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Home My WebLink About20091226 Ver 1_More Info Received_20091210??", NCDENR North Carolina Department of Environment and Natural Resources Division of'Alater Qu<iiity Beverly eaves =erdde Coieen H. Sullins Dee Freeigan Governor Director Seoret?.iry December 7, 2009 CERTIFIED MAIL: RETURN RECEIPT REQUESTED DWQ Project # 2009-1226 Wake County Ashraf H. Allouba 219 Kirkfield Drive Irv/ Cary, NC 27518 ? Ll-mn Subject Property: Ashraf Allouba - 219 Kirkfield Drive, Cary, NC Ut to Swift Creek [030402,27-43-(1), WSIII, NSW] DEC 1 1) 2009 REQUEST FOR MORE INFORMATION DENR • WATER QUALITY VO ANDS AND STORmVVATER BRANCH Dear Mr. Allouba: On November 13, 2009, the Division of Water Quality (DWQ) received your minor variance application dated November 13, 2009 to impact 266.5 square feet of Zone 2 of the protected riparian buffers to construct the proposed 10' x 24' addition along the east side of an existing residence at the subject property. The DWQ has determined that your application was incomplete and/or provided inaccurate information as discussed below. The DWQ will require additional information in order to process your application to ' pact protected wetlands and/or streams on the subject property. Therefore, unless we e will place this project on hold as incomplete until we receive t his a 7 Iona m o ma ion. wo not receive the requested information, your project will be formally returned as incomplete. Please provide the following information so that we may continue to review your project. Additional Information Requested: 1. Please increase the bioretention soil media depth from 12" to 24". Depth of washed sand below the planting soil media can be reduced. 2. Specify the Phosphorus (P) Index of the proposed soil media on the Plan. 3. This office recommends that the top surface of the outlet level spreader/overflow weir should be flattened to evenly and uniformly distribute the excess flow along the entire 11-12 feet. Please provide some energy dissipation measures at the bottom of the wall where the overflow occurs. Please provide underdrain sizing calculations, and please note that a minimum of two (2) underdrains are re fired. 5?lease make the necessary corrections as follows: a. Provide the minimum volume required and treatment volume provided; b. Surface area at the top of the bioretention cell, and the corresponding dimensions (length and width); c. Change the value for the temporary pool elevation - this is the elevation of the top of the ponding depth, or top of overflow weir/level spreader elevation. 401 Oversighti'Ex;ress Review Per; ttng Unit 1650 ivla' Sei roe Center. Raleigh. NortlCarc lna 2: 699-1650 Lo ation ' 21 23 Craairee Bleu R6ieig!1 P girth a`J;r a 27,604 919-733-1786 If FAX 919-7313-6893 ntemel: htt;:-r`h2o enrstate.nc asircaetan:i: One North Caro I i ti. t Underdrain Calculationsfor DWQ Project #2009-1226 Allouba Residence 219 Kirkfield Drive, Cary, NC 27518 12/9/09 Flow Rate through soil media by Darcy's Law L thickness of soil layer 2.00 ft AH change in head 2.67 ft K hydraulic conductivity assume range from 2 to 4 in/hr q Flow per cross-sectional area q = K*AH/L K= 2 3 4 5 6 q = 2.67 4 5.33 6.67 8 in/hr per unit < Bioretention Area = 33.33 sq. ft. total Flow = 0.002 0.003 0.004 0.005 0.006 cu ft. per seco Size pipe system at 10 x calculated amount: 0.02 0.03 0.04 0.05 0.06 c.f.s. required pipe diameter by Manning's eqn.: assume 'n' = 0.011 at 0.5% slope: 1.86 2.16 2.41 2.62 2.8 inch diameter total diameter required = max of 2.8" for 10 x calculated flow with K=6 Therefore 2-4" drains are sufficient D gg A @ =? 