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Home My WebLink About20091097 Ver 1_More Info Received_20100128EE LLP "Setting the Standard for Service" - - Geotechnlcal • Construction Materials • Environmental • Facilities NC Registered Engineering Firm F-1078 January 27, 2010 Mr. Alan Johnson NCDENR - Division of Water Quality Mooresville Regional Office 610 East Center Avenue, Suite 301 Mooresville, North Carolina 28115 Subject: Response to December 3, 2009 Letter - DWQ # 09-1097 Request for 401 Water Quality Certification Doves Nest/United Family Services Charlotte, Mecklenburg County, North Carolina ECS Project 09-17902 Dear Mr. Johnson: FC7B fl. 2M DENR - WATER QUALITY 11IEn A4DS AND STORl&NTER BRANCH ECS submitted an application for a 401 Water Quality Certification for the above referenced site that was received by your office on October 15, 2009. A North Carolina DWQ letter dated December 3, 2009 (Attachment) requests that modifications be made to further reduce the impact to the stream. Lincoln Harris has redesigned the stormwater pond/site to further minimize the proposed impacts to the unmitigable stream. The PCN that was submitted on October 14, 2009 proposed impacts to 377 linear feet (1,673 square feet) of unmitigable stream channel. Based on correspondence with the DWQ, the site layout was redesigned and the pond was resized and shaped. The revised stormwater pond and calculations are included as attachments. The impacts have been reduced to 296 linear feet (1,323 square feet) of unmitigable stream channel. As you will recall from the site visit, the aquatic habitat of the stream increased as we approached the southern boundary. The stream impacts have been reduced to avoid impacts to 81 additional feet of this portion of the stream. On behalf of Lincoln Harris, I am requesting that a 401 Water Quality Certification be issued to authorize the impact to 296 linear feet of unmitigable stream channel. There are no other stream or wetland impacts associated with this project. Based on the stream being classified as non-mitigable, mitigation is not proposed. 4811 Koger Boulevard • Greensboro, NC 27407 . T. 336-856-7150 . F: 336-856-7160 www.ecslimited.com ECS Carolinas, LLP . ECS Florida. LLC • ECS Mid-Atlantic, LLC - ECS Southeast, LLC a ECS Texas, LLP Response to December 3, 2009 Letter - DWQ # 09-1097 Request for 401 Water Quality Certification Doves Nest/United Family Services Charlotte, Mecklenburg County, North Carolina ECS Project 09-17902 Please feel free to contact me at (336) 856-7150 if you have any questions concerning this request or if additional information is required. Thank you in advance for your timely consideration of this matter. Sincerely, ECS Carolinas, LLP Michael T. Brame Senior Environmental Scientist ?--az k- Denise M. Poulos, LSS Principal Scientist Attachments: NCDWQ Letter Dated December 3, 2009 Vicinity Map Existing Conditions Site Plan Grading Plan Preliminary Stormwater Management Facility Design cc: Mr. Steve Chapin/USACE 2 fF', i /• t l t t ? a= t C Y'? '-SITE I t t ?? 1 , G 17 VICINITY MAP N.T.S. OF-5-09000 UNMD FANIILY SERVICES THE JOHN R. McADAMS ursogooo-VM WEST BOULEVARD COMPANY, INC. E2S Y ' r scat!' T CHARLOTTE, NORM CAROLINA CF I»1F1NEFtSJSUfi2 ENCfiP7E[4? /f . ` 6703 CARASEL ROAD) SUITE 205 '', nz?r 10-16-2009 vicll '? m" (704) 527-UND Cdt:aUNA 28220 F ( 4h; ?1V? Q fr ] 4• - r;t' ? ' n cf) T ,• r : r t y Fr i r v ;, GO I 1 - ,. .. - e f w 1 . , ?. 1 , i - i , + r . k i sw < < f ` r k ,! C S ! - t rp , FE R w - VS as _ t co I. X ?.• t 4,.'4 w^". - . ( .,.... ?. ` .. „-.. ,.... I ., ! 1. ' ,.. PROJECT N0: UFS-09000 .? FILENAME: UFS09000-EX se,v1F` 1"=200' uA3L: 1-26-2010 U UED FAMILY SERVICES JITHEJOHNR.MeAD WEST BOULEVARD COMPANY, INC. CHARLOWE, NORTH CAROLINA ENGINEERS/PLANNERS/SURVEYORS ??q 6701 CARMEL ROAD, SUITE 205 EXISTING CONDT'''iONS (704) 527 ,08 ?RTH CAROLINA 28226 f, rte" -?...L°?. -,.. f ? z? y ^?,s5? Fl _ _ ,,,.„_, _ _ - -- F.? 1 S I f 1F? ?? 11 I ? ?1 s i e s 1 ''?'. A h_ J'1 E v y R 'm t t e J ' t y /r I+ n /'a5 C 9U"?E.AMAILWAY a_?. 