1 Time: .0833 hrs ------------------------------------------------------------------------ ------------------------- Total Tc: .0833 hrs Calculated Tc < Min.Tc: Use Minimum Tc... Use Tc = .0833 hrs Page 3.01 S/N: DOYXYWH3NLBE PondPack (10.00.015.00) 10:27 AM Withers & Ravenel 6/6/2006 Type.... Tc Calcs Name.... TO BMP 1 File.... K:\04\04-460\04467\H&H\pondpack\40wade_BMP1.ppw Page 3.02 ------------------------------------------------------------------------ Tc Equations used... ------------------------------------------------------------------------ ___= User Defined ______________________________________________________ Tc = Value entered by user Where: Tc = Time of concentration S/N: DOYXYWH3NLBE Withers & Ravenel PondPack (10.00.015.00) 10:27 AM 6/6/2006 Type.... Tc Calcs Name.... TO BMP 2 File.... K:\04\04-460\04467\H&H\pondpack\40wade_BMPl.ppw Page 3.03 TIME OF CONCENTRATION CALCULATOR. Segment #1: Tc: User Defined Segment #1 Time: .0833 hrs ------------------------------------------------------------------------ Total Tc: .0833 hrs Calculated Tc < Min.Tc: Use Minimum Tc... Use Tc = .0833 hrs ------------------------- ------------------------- S/N: DOYXYWH3NLBE Withers & Ravenel PondPack (10.00.015.00) 10:27 AM 6/6/2006 Type.... Tc Calcs Name.... TO BMP 2 File.... K:\04\04-460\04467\H&H\pondpack\40wade_BMP1.ppw Page 3.04 ------------------------------------------------------------------------ Tc Equations used... ------------------------------------------------------------------------ ___= User Defined =----------------------------------------------------- Tc = Value entered by user Where: Tc = Time of concentration S/N: DOYXYWH3NLBE Withers & Ravenel PondPack (10.00.015.00) 1.0:27 AM 6/6/2006 Type.... Runoff CN-Area Name.... TO BMP 1 File.... K:\09\04-460\04467\H&H\pondpack\40wade BMPl.ppw Page 9.01 RUNOFF CURVE NUMBER DATA .......................................................................... .......................................................................... Impervious Area Adjustment Adjusted Soi-1/Surface Description CN acres oC oUC CN Urban Districts - Commercial & Busi 92 16.150 92.00 BMP Area 61 .940 61.00 COMPOSITE AREA & WEIGHTED CN ---> 17.090 90.29 (90) ........................................................................... ........................................................................... S/N: DOYXYWH3NLBE PondPack (10.00.015.00) 10:27 AM Withers & Ravenel 6/6/2006 • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Type.... Runoff CN-Area Name.... TO BMP 2 File.... K:\04\04-460\04967\H&H\pondpack\40wade_BMPl.ppw RUNOFF CURVE NUMBER DATA -------------------------------------------------------------------------- Impervious Area Adjustment Adjusted Soil/Surface Description CN acres oC oUC CN -------------------------------- ---- --------- ----- ----- ------ Urban Districts - Commercial & Busi 92 9.320 92.00 BMP Area 61 .840 61.00 COMPOSITE AREA & WEIGHTED CN ---> 10.160 89.44 (89) Page 4.02 S/N: DOYXYWH3NLBE PondPack (10.00.015.00) 10:27 AM Withers & Ravenel 6/6/2006 Type.... Vol: Elev-Area Name.... BMP 1 File.... K:\04\04-460\04467\H&H\pondpack\40wade BMPl.ppw Page 5.01 Elevation Planimeter Area Al+A2+sgr(A1*A2) Volume Volume Sum (ft) (sq.in) (sq.ft) (sq.ft) (cu.ft) (cu.ft) 382.00 ----- 25436 0 0 0 383.00 ----- 27064 78737 26246 26246 384.00 28510 83352 27784 59030 385.00 ----- 30003 87760 29253 83283 POND VOLUME EQUATIONS * Incremental. volume computed by the Conic Method for Reservoir Volumes. Volume = (1/3) * (EL2-EL1) (Areal + Areal + sq.rt.