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Home My WebLink AboutWPO200500055 Calculations Stormwater Management Plan 2005-07-12 . t. g., c79) 0 COP 2ioboRI- 70 �EPP Stormwater Management �6' Facility White Gables Albemarle County, Virginia 5 November 2003 Revised 17 November 2003 Revised 2 December 2003 Revised 10 December 2003 \.44-p,LTH O Revised 7 January 2005 1 IL 4' cZ Revised 2 May 2005 + Revised 20 June 2005 : �' Robert B. McKee r + lrc. No. 7783 • • J • Revised 12 July 2005 , ' `f O `rsIONAL'005 A'IE: * ; VIcKEE CARSON t i NEERS ' LANDSCAPE ARCHITECTS ' PLANNERS u,w I HIGH STREET • CHARLOTTESVILLE,VIRGINIA 22902 434.979.7522 tel 434.977.1194 fax www.mckeecarson.com RECEIVED JUL 13 2005 COMMUNITY DEVELOPMENT Introduction This 7.1-acre site, located just west of Charlottesville on U.S. Route 250 (Ivy Road), is to be developed as residential condominiums. At ultimate buildout, it is expected to consist of six new pavilion buildings in addition to the existing historic structure. Phase 1 of the plan builds the driveway and parking areas, much of the infrastructure, and two of the pavilions. Each pavilion contains 10 condominium units. This site is within the designated Development Area of Albemarle County and is not within a reservoir watershed. Stormwater management at White Gables consists of water quality control measures as well as runoff control facilities. The site is divided by a drainage divide into two major drainage areas: the front, or south, portion of the site,which drains toward Ivy Road and consists of approximately 2.5 acres; and the rear (north) portion,which drains toward the C&O Railroad and encompasses approximately 4.6 acres. Construction on the front portion will consist primarily of the creation or relocation of a driveway and sidewalk. The existing building straddles the drainage divide,while all new buildings will be located in the rear portion. All stormwater management structures will be located in the rear portion of the site. BMP Computations Using the spreadsheet provided by the County of Albemarle, the BMP requirements have been determined for the front and rear portions of the site separately. Please refer to the worksheets and BMP Drainage Areas map in Appendix A. For the purpose of these computations,the post-development watershed boundary is used for both pre- and post- development conditions. This is done so that a direct comparison may be made of impervious areas for each of the watersheds under study. The property boundary forms the remaining limits of each computational area. As indicated in Appendix A, the front portion of the site has a removal rate requirement (%RR) of 18%, and a water quality volume (V) of 43.3 cubic yards;for the rear portion, a %RR of 53% is indicated, with a V of 122.1 cubic yards. Pursuant to conversations with the Water Resources Officer of the County of Albemarle,no BMP measures are proposed in the front area. In the rear area, the site will be served at final build-out by one StormFilter vault and an area of pervious pavement with a base of porous aggregate. Overflow from the StormFilter vault is routed through an underground detention vault (see below for detention requirements and computations). StormFilters One StormFilter vault with sixteen (16) filters is proposed as part of the overall BMP plan. These filters are designed to remove pollutants after the water quality volume (WQV) has been stored in the Stormtech system; accommodating the water quality volume from the drainage area captured by the stormdrain system. 