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Home My WebLink About19970694 Ver 1_Stormwater Info_20011121 THE JOHN R. McADAMS COMPANY, IN KERR DRUGS REGIONAL OFFICES SAND FILTER DESIGN CALCULATIONS WAKE COUNTY, NC KER 01020 DWQ Project # 970694 J.E. SCHRUM, E.I. Nove, 21, 2001 24601 1 -1!/H111111,11" CIVIL ENGINEERING • LAND PLANNING • SURVEYING PO Box 14005 • Research Triangle Park, NC 27709 • (919) 361-5000 • fax (919) 361-2269 www.johnrmcadams.com KERR DRUG CORPORATE OFFICES Sanci f,i°Itel- Desigi7Calculations General D4,sc.:rp-dam -Located on the corner of New Palls of the Neuse Road and Common Oaks Drive, Kerr Drug Corporate Offices will consist of office buildings and associated utilities and parking. This property is located in the Wakefield Development and is therefore subject to a 401 Water Quality Certification under DWQ Project # 970694. This permit requires an approved stormwater management program which meets 85% TSS removal. The property is also subject to the City of Raleigh Neuse River Basin Stormwater Rules, which require that all property proposed for development shall submit a nitrogen loading analysis and determine the impact of stormwater runoff on downstream areas in the two- year storm event. The site is composed of one sub-basin. All impervious portions of the sub-basin will be diverted to a sand-filter in post-development in order to reduce post-development nitrogen loading and as the means of meeting the 85% TSS removal requirement. The sand filter will also detain runoff from the two-year storm event to pre-development levels. The included Summary of Results demonstrates that the sand filter meets all design requirements put forth by the NCDENR Stormwater Best Management Practices (BMP, April 1999). This includes meeting the requirements of surface area in both the sediment and sand chamber and the volumetric requirements based upon storage of the 1" rainfall. The sand filter also passes the flow resulting from the 100-year storm event with 0.52 ft of freeboard from the water surface elevation to the top of berm. This analysis satisfies the requirements set forth by the City of Raleigh Program for Nitrogen Control with no further analysis required. Calculation jllethodology for Stormwater Impact Arrczlysis • HEC-IIMS version 2.1.2 was used to calculate all flow rates in the report" Additionally, FIEC-I-IMS was used to route the detention provided by the sand filter and determine the water surface elevation (WSE) in the pond resulttnS from each storm event. • PondPack v7.0 was used to generate the rating curve modeling the outlet hydraulics of the sand filter. This rating curve was then entered into the reservoir element in HEC-HMS and utilized to route the sand filter. • Rainfall data used in the analysis is from USWB TP-40 and NOAA Hydro-35. • Using the Wake County Soil Survey, the majority of on-site soils were determined to be Hydrologic Soil Group `B'. Therefore, the SCS Curve Numbers were selected appropriately. • On-site topography is from field survey. • Time of Concentration (TJ was calculated using the Penn State Urban Hydrology Model software (1989), which calculates the T,; using SCS TR55 method (1986). • Nitrogen removal calculations were accomplished using the "Neuse River Basin: Model Stormwater Program for Nitrogen Control", NCDENR - Division of Water Quality. August 30, 1999. SAND FILTER SUMRESULTS.xls SAND FILTER K`R 01020 SUMMARY OF RESULTS V V h \S J -S SAND FILTER WATER-QUALITY ASPECT* Aspect Va ie Sediment Chamber- SA Required 1570 SA Provided. 