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Home My WebLink AboutSW8000731_COMPLIANCE_20001019I STORMWATER DIVISION CODING SHEET POST -CONSTRUCTION PERMITS PERMIT NO. SW �� I DOC TYPE ❑ CURRENT PERMIT I. I ❑ APPROVED PLANS ❑ HISTORICAL FILE COMPLIANCE EVALUATION INSPECTION DOC DATE U YYYYM M D D INFILTRATION BASIN ANALYSIS DATE: PROJECT NAME: DRAINAGE BASIN: RECEIVING STREAM Index No.: SITE AREA 3.1 19-Oct-2000 Davis Tract CFR Hewletts Creek 18-87-26 . acres IMPERVIOUS AREA CAI CULATION 14 LOTS a�2700 STREET SW OTHER % IMPERVIOUS, 1= ELEVATION OF SEASONAL HIGH WATER TABLE REPORTED INFILTRATION RATE SURFACE AREAS AND ELEVATIONS BOTTOM STORAGE Elev. (ft) Area 20 0 FILENAME: S:1WQS11NBASIN1000731.WK1 PROJECT #: 000731 REVIEWER: Lewis CLASS: SA If ORW, is site within the 575' AEC? DRAINAGE AREA: [7 jgEg5M SF 37800 SQUARE FEET 11517 SQUARE FEET 3049 SQUARE FEET SQUARE FEET TOTAL 52366 SQUARE FEET RV= .05+.009 (1) 6280 SQUARE FEET SQUARE FEET SQUARE FEET 14080 SQUARE FEET VOLUME 1 DEPTH 1 DRAWDOWN CALCULATION DESIGN STORM, INCHES DESIGN VOLUME TOTAL VOLUME AVAILABLE FEET MSL D 5<�CFIHRISF (4" CAPACITY IN BASIN) "'67.35:OUBIC FEET _ _2036OJCUBIC FEET DEPTH OF RUNOFF 2 OO;IFEET TIME TO DRAWDOWN 03: DAYS MUST BE <5 COMMENTS i Volume and drawdown are (not) within Design Requirements. 9/18w I DAVIS TRACT 99074 CDC 10-year Storm WATERSHED DATA Total Drainage Area ft. acres 135 070 3.10 Impervious Area Land Use ; S . ft. acres buildings I 37,800 0.87 parkinglasphalt 1 11,517 0.26 concrete I 3 DQ 0.07 Totai 1 52,366 1.20 INFILTRATION SYSTEM: Volume of first 3 inches of runoff = (Impervious area) V= 18,260.50 cu-ft Required basin storage: Vr- 18,260.50 cu-ft Volume provided: Vp= 20,360.00 cu-ft bottom elev: DRAWDOWN RATE: 1 RATE OF INFILTRATION: B IN/HR DEPTH OF BASIN: 1 24IN DRAW DOWN RATE:241N / 61N/HR = 4.0 HRS. RED C�IVED 1 SEP1s 2000 DWQ PROJ # �C'u12(b Z 31 Ma - M we 6,280 sf 4,080 sf % impervious - 0.388 = 38,8% say 39.0% CPRE = 0.25 CPOST = {% imp.)(,96)+(1-% imp.)(.25) 0.53 12 = 5.06 in/hr 110 = 6.30 in/hr 125 = 7.13 in/hr (8.4 in/hr FROM SOILS REPORT) x I. 2. K 9 The DIVISION OF WATER QUALITY INFILTRATION SYSTEM INVESTIGATION bore depth E-4 JCYvCa'�� The type of 24- 4 The expected infiltration rate: 6 �c✓�� V The depth tc the Seasonal High Water Table: 5 . Additional clomments: P&'qk 17 r Signature of Regional Office Personnel: I( � r-e r -inch-Lewis, DWQ S Ai v,�1 i Permit Application No. 9 Q '9 S :1W QSISTORMWATIFORMSIINFINVST. FOR Vincent Lewis, Soil Scientist Date t JOt.1-26--00 16 = So i 1 tech 9106869114 P.02 ENGINEERING INC. 2592 HOPE BRILLS ROAD FAYETTEVILLE, NC 28306 910-426-2323 I Tripp Engineering, P,C. July 8,2000 19 Chesty ut Street Wilmington, North Carolina 28401 Attention: I Mr, Charles Cazier Reference: Infiltration Evaluation Davis Tract Wilmington, North Carolina Job No.: 3469-00 Dear Mr. Cazier Soil Tech' Engineering, Inc. has conducted an evaluation of the existing site conditions for the development of the Qavis tract located on Beasley Road in Wilmington, North Carolina, The purpose of the evaluation was to determine the sites subsu face characteristics for discharge of stormwater runoff. We condo cted an investigation of the subsurface soils at the two designated stormwater infiltration area indicated on the