2 The filters accepts the runoff from the roofs of Pavilions I and III as well as the future Pavilion V; it also includes a portion of the Pavilion I and III driveway, the entrance walkway to Pavilion III, and a small part of the loop road. The filters also drain the front portions of the roofs of future Pavilions II and IV, the rear of the existing manor house, and a portion of the loop road as well as several scattered paved surfaces. Filter computations are included in Appendix A. Each subarea drains to a Stormgate flow splitter just upstream of the Stormtech storage facility. The splitter allows the water quality volume for each subarea to be directed to the Stormtech storage areas. For larger storms, after the water quality volume is handled,the Stormtech system will be full and any additional flow will be handled by the detention facility (described below). Pervious Pavement Pervious pavement is to be installed where indicated on the plans. The system is to consist of a pervious surface over 4" of sand over filter fabric over 18" of#57 aggregate base. A 4" perforated pipe will be installed in the top 6" of aggregate to handle any overflow, as subsurface soil conditions preclude effective infiltration. Refer to detail E on Sheet 32 of the plans. Detention In addition to the storage provided by the Stormtech system, and pervious pavement aggregate base, an underground detention facility is proposed to limit the post-development peak runoff rates. As the stormwater management for this site is complex, some simplifying assumptions are made for computation purposes. First, it is assumed that all offsite runoff is unaffected by this development;no offsite areas are included in the computations. Second,the areas of pervious pavement are assumed to have a runoff coefficient similar to that of lawn areas (CN=75); however, the storage capacity of the void spaces under the pervious pavement is ignored (this essentially treats the grasspaved areas as ordinary lawn). Third the, runoff from the front portion of the site (see "BMP Computations" above) is not considered in these computations. Finally, it is noted that while the site has multiple discharge locations (including sheet flow runoff and pipe outfalls), these computations consider both the pre-and post-development areas to have a single effective discharge point, which allows direct comparison between pre- and post-development runoff condition; the longest runoff travel time is used to compute rainfall intensity for the design storms. Refer to the drainage area map provided in Appendix A ("BMP drainage areas") for a graphical depiction of the study area, including impervious surfaces considered in the computations. 3 Although the area under consideration is small (less than 5 acres), the SCS Method is used to compute pre- and post-development runoff. This is due to the complexity of the developed site and limitations inherent within the Rational Method modeling software. Pursuant to Albemarle County standards, the storms considered are the 2-, 10-and 100-year frequency storms. The goal of the detention facility is to attenuate the runoff from the 2- and 10-year storms to their pre-development levels or below, and to accommodate the runoff from the 100- year storm so as to avoid property damage from flooding. Pre-development Runoff Pre-development runoff is calculated in Appendix B. Peak runoff rates are determined to be 10.48,20.66 and 34.18 cfs for the 2-, 10- and 100-year storm events,respectively. Post-development Runoff Post-development computations are included in Appendix B. These computations consider the storage capacity of the StormFilters as described above, and a 42.7'x 38.8'x 7.21' deep rectangular underground detention structure. The outlet configuration for the detention structure consists of a 5.33'rectangular weir with a rectangular orifice for the 10-yr storm; a 8" circular orifice at the base of the weir wall for the 2-yr storm; and a 24" diameter discharge pipe. The outlet also passes the 100-yr storm as required. Given this configuration, and taking into account the area by-passing the detention facility,the total runoff from the rear of the site is computed to be 10.47 and 20.27 for the 2- and 10-year storm events,respectively. These values are comparable to the runoff rates calculated in the approved December 2003 White Gables plan (Q2= 9.07 cfs and Qio= 20.67). No backwater is therefore expected to pond on the surface or encroach upon the buildings. Conclusion The BMP facilities meet the requirements outlined above. The detention facility meets the design goals. 