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Home My WebLink AboutSW8120206_COMPLIANCE_20120320STORMWATER DIVISION CODING SHEET POST -CONSTRUCTION PERMITS PERMIT NO. SW DOC TYPE ❑ CURRENT PERMIT ❑ APPROVED PLANS ❑ HISTORICAL FILE COMPLIANCE EVALUATION INSPECTION DOC DATE WWMMDD INFILTRATION BASIN ANALYSIS FOR PHASE II AND 2008 PROJECTS Formula FILENAME: S:IWQSIexcel spreadsheetsllNBASIN1120206 User in ut PROJECT NUMBER: SW8 120206 Current Date 20-Mar-12 PROJECT NAME: BC Habitat for Humanity Basin 2 Original Run Date: DRAINAGE BASIN: Lumber REVIEWER: Chris Baker 11f RECEIVING STREAM: Jinnys Branch CLASS: C;Sw Index No.: 15-25-2-16-1-(1) ORW, is site within the 575' AEC? Y N RULES ("2008" or "Ph2") 2008 1 (Use a comma (') before entering 2006) PROJECT AREA 1.73 acres Overall DA 11626 Sf = 0.271 acres 11626 sf (reduce overall DA by previously permitted BUA amount) DA for Proposed BUA 0 DA for Prev.Permitted BUA sf (assume DA = previously permitted BUA) IMPERVIOUS AREA CALCULATION Previously permitted Prop. BUA BUA at diff. DS C value BUILDINGS PARKING/ASPHALT CONCRETE OFFSITE OTHER/FUTURE Subtotals Total Overall % IMPERVIOUS, I= New BUA % impervious = Ex. BUA % impervious = VOLUME CALCULATION Previously permitted BUA Design Storm Previously permitted BUA volume 1 yr. 24 hour precipitation depth (inches) Predevelopment C value from consultant 1 yr. 24 hr. Pre -development volume 1 yr. 24 hr. Post -development volume 1.5" volume for New BUA 2008 Design Volume Phase 2 Design Volume SURFACE AREAS 1 ELEVATIO BOTTOM TOP/BYPASS VOLUME PROVIDED 954.50 SOILS INFORMATION ELEVATION OF SEASONAL SOIL TYPE REPORTED INFILTRATION Time to Draw Down 10 YEAR STORM (WAIVE BYPASS & VFS) Runoff depth for 10yr 24 hr storm, inches Volume of 10 yr. 24 hr storm = volume infiltrated in 24 hours = Remaining volume to store = 30 35 3 7606 1 0.98 0.95 0.95 0,95 Cc= 10.71 Pre Rv Post Rv 0.05 0.64 0.05 0.64 0.05 0.05 inches cf 928 3.80 184 2352 928 928 cubic feet cubic feet cubic feet cubic feet NSIVOLUMES Elev. (ft) Area, sq ft Inc. Volume Acc, Volume 37.50 449 38.50 1,460 955 955 38.50 1,460 0 955 38.50 1,460 0 955 cf (most likely I" or 1. 5' from NOAA chart does not include exis HIGH WATER TABLE 34.5 fmsi sand RATE 13 in / hr 1.9 hours from NOAA chart 0 CF 5837 CF, at T=1 day, v= (2 x k x A) -5837 1CF OK? YES cf (most likely I" or 1. 5' from NOAA chart does not include exis HIGH WATER TABLE 34.5 fmsi sand RATE 13 in / hr 1.9 hours from NOAA chart 0 CF 5837 CF, at T=1 day, v= (2 x k x A) -5837 1CF OK? YES from NOAA chart 0 CF 5837 CF, at T=1 day, v= (2 x k x A) -5837 1CF OK? YES INFILTRATION BASIN ANALYSIS FOR PHASE 11 AND 2008 PROJECTS Formula FILENAME: 1S.WQSlexcel spreadsheelsllNBASIN1120206 user input PROJECT NUMBER: SW8 120206 Current Date 20-Mar-12 PROJECT NAME: BC Habitat for Humanity Basin 1 Original Run Date: DRAINAGE BASIN: Lumber REVIEWER: Chris Baker RECEIVING STREAM: Jinnys Branch CLASS: C;Sw Index No.: 15-25-2-16-1-(1) 111' ORW, is site within the 575' AEC? Y N RULES ("2008" or "Ph2") 2008 (Use a comma (') before entering 2008) PROJECT AREA 1.73 acres Overall DA 63626 Sf = 1.46 acres DA for Proposed BUA 63626 sf (reduce overall DA by previously permitted BUA amount) DA for Prev.Permitted BUA I o sf (assume DA = previously permitted BUA) IMPERVIOUS AREA CALCULATION BUILDINGS PARKING/ASPHALT CONCRETE OFFSITE OTHER/FUTURE permitted Prop. BUA BUA at diff. DS C value 9000 1 13378 0.98 1688 0.95 0.95 2500 0.95 Subtotals 265661 0 Cc= 10.53 Total 1 265661 1 Overall % IMPERVIOUS, 1= New BUA % impervious = Ex. BUA % impervious VOLUME CALCULATION Previously permitted BUA Design Storm Previously permitted BUA volume 1 yr. 24 hour precipitation depth (inchesj Predevelopment C value