provided site sketch on July 6, 2000, The purpose of our investigation vfas to determine the suitability of the in -place soils for the discharge of stormwater runoff. We investigated the subsurface soils to a depth of six Feet below the existing ground surface. We also classified each subsurface strata encountered by depth and obtained representative soils samples of each strata at the designated locations. Selected soil samples were tested in our laboratory for grain size structure in accordance with the American Society for Testing and Materials (ASTIVI) procedures entitled ASTPA D-422- "Particle Size Analysis of Soils". Our sampling lindicated that the subsurface soils at the test #ocation to be moderately drainable, fine grained sands. eC. 0 ' s J�91-26-00 16:08 Soiltech 910686§114 P.03 Infiltration Evaluation Davis Tract Wilmington, North Carolina Page Two We also conducted an evalualion of the subsurface infiltratio , at the designated location. The infiltration rate of the in -place soils at each location was determined at a depth of 36 inches below the existing surface. The infiltration rate at location # 1 was found to be 0.14 inches per minute, +at location #2 was 0.17 inches per minute. We did not encounter groundwater at the location investigated to a depth of six feet below the existing grourj d surface. In our opinion, the seasonal high groundwater condition is anticipated to be below the depths explored due to the high croma soil coloration, at a depth of 6 feet, which indicates a well drained condition. Please find the results of our field and laboratory tests and a sketch indicating the locations checked, Please contact us if you have questions. Very truly yours, SOIL TECH ENGINEERING, INC. Parks A. Downing, Jr. Manager PADjr:JPltm i JWl-26-00 16:09 Soiitech 9106869114 P.04 Infiltration Evaluation Davis Tract Wilmington, North Carolina Job No.: 3469 - 00 July 6, 2000 #1 0" - 12" Black Gray Silty Fine to Medium SAND wl Organics 12" - 24" White Silty Fine to Medium SAND 24" - 36" Brown Silty Fine to Medium SAND 36' - 72" White Gray Fine to Medium SAND Groundwater was not encountered to a depth of 6 feet below the existing surface. Seasonal high groundwater predicted at in excess of 6 feet below the existing surface. Infiltration Rate : 0.14 inches per minute Test was conducted at 36 inches below the existing surface. #2 0" - 12" Black Gray Silty Fine to Medium SAND wl Organics 12" - 24" White Gray Silty Fine to! Medium SAND 24" - 36" Brown Silty Fine to Medium SAND 36" - 72" Gray Brown Fine to Medium SAND Groundwater was not encountered to a depth of 6 feet below the existing surface. Seasonal high groundwater predicted at in excess of 6 feet below the existing surface. Infiltration Rate : 0.17 inches per minute Test was conducted at 36 inches below the existing surface. CI) O V) 0 rt m n ® Denotes locations of �nfiltratian testing. Bavi s TT'act I wilmingwn, North Cam] ina _ 0 Job NO.: 3469 -00 361-26-00 16:09I So;1tech 9106869114 P_06 Location: Depth I # # 40 # 80 4 # 2oo I Percent Moisture: Soil Descri ption : i Grain Size Analysis Davis Tract Wilmington, North Carolina Job No.: 3469 - 00 #1 36" - 72" #2 36'' - 72" 100.0 99.9 12.3 12.7 4.3 6.1 2.7 % 5.9 % White Gray Gray Brown Fine to Fine to Medium Medium SAND SAND