2090 ,- . 7-- Vol Required 2354 ,t3 Vol Provided 5456 ,ft3 Sand Chamber - SA Required 1570 ft' SA Provided 1593 ft2 Vol Required 2354 ft3 Vol Provided 4422 ft3 I " Storm R/O Vol Re 'd 6374 ft3 I " Storm R/O Vol Prov'd 17018 ft3 Drawdown Time 16.30 hours TSS Removal Efficiency 85% DETENTION PERFORMANCE: J. E. SCHRUM, E.I. 11/14/01 6 av Pre- , Post- development development % Change cfs cfs 2-YEAR STORM EVENT 0.92 0.64 y0% 1 ROUTING PERFORMANCE: Aspect Value In Value Out Q, 10.1 cfs 0.2 cFs- Q10 20.2 cfs 10.4 cfs Quo 32.5 cfs 28.3 cfs WSEL, 217.01 ft WSELio 217.36 ft WSELioo 217.78 ft Top of Berm 218.30 ft HEC-HMS Project: KER 99030 Basin Model. fii PRE-DEVELOPMENT HEC-HMS INPUTS.xls PRE-DEVELOPMENT KER 01020 HEC-HMS INPUTS PRE-DEI'ELOPMEi. Drainage Area Description =_> Total Drainage Area = Impervious area = 0.00 AC @ c= Open / Grassy / Landscaped Area = 0.00 AC @ c= Wooded Area = 6.41 AC @ c= Other undescribed area = 0.00 AC @ c= J.E. SCHRUM, E.I. 11 /14/01 0.95 and CN = 98.0 0.27 and CN = 61.0 0. IS and CN = 55.0 0.00 and CN = 0.0 Total DA = 6.41 AC @ c= 0.15 and CN = 55.0 1 = 0.0100156 sq. miles Desigir Storm Deseriptiott / Watershed Sensitivity => Time of Concentration = 8.3 minutes HEC-HMS INPUTS.xls PRE-DEV Tc KER 0102-0 Time of Concentration Information: Segment l: Overland Flow Length = 50 ft Height = 2.00 ft Slope = 0.0100 ft/ ft Manninss'n' = 0.24 Dense Grasses P (2-year, 6-hour) = 3.6 inches Segment 2: Concentrated Flow Length = 606 ft Height = 40 ft Slope = 0.0660 ft/ ft Unpaved J.E. SCHRUM, E.I. 11/13/01 Time of Concentration minutes HMS w Summary of Results Project KER 99030 Run Name : 2-YR PRE Start of Run 09Aug01 1200 Basin Model PRE-DEVELOPMENT End of Run l0Aug01 1200 Met. Model 2-YEAR Execution Time 19Nov01 1900 Control Specs 1-MINUTE dT .-Y- -9-Lk- Discharge Time of Element Volume Drainage Peak Peak (ac Area (cfs) ft) (sq mi) PRE-DEVELOPMENT 0.92329 10 Aug 01 0012 0.12855 0. 010 HEC-HMS INPUTS.xis J.E SCHRUM, E.I. POST-DEV TO DET 11/14101 KER 01020 HEC-HiV1S (NPLITS TO DETENTION , iREA Drainage Area Description ==> Total Drainage Area = Impervious area = 2.22 AC @ c= 0.95 and CN = 98.0 Open / Grassy / Landscaped Area = 1.72 AC @ c= 0.27 and CN = 61.0 Wooded Area = 0.42 AC @ c= 0. 15 and CN = 55.0 Other undescribed area = 0.00 AC @ c= 0.00 and CN = 0.0 Total DA = 4.36 AC ((b, c 0.60 and CN = 79 -or- 0.0068125 sq miles Design Storm Description / Watershed Sensitivity => Time of Concentration = 5.0 minutes (Assume minimum Tc) 40 HEC-HMS INPUTS.xls J. E. SCHRUM, E.I. POST-DEV BYPASS 11/14/01 KER 01020 HEC-HMS IMIS BYPASS DETENTION AREA Drai?rage Area Description ==> Total Drainage Area = Impervious area = 0.00 AC @ c= 0.95 and CN = 98.0 Open / Grassy / Landscaped Area = 1.19 AC @ c= 0.27 and CN = 61.0 Wooded Area = 0.86 AC @ c= 0.15 and CN = 55.0 Other undescribed area = 0.00 AC @ c= 0.00 and CN = 0.0 Total DA = 2.05 AC P. c= 0.22 and CN = 58 -or- 0.0032031 sq miles Design Storm Description / Watershed Sensitivity ==> Time of Concentration = 5.0 minutes (Assume