4 _ __ _ _ - -- 1 yytt, LEGEND McKEECARSON DRAINAGE AREA 1 DRAINAGE AREA 2 REMAINING DRAINAGE AREA I CONSUL LAND GLANPSHPE 4ENtiING ffEEPS CiS 1.02 ac 113 AC BYPASSES STORMWATER SYSTEM TO E2 INLET TO F2 INLET 301 East Hugh 3Yeelenedonesvlaa•VA 22902 w34 ww.]9-]522 .J .mcxaecerspuom 1 I McKae Carsonand Fetl 9prConc ptt,Lb. reserves acommon law mMnp .n \ \ pM pronyu.uuee.m ga ay. .Mbeaa, \1 \ V _ _ deeps awdaa deuik mbpanearetlre \ 1 `` `` ' ' , pmpMOlYIXee Grsonend FeN Spwl //`J Colicep4 Vd Resephmare nolb Ee I 1111111.6.121111•— I reproducedt WnOM wmpmdineMb�m or r nix entry lo \\ I �-L__1J _—J,— —I- -- ..11111r �� assigned maM�nwlYmMOM'aster 4 _ Li aelamngw pewdsson end nonvm I \ _ - a ern ne,uxee Carson orFeuSpan d \\� I - 11 — '/// i - i Concepts Lid p • I - .-_ I �� • , , , „/ I `�\ I-- I----� _ I I / IP Pir Imo. i . Nirs........0 f Cn p X ‘ IMP* . 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'' ` Of Appendix A BMP Computations StormFilter Computations Short Version BMP Computations ror Worksheets 2 - 6 Albemarle County Water Protection Ordinance: SCS Plan: White Gables Water Resources Area: Development Area Preparer: McKee Carson Date: 10/31/2003 Project Drainage Area Designation Rear of Site L storm pollutant export in pounds, L= [P(Pj)Rv/12] [C(A)2.72] Rv mean runoff coefficient, Rv=0.05+0.009(I) Pj small storm correction factor,0.9 I percent imperviousness P annual precipitation,43"in Albemarle A project area in acres in subject drainage area, A= 4.60 C pollutant concentration, mg/I or ppm target phosphorus f factor applied to RR ✓ required treatment volume in cy, 0.5"over imperv.area= A(1)43560(0.5/12)/27 RR required removal , L(post)-f x L(pre) %RR removal efficiency, RR100/L(post) Impervious Cover Computation (values in feet&square feet) 'Item, Area post-development Area Roads Length Width subtotal Length Width subtotal 0 0 0 0 0 0 0 0' 0 0 0 0 0 0 0 0 0 0 0 0 Driveways Length Width no. subtotal Length Width no. subtotal and walks 0 0 0 3361 0 0 0 0 0 0 0 0 0 0 0 0 0 3361 0 21142 Parking Lots 1 2 3 4 1 2 3 4 0 0 0 Structures Area no. subtotal Area no. subtotal 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 66708 • Actively-grazed pasture& Area Area yards and cultivated turf 195218 x 0.08= 15617.44 112526 x 0.08= 9002.08 Active crop land Area Area 0x0.25= 0 x0.25= 0 Other Impervious Areas 1797 0 Impervious Cover 10% 48% I(pre) I(post) Rv(post) V 0.49 149.5 New Development(For Development Areas,existing impervious cover<=20%) C f I (pre)* Rv(pre) L(pre) L(post) RR %RR Area Type 0.70 :1.00 - 20% 0.23 6.50 13.70 7.20 53% Development Area 0.35 1'.00 :g% 0.14 2.02 6.85 4.82 70% Drinking Water Watersheds 0.40 Lao. 1% 0.14 2.31 7.83 5.51 70% Other Rural Land min.values Redevelopment(For Development Areas,existing impervious cover>20%) C f I (pre)* Rv(pre) L(pre) L(post) RR %RR Area Type 0.70 0.90 20% 0.23 6.50 13.70 7.85 57% Development Area 0.35 0.85 0% 0.14 2.02 6.85 5.13 75% Drinking Water Watersheds 0.40 0.85 1% 0.14 2.31 7.83 5.86 75% Other Rural Land Interim Manual, Page 70 rev.31 March 1998 GEB Short Version BMP Computations ror Worksheets 2 - 6 Albemarle County Water Protection Ordinance: SCS Method Plan: White Gables Water Resources Area: Development Area Preparer: McKee Carson Date: 3/9/2005 Project Drainage Area Designation Captured Rear of Site L storm pollutant export in pounds, L=[P(Pj)Rv/12 j[C(A)2.72) Rv mean runoff coefficient, Rv=0.05+0.009(1) Pj small storm correction factor,0.9 I percent imperviousness P annual precipitation,43"in Albemarle A project area in acres in subject drainage area, A 2.42 C pollutant concentration, mg/I or ppm target phosphorus f factor applied to RR ✓ required treatment volume in cy, 0.5"over imperv.area= A(I)43560(0.5/12)/27 RR required removal, L(post)-f x L(pre) %RR removal efficiency, RR100/L(post) Impervious Cover Computation(values in feet&square feet) Item pre-development Area post-development Area Roads Length Width subtotal Length Width subtotal 0 0 0 0 0 6514 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 6514 Driveways Length Width no. subtotal Length Width no. subtotal and walks 0 0 0 0 _ 0 0 0 3426 0 0 0 0 0 0 b 1590 0 0 0 0 0 0 5016 Parking Lots 1 2 3 4 1 2 3 4 0 0 0 0 0 0 0 0 0 0 Structures Area no. subtotal Area no. subtotal 0 0 2046 0 0 2046 0 0 0 0 0 52018 0 0 0 2046 0 66708 -Actively-grazed pasture& Area Area yards and cultivated turf 92711 x 0.08= 7416.88 11122 x 0.08= 889.76 Active crop land Area Area Ox0.25= 0 x0.25= 0 Other Impervious Areas 0 0 Impervious Cover 9% 75% I(pre) l(post) Rv(post) V 0.72 122.1 New Development(For Development Areas,existing impervious cover<=20%) C f I (pre)* Rv(pre) L(pre) L(post) RR %RR Area Type - 0.70 , . 