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Home My WebLink AboutSW8061118_COMPLIANCE_20061201STORMWATER DIVISION CODING SHEET POST -CONSTRUCTION PERMITS PERMIT NO. SW ItO�DIII6 DOC TYPE ❑ CURRENT PERMIT ❑ APPROVED PLANS ❑ HISTORICAL FILE %COMPLIANCE EVALUATION INSPECTION DOC DATE .222'a42O/ YYYYMMDD WET DETENTION POND ANALYSIS FILE NAME S:IWQSISTORMWATERIEXCELSPREADSHEETSIPOND1061118 WK1 PROJECT # SW8 06E1i=11 81� ., REVIEWER C' Baker' PROJECT NAME�Materiel LaydownlSteckp IIIi eKnoxRdDATE 01-Dec-06 Receiving Stream �S alesles Creek Class SC,HQW NSA i Drainage Basin „White0ak�,;' ,, Index No Site Area ��'I111ii1il1i{�,1,119120,IFI acres Drainage Area fII,li111;287932"00! square feet Area in Acres 661 IMPERVIOUS AREAS Rational C Buildings j'��I��I��;i;��i square feet Parking �r;jj ,�; ��,�„ �„ l�,� square feet SW ll �ii a�a �z square feet Other !r.,al'240000 00 square feet TOTAL SURFACE AREA CALCULATION square feet square feet square feet square feet Rational Cc= 003 % IMPERVIOUS 83 35% SAIDA Ratio 8 34% Des Depth ;0',= R #IM511 i^„'i3115 Req SA 24000 sf TSS, 85 or 90 ;;,' �,'�= ",k "a1' 1190 Prov SA ;'.11,1,', 24286'; sf VOLUME CALCULATION "' place a "1" in the box if Rational is used Rational ?* Des Storm it#;Y>,'';; 1r1'11001 inches Rv= 0 800 Bottom msl Perm Pool "�'�i;l'r',�'I120�00 msl Design Pool 1120,73 msl Storage met @elev 18 46 msl Req Volume 19200 cf Vol Prov at DP 49053 1cf ULATION FOREBAY Perm Pool Volume= '5535*1, j Req Forebay Volume= 110702 Provided Volume= 1 ,193718'10011: s Percent= 35 0% Area Inc Vol Acc Vol ,'f�,i 111,285�'00 �! 0 00 15©1P700. `, 13151 00 1315100 Avg Head = 031 ft Q2 Area = 5 94 sq inches Flow Q2, cfs 0 111 cfs Q5 Area = 2 38 sq inches Flow Q5, cfs 0 044 cfs Orifice Area 4 91 sq inches No of Orifices ;' '' it".,' ;F'; ,1 ii Q= 0 092 cfs Diameter, inches ,' ; a ,;P2, 50f weir H x W T'' ��';i"i''' ; '�1:a' �' 10,1 in x in Drawdown = 2 4 days Surface Area @DP = 25205 sq ft Falling Head Drawdown = 3 0 days C= 3305761905 L= -0 063 COMMENTS Surface Area, Volume and Orifice are within Design Guidelines Material Laydown/Stockpile Area - Knox Road Pond Calculations Drainage Area Off -Site Drainage Area = 0 AC Drainage Area = 6 61 AC Total Drainage Area = 6 61 AC Off -Site Impervious Area = 0 AC Impervious Area = 5 5 AC Total Impervious Area = 55 AC Percent Impervious = 83% Permanent Pool Depth = 3 5-FT Pond Surface Area SA/DA Ratio = 8 3 (From NC DENR BMP Manual SA/DA Ratios for Coastal Counties) Surface Area Required = (8 3/100)*6 61 AC = 055 AC = 23,898 SQ-FT Surface Area Provided = 24,286 SO -FT Volume to be Controlled Volume (V) = Design Rainfall * R_v * Drainage Area R_v = 0 05+0 009*1 1= Percent Impervious = 83 R_v = 797 WIN Design Rainfall = 1-IN V = (1-IN) * 0 797 IN/IN * 1 FT/121N * 6 61 AC V = 0 44 AC -FT 19,123 CU-FT Drawdown Time Calculations Temporary Pool Depth 0 72 FT Average Head on Orifice h = 0 36 FT Orifice Equation = Q = CA * A * (2*g*h)^1/2 C_d= 06 3-IN ORIFICE A = 0 049 SO -FT Q = 0 14 CFS V/Q = 134,850 SECONDS = 1 56 DAYS 2 5-IN ORIFICE A = 0 034 SO -FT Q = 0 10 CFS V/Q = 194,184 SECONDS = 2 25 DAYS 2-IN ORIFICE A = 0 022 SO -FT Q = 0 06 CFS V/Q w 303,413 SECONDS = 3 51 DAYS Therefore a 2 5-IN Orifice will provide acceptable drawdown time MATERIAL LAYDOWN/STOCKPILE AREA - KNOX ROAD POND STAGE -STORAGE TABLE ELEVATION