from consultant 1 yr. 24 hr. Pre -development volume 1 1 yr. 24 hr. Post -development volume 1.5" volume for New BUA 2008 Design Volume Phase 2 Design Volume SURFACE AREAS 1 ELEVATIO BOTTOM TOP/BYPASS 41.8% 41.8% Pre Rv I Post Rv 0.05 0.43 0.05 0.43 1.50 inches o cf 3.80 1007 cubic feet 8579 cubic feet 3386 cubic feet 3386 cubic feet 3386 cubic feet NSIVOLUMES Elev. (ft) Area, sq ft Inc. Volume Acc. Volume 37.50 3,809 1 38.50 6,113 4961 J 4961 38.50 1 6,113 0 1 4961 38.50 6,113 0 T 4961 VOLUME PROVIDED 4961.00 SOILS INFORMATION cf J' or 1.5' from NOAA chart I does not include exis I HIGH WATER TABLE 34.5 fmsl sand RATE 13 in / hr 0.8 hours ELEVATION OF SEASONAL SOIL TYPE REPORTED INFILTRATION Time tc Draw Dawn 10 YEAR STORM (WAIVE BYPASS & VFS) Runoff depth for 10 yr 24 hr storm, inches Volume of 10 yr. 24 hr storm = Volume infiltrated in 24 hours = Remaining volume to store = from NOAA chart 0 CF 49517 CF, at T=1 day, V= (2 x k x A) -49517 CF OK? YES '� ECS C. A R O L I N A S , UP "Setting the Standard for Service" — i . Geotechnical • Construction Materials • Environmental - Facilities NC Registered Engineering Firm F-107B October 7, 2011 Mr. Chris Russell, P.E. East Coast Engineering, P.C. P.O. Box 2469 Shallotte, North Carolina 28459 Reference: Report of Infiltration Testing Habitat for Humanity Project Ocean Isle, Brunswick County, North Carolina ECS Project No. 22.17115 Dear Mr. Russell: ECS Carolinas, LLP (ECS) recently conducted infiltration testing for the proposed stormwater best management practice (BMP) areas at the Habitat for Humanity Project site in Ocean Isle, Brunswick County, North Carolina. This letter, with attachments, is the report of our testing. Field Testing On October 5, 2011, ECS met with Mr. Allen Lewis with East Coast Engineedng, PC and Mr. Vincent Lewis with NCDENR in order to conduct an exploration of the subsurface soil and groundwater conditions at five requested locations shown on the attached Test Location Plan (Figure 1), The locations were surveyed prior to ECS's visit. The purpose of this exploration was to obtain subsurface information of the in - place soils for the proposed stormwater BMP areas. ECS explored the subsurface soil and groundwater conditions by advancing one hand auger boring into the existing ground surface at the requested boring locations. ECS visually classified the subsurface soils and obtained representative samples of each soil type encountered. ECS also recorded the groundwater level and the seasonal high water table (SHWT) observed at the time of the hand auger borings. The attached Infiltration Testing Form provides a summary of the subsurface conditions encountered at the hand auger boring locations. The groundwater level and the SHWT were estimated at the boring locations below the existing grade elevation. A summary of the findings are as follows: Location Water'Level SHWT. 1 Winches 65 inches 2 48 inches 38 inches 3 48 inches Winches 4 40 inches 30 inches 5 Winches 65 inches ECS has conducted five infiltration tests utilizing a compact constant head permeameter near the hand auger borings to estimate the infiltration rate for the subsurface soils. Infiltration tests are typically conducted at two feet above the SHWT. If the SHWT is less than three feet, the tests are conducted at ten inches below the surface elevation. I,Y C , 7211 Ogden Business park, Suite 201, Wilmington, NG 28411 - T- 910-686-9114 • F: 910-686-9666 • www.ecslimfted.com ECS Capitol Services, PLLC • ECS Carolinas, LLP • ECS Florida, LLC • ECS Midwest, LLC • ECS Mid -Atlantic, LLC • ECS Southeast, LLC • ECS Texas, LLP Report of Infiltration Testing Habitat for Humanity Project Ocean Isle, Brunswick County, North Carolina