(Areal*Area2)) where: EL1, EL2 = Lower and upper elevations of the increment Areal,Area2 = Areas computed for EL1, EL2, respectively Volume = Incremental- volume between EL1 and EL2 S/N: DOYXYWH3NLBE PondPack (10.00.015.00) 10:27 AM Withers & Ravenel 6/6/2006 • • • • • • • • • • • • • • • • • • • • Type.... Vol: Elev-Area Name.... BMP2 File.... K:\04\04-460\04467\H&H\pondpack\40wade BMPl.ppw Elevation Planimeter Area Al+A2+sgr(A1*A2) Volume Volume Sum (ft) ------------ (sq.in) (sq.ft) --------------------- (sq.ft) ---------------- (cu.ft) ---------- (cu.ft) ------------- 382.00 ----- 18723 0 0 0 383.00 20501 58816 19605 19605 384.00 ----- 22335 64234 2141.1 41017 385.00 ----- 24226 69822 23274 64291 POND VOLUME EQUATIONS * Incremental volume computed by the Conic Method for Reservoir Volumes. Volume = (1/3) (EL2-EL1) * (Areal + Areal + sq.rt.(Areal*Area2)) where: ELl, EL2 = Lower and upper elevations of the increment Areal,Area2 = Areas computed for EL1, EL2, respectively Volume = Incremental. volume between EL1 and EL2 Page 5.02 S/N: DOYXYWH3NLBE PondPack (10.00.015.00) 10:27 AM Withers & Ravenel 6/6/2006 Type.... Outlet Input Data Name.... BMP 1 Outlet File.... K:\04\09-460\04467\H&H\pondpack\40wade BMPl.ppw REQUESTED POND WS ELEVATIONS: Min. Elev.= 382.00 ft Increment = .O1 ft Max. Elev.= 385.00 ft OUTLET CONNECTIVITY ---> Forward Flow Only (Upstream to DnStream) <--- Reverse Flow Only (DnStream to Upstream) <---> Forward and. Reverse Both Allowed Page 6.01 Structure No. Outfall E1, ft E2, ft ----------------- ---- ------- --------- --------- Orifice-Circular 00 ---> TW 382.000 385.000 Weir-Rectangular WO ---> TW 384.000 385.000 TW SETUP, DS Channel S/N: DOYXYWH3NLBE Withers & Ravenel PondPack (10.00.01.5.00) 10:27 AM 6/6/2006 Type.... Outlet Input Data Name.... BMP 1 Outlet File.... K:\04\04-460\04467\H&H\pondpack\40wade BMPl.ppw OUTLET STRUCTURE INPUT DATA Structure ID = 00 Structure Type = Orifice-Circular ------------------------------------ # of Openings = 1 Invert Elev. = 382.00 ft Diameter = .2500 ft Orifice Coeff. _ .600 Structure ID Structure Type # of Openings Crest Elev. Weir Length Weir Coeff. Weir TW effects (Use adjustment equation) Structure ID = TW Structure Type = TW SETUP, DS Channel FREE OUTFACE CONDITIONS SPECIFIED CONVERGENCE TOLERANCES ... Maximum Iterations= 40 Min. TW tolerance = .O1 ft Max. TW tolerance = .O1 ft Min. HW tolerance = .01 ft Max. HW tolerance = .01 ft Min. Q tolerance _ .00 cfs Max. Q tolerance = .00 cfs WO Weir-Rectangular 1 389.00 ft 50.00 ft 3.000000 Page 6.02 S/N: DOYXYWH3NLBE PondPack (10.00.015.00) 10:27 AM Withers & Ravenel 6/6/2006 Type.... Composite Rating Curve Name.... BMP 1 Outlet File.... K:\04\09-460\04467\H&H\pondpack\90wade BMPl.ppw Page 6.03 ***** COMPOSITE OUTFLOW SUMMARY **** WS Elev, Total Q Notes ----- - --- Converg e ------------------------- Elev. Q TW Elev Error ft cfs ft +/-f t. Contributing Structures 382.00 .00 Free Outfall None contributing 382.01 .00 Free Outfall 00 382.02 .00 Free Outfall 00 382.03 .00 Free Outfall 00 382.04 .00 Free Outfall 00 382.05 .00 Free Outfall 00 382.06 .O1 Free Outfall 00 382.07 .O1 Free Outfall 00 382.08 .O1 Free Outfall 00 382.09 .O1 Free Outfall 00 382.10 .02 Free Outfall 00 382.11 .02 Free Outfall 00 382.12 .02 Free Outfall 00 382.13 .03 Free Outfall 00 382.14 .03 Free Outfall 00 382.15 .03 Free Outfall 00 382.16 .04 Free Outfall 00 382.17 .04 Free Outfall 00 382.18 .05 Free Outfall 00 382.19 .05 Free Outfall 00 382.20 .06 Free Outfall 00 382.21 .06 Free Outfall 00 382.22 .07 Free Outfall 00 382.23 .07 Free Outfall 00 382.24 .08 Free Outfall 00 382.25 .08 Free Outfall 00 382.26 .09 Free Outfall 00 382.27 .09 Free Outfall 00 382.28 .09 Free Outfall 00 382.29 .10 Free Outfall 00 382.30 .10 Free Outfall 00 382.31 .10 Free Outfall 00 382.32 .10 Free Outfall 00 382.33 .11 Free Outfall 00 382.34 .11 Free Outfall 00 382.35 .11 Free Outfall 00 382.36 .11 Free Outfall 00 382.37 .12 Free Outfall 00 S/N: DOYXYWH3NLBE Withers & Ravenel PondPack (10.00.015.00) 10:27 AM 6/6/2006 Type.... Composite Rating Curve Name.... BMP 1 Outlet File.... K:\04\04-460\04467\H&H\pondpack\40wade BMPl.ppw Page 6.04 ***** COMPOSITE OUTFLOW SUMMARY **** WS E1ev, Total Q Notes -------- -------- ----- --- Converg e ------------------------- Elev. Q TW E 1ev Error ft cfs ft +/-ft Contributing Structures 382.38 .12 Free Outfall 00 382.39 .12 Free Outfall 00 382.40 .12 Free Outfall 00 382.91 .13 Free Outfall 00 382.42 .13 Free Outfall 00 382.43 .13 Free Outfall 00 382.44 .13 Free Outfall 00 382.45 .13 Free Outfall 00 382.46 .14 Free Outfall 00 382.47 .14 Free Outfall 00 382.98 .14 Free Outfall 00 382.99 .14 Free Outfall 00 382.50 .14 Free Outfall 00 382.51 .15 Free Outfall 00 382.52 .15 Free Outfall 00 382.53 .15 Free Outfall 00 382.54 .15 Free Outfall 00 382.55 .15 Free Outfall 00 382.56 .16 Free Outfall 00 382.57 .16 Free Outfall 00 382.58 .16 Free Outfall 00 382.59 .16 Free Outfall 00 382.60 .16 Free Outfall 00 382.61 .16 Free Outfall 00 382.62 .17 Free Outfall 00 382.63 .17 Free Outfall 00 382.64 .17 Free Outfall 00 382.65 .17 Free Outfall 00 382.66 .17 Free Outfall 00 382.67 .17 Free Outfall 00 382.68 .18 Free Outfall 00 382.69 .18 Free Outfall 00 382.70 .18 Free Outfall 00 382.71 .18 Free Outfall 00 382.72 .18 Free Outfall 00 382.73 .18 Free Outfall 00 382.74 .19 Free Outfall 00 382.75 .19 Free Outfall 00 S/N: DOYXYWH3NLBE Withers & Ravenel. PondPack (10.00.015.00) 10:27 AM 6/6/2006 Type.... Composite Rating Curve Name.... BMP 1 Outlet File.... K:\04\04-460\09467\H&H\pondpack\40wade BMPl.ppw Page 6.05 ***** COMPOSITE OUTFLOW SUMMARY **** WS Elev, Total Q Notes -------- -------- ----- --- Converg e Elev. Q TW E lev Error ft cfs f t +/-ft Contributing Structures --- -------- 382.76 ------- .19 ----- Free --- ----- Outfall ----------------------- 00 382.77 .19 Free Outfall 00 382.78 .19 Free Outfall 00 382.79 .19 Free Outfall 00 382.80 .19 Free Outfall 00 382.81. .20 Free Outfall 00 382.82 .20 Free Outfall 00 382.83 .20 Free Outfall 00 382.84 .20 Free Outfall 00 382.85 .20 Free Outfall 00 382.86 .20 Free Outfall 00 382.87 .20 Free Outfall 00 382.88 .21 Free Outfall 00 382.89 .21 Free Outfall 00 382.90 .21 Free Outfall 00 382.91 .21 Free Outfall 00 382.92 .21 Free Outfall 00 382.93 .21 Free Outfall 00 382.94 .21 Free Outfall 00 382.95 .21 Free Outfall 00 382.96 .22 Free Outfall 00 382.97 .22 Free Outfall 00 382.98 .22 Free Outfall 00 382.99 .22 Free Outfall 00 383.00 .22 Free Outfall 00 383.01. .22 Free Outfall 00 383.02 .22 Free Outfall 00 383.03 .22 Free Outfall 00 383.04 .23 Free Outfall 00 383.05 .23 Free Outfall 00 383.06 .23 Free Outfall 00 383.07 .23 Free Outfall 00 383.08 .23 Free Outfall 00 383.09 .23 Free Outfall 00 383.10 .23 Free Outfall 00 383.11. .23 Free Outfall 00 383.12 .29 Free Outfall 00 383.13 .29 Free Outfall 00 S/N: DOYXYWH3NLBE Withers & Ravenel PondPack (10.00.015.00) 10:27 AM 6/6/2006 Type.... Composite Rating Curve Name.... BMP 1 Outlet File.... K:\04\09-460\04467\H&H\pondpack\40wade BMPl.ppw Page 6.06 ***** COMPOSITE OUTFLOW SUMMARY **** WS Elev, Total Q Notes -------- -------- ----- --- Converge ------------------------- Elev. Q TW Elev Error ft -------- cfs ------- ft +/-ft -------- ----- Contributing Structures -------------------------- 383.19 .24 Free Outfall 00 383.15 .24 Free Outfall 00 383.16 .24 Free Outfall 00 383.17 .24 Free Outfall 00 383.18 .24 Free Outfall 00 383.19 .24 Free Outfall 00 383.20 .24 Free Outfall 00 383.21 .25 Free Outfall 00 383.22 .25 Free Outfall 00 383.23 .25 Free Outfall 00 383.24 .25 Free Outfall 00 