FT) SURFACE AREA (SQ FT) ELEV VOLUME CU FT) SUB -VOLUME CU FT SURFACE AREA AC 1650 0 1,454 000 1700 11,285 1,881 3,335 026 1800 15,017 13,107 16,442 034 1900 19,350 17,138 33,579 044 2000 24,286 21,771 55,351 056 2100 28,500 26,365 81,716 065 Forebay Volume as a Percentage of Total Pond Volume = 24% The following illustrates the stage -storage table broken down into forebay stage -storage and main pond stage -storage MAIN BASIN STAGE STORAGE TABLE ELEVATION (FT) PURFACE AREA SQ FT) ELEV VOLUME CU FT) SUB -VOLUME CU FT) 1650 0 0 1700 7,924 1,321 1,321 1800 9,938 8,912 10,233 1900 12,110 11,006 21,239 2000 14,440 13,258 34,497 FOREBAY STAGE -STORAGE TABLE ELEVATION FT) SURFACE AREA (SQ FT) I ELEV VOLUME CU FT) SUB -VOLUME CU FT 1650 0 0 1700 3,361 560 560 1800 5,079 4,187 4,747 1900 7,240 6,124 10,871 2000 9,846 8,507 19,378 WHITE OAK RIVER BASIN Name of Stream Subbasm Stream Index Number Map Number Class Northeast Creek WCK02 19-16-(0 5) H29SE4 SC,NSW Northeast Creek WOK02 19-16-(3 5) I29NE1 SC,HQW,NSW Northeast Creek WOK02 19-16-(4 5) I29NW3 SC,NSW Northwest Prong Newport River WOK03 21-2 H31SW5 C Old Channel WOK05 21-35-7-8-1 H33SE4 SA,ORW Oyster Creek WOK03 21-23 H32SWB SA,HQW Oyster Creek WOK04 21-35-7-18 H33SW4 SA,ORW Parrot Swamp WOK01 19-41-16-4 I30NW5 SA,HQW Pasture Branch WOK01 19-41-16-2 I30NW1 SA,HQW Pasture Creek WOK04 21-35-7-10-7 H33SW3 SA,HQW Peak Swamp WOK03 21-3-4 H31SW8 C Peltier Creek WOK03 20-36-11 I31NE3 SB # Pettiford Creek WOK01 20-29-1 I30NE3 SA, HQW Pettlford Creek Bay WOK01 20-29 130NE1 SA,HQW Pitts Creek (Hargetts Creek) WOK01 20-21 H30SW9 SA,HQW Point of Grass Creek WOK05 21-35-7-1 H33NEB SA,ORW Poplar Creek WOK02 19-16-2-3 H29SE7 C,NSW Queen Creek WOK01 19-41-16 130NW1 SA,HQW Rawson Creek WOK05 21-35-7-35 I33NW4 SA,ORW Rocky Run WOK02 19-16-2-2 129NE2 C,NSW Rogers Hay WOK02 19-39-1 J29NW2 SA HQW Roosevelt Natural Area Swamp WOK03 20-36-9 5-(1) I31NE4 C,Sw,ORW Roosevelt Natural Area Swamp WOK03 20-36-9 5-(2) I31NE4 SA,Sw,ORW Russell Creek WOK03 21-26 H32SW9 SA, HQW Salliers Bay WOK02 19-41-3 129SE5 SA,HQW Salters Creek NEU14 21-35-7-10-2 H33NW9 SC Salters Creek WOK04 21-35-7-10-2 H33NW9 SC Sanders Creek WOK03 20-36-4-1 I30NE3 SA,HQW Sanders Creek WOK03 20-36-6 131NW4 SA,ORW Sandy Branch WOK03 20-36-7-1-1-1 I31NW1 SA,HQW Sandy Branch WOK03 21-13 H31SE8 C Sandy Run Branch WOK02 19-10-1 H29SW9 SC,NSW Saunders Creek WOK01 19-41-12 130SW2 SA,HQW rScales�iCreek WOK02 1a9-16� H29SW9 SC,HQW NSW School House Branch WOK03 21-8 H31SE7 C Schoolhouse Branch WOK01 20-23-1 H30SE7 SA,HQW Shacklefoot Channel WOK01 19-41-9 I30SW2 SA,HQW Sheep Pen Creek WOK05 21-35-7-6 H33SE4 SA,HQW Sheep Pen Creek WOK05 21-35-7-32 I33NW4 SA,ORW Shoe Branch WOK03 21-6 H31SW6 C Sikes Branch WOK03 20-36-6-1-1 I31NW4 SA,HQW Sleepy Creek WOK04 21-35-1-12-1 I32NE3 SA,HQW Smiths Swamp WOKG3 21-9 H31SW9 C Smiths Swamp Branch WOK03 21-10 H31SE7 C Smyrna Creek WOK04 21-35-7-22-1 H33SW4 SA,HQW Sneads Creek WOK02 19-33-1 I29SW3 SA,HQW Snows Swamp Branch WOK03 21-12 H31SE7 C Socoe Creek WOK02 19-9-2 H29SW8 SC NSW South Fork White Oak River WOK01 20-3 H29NE7 C South Leopard Creek WOK04 21-35-1-7-3 H32SES SA,HQW Southwest Creek WOK02 19-17-(0 5) H28SE4 C,NSW Southwest Creek WOK02 19-17-(6 5) I29NW5 C,HQW,NSW Southwest Prong Newport River WOK03 21-3 H316W8 C Spit Bay WOK04 21-35-7-21 H335W7 SA,HQW Page 6 of 8