1891 pG 433 ul } I {yE1 lit D „, 1 f V) - l z ns ,. C r / If ?1 I tE ti tv > t'j U C I,> rq Lh C) tA 1 ! E I! } Jtl `? s k\-- m SWn-boo= ?ZMm.N?¢??9 ? amp !ll?Ill lllttt; Z --p YTDQc ? .. I PROJECT N10 UFS-09000 UNITED FAMILY SERVICES THE JOHN R. McADAMS - FILENAME: uFS09000-Sl WEST BOULEVARD COMPANY, INC. SCALE', 7`'=200' CHARLO=, NORTH CAROLINA ENGINEERS/PLANNERS/SURVEYORS 6701 CARMEL ROAD, 3UCI"E 205 ?/,^ 7-2s-200 SITE PLAN CHARLOTTE, NORTH CAROLINA 28228 (704) 527-0800 ft[,R} ? 4 !s ?! 1 7-z -Tl .?. ? ?,? .N>4+ r`[ C! Icy r?ir?t?n n • \\ll \ F IK, i x ' {{{???!!!777 ?t _ r1l ?t S ?3. ??? d y Iy f t /W r , f wa ? / r _ p s r t, ZT.p t Y f. i 1 ? n. r? i y •,--..gy PROTECT 110. UFS-09000 i% U=D FAMILY SERVICES J1 THE JOHN R. McADAMS FILKNAMI?. OF 509000-G1 . BouLEVARn VMS COMPANY, INC. y , SCALE: 1 "= 200` CHARLOTTE, NORTH CAROLINA ENGINEERS/PLANNERS/SURVEYORS 6702 CARMEL ROAD, SUITE 205 oxsL GRADING PT w N ?LV CHARLOTTE, NORTH CAROLINA 28228 (704) 529-0800 United Family Services Preliminary Stormwater Management Facility Design J.C. Diaz. PE Dove's Nest Stage-Storage 1/25/2010 UFS-09000 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) 678.00 0.0 17013 679.00 1.0 20392 18702 18702 18702 1.01 680.00 _ 2.0 - 22041 ? 21216 21216 _ 39918 _ 1.98 681.00 3.0 23747 22894 22894 62812 2.97 682.00 4.0 25509 24628 24628 87440 3.99 683.00 5.0 27328 26418 26418 113858 5.06 120000 Storage vs. Stage °-- - 100000 1 y = 18,538.1378x1.1201 R2 = 0.9998 80000 d 60000 rn A n 40000 r I 20000 0 0. 0 1.0 2.0 3.0 4.0 5.0 6 .0 Stage (feet) Ks = 18,538.1 b = 1.1201 X:\Projects\UFS\UFS-09000\Storm\Preliminary Design\Design Files\Preliminary Stormwater Management Facility Design Page 1 United Family Services Preliminary Stormwater Management Facility Design J.C. Diaz, PE Dove's Nest Water Quality Volume 1/25/2010 UFS-09000 L CALCULATION OF 1" VOLUME FOR WATER QUALITY The runoff to the pond for the 1 " stone detention requirement is calculated using the Schueler Method in accordance with the Charlotte-Mecklenburg BMP Design Manual, (April 2008). WQ v = (P)(R v)(A)112 WQv = water quality volume (in acre-ft) Rv = 0.05+0.009(1) where I is percent impervious cover A = area in acres P = rainfall (in inches) Input data: Impervious area = 7,17 acres (assumptions: 4 ac imp onsite, 70% imp for offsite) Total area, A = 11.45 acres (includes contributing area from offsite) Percent impervious cover, I = 62.6 % Rainfall, P = I inches Calculated values: RV = 0.61 WQv = 0.59 acre-ft i Therefore, total runoff from precipitation in question = 25,506 CF This amount of runoff must be stored in the pond above 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. H. CALCULATION•OF DEPTH REQUIRED FOR RUNOFF STORAGE POOL (ABOVE NORMAL POOL) Normal pool depth (above invert) = 0.00 feet Storage provided at permanent pool depth = 0 CF (calculated) Total storage required for normal + storage pool = 25506 CF Ks = 18538.1 b = 1.1201 Invert Elevation= 678.00 Stage (above invert) associated with this storage = 1.33 feet i Therefore, depth required above normal pool for storm storage = 1.33 feet 15.96 inches Therefore set crest of principal spillway at stage = 1.50 feet and EL = 679.50 feet At principal spillway crest, storm pool storage provided = 29,195 CF 1 X:\Projects\UFS\UFS-09000\Storm\Preliminary Design\Design Files\Preliminary Stormwater Management Facility Design Page 2 United Family Services Prelin Dove's Nest UFS-09000 1. SURFACE AREA Impervious Area = 7.17 Drainage Area = 11.45 unary Stormwater Management Facility Design J.C. Diaz, PE DWQ Surface Area Sizing 1/25/2010 acres (assumptions: 4 ac imp onsite, 70% imp for offsite) acres (includes contributing area from offsite) % Impervious = 63% Average Depth = Accumulated Contour Volume / Surface Area Average Depth = 3.0 ft. assume minimum average depth Per NCDENR "Stormwater Best Management Practices", the required SA/DA ratio -? 3.0 3.0 4.0 Lower Boundary --> 60.0 2.40 2.03 Site % impervious --> 62.6 2.53 2.53 2.13 Upper Boundary - 70.0 2.88 2.40 Area Required = 12600 sq.ft. Area Provided = 17013 s .ft. X:\Projects\UFS\UFS-09000\Storm\Preliminary Design\Design Files\Preliminary Stormwater Management Facility Design Page 3