minimum Tc) ID Sand Filter Design.sls J. E. SCI IRU%v I, E. 1. Sand Filter 1 11/ 14/01 KER 01020 ==> Hydrograplr Generation The total drainage area, SCS CN and time of concentration are input into HEC-HMS Drainage Area Description ==> Total Drainage Area = Impervious area = 2.22 AC @ c= 0.95 and CN = 98.0 Open / Grassy / Area = 1.72 AC a c= 0.27 and CN = 61.0 Wooded Area = 0.42 AC @ c= 0.15 and CN = 55.0 Other undescribed area = 0.00 AC @ c= 0.00 and CN = 0.0 Total DA = 4.36 AC c= 0.60 and CN = 79 -or- 0.0068125 sq. miles Design Storm Description / Watershed Sensitivity => Time of Concentration = 5.0 minutes (Minimum Tc) Required Parameters for Sand Filter The sand filter is deigned per the guidelines established by NCDEHNR. Rf: "Stormwater Bert Management Practices, ACDEHNR (April 1999) Sediment Chamber Parameters === Surface Area = 1569.6 ft' Volume = 2354.4 W Sand Filter Chamber Parameters = Surface Area = 1569.6 ft` Volume = 2354.4 ft' I OF I i HEC-HMS Project: KER 99030 Basin Model: TO SAND FILTER ISAND ILTER SAM) FILTEl' SFAGE-STORAG. .M.S 'SAND FILTER KER 01020 St.wye-Storage Function Project Name: KERR DRUG CORPORATE OFFICES Designer: J. E. SCI IRUM, E.I. Job Number: KER 99030 Date: 11/14/01 Average Incremental Accumulated Estimated Contour Contour Contour Contour Stage Contour Stage Area Area Volume Volume w/ S-S Fxn (feet) (feet) (SF) (SF) (CF) (CF) (feet) 214.0 0.0 3589 216.0 2.0 5995 4792 9584 9584 2.00 218.0 4.0 8961 7478 14956 24540 4.00 30000 25000 t% 20000 U ai 15000 m o 10000 5000 0 Storage vs. Stage y = 3743x'.311 R2 = 1 0.0 1.0 2.0 3.0 Stage (feet) Ks = 37431 b = 1.3564 4.0 5.0 J.F. SCIJIZUM, li.l. 11/14/01 I OF 1 Type.... Outlet Input Data Page 1.01 Name.... SAND FILTER OUT File.... C:\HAESTAD\PPKW\KER 99030\SAND FILTER.PPW REQUESTED POND WS ELEVATIONS: Min. Elev.= 214.00 ft Increment = .25 ft Max. Elev.= 218.00 ft OUTLET CONNECTIVITY ---> Forward <--- Reverse < --- > Forward Structure ----------------- Stand Pipe Culvert-Circular TW SETUP, DS Channel Flow Flow and No. RI BA Only (UpStream Only (DnStream teverse Both Al Outfall ---> BA ---> TW to DnStream) to UpStream) lowed E1, ft E2, ft --------- -------- 217.000 218.000 212.400 218.000 S/N: 921AO1506A8B The John R. McAdams Company PondPack Ver: 7.0 (325) Compute Time: 16:30:28 Date: 11-13-2001 Type.... Outlet Input Data Name.... SAND FILTER OUT File.... C:\HAESTAD\PPKW\KER 99030\SAND FILTER.PPW OUTLET STRUCTURE INPUT DATA Page 1.02 Structure ID = RI Structure Type = Stand Pipe ----------------- # of Openings ------------- = 1 ------ Invert Elev. = 217.00 ft Diameter = 5.0000 ft Orifice Area = 19.6350 sq.ft Orifice Coeff. _ .600 Weir Length = 15.71 ft - Weir Coeff. = 3.000 K, Submerged = .000 K. Reverse = 1.000 Kb,Barrel = .000000 (per ft of full flow) Barrel Length = .00 ft Mannings n = .0000 S/N: 921AO1506A8B The John R. McAdams Company PondPack Ver: 7.0 (325) Compute Time: 16:30:28 Date: 11-13-2001 Type.... Outlet Input Data Name.... SAND FILTER OUT File.... C:\HAESTAD\PPKW\KER 99030\SAND FILTER.PPW OUTLET STRO.CTURE IN-PUT DATA Structure ID = BA Structure Type = Culvert-Circular ----------------- No. Barrels ------------- = 1 ------ Barrel Diameter = 2.0000 ft Upstream Invert = 212.40 ft Dnstream Invert = 212.00 ft Horiz. Length = 45.00 ft Barrel Length = 45.00 ft