383.25 .25 Free Outfall 00 383.26 .25 Free Outfall 00 383.27 .25 Free Outfall 00 383.28 .25 Free Outfall 00 383.29 .26 Free Outfall 00 383.30 .26 Free Outfall 00 383.31 .26 Free Outfall 00 383.32 .26 Free Outfall 00 383.33 .26 Free Outfall 00 383.34 .26 Free Outfall 00 383.35 .26 Free Outfall 00 383.36 .26 Free Outfall 00 383.37 .26 Free Outfall 00 383.38 .26 Free Outfall 00 383.39 .27 Free Outfall 00 383.90 .27 Free Outfall 00 383.41 .27 Free Outfall 00 383.42 .27 Free Outfall 00 383.43 .27 Free Outfall 00 383.94 .2"7 Free Outfall 00 383.95 .27 Free Outfall 00 383.46 .27 Free Outfall 00 383.47 .27 Free Outfall 00 383.48 .28 Free Outfall 00 383.99 .28 Free Outfall 00 383.50 .28 Free Outfall 00 383.51. .28 Free Outfall 00 S/N: DOYXYWH3NLBE Withers & Ravenel PondPack (10.00.015.00) 10:27 AM 6/6/2006 Type.... Composite Rating Curve Name.... BMP 1 Outlet File.... K:\04\04-460\04467\H&H\pondpack\40wade_BMPl.ppw ***** COMPOSITE OUTFLOW SUMMARY **** WS Elev, Total Q Notes -------- -------- ------ -- Converge ------------------------- Elev. Q TW El ev Error ft cfs ft -- +/-ft -- ----- Contributing Structures -------------------------- -------- 383.52 ------- .28 ---- Free Outfall 00 383.53 .28 Free Outfall 00 383.54 .28 Free Outfall 00 383.55 .28 Free Outfall 00 383.56 .28 Free Outfall 00 383.57 .28 Free Outfall 00 383.58 .28 Free Outfall 00 383.59 .29 Free Outfall 00 383.60 .29 Free Outfall 00 383.61 .29 Free Outfall 00 383.62 .29 Free Outfall 00 383.63 ,29 Free Outfall 00 383.64 .29 Free Outfall 00 383.65 .29 Free Outfall 00 383.66 .29 Free Outfall 00 383.67 .29 Free Outfall 00 383.68 .29 Free Outfall 00 383.69 .30 Free Outfall 00 383.70 .30 Free Outfall 00 383.71 .30 Free Outfall 00 383.72 .30 Free Outfall 00 383.73 .30 Free Outfall 00 383.74 .30 Free Outfall 00 383.75 .30 Free Outfall 00 383.76 .30 Free Outfall 00 383.77 .30 Free Outfall 00 383.78 .30 Free Outfall 00 383.79 .30 Free Outfall 00 383.80 .31 Free Outfall 00 383.81 .31 Free Outfall 00 383.82 .31 Free Outfall 00 383.83 .31 Free Outfall 00 383.84 .31 Free Outfall 00 383.85 .31 Free Outfall 00 383.86 .31 Free Outfall 00 383.87 .31 Free Outfall 00 383.88 .31 Free Outfall 00 383.89 .31 Free Outfall 00 Page 6.07 S/N: DOYXYWH3NLBE Withers & Ravenel. PondPack (10.00.015.00) 10:27 AM 6/6/2006 • • • • • • • • • • • • • • • Type.... Composite Rating Curve Name.... BMP 1 Outlet File.... K:\04\04-460\04967\H&H\pondpack\40wade_BMPl.ppw ***** COMPOSITE OUTFLOW SUMMARY **** WS Elev, Total Q Notes -------- -------- ------ -- Converge -- ----------------------- Elev. Q TW El ev Error ft cfs ft +/-ft ---- Contributing Structures -------------------------- -------- 383.90 ------- .31 ------ Free -- - Outfall 00 383.91 .32 Free Outfall 00 383.92 .32 Free Outfall 00 383.93 .32 Free Outfall 00 383.94 .32 Free Outfall 00 383.95 .32 Free Outfall 00 383.96 .32 Free Outfall 00 383.97 .32 Free Outfall 00 383.98 .32 Free Outfall 00 383.99 .32 Free Outfall 00 384.00 .32 Free Outfall 00 +WO 384.01 .47 Free Outfall 00 +WO 384.02 .75 Free Outfall 00 +WO 384.03 1.11 Free Outfall 00 +WO 384.04 1.53 Free Outfall 00 +WO 384.05 2.00 Free Outfall 00 +WO 384.06 2.53 Free Outfall 00 +WO 384.07 3.11 Free Outfall 00 +WO 384.08 3.72 Free Outfall 00 +WO 384.09 4.38 Free Outfal.l 00 +WO 384.10 5.08 Free Outfall 00 +WO 384.11 5.80 Free Outfall 00 +WO 384.12 6.57 Free Outfall 00 +WO 384.13 7.37 Free Outfall 00 +WO 384.14 8.19 Free Outfall 00 +WO 384.1.5 9.05 Free Outfall 00 +WO 384.16 9.94 Free Outfall 00 +WO 384.17 10.85 Free Outfall 00 +WO 384.18 11.79 Free Outfall 00 +WO 384.19 12.76 Free Outfall 00 +WO 384.20 13.76 Free Outfall 00 +WO 384.21 14.78 Free Outfall 00 +WO 384.22 15.82 Free Outfall 00 +WO 384.23 16.89 Free Outfall 00 +WO 384.24 17.98 Free Outfall 00 +WO 384.25 19.09 Free Outfall 00 +WO 384.26 20.23 Free Outfall 00 +WO 384.27 21.39 Free Outfall 00 +WO Page 6.08 S/N: DOYXYWH3NLBE PondPack (10.00.015.00) 10:27 AM Withers & Ravenel 6/6/2006 Type.... Composite Rating Curve Name.... BMP 1 Outlet File.... K:\04\04-460\04467\H&H\pondpack\40wade_BMPl.ppw Page 6.09 ***** COMPOSITE OUTFLOW SUMMARY **** WS Elev, Total Q Notes -------- -------- ------ -- Converge -- ----------------------- Elev. Q TW El ev Error ft cfs ft +/-ft -- Contributing Structures -------------------------- -------- 384.28 ------- 22.57 ------ Free -- --- Outfall 00 +WO 384.29 23.77 Free Outfall 00 +WO 384.30 24.99 Free Outfall 00 +WO 384.31 26.24 Free Outfall 00 +WO 384.32 27.50 Free Outfall 00 +WO 384.33 28.78 Free Outfall 00 +WO 384.34 30.09 Free Outfall 00 +w0 384.35 31.41 Free Outfall 00 +WO 384.36 32.75 Free Outfall 00 +WO 384.37 34.11 Free Outfall 00 +WO 389.38 35.49 Free Outfall 00 +WO 384.39 36.89 Free Outfall 00 +WO 384.40 38.30 Free Outfall 00 +WO 384.41 39.74 Free Outfall 00 +WO 384.42 91.19 Free Outfall 00 +WO 384.43 42.65 Free Outfall 00 +WO 384.44 44.14 Free Outfall 00 +WO 384.45 45.64 Free Outfall 00 +WO 384.46 47.16 Free Outfall 00 +WO 384.47 98.69 Free Outfall 00 +WO 384.48 50.25 Free Outfall 00 +WO 384.49 51.81 Free Outfall 00 +WO 384.50 53.40 Free Outfall 00 +WO 384.51 55.00 Free Outfall 00 +WO 384.52 56.61 Free Outfall 00 +WO 384.53 58.24 Free Outfall 00 +WO 384.54 59.89 Free Outfall 00 +WO 384.55 61.55 Free Outfall 00 +WO 384.56 63.23 Free Outfall 00 +WO 384.57 64.92 Free Outfall 00 +WO 384.58 66.63 Free Outfall 00 +WO 384.59 68.35 Free Outfall 00 +WO 384.60 70.09 Free Outfall 00 +WO 384.61 71.83 Free Outfall 00 +WO 384.62 73.60 Free Outfall 00 +WO 384.63 75.38 Free Outfall 00 +WO 384.64 77.18 Free Outfall 00 +WO 384.65 78.98 Free Outfall 00 +WO S/N: DOYXYWH3NLBE Withers & Ravenel PondPack (10.00.015.00) 10:27 AM 6/6/2006 Type.... Composite Rating Curve Name.... BMP 1 Outlet File.... K:\04\04-460\04467\H&H\pondpack\40wade_BMPl.ppw ***** COMPOSITE OUTFLOW SUMMARY **** WS Elev, Total Q Notes -------- -------- -- - Converge -- ----------------------- Elev. Q TW El ev Error ft cfs ft +/-ft ----- Contributing Structures -------------------------- -------- 384.66 ------- 80.80 ------ Free -- Outfall 00 +WO 384.67 82.64 Free Outfall 00 +WO 384.68 84.49 Free Outfall 00 +WO 384.69 86.35 Free Outfall 00 +WO 384.70 88.23 Free Outfall 00 +WO 384.71 90.12 Free Outfall 00 +WO 384.72 92.02 Free Outfall 00 +WO 384.73 93.94 Free Outfall 00 +WO 384.74 95.87 Free Outfall 00 +WO 384.75 97.81 Free Outfall 00 +WO 384.76 99.77 Free Outfall 00 +WO 384.77 101.73 Free Outfall 00 +WO 384.78 103.72 Free Outfall 00 +WO 384.79 105.71 Free Outfall 00 +WO 384.80 107.72 Free Outfall 00 +WO 389.81 109.74 Free Outfall 00 +WO 384.82 111.77 Free Outfall 00 +WO 384.83 113.81 Free Outfall 00 +WO 384.84 115.87 Free Outfall 00 +WO 384.85 117.94 Free Outfall 00 +WO 384.86 120.02 Free Outfall 00 +WO 384.87 122.11 Free Outfall 00 +WO 384.88 124.22 Free Outfall 00 +WO 384.89 126.34 Free Outfall 00 +WO 384.90 128.46 Free Outfall 00 +WO 384.91 130.61 Free Outfall 00 +WO 384.92 132.76 Free Outfall 00 +WO 384.93 134.92 Free Outfall 00 +WO 384.94 137.10 Free Outfall 00 +WO 384.95 139.29 Free Outfall 00 +WO 384.96 141.99 Free Outfall 00 +WO 384.97 143.70 Free Outfall 00 +WO 389.98 145.92 Free Outfall 00 +WO 389.99 198.15 Free Outfall 00 +WO 385.00 150.40 Free Outfall 00 +WO Page 6.10 S/N: DOYXYWH3NLBE Withers & Ravenel PondPack (10.00.015.00) 10:27 AM 6/6/2006 Type.... Outlet Input Data Name.... BMP 2 Outlet File.... K:\04\04-460\04467\H&H\pondpack\40wade_BMPl..ppw Page 6.11 REQUESTED POND WS ELEVATIONS: Min. Elev.