1.00 '.20% 0.23 3.42 10.78 7.36 68% Development Area '0:35 i '1(00 0% 0.13 0.97 5.39 4.42 82% Drinking Water Watersheds 0.40 1.00 1% 0.13 1.11 6.16 5.05 82% Other Rural Land *min.values Redevelopment(For Development Areas,existing impervious cover>20%) C f I (pre)* Rv(pre) L(pre) L(post) RR %RR Area Type 0.70 0.90 20% 0.23 3.42 10.78 7.70 71% Development Area 0.35 0.85 0% 0.13 0.97 5.39 4.56 85% Drinking Water Watersheds 0.40 0.85 1% 0.13 1.11 6.16 5.22 85% Other Rural Land Interim Manual, Page 70 rev.31 March 1998 GEB _c;) ±.„ \A, C.J NN. ‘.0,1 7)- ‘ CI \ \ Appendix B Pre-Development Runoff Computations Post-Development Runoff and Detention Computations Job File: E: \PROJECT F1LES\0406-WHITE GABLES PHASE 1 CA\DESIGN CALCS\B'Y-PASS-V10-SCS.PPW Pain Dir: E: \PROJECT FILES\0406-WHITE GABLES PHASE 1 CA\DESIGN CALCS'\ JOB TITLE , d Project Date: 4/28/2005 \14•` -'� Project Engineer: Mike J% V Project Title: White Gables:lby-pass Project Comments: • S/N: D1YXYWGWM4CC Mckee Carson PondPack (10.00.016.00) 10:56 AM 5/2/2005 J . Table of Contents i ***„****************** MASTER SUMMARY *********.************* Watershed Master Network Summary 1.01 ********************** CN CALCULATIONS ********************* SUBAREA 10 Runoff CN-Area 2.01 S/N: D1YXYWGWMIICC Mckee Carson PondPack (10.00.016.00) 10:56 AM • 5/2/2005 Type. . . . Master Network Summary Page 1.01 Name. . . . Watershed File. . . . E: \PROJECT FILES\0406-WHITE GABLES PHASE 1 CA\DESIGN CALCS\by-pass-v10-scs.ppw MASTER DESIGN STORM SUMMARY Network Storm Collection: Albemarle County Total Depth Rainfall Return Event in Type RNF ID 5 5.0000 Synthetic Curve Typell 24hr 100 8.5000 Synthetic Curve Typell 24hr 1 3.3000 Synthetic Curve Typell 24hr 2 4.0000 Synthetic Curve Typell 24hr 10 6.0000 Synthetic Curve Typell 24hr MASTER NETWORK SUMMARY SOS Unit Hydrograph Method (*Node=Outfall; +Node=Diversion;) (Trun= HYG Truncation: Blank-None; L=Left; R=Rt; LR=Left&Rt) Max Return HYG Vol Qpeak Qpeak Max WSEL Pond Storage Node ID Type Event ac-ft Trun hrs cfs ft ac-ft *OUT 10 JCT 5 .693 12.0000 10.37 *OUT 10 JCT 100 1.478 12.0000 421.84f. *OUT 10 JCT 1 .349 12.0500 5.25 *OUT 10 JOT 2 .486 12.0500 1\- al:, *OUT 10 JCT 10 .910 12.0000 L1 3s POND 10 IN POND 5 .693 12.0000 10.37 POND 10 IN POND 100 1.478 12.0000 21.84 POND 10 IN POND 1 .349 12.0500 5.25 POND 10 IN POND 2 .486 12.0500 7.31 POND 10 IN POND 10 .910 12.0000 13.61 POND 10 OUT POND 5 .693 12.0000 10.37 POND 10 OUT POND 100 1.478 12.0000 21.84 POND 10 OUT POND 1 .349 12.0500 5.25 POND 10 OUT POND 2 .486 12.0500 7.31 POND 10 OUT POND 10 .910 12.0000 13.61 S/N: DIYXYWGWM4CC Mckee Carson PondPack (10.00.016.00) 10:56 AM 5/2/2005 Type. . . . Master Network Summary Page 1.02 Name. . . . Watershed File. . . . E:\PP.OJECT FILES\0406-WHITE GABLES PHASE 1 CA\DESIGN CALCS\by-pass-v10-scs.pp'W MASTER NETWORK SUMMARY SCS Unit Hydrograph Method (*Node=Outfali; +Node=Diversion; ) Mfrun= HYG Truncation: Blank=None; L=Left; R=Rt; LR=Left&Rt) Max Return HYG Vol Qpeak Qpeak Max WSEL Pond Storage Node ID Type Event ac-ft Trun hrs cfs ft ac-ft SUBAREA 10 AREA 5 .693 12.Q0.00 10.37 SUBAREA 10 AREA 100 1.478 12.0000 21.84 SUBAREA 10 AREA 1 .349 12.0500 5.25 SUBAREA 10 AREA 2 .486 12.0500 7.31 SUBAREA 10 AREA 10 .910 12.0000 13.61 S/N: D1YWYWGWM4CC Mckee Carson PondPack (10.00.016.00) 10:56 AM 5/2/2005 J . Type Runoff CN-Area Page 2.01 Name SUBAREA 10 RUNOFF CURVE NUMBER DATA Impervious Area Adjustment Adjusted Soil/Surface Description CN acres %C %UC CN pervious by-pass 74 2.380 74.00 impervious by-pass 98 .589 98.00 COMPOSITE AREA & WEIGHTED CN ---> 2.969 78.76 (79) S/N: DIYXYWGWM4CC Mckee Carson PondPack (10.00.016.00) 10:56 AM 5/2/2005 Job File: E:\PROJECT-FILES\0219-WHITE GABLES\0219 DESIGN\DETENTION;PRE:DEV.ELOPMENTtPPYI Rain Dir: C:\HAESTAD\PPKW\RAINFALL\ JOB TITLE Pre-development Computations ��L c I'c I?