Barrel Slope = .00889 ft/ft OUTLET CONTROL DATA... Mannings n = .0130 Ke = 1.5000 Kb = .012411 Kr = 1.0000 HW Convergence = .001 INLET CONTROL DATA... Equation form = 1 Inlet Control K = .0098 Inlet Control M = 2.0000 Inlet Control c = .03980 Inlet Control Y = .6700 T1 ratio (HW/D) = 1.156 T2 ratio (HW/D) = 1.302 Slope Factor = -.500 Page 1.03 (forward entrance loss) (per ft of full flow) (reverse entrance loss) +/- ft 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 T1 & T2... At T1 Elev = 214.71 ft ---> Flow 15.55 cfs At T2 Elev = 215.00 ft ---> Flow = 17.77 cfs Structure ID = TW Structure Type = TW SETUP, DS Channel ------------------------------------ FREE OUTFALL CONDITIONS SPECIFIED CONVERGENCE TOLERANCES... Maximum Iterations= 30 Min. TW tolerance = .01 ft Max. TW tolerance = .01 ft Min. HW tolerance = .01 ft Max. HW tolerance = .01 ft Min. Q tolerance = .10 cfs Max. Q tolerance = .10 cfs S/N: 921AO1506A8B The John R. McAdams Company PondPack Ver: 7.0 (325) Compute Time: 16:30:28 Date: 11-13-2001 Type .... Composite Rating Curve Name.... SAND FILTER OUT File.... C:\HAESTAD\PPKW\KER 99030\SAND FILTER.PPW ***** COMPOSITE OUTFLOW SUMMARY **** WS Elev," Total Q Notes ---------------- ------ -- Converge ----- -- ------------------ Elev. Q TW Elev Error ft cfs ft +/-ft Contr ibuting Structures -------- 214:00 ------- .00 ------ Free -- ----- - Outfall ----- (no -- Q: ------------------ RI BA) 214.25 .00 Free Outfall (no Q: RI BA) 214.50 .00 Free Outfall (no Q: RI BA) 214.75 .00 Free Outfall (no Q: RI,BA) 215.00 .00 Free Outfall (no Q: RI,BA) 215.25 .00 Free Outfall (no Q: RI BA) 215.50 .00 Free Outfall (no Q: RI BA) 215.75 .00 Free Outfall (no Q: RI,BA) 216.00 .00 Free Outfall (no Q: R I BA) 216.25 .00 Free Outfall (no Q: RI BA) 216.50 .00 Free Outfall (no Q: RI BA) 216.75 .00 Free Outfall (no Q: RI BA) 217.00 .00 Free Outfall (no Q: RI BA) 217.25 5.89 Free Outfall RI,-BA 217.50 16.66 Free Outfall RI BA 217.75 28.19 Free Outfall RI BA 218.00 29.07 Free Outfall RI BA Page 1.06 S/N: 921AO1506A8B The John R. McAdams Company PondPack Ver: 7.0 (325) Compute Time: 16:30:28 Date: 11-13-2001 Rating Curve.xls Riser - Barrel RER.01020 Rating Curve Calculdflon 'Basin outTow based upon output from PondPacl: rating curve (See,previous.pa Stage-Storage Funelfon -> Ks = 3743 b = 1.3564 Zo = 214 Basin WSEL (feet) Basin Outflow (cfs) Storage (ft') (acre-ft) 214.00 0.00 0 0.000 214.25 0.00 571 0.013 214,50 0.00 1462 0.034 214.75 0.00 2534 0.058 215.00 0.00 3743 0.086 21525 0.00 5066 0.116 215.50 0.00 6487 0.149 215.75 0 00 7996 0.184 216.00 0.00 9584 0.220 216.25 0.00 11244 0.258 216.50 0.00 12971 0.298 216.75 0.00 14762 0.339 217.00 0.00 16611 0.381 217.25 5.89 18516 0.425 217.50 16.66 20474 0.470 217.75 28.19 22482 0.516 218.00 29.07 24539 0.563 J 1?. SCHRIA t, F. 1. I1;I3101 1 OF I HMS W Summary of Results Project KER 99030 Run Name : 2-YR POST Start of Run 09Aug01 1200 Basin Model POST-DEVELOPMENT End of Run 10Aug01 1200 Met. Model 2-YEAR Execution Time 14Nov01 1357 Control Specs 1-MINUTE dT Hydrologic Discharge Time of Volume Drainage Element Peak Peak (ac Area (cfs) ft) (sq mi) TO SAND FILTER 10.089 10 Aug 01 0005 0.47650 0.007 SAND FILTER 0.21498 10 Aug 01 0436 0.084835 0.007 SAND.FILTER BYPASS 0.64440 10 Aug 01 0008 0.056271 0.003 Junction-1 0.64440 10 Aug 01 0008 0.14111 0.010 HMS * Summary of Results for SAND FILTER Project KER 99030 Run Name 2-YR POST Start of Run 09Aug01 1200 Basin Model POST-DEVELOPMENT End of Run 10Agg01 1200 Met. Model 2-YEAR Execution Time 14Nov01 1357 Control Specs 1-MINUTE dT Computed Results Peak Inflow 10 .089 (cfs) Date/Time of Peak Inflow 10 Aug 01 0005 Peak Outflow 0. 