= 382.00 ft. Increment = .05 ft Max. Elev.= 385.00 ft OUTLET CONNECTIVITY ---> Forward Flow Only (Upstream to DnStream) <--- Reverse Flow Only (DnStream to Upstream) <---> Forward and Reverse Both Allowed Structure No. Outfall E1, ft E2, ft Inlet Box RO ---> CO 383.200 385.000 Orifice-Circular 00 ---> CO 382.000 385.000 Culvert-Circular CO ---> TW 377.000 385.000 TW SETUP, DS Channel S/N: DOYXYWH3NLBE Withers & Ravenel PondPack (10.00.015.00) 10:27 AM 6/6/2006 Type.... Outlet Input Data Name.... BMP 2 Outlet File.... K:\04\09-960\04467\H&H\pondpack\40wade BMPl.ppw Page 6.12 OUTLET STRUCTURE INPUT DATA Structure ID = RO Structure Type = Inlet Box # of Openings = 1 Invert Elev. = 383.20 ft Orifice Area = 25.0000 sq.ft. Orifice Coeff. _ .600 Weir Length = 20.00 ft Weir Coeff. = 3.000 K, Reverse = 1.000 Mannings n = .0000 Kev,Charged Riser = .000 Weir Submergence = No Structure ID = 00 Structure Type = Orifice-Circular ------------------------------------ # of Openings = 1 Invert Elev. = 382.00 ft Diameter = .2083 ft Orifice Coeff. _ .600 S/N: DOYXYWH3NLBE PondPack (10.00.015.00) 10:27 AM Withers & Ravenel 6/6/2006 • • • • • • s • • • • • • • • • • • • • • • • • • • • • • Type.... Outlet Input Data Name.... BMP 2 Outlet File.... K:\04\04-960\04467\H&H\pondpack\40wade_BMPl.ppw OUTLET STRUCTURE INPUT DATA Structure ID = CO Structure Type -------- = Culvert-Circular ------------------ ---------- No. Barrels = 1 Barrel Diameter = 3.0000 ft Upstream Invert = 377.00 ft Dnstream Invert = 375.00 ft Horiz. Length = 65.00 ft Barrel Length = 65.03 ft Barrel Slope = .03077 ft/ft OUTLET CONTROL DATA... Mannings n = .0130 Ke = .5000 Kb = .007228 Kr = .5000 HW Convergence = .001 Page 6.13 (forward entrance loss) (per ft of full flow) (reverse entrance loss) +/- ft INLET CONTROL DATA... Equati on form = 1 Inlet Control K = .0098 Inlet Control M = 2.0000 Inlet Control c = .03980 Inlet Control Y = .6700 Tl ratio (HW/D) = 1.145 T2 ratio (HW/D) = 1.291 Slope Factor = -.500 Use unsubmerged inlet control Form 1 equ. below T1 elev. Use submerged inlet control Form 1 equ. above T2 elev. In transition zone between unsubmerged and submerged inlet control, interpolate between flows at Tl & T2... At T1 Elev = 380.43 ft ---> Flow = 42.85 cfs At T2 Elev = 380.87 ft ---> Flow = 48.97 cfs Structure ID = TW Structure Type = TW SETUP, DS Channel ------------------------------------ FREE OUTFACE CONDITIONS SPECIFIED CONVERGENCE TOLERANCES ... Maxi mum Iterations= 40 Min. TW tolerance = .Ol ft Max. TW tolerance = .O1 ft Min. HW tolerance = .Ol ft Max. HW tolerance = .Ol ft Min. Q tolerance = .00 cfs Max. Q tolerance = .00 cfs S/N: DOYXYWH3NLBE PondPack (10.00.015.00) 10:27 AM Withers & Ravenel 6/6/2006 Type.... Composite Rating Curve Name.... BMP 2 Outlet File.... K:\04\04-460\04467\H&H\pondpack\40wade_BMPl.ppw Page 6.14 ***** COMPOSITE OUTFLOW SUMMARY **** WS Elev, Total Q Notes -------- -------- ------ -- Converge ----------- -- ------------ Elev. Q TW E1 ev Error ft cfs ft +/-ft Contributing ------------- Structures ------------ -------- 382.00 ------- .00 ------ Free -- ----- - Outfall (no Q: RO, OO ,CO) 382.05 .00 Free Outfall OO,CO (no Q: RO) 382.10 .01 Free Outfall. OO,CO (no Q: RO) 382.15 .03 Free Outfall OO,CO (no Q: RO) 382.20 .05 Free Outfall OO,CO (no Q: RO) 382.25 .06 Free Outfall OO,CO (no Q: RO) 382.30 .07 Free Outfall. OO,CO (no Q: RO) 382.35 .08 Free Outfall OO,CO (no Q: RO) 382.40 .09 Free Outfall OO,CO (no Q: RO) 382.45 .10 Free Outfall OO,CO (no Q: RO) 382.50 .10 Free Outfall OO,CO (no Q: RO) 382.55 .11 Free Outfall OO,CO (no Q: RO) 382.60 .11 Free Outfall OO,CO (no Q: RO) 382.65 .12 Free Outfall OO,CO (no Q: RO) 382.70 .13 Free Outfall OO,CO (no Q: RO) 382.75 .13 Free Outfall OO,CO (no Q: RO) 382.80 .14 Free Outfall OO,CO (no Q: RO) 382.85 .14 Free Outfall OO,CO (no Q: RO) 382.90 .15 Free Outfall OO,CO (no Q: RO) 382.95 .15 Free Outfall OO,CO (no Q: RO) 383.00 .15 Free Outfall OO,CO (no Q: RO) 383.05 .16 Free Outfall OO,CO (no Q: RO) 383.10 .16 Free Outfall OO,CO (no Q: RO) 383.15 .17 Free Outfall. OO,CO (no Q: RO) 383.20 .17 Free Outfall OO,CO (no Q: RO) 383.25 .85 Free Outfall RO,OO,CO 383.30 2.08 Free Outfall RO,OO,CO 383.35 3.67 Free Outfall RO,OO,CO 383.40 5.55 Free Outfall RO,OO,CO 383.45 7.68 Free Outfall RO,OO,CO 383.50 10.05 Free Outfall RO,OO,CO 383.55 12.62 Free Outfall RO,OO,CO 383.60 15.38 Free Outfall RO,OO,CO 383.65 18.32 Free Outfall RO,OO,CO 383.70 21.42 Free Outfall RO,OO,CO 383.75 24.67 Free Outfall_ RO,OO,CO 383.80 28.11 Free Outfall RO,OO,CO 383.85 31.67 Free Outfall RO,OO,CO S/N: DOYXYWH3NLBE Withers & Ravenel PondPack (10.00.015.00) 10:27 AM 6/6/2006 Type.... Composite Rating Curve Name.... BMP 2 Outlet File.... K:\04\04-460\04467\H&H\pondpack\90wade BMPl.ppw Page 6.15 ***** COMPOSITE OUTFLOW SUMMARY **** WS Elev, Total Q Notes -------- -------- ----- --- Converge ---------- --------------- Elev. Q TW Elev Error ft cfs ft +/-ft Contributi ng Structures -------- 383.90 ------- 35.36 ----- Free --- ----- - Outfall ---------- RO,OO,CO --------------- 383.95 39.21 Free Outfall RO,OO,CO 384.00 43.14 Free Outfall RO,OO,CO 384.05 97.23 Free Outfall RO,OO,CO 384.10 51.45 Free Outfall RO,OO,CO 384.15 55.77 Free Outfall RO,OO,CO 384.20 60.20 Free Outfall RO,OO,CO 384.25 64.73 Free Outfall RO,OO,CO 384.30 69.38 Free Outfall RO,OO,CO 384.35 79.19 Free Outfall RO,OO,CO 384.40 78.95 Free Outfall RO,OO,CO 384.95 82.99 Free Outfall RO,CO (no Q: 00) 384.50 83.36 Free Outfall RO,CO (no Q: 00) 389.55 83.74 Free Outfall RO,CO (no Q: 00) 384.60 84.11 Free Outfall RO,OO,CO 384.65 84.50 Free Outfall RO,OO,CO 384.70 84.85 Free Outfall RO,CO (no Q: 00) 384.75 85.23 Free Outfall RO,CO (no Q: 00) 384.80 85.59 Free Outfall RO,CO (no Q: 00) 384.85 85.96 Free Outfall RO,OO,CO 384.90 86.33 Free Outfall RO,OO,CO 384.95 86.69 Free Outfall RO,CO (no Q: 00) 385.00 87.05 Free Outfall RO,CO (no Q: 00) S/N: DOYXYWH3NLBE Withers & Ravenel PondPack (10.00.015.00) 10:27 AM 6/6/2006 BMP SIZING CALCULATION S Project Name: 40/WADE City/State: Raleigh, NC Project #: 204467 Date: 6-Jun-06 Table 1.1 Surface Area to Drainage Area Ratio for Permanent Pool Sizing for 859'° Pollutant Ramnval Fffirinnrv in thn Piarlmnnt Impervious Cover Permanent Pool Depth (feet) 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10 0.59 0.49 0.43 0.35 0.31 0.29 0.26 20 0.97 0.79 0.70 0.59 0.51 0.46 0.44 30 1.34 1.08 0.97 0.83 0.70 0.64 0.62 40 1.73 1.43 1.25 1.05 0.90 0.82 0.77 50 2.06 1.73 1.50 1.30 1.09 1.00 0.92 60 2.40 2.03 1.71 1.51 1.29 1.18 1.10 70 2.88 2.40 2.07 1.79 1.54 1.35 1.26 80 3.36 2.78 2.38 2.10 1.86 1.60 1.42 90 3.74 3.10 2.66 2.34 2.11 1.83 1.67 Source: NCDENR/DWQ Stormwater Best Management Practices, pg. 5, April 1999 STORMWATER BMP #1 -WETLAND (85% TSS Removal 8 40% TN Removal) Land Use Area (ac) % IA Imp. Area (ac) Commercial 16.15 85 13.7 BMP Area 0.94 0 0.0 Totals 17.09 13.7 Total % Impervious Surface Area = 80.3 Normal Pool De th 3 4 5 6 7 8 9 SA/DA Ratio 3.37 2.54 2.33 2.04 1.66 1.55 1.53 Minimum Surface Area Re wired Acres 0.58 0.43 0.40 0.35 0.28 0.26 0.26 Sq. Ft 25105.07 18904.45 17336.29 15170.16 12329.20 11507.90 11359.01 Surface Area of Permanent Pool: Assumed depth = 3 feet SA/DA ratio = 3.37 % From Table 1.1 Minimum pond surface area (SA) _ (DA * SA/DA ratio)/100 SA = 0.576 acres 25105 sq. ft. Normal pool elevation = 382.00 feet Surface area provided = 0.584 acres 25436 sq. ft. First Flush Volume Calculation (1" of Rainfall) Using the runoff volume calculations in the "Discreet Curve Number Method" as recommended by Dr. Bill Hunt, NC State University S=(1000/CN)-10 S= Potential maximum Retention after runoff begins (inches) R/O=(P-0.25)2/(P+0.85) R/O= Runoff (inches) P= Rainfall depth (in) Impervious Areas (CN=98) : S= 0.20 inches R/O = 0.79 inches Runoff Volume = > V= 10.86 acre-inches Pervious Areas (CN=61): S= 6.39 inches R/O= 0.01 inches Runoff Volume = > V= 0.04 acre-inches Total runoff volume from 1-inch precipitation (Sum of runoff volume from impervious and pervious areas): V, = 10.900 acre-inches 0.908 acre-ft 39567 cf Water quality pool elevation= 384.00 feet Storage volume provided = 1.240 acre-ft 54030 cu. ft. Project Name: 40/WADE Project #: 204467 City/State: Raleigh, NC Date: 6/6/2006 STORMWATER BMP #1 -WETLAND (85% TSS Removal 8 40% TN Removal) Orifice Calculator Variables WQ Volume: Head: Draw down time: Orifice Area = Orifice Diameter = 1.06 Acre-ft 1.50 ft 62 hrs 46173.6 cf 0.75 ft 223200 s Constants g= Cd = 32.2 ft/sZ 0.6 Max Q = 0.049611 sq. ft 3.0 in 0.29 cfs 7.143931 sq. in • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Project Name: 40/WADE Project #: 204467 City/State: Raleigh, NC Date: 6-Jun-06 Table 1.1 Surface Area to Drainage Area Ratio for Permanent Pool Sizing for 85% Pollutant RPmnval Effirirnrv in the Pirdmnnt % Impervious Cover Permanent Pool Depth (feet) 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10 0.59 0.49 0.43 0.35 0.31 0.29 0.26 20 0.97 0.79 0.70 0.59 0.51 0.46 0.44 30 1.34 1.08 0.97 0.83 0.70 0.64 0.62 40 1.73 1.43 1.25 1.05 0.90 0.82 0.77 50 2.06 1.73 1.50 1.30 1.09 1.00 0.92 60 2.40 2.03 1.71 1.51 1.29 1.18 1.10 70 2.88 2.40 2.07 1.79 1.54 1.35 1.26 80 3.36 2.78 2.38 2.10 1.86 1.60 1.42 90 3.74 3.10 2.66 2.34 2.11 1.83 1.67 Source: NCUtN WUW(Z Stormwater best Management Nractices, pg. 5, April 7999 STORMWATER BMP #2 -WETLAND (85% TSS Removal & 40% TN Removal) Land Use Area (ac) % IA Imp. Area (ac) Commercial 9.33 85 7.9 BMP Area 0.84 0 0.0 Totals 10.17 7.9 Total % Impervious Surface Area = 78.0 Normal Pool De th 3 4 5 6 7 8 9 SA/DA Ratio 3.26 2.47 2.27 1.98 1.61 1.50 1.48 Minimum Surface Area Re wired Acres 0.33 0.25 0.23 0.20 0.16 0.15 0.15 Sq. Ft 14455.30 10948.44 10036.03 8778.17 7139.51 6661.15 6572.55 Surface Area of Permanent Pool: Assumed depth = 3 SA/DA ratio = 3.26 Minimum pond surface area (SA) _ (I SA = 0.332 14455 feet % From Table 1.1 JA * SA/DA ratio)/100 acres sq. ft. Normal pool elevation = 382.00 feet Surface area provided = 0.584 acres 25436 sq. ft. First Flush Volume Calculation (1" of Rainfall) Using the runoff volume calculations in the "Discreet Curve Number Method" as recommended by Dr. Bill Hunt, NC State University S=(1000/CN)-10 S= Potential maximum Retention after runoff begins (inches) R/0=(P-0.2S)Z/(P+0.85) R/0= Runoff (inches) P= Rainfall depth (in) Impervious Areas (CN=98): S= 0.20 inches R/0= 0.79 inches Runoff Volume => V= 6.27 acre-inches Pervious Areas (CN=61): S= 6.39 inches R/O = 0.01 inches Runoff Volume = > V= 0.03 acre-inches Total runoff volume from 1-inch precipitation (Sum of runoff volume from impervious and pervious areas): Vt = 6.301 acre-inches 0.525 acre-k 22872 cf Water quality pool elevation= 384.00 feet Storage volume provided = 1.240 acre-ft 54030 cu. ft. Project Name: 40/WADE Project #: 204467 City/State: Raleigh, NC Date: 6/6/2006 STORMWATER BMP #2 -WETLAND (85% TSS Removal 8 40% TN Removal) Orifice Calculator Variables WQ Volume: 1.240358 Acre-ft Head: 2.00 ft Draw down time: 51 hrs 54030 cf 1ft 183600 s Constants g= Cd = Orifice Area = 0.061 118 sq. ft Orifice Diameter = 3.3 in 8.800971 sq. in 32.2 ft/s2 0.6 Max Q = 0.42 cfs