�r�` " ' White Gables S/N: 021701D06A87 McKee Carson PondPack Ver: 7.5 (765) Compute Time: 08:23:06 Date: 12-02-2003 Type. . . . Master Network Summary Page 1.01 Name. . . . Watershed File. . . . E: \PROJECT-FILES\0219-WHITE GABLES\0219 DESIGN\DETENTION`.PEE-DEVELOPMENT.PPW MASTER DESIGN STORM SUMMARY Default Network Design Storm File, ID ALBCO.RNQ Albemarle Total Depth Rainfall Return Event in Type RNF File RNF ID SC 1 3.3000 Synthetic Curve SCSTYPES TypelI 24hr SC 2 4.0000 Synthetic Curve SCSTYPES Typell 24hr SC 10 6.0000 Synthetic Curve SCSTYPES Typell 24hr SC 100 8.5000 Synthetic Curve SCSTYPES Typell 24hr MASTER NETWORK SUMMARY SCS Unit Hydrograph Method (*Node=Outfall; +Node=Diversion;) (Trun= HYG Truncation: Blank=None; L=Left; R=Rt; LR=Left&Rt) Max Return HYG Vol Qpeak Qpeak Max WSEL Pond Storage Node ID Type Event ac-ft Trun min cfs ft ac-ft *PRE-DEV RUNOFF JCT 1 .446 720.00 7.21 *PRE-DEV RUNOFF JCT 2 .639 720.00 ;44?B , *PRE-DEV RUNOFF JCT 10 1.258 720.00 �..,66 *PRE-DEV RUNOFF JCT 100 2.106 719.00 318 REAR AREA AREA 1 .446 720.00 7.21 REAR AREA AREA 2 .639 720.00 10.48 REAR AREA AREA 10 1.258 720.00 20.66 REAR AREA AREA 100 2.106 719.00 34.18 S/N: 021701D06A87 McKee Carson.: PondPack Ver: 7.5 (765) Compute Time: 08:23:06 Date: 12-02-2003 • Type. . . . Design Storms Page 2.01 Name. . . . Albemarle File. . . . C:\HAESTAD\PPKW\RAINFALL\ALBCO.RNQ Title. . . Pre-development Computations White Gables DESIGN STORMS SUMMARY Design Storm File,ID = ALBCO.RNQ Albemarle Storm Tag Name = SC 1 Description: Albemarle County 001 Year Data Type, File, ID = Synthetic Storm SCSTYPES.RNF Typell 24hr Storm Frequency = 1 yr Total Rainfall Depth= 3.3000 in Duration Multiplier = 1 Resulting Duration = 1440.00 min Resulting Start Time= .00 min Step= 6.00 min End= 1440.00 min Storm Tag Name = SC 2 Description: Albemarle County 002 Year Data Type, File, ID = Synthetic Storm SCSTYPES.RNF Typell 24hr Storm Frequency = 2 yr Total Rainfall Depth= 4.0000 in Duration Multiplier = 1 Resulting Duration = 1440.00 min Resulting Start Time= .00 min Step= 6.00 min End= 1440.00 min Storm Tag Name = SC 10 Description: Albemarle County 010 Year Data Type, File, ID = Synthetic Storm SCSTYPES.RNF Typell 24hr Storm Frequency = 10 yr Total Rainfall Depth= 6.0000 in Duration Multiplier = 1 Resulting Duration = 1440.00 min Resulting Start Time= .00 min Step= 6.00 min End= 1440.00 min Storm Tag Name = SC 100 Description: Albemarle County 100 Year Data Type, File, ID = Synthetic Storm SCSTYPES.RNF Typell 24hr Storm Frequency = 100 yr 'Total Rainfall Depth= 8.5000 in Duration Multiplier = 1 Resulting Duration = 1440.00 min Resulting Start Time= .00 min Step= 6.00 min End= 1440.00 min S/N: 021701D06A87 McKee Carson PondPack Ver: 7.5 (765) Compute Time: 08:23:06 Date: 12-02-2003 Type. . . . Tc Cabs Page 3.01 Name. . . . REAR AREA File. . . . E:\PROJECT-FILES\0219-WHITE GABLES\0219 DESIGN\DETENTION\PRE-DEVELOPMENT.PPW TIME OF CONCENTRATION CALCULATOR Segment #1: Tc: User Defined Description: Time of conc. , sheet & SC flow Segment #1 Time: 10.00 min Total Tc: 10.00 min S/N: 021701D06A87 McKee Carson— PondPack Ver: 7.5 (765) Compute Time: 08:23:06 Date: 12-02-2003 Type. . . . Runoff CN-Area Page 4 .01 Name. . . . REAR AREA File. . . . E:\PROJECT-FILES\0219-WHITE GABLES\0219 DESIGN\DETENTION\PRE-DEVELOPMENT.PPW RUNOFF CURVE NUMBER DATA Impervious Area Adjustment Adjusted Soil/Surface Description CN acres %C %UC CN impervious 98 .120 98.00 HSG C lawn 74 4.480 74 .00 COMPOSITE AREA & WEIGHTED CN 4.600 74.63 (75) S/N: 021701D06A87 McKee Carson' PondPack Ver: 7.5 (765) Compute Time: 08:23 :06 Date: 12-02-2003 • Type. . . . SCS Unit Hyd. Summary Page 5.04 Name. . . . REAR AREA Tag: SC 2 Event: 2 yr File. . . . E:\PROJECT-FILES\0219-WHITE GAELES\0219 DESIGN\DETENTION\PRE-DEVELOPMENT.PPW Storm. . . Typell 24hr Tag: SC 2 SCS UNIT HYDROGRAPH METHOD STORM EVENT: 2 year storm Duration - = 1440.00 min Rain Depth = 4 .0000 in Rain Dir = C:\HAESTAD\PPKW\RAINFALL\ Rain File -ID = SCSTYPES.RNF - Typell 24hr Unit Hyd Type = Default Curvilinear HYG Dir = E:\PROJECT-FILES\0219-WHITE GABLES\0219 DESIGN\DETENTION\ HYG File - ID = - REAR AREA SC 2 Tc = 10.00 min Drainage Area = 4.600 acres Runoff CN= 75 Computational Time Increment = 1.333 min Computed Peak Time = 720.00 min Computed Peak Flow = 10.48 cfs Time Increment for HYG File = 1.00 min Peak Time, Interpolated Output = 720.00 min Peak Flow, Interpolated Output = 10.48 cfs DRAINAGE AREA ID:REAR AREA CN = 75 Area = 4.600 acres S = 3.3333 in 0.29 = .6667 in Cumulative Runoff 1.6667 in .639 ac-ft HYG Volume. . . .639 ac-ft (area under HYG curve) ***** UNIT HYDROGRAPH PARAMETERS ***** Time Concentration, Tc = 10.000 min (ID: REAR AREA) Computational Incr, Tm = 1.333 min = 0.20000 Tp Unit Hyd. Shape Factor = 483.432 (37.46% under rising limb) K = 483 .43/645.333, K = .7491 (also, K = 2/(1+(Tr/Tp) ) Receding/Rising, Tr/Tp = 1.6698 (solved from K = .7491) Unit peak, qp = 31.27 cfs Unit peak time Tp = 6.667 min Unit receding limb, Tr = 26.667 min • Total unit time, Tb = 33.333 min S/N: 021701D06A87 McKee Carson PondPack Ver: 7.5 (765) Compute Time: 08:23:06 Date: 12-02-2003 Type. . . . SCS Unit Hyd. Summary Page 5. 05 Name. . . . REAR AREA Tag: SC 10 Event: 10 yr File. . . . E:\PROJECT-FILES\0219-WHITE GABLES\0219 DESIGN\DETENTION\PRE-DEVELOPMENT.PPW Storm. . . Tyrrell 24hr Tag: SC 10 SCS UNIT HYDROGRAPH METHOD STORM EVENT: 10 year storm Duration = 1440.00 min Rain Depth = 6.0000 in Rain Dir = C:\HAESTAD\PPKW\RAINFALL\ Rain File -ID = SCSTYPES.RNF - Typell 24hr Unit Hyd Type = Default Curvilinear HYG Dir = E:\PROJECT-FILES\0219-WHITE GABLES\0219 DESIGN\DETENTION\ HYG File - ID = - REAR AREA SC 10 Tc = 10.00 min Drainage Area = 4.600 acres Runoff CN= 75 Computational Time Increment = 1.333 min Computed Peak Time = 720.00 min Computed Peak Flow = 20.66 cfs Time Increment for HYG File = 1.00 min Peak Time, Interpolated Output = 720.00 min Peak Flow, Interpolated Output = 20.66 cfs DRAINAGE AREA ID:REAR AREA CN = 75 Area = 4.600 acres S = 3.3333 in 0.2S = .6667 in Cumulative Runoff 3.2821 in 1.258 ac-ft HYG Volume. . . 1.258 ac-ft (area under HYG curve) ***** UNIT HYDROGRAPH PARAMETERS ***** Time Concentration, Tc = 10.000 min (ID: REAR AREA) Computational Incr, Tm = 1.333 min = 0.20000 Tp Unit Hyd. Shape Factor = 483.432 (37.46% under rising limb) K = 483.43/645.333, K = .7491 (also, K = 2/(1+(Tr/Tp) ) Receding/Rising, Tr/Tp = 1.6698 (solved from K = .7491) Unit peak, qp = 31.27 cfs Unit peak time Tp = 6.667 min Unit receding limb, Tr = 26.667 min Total unit time, Tb = 33.333 min S/N: 021701006A87 McKee Carson PondPack Ver: 7.5 (765) Compute Time: 08:23:06 Date: 12-02-2003 Type. . . . SCS Unit Hyd. Summary Page 5.06 Name. . . . REAR AREA Tag: SC 100 Event: 100 yr File. . . . E:\PROJECT-FILES\0219-WHITE GABLES\0219 DESIGN\DETENTION\PP.E-DEVELOPMENT.PPW Storm. . . Typell 24hr Tag: SC 100 SCS UNIT HYDROGRAPH METHOD STORM EVENT: 100 year storm Duration = 1440.00 min Rain Depth = 8.5000 in Rain Dir = C:\HAESTAD\PPKW\RAINFALL\ Rain File -ID = SCSTYPES.RNF - Typell 24hr Unit Hyd Type = Default Curvilinear HYG Dir = E:\PROJECT-FILES\0219-WHITE GABLES\0219 DESIGN\DETENTION\ HYG File - ID = - REAR AREA SC 100 Tc = 10.00 min Drainage Area = 4.600 acres Runoff. CN= 75 Computational Time Increment = 1.333 min Computed Peak Time = 718.67 min Computed Peak Flow = 34.21 cfs Time Increment for HYG File = 1.00 min Peak Time, Interpolated Output = 719.00 min Peak Flow, Interpolated Output = 34.18 cfs DRAINAGE AREA ID:REAR AREA CN = 75 Area = 4.600 acres S = 3.3333 in 0.25 = .6667 in Cumulative Runoff 5.4950 in 2.106 ac-ft HYG Volume. . . 2.106 ac-ft (area under HYG curve) ***** UNIT HYDROGRAPH PARAMETERS ***** Time Concentration, Tc = 10.000 min (ID: REAR AREA) Computational Incr, Tm = 1.333 min = 0.20000 Tp Unit Hyd. Shape Factor = 483.432 (37.46% under rising limb) K = 483.43/645.333, K = .7491 (also, K = 2/(1+(Tr/Tp)) Receding/Rising, Tr/Tp = 1.6698 (solved from K = .7491) Unit peak, qp = 31.27 cfs Unit peak time Tp = 6.667 min Unit receding limb, Tr = 26.667 min Total unit time, Tb = 33.333 min S/N: 021701D06A87 McKee Carson PondPack Ver: 7.5 (765) Compute Time: 08:23:06 Date: 12-02-2003 RainTank Calculator Contact: Project Name: Company: Location: Phone: Fax: Step 1 Enter the required storage