21498 (cfs) Date/Time of Peak Outflow 10 Aug 01 0436 Total Inflow 1. 31 (in) Peak Storage 0.39261(ac-ft) Total Outflow 0. 23 (in) Peak Elevation 217.01(ft) HMS * Summary of Results Project KER 99030 Run Name : 10-YEAR POST Start of Run 09Aug01 1200 Basin Model POST-DEVELOPMENT End of Run 10Aug01 1200 Met. Model 10-YEAR Execution Time 14Nov01 1357 Control Specs 1-MINUTE dT 10 Hydrologic Discharge Time of Volume Drainage Element Peak Peak (ac Area (cfs) ft) (sq mi) TO SAND FILTER 20.151 SAND FILTER 10.430 SAND FILTER BYPASS 3.7914 Junction-1 12.821 10 Aug 01 0004 1.1197 0.007 10 Aug 01 0012 0.72736 0.007 10 Aug 01 0005 0.23072 0.003 10 Aug 01. 0011 0.95808 0.010 HMS * Summary of Results for SAND FILTER Project KER 99030 Run Name 10-YEAR POST Start of Run 09Aug01 1200 Basin Model POST-DEVELOPMENT End of Run 10Aug01 1200 Met. Model 10-YEAR Execution Time 14Nov01 1357 Control Specs 1-MINUTE dT Computed Results Peak Inflow 20 .151 (cfs) Date/Time of Peak Inflow : 10 Aug 01 0004 Peak Outflow 10 .430 (cfs) Date/Tine of Peak Outflow 10 Aug 01 0012 Total Inflow 3. 08 (in) Peak Storage 0.45397(ac-ft) Total outflow 2. 00 (in) Peak Elevation 217.36(ft) HM'S' * Summary of Results Project KER 99030 Run Name : 100-YR Start of Run 09Aug01 1200 Basin Model POST-DEVELOPMENT End of Run 10Aug01 1200 Met. Model 100-YEAR Execution Time 14Nov01 1358 Control Specs 1-MINUTE dT Hydrologic Discharge Time of Volume Drainage Element Peak Peak (ac Area (cfs) ft) (sq mi) TO SAND FILTER 32.465 10 Aug 01 0004 1.9997 0.007 SAND FILTER 28.283 10 Aug 01 0007 1.6064 0.007 SAND FILTER BYPASS 8.6407 10 Aug 01 0005 0.53102 0.003 Junction-1 36 .635 10 Aug 01 0006 2.1375 0.010 HMS * Summary of Results for SAND FILTER Project KER 99030 Run Name 100-YR Start of Run 09Aug01 1200 Basin Model POST-DEVELOPMENT End of Run 10Aug01 1200 Met. Model 100-YEAR Execution Time 14Nov01 1358 Control Specs 1-MINUTE dT Computed Results Peak Inflow 32.465 (cfs) Date/Tine of Peak Inflow 10 Aug 01 0004 Peak Outflow 28.283 (cfs) Date/Tine of Peak Outflow 10 Aug 01 0007 Total Inflow S.S0 (in) Peak Storage 0.53210(ac-ft) Total Outflow 4.42 (in) Peak Elevation 217.78(ft) Qualpond.xls Sand Filter KER 01020 Water Quality Pond Design Sheet Project Name: KERR DRUG CORPORATE OFFICES Designer: J. E. Schrum, E.I. Job Number: KER 01020 Date: 11/14/01 Ks = 3897.7 b = 1.3416 Calculation of Runoff Volume required for storage The runoff to the pond for the 1 storm detention requirement is calculated using the SCS curve number method. Impervious areas that directly enter the pond are counted as Directly Connected Impervious Areas (DCIAs). No infiltration calculation will be provided for these areas. Areas not directly connected will be accounted for in a composite curve number. From SCS Soils Survey map, predominant hydrologic soil type = B Using basic SCS runoff methodology, with no adjustments made to initial abstractions (0.2'S and 0.8'S). Impervious Area, directly