ECS Project No. 22.17115 October 7, 2011 Field Test Results Below is a summary of the infiltration test results: Location Description Depth Inches/ hour 1 Tan/orange fine to med. SAND 41 inches 13.2 2 White fine to med. SAND 17 inches 18.4 3 White fine to med. SAND 12 inches 22.1 4 White fine to med. SAND 12 inches 19.2 5 Tan/orange fine to med. SAND 41 inches 14.0 Infiltration rates and SHWT may vary within the proposed site due to changes in elevation and subsurface conditions. Closure The activities and evaluative approaches used in this assessment are consistent with those normally employed in assessments of this type. ECS's testing of site conditions has been based on our understanding of the project information and the data obtained during our field activities. ECS appreciates the opportunity to provide our services to you on this project. If you have any questions concerning this report or this project, please contact us at (910) 686- 9114. Respectfully, ECS CAROLINAS, LLP K. Brooks Wall Project Manager Attachments: Figure 1 - Test Location Plan Infiltration Testing Form K 1s J. Stamm Principal 2 y I t 1 t l 1 \ t II• \I j ! 1 I � 1 I I I ! I I \ t i 1 I u m 1 "r--------^-----`---^ -- ! PO ", I I 3 I ICI 2 1 ^----I I LAJ .'1 I L� I o O x j ! I ] III I I III rl 1 ffx I I I 5 0 p I LI IIIII I I f I I i! II I y I I € I ! 1 I �. r----- — a APPROXIMATE TEST LOCATIONS Habitat for Humanity - - Figure 1— Test Location Plan Ocean Isle, NC ECS Project # 22.17115 Provided by: East Coast October 5, 2011 Engineering, P.C. KBW ��►i��ILill�►� Infiltration Testing Form Habitat for Humanity Site Ocean Isle, Brunswick County, North Carolina ECS Project No. 22.17115 October 5, 2011 Location Depth Soil Description 1 0-25" White fine to med. SAND 25"-80" Tanlorange fine to med. SAND Seasonal High Water Table was estimated to be at 65 inches below the existing grade elevation. Infiltration Rate: 13.2 inches per hour Test was conducted at 41 inches below existing grade elevation Groundwater was encountered at 80 inches below the existing grade elevation. Location Depth Soil Description 2 0-24" White fine to med. SAND 24"-32" Hardpan 32"-48" Tan fine SAND Seasonal High Water Table was estimated to be at 38 inches below the existing grade elevation. Infiltration Rate: 18.4 inches per hour Test was conducted at 17 inches below existing grade elevation Groundwater was encountered at 48 inches below the existing grade elevation. Location D�eyth Soil Description 3 0-24" White fine to med. SAND 24"-32" Hardpan 32"-48" Tan fine SAND Seasonal High Water Table was estimated to be at 36 inches below the existing grade elevation. Infiltration Rate: 22.1 inches per hour Test was conducted at 12 inches below existing grade elevation Groundwater was encountered at 48 inches below the existing grade elevation. Infiltration Testing Form Habitat for Humanity Site Ocean Isle, Brunswick County, North Carolina ECS Project No. 22.17115 October 5, 2011 Location Depth Soil Description 4 0-20" White fine to med. SAND 20"-28" Hardpan 28"-48" Tan fine SAND Seasonal High Water Table was estimated to be at 30 inches below the existing grade elevation. Infiltration Rate: 19.2 inches per hour Test was conducted at 12 inches below existing grade elevation Groundwater was encountered at 40 inches below the existing grade elevation. Location Depth Soil Description 5 0-25" White fine to med. SAND 25"-80" Tan/orange fine to med. SAND Seasonal High Water Table was estimated to be at 65 inches below the existing grade elevation. Infiltration Rate: 14.0 inches per hour Test was conducted at 41 inches below existing grade elevation Groundwater was encountered at 80 inches below the existing grade elevation. r.