capacity in cubic feet. 11,000 cf Volume of Tanks Required: 11,578.95 cf Step 2 Using the buttons, select a depth from the table below. Remember that the deeper the system, the more economic it becomes. Of course you'll typically want the bottom of the system to be above the water table or hard-pan, keeping in mind you need 12" of cover above the system (24"for parking lots or roads). Depth Options and Corresponding Number of Tanks Required Tank Style Depth Number of Tanks Required O Single Tanks 1.48' 2,608 O Double Tanks 2.89' 1,333 O Triple Tanks 4.3' 896 O Quad Tanks 5.71' 675 0 Pent Tanks 7.12' 541 Step 3 Configure System Dimensions. Enter the length available on the site to install the system (in feet). The worksheet will then show you the width and length in terms of total number of tanks, the footprint of your system, and the footprint of the excavation, allowing a 2' perimeter to compact backfill. Length available: 48 Feet Number of units long: 19 Footprint: 42.70 Feet Long Number of units wide: 29 38.81 Feet Wide Tanks used in Excavatiion Footprint: 46.70 Feet Long selected system: 551 42.81 Feet Wide ' Step 4 Check the box below if the RainTank is located below a parking lot or any area subject to traffic loads. ❑Yes,there will be traffic loads above the RainTank. Step 5 Check the box below if you would like to include a liner in your system to allow you to harvest/recycle water in the system for use in irrigating the landscaping. ❑Yes,I'd like to indude a liner in the system to recycle water. Step 6 The next worksheet contains a list of all the materials you will need to build this system. Please review this form. If you like, you can fill in unit costs for all items and determine an estimate for the total system including installation. ACF ACF Environmental 1-800-448-3636 sal es(ffiacfen v iron m ental.com www.acfenvironmental.com Job File: E:\PROJECT FILES\0406-WHITE GABLES PHASE 1 CA\DESIGN CALCS\0406 ROUTING.PPW Rain Dir: E:\PROJECT FILES\0406-WHITE GABLES PHASE 1 CA\DESIGN CALCS\ JOB TITLE Project Date: 4/27/2005 Project Engineer: Mike Project Title: Watershed Project Comments: White Gables SWM design - System includes Raintank, Stormtech SC-740's and StormFilters with Stormgate flow splitters. The analysis is done using the SCS method. SIN: DIYXYWGWM4CC Mckee Carson PondPack (10.00.016.00) 5:45 PM 7/12/2005 Table of Contents i ********************** MASTER SUMMARY ********************** Watershed Master Network Summary 1.01 *************** NETWORK SUMMARIES (DETAILED) *************** Watershed 2 Executive Summary (Nodes) 2.01 ****************** DESIGN STORMS SUMMARY ******************* • Alb. Cnty. storm Design Storms 3.01 ********************** CN CALCULATIONS ********************* PROP. CONDITIONS Runoff CN-Area 4.01 *********************** POND VOLUMES *********************** POND 10 Vol: Elev-Area 5.01 S/N: DIYXYWGWM4CC Mckee Carson PondPack (10.00.016.00) 5:45 PM 7/12/2005 Type. . . . Master Network Summary Page 1.01 Name. . . . Watershed File. . . . E:\PROJECT FILES\0406-WHITE GABLES PHASE 1 CA\DESIGN CALCS\0406 Routing.ppw MASTER DESIGN STORM SUMMARY Network Storm Collection: Alb. Cnty. storm Total Depth Rainfall Return Event in Type RNF ID 2 4.0000 Synthetic Curve Typell 24hr 10 6.0000 Synthetic Curve Typell 24hr 100 8.5000 Synthetic Curve Typell 24hr MASTER NETWORK SUMMARY SCS Unit Hydrograph Method (*Node=Outfall; +Node=Diversion;) (Trun= HYG Truncation: Blank=None; L=Left; R=Rt; LR=Left&Rt) Max Return HYG Vol Qpeak Qpeak Max WSEL Pond Storage Node ID Type Event ac-ft Trun hrs cfs ft ac-ft *OUT 10 JCT 2 .512 12.1500 3.16 *OUT 10 JCT 10 .860 12.1500 6.66 *OUT 10 JCT 100 1.304 12.0500 18.62 POND 10 IN POND 2 .513 12.0000 8.15 POND 10 IN POND 10 .860 12.0000 13.28 POND 10 IN POND 100 1.304 12.0000 19.60 POND 10 OUT POND ` .512 12.1500 ''3 16 . 597..411 .147 liCiPOND 10 OUT POND papa .860 12.1500 i6 6 . 