connected (DCIA) = 2.22 acres @CN= 98 Other areas draining to pond (not DCIA) = 2.14 acres @CN= 61 Runoff from DCIAs =_> Precipitation amount = 1.0 inches S = 0.204 inches (calculated) Q" = 0.791 inches (calculated) Runoff volume = 6374 CF Runoff from non-connected areas =_> Precipitation amount = 1.0 inches S = 6.393 inches (calculated) Q' = 0.000 inches (calculated) Runoff volume = 0 CF Therefore, total runoff from precipitation in question = 6374 CF This amount of runoff must be stored in the pond above normal pool elevation, and be released in a period of two (2) to five (5) days, by an inverted PVC siphon, the invert end of which is set at permanent pool elevation. J.E. SCHRUM, E.I. Page 1 Qualpond.xls Sand Filter KER 01020 Calculation of depth required for runoff storage pool (above normal p6M Normal pool depth (above invert) = 0.00 feet Storage provided at permanent pool depth = 0 CF (calculated) Total storage required for normal + storage pool = 6374 CF Stage (above invert) associated with this storage = 1.44 feet J.E. SCHRUM, E.I. Therefore, depth required above normal pool for storm storage = 1.44 feet 17.31 inches Therefore set crest of principal spillway at stage = 3.00 feet (Note: crest elevation is set based upon the and EL = 217.00 feet detention aspect of the sand filter.) At principal spillway crest, storm pool storage provided = 17018 CF Page 2 sand filter drawdown.xis Sand Filter #1 KER 01020 Sand Filter Drain Pipe Design Sheet D siphon = No. siphons = Ks = b= Cd siphon = Siphon Invert = Volume @ Normal Pool = Basin Invert = 6 inches 1 3897.7 1.3416 0.60 212.50 feet 0 CF 214.00 feet WSEL feet Vol. Remaining c Siphon Flow cfs Avg. Flow cfs Incr. Vol. c Incr. Time sec 215.761 8328 1.638 215.617 7424 1.598 1.618 903.3 558.3 215.472 6548 1.557 1.578 876.2 555.3 215.328 5701 1.515 1.536 847.2 551.4 215.183 4885 1.472 1.494 816.3 546.4 215.039 4102 1.428 1.450 782.9 539.8 214.894 3355 1.382 1.405 746.5 531.2 214.750 2649 1.335 1.359 706.2 519.9 214.605 1988 1.286 1.310 661.0 504.5 214.461 1379 1.235 1.260 608.9 483.2 214.317 833 1.181 1.208 546.3 452.2 Drawdown Time = 0.06 days By comparison, if calculated by the average head over the orifice (assuming average head is half the total depth), the result would be: Average driving head on orifice = 1.381 feet Orifice composite loss coefficient = 0.600 X-Sectional area of 1 - 6" inverted siphon = 0.196 ft2 Q = 1.1108 cfs Drawdown Time = Volume / Flowrate / 86400 (sec/day) Drawdown Time = 0.09 days Conclusion : Use 1 - 6" Diameter PVC drain pipe to drawdown the accumulated volume from the 1.0 " storm runoff, with a required time of about 0.08 days Therefore, the pipe will not constrain the drainage of the sand media. J.E. SCHRUM, E.I. 11/14/01 SIPHONS.XLS sand filter drawdown.xis Sand Filter #1 KER 01020 Drainage through the Sand Media: J.E. SCHRUM, E.I. 11/14/01 Per NC DENR DWQ, the sand to be used in the filter is to be less than 2 mm in average diameter. DWQ assumes this sand to have a permeability of 0.04 gal/min/SF (with 1 foot of head over the sand surface). Average depth of water over sand surface (1/2 maximum depth) = 0.8805 feet The DWQ assumption for sand permeability will be used. Calculation of drawdown time through the sand =_> Surface area of horizontal sand