59 60 .231 D' 1 POND 10 OUT POND .304 12.0500 78 2 00:•39 : .261 PROP. CONDITIONS AREA 2 .513 12.0000 8.15 PROP. CONDITIONS AREA 10 .860 12.0000 13.28 PROP. CONDITIONS AREA 100 1.304 12.0000 19.60 S/N: DIYXYWGWM4CC Mckee Carson PondPack (10.00.016.00) 5:45 PM 7/12/2005 Type. . . . Design Storms Page 3.01 Name. . . . Alb. Cnty. storm File. . . . E:\PROJECT FILES\0406-WHITE GABLES PHASE 1 CA\DESIGN CALCS\0406 Routing.ppw Title. . . Project Date: 4/27/2005 Project Engineer: Mike Project Title: Watershed Project Comments: White Gables SWM design - System includes Raintank, Stormtech SC-740's and StormFilters with Stormgate flow splitters. The analysis is done using the SCS method. DESIGN STORMS SUMMARY Design Storm File,ID = Alb. Cnty. storm Storm Tag Name = 2 Data Type, File, ID = Synthetic Storm Typell 24hr Storm Frequency = 2 yr Total Rainfall Depth= 4.0000 in Duration Multiplier = 1 Resulting Duration = 24.0000 hrs Resulting Start Time= .0000 hrs Step= .1000 hrs End= 24.0000 hrs Storm Tag Name = 10 Data Type, File, ID = Synthetic Storm Typell 24hr Storm Frequency = 10 yr Total Rainfall Depth= 6.0000 in Duration Multiplier = 1 Resulting Duration = 24.0000 hrs Resulting Start Time= .0000 hrs Step= .1000 hrs End= 24.0000 hrs Storm Tag Name = 100 Data Type, File, ID = Synthetic Storm Typell 24hr Storm Frequency = 100 yr Total Rainfall Depth= 8.5000 in Duration Multiplier = 1 Resulting Duration = 24.0000 hrs Resulting Start Time= .0000 hrs Step= .1000 hrs End= 24.0000 hrs S/N: DIYXYWGWM4CC Mckee Carson PondPack (10.00.016.00) 5:45 PM 7/12/2005 Type. . . . Runoff CN-Area Page 4.01 Name. . . . PROP. CONDITIONS File. . . . E:\PROJECT FILES\0406-WHITE GABLES PHASE 1 CA\DESIGN CALCS\0406 Routing.ppw RUNOFF CURVE NUMBER DATA Impervious Area Adjustment Adjusted Soil/Surface Description CN acres %C %UC CN Pervious 74 .810 74.00 Impervious 98 1.370 98.00 COMPOSITE AREA 6 WEIGHTED CN ---> 2.180 89.08 (89) S/N: DIYXYWGWM4CC Mckee Carson PondPack (10.00.016.00) 5:45 PM 7/12/2005 Type. . . . Vol: Elev-Area Page 5.01 Name. . . . POND 10 Elevation Planimeter Area Al+A2+sgr(A1*A2) Volume Volume Sum (ft) (sq.in) (acres) (acres) (ac-ft) (ac-ft) 593.54 .0380 .0000 .000 .000 600.66 .0380 .1141 .271 .271 POND VOLUME EQUATIONS * Incremental volume computed by the Conic Method for Reservoir Volumes. Volume = (1/3) * (EL2-EL1) * (Areal + Area2 + 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 /d56 Z -5c. ae ar 5 �7 it( Y`4Z,7 = /G .26 Mckee Carson S/N: DIYXYWGWM4CC 7/12/2005 PondPack (10.00.016.00) 5:45 PM Type. . . . Outlet Input Data Page 1.01 Name. . . . Outlet 5 File. . . . E:\PROJECT FILES\0406-WHITE GABLES PHASE 1 CA\DESIGN CALCS\0406 Routing.ppw Title. . . Project Date: 4/27/2005 Project Engineer: Mike Project Title: Watershed Project Comments: White Gables SWM design - System includes Raintank, Stormtech SC-740's and StormFilters with Stormgate flow splitters. The analysis is done using the SCS method. REQUESTED POND WS ELEVATIONS: Min. Elev.= 593.54 ft Increment = .10 ft Max. Elev.= 600.66 ft OUTLET CONNECTIVITY ---> Forward Flow Only (Upstream to DnStream) <--- Reverse Flow Only (DnStream to Upstream) <---> Forward and Reverse Both Allowed Structure No. Outfall El, ft E2, ft Orifice-Circular LF ---> TW 593.540 600.660 Orifice-Area 00 ---> TW 597.417 600.660 Weir-Rectangular WO ---> TW 599.600 600.660 TW SETUP, DS Channel S/N: DIYXYWGWM4CC Mckee Carson PondPack (10.00.016.00) 5:52 PM 7/12/2005 Type. . . . Outlet Input Data Page 1.02 Name. . . . Outlet 5 File. . . . E:\PROJECT FILES\0406-WHITE GABLES PHASE 1 CA\DESIGN CALCS\0406 Routing.ppw Title. . . Project Date: 4/27/2005 Project Engineer: Mike Project Title: Watershed Project Comments: White Gables SWM design - System includes Raintank, Stormtech SC-740's and StormFilters with Stormgate flow splitters. The analysis is done using the SCS method. OUTLET STRUCTURE INPUT DATA Structure ID = LF Structure Type = Orifice-Circular # of Openings = 1 Invert Elev. = 593.54 ft Diameter = .6667 ft Orifice Coeff. _ .600 Structure ID = 00 Structure Type = Orifice-Area # of Openings = 1 Invert Elev. = 597.42 ft Area = .3333 sq.ft Top of Orifice = 597.58 ft Datum Elev. = 597.42 ft Orifice Coeff. _ .667 Structure ID = WO Structure Type = Weir-Rectangular # of Openings = 1 Crest Elev. = 599.60 ft Weir Length = 5.33 ft Weir Coeff. = 3.000000 Weir TW effects (Use adjustment equation) S/N: DIYXYWGWM4CC Mckee Carson PondPack (10.00.016.00) 5:52 PM 7/12/2005