surface = 1593 SF Assumed permeability of sand = 0.04 gal/min/SF Volume stored during storm of interest = 8328 CF Time required to drawdown through the sand media = 0.68 days In this case, the sand media is the restricting factor, resulting in a drawdown time of 0.68 days (16.3 hours). This is within the DWQ requirement that requires the sand filter drained within a 24 hour time period. SIPHONS.XLS conc riser antiflotation.xis SAND FILTER KER 01020 Manhole Riser/Barrel Anti-Flotation Calculation Sheet Input Data =_> Inside diameter of manhole = 5.0 feet Wall thickness of manhole = 6.0 inches Base thickness of manhole = 8.0 inches Base diameter of manhole = 6.0 feet Inside height of Manhole = 4.6 feet Concrete unit weight = 142.0 PCF OD of barrel exiting manhole = 30.0 inches Size of drain pipe (if present) = 1.5 inches Trash Rack water displacement = 64.1 CF Concrete Present =_> Total amount of concrete: Base of Manhole = 18.850 CF Manhole Walls = 39.741 CF Adjust for openings: Opening for barrel = 2.454 CF Opening for drain pipe = 0.006 CF J.E. SCHRUM, E.I. 11/14/01 Note: NC Products lists unit wt. of manhole concrete at 142 PCF. Total Concrete present, adjusted for openings = 56.130 CF Weight of concrete present = 7971 lbs Amount of water displaced =_> Displacement by concrete = 56.130 CF Displacement by open air in riser = 90.321 CF Displacement by trash rack = 64.140 CF Total water displaced by riser/barrel structure = 210.591 CF Weight of water displaced = 13141 lbs Page 1 conc riser antiflotation.xls J.E. SCHRUM, E.I. SAND FILTER 11/14/01 KER 01020 Calculate. amount of concrete to be added to riser =_> Safety factor to use = 1.15 (recommend 1.15 or higher) Must add = 7142 Ibs concrete foebuoyancl Concrete unit weight for use = 142 PCF (note above observation for NCP concrete) Buoyant weight of this concrete = 79.60 PCF Buoyant, with safety factor applied = 69.22 PCF Therefore, must add = 103.175 CF of concrete Standard based described above = 18.850 CF of concrete Therefore, base design must have = 122.025 CF of concrete Calculate size of base for riser assembly =_> Diameter = 8.000 feet Thickness = 30.0 inches Concrete Present = 125.664 CF OK Check validity of base as designed =_> Total Water Displaced = 317.406 CF Total Concrete Present = 162.945 CF Total Water Displaced = 19806 Ibs Total Concrete Present = 23138 Ibs Actual safety factor = 1.17 OK Results of design =_> Base diameter = 8.00 feet Base Thickness = 30.00 inches CY of concrete total in base = 4.52 CY Concrete unit weight in added base >= 142 PCF Page 2 VEL DIS.xIs 24" RCP - UNDEFINED CHANNEL KER 01020 NRCD Land Quality Section Pipe Design Entering the following values will provide you with the expected outlet velocity and depth of flow in a pipe, assuming the Mannings roughness number is constant over the entire length of the pipe. flow Q in cfs : 10.43 slope S in % : 0.89 pipe diameter D in in.: 24 Manning number n : 0.013 Flow depth (ft) = 1.03 Outlet velocity (fps) = 6.863 NRCD Land Quality Section NYDOT Dissipator Design Results Pipe diameter (ft) 2.00 Outlet velocity (fps) 6.86 Apron length (ft) 12 AVG DIAM STONE THICKNESS (inches) CLASS (inches) -------- ----- --------- 3 A 9 << 6 B 22 >> 13 B or 1 22 23 2 27 W=LA+Do W=12+2 W=14 SAY 14 ft J.E. SCHRUM, E.I. 11/14/01