54 DEC 1 0 2009 DENR - WATFR QUALITY WETLANOS AND STORWIATER BRANCH Permit Number:-#2009-1226 kTI-KWA O? WAfE'9. NCDENR STORMWATER MANAGEMENT PERMIT APPLICATION FORM 401 CERTIFICATION APPLICATION FORM BIORETENTION CELL SUPPLEMENT This form must be filled out, printed and submitted. The Required Items Checklist (Part III) must be printed, filled out and submitted along with all of the req uired information. i. PROJECT WFORMATION Project name Addition to Allouba Residence, 219 Kirkfield Drive, Cary, NC Contact name Howard A. Partner, R.L.A. Phone number 919-286-6638 Date August 23, 2009 Drainage area number 1 of 1 III. DESIGN INFORMATION Site Characteristics Drainage area 267 ft2 Impervious area 267 ft2 Percent impervious 100.0% % Design rainfall depth 1.0 inch Peak Flow Calculations Is pre/post control of the 1-yr, 24-hr peak flow required? 1-yr, 24-hr runoff depth 1-yr, 24-hr intensity Pre-development 1-yr, 24-hr peak flow Post-development 1-yr, 24-hr peak flow Pre/Post 1-yr, 24-hr peak control Storage Volume: Non-SA Waters Minimum volume required Volume provided Storage Volume: SA Waters 1.5" runoff volume Pre-development 1-yr, 24-hr runoff Post-development 1-yr, 24-hr runoff Minimum volume required Volume provided Cell Dimensions Ponding depth of water Ponding depth of water Surface area of the top of the bioretention cell Length: Width: -or- Radius Media and Soils Summary Drawdown time, ponded volume Drawdown time, to 24 inches below surface Drawdown time, total: In-situ soil: Soil permeability Planting media soil: Soil permeability Soil composition % Sand (by weight) % Fines (by weight) % Organic (by weight) Form SW401-Bioretention-Rev.8 July 30, 2009 N (Y or N) 2.87 in 0.12 in/hr 0.002 ft3/sec 0.026 ft3/sec 0.024 ft3/sec 22.2 ft3 22.2 ft3 OK n/a ft3 _ ft3 _ ft3 n/a ft3 ft3 8 inches Insufficient ponding depth. 0.67 ft 33.3 ft2 OK 10 ft ji I 34 OK Insufficient length ft 12 hr OK 12 hr OK 24 hr 0.52 in/hr OK 2.00 in/hr OK 86% OK 10% OK 4% OK Information Revised 13-292-per DWQ comments Parts I and II. Design Summary, Page 1 of 2 Phosphorus Index (P-Index) of media 20 (unitless) OK Basin Elevations Temporary pool elevation 385.00 fmsl Type of bioretention cell (answer "Y" to only one of the two following questions): Is this a grassed cell? N (Y or N) Is this a cell with trees/shrubs? Y (Y or N) Insufficient media depth Planting elevation (top of the mulch or grass sod layer) 384.33 fmsl Depth of mulch 2 inches OK Bottom of the planting media soil 383.33 fmsl Planting media depth 1 ft Depth of washed sand below planting media soil 2 ft Are underdrains being installed? How many clean out pipes are being installed? What factor of safety is used for sizing the underdrains? (See BMP Manual Section 123.6) Additional distance between the bottom of the planting media and the bottom of the cell to account for underdrains Bottom of the cell required SHWT elevation Distance from bottom to SHWT Internal Water Storage Zone (IWS) Does the design include IWS Elevation of the top of the upturned elbow Separation of IWS and Surface Planting Plan Number of tree species Number of shrub species Number of herbaceous groundcover species Additional Information VUCJ VUIUI I It III tALImJ UI UIC umllylI VUIUI I It Uypdb6 LI It UIUI=1 IuL)1I -11 Does volume in excess of the design volume flow evenly distributed through a vegetated filter? What is the length of the vegetated filter? Does the design use a level spreader to evenly distribute flow? Is the BMP located at least 30 feet from surface waters (50 feet if SA waters)? Is the BMP located at least 100 feet from water supply wells? Are the vegetated side slopes equal to or less than 3:1? Is the BMP located in a proposed drainage easement with access to a public Riqht of Way (ROW)? Inlet velocity (from treatment system) Is the area surrounding the cell likely to undergo development in the future? Are the slopes draining to the bioretention cell greater than 20%? Is the drainage area permanently stabilized? Pretreatment Used (Indicate Type Used with an "X" in the shaded cell) Gravel and grass IR'inrhas nraval fnllnwari by 3-5 ft of nrattl Grassed swale Forebay Other Y (Y or N) 1 OK 2 OK 1ft 380.33 fmsl 375 fmsl 5.33 ft OK N (Y or N) fmsl 384.33 ft 0 0 3 OK Permit Number: #2009-1226 Wake County Y (Y or N) OK Y (Y or N) OK 10 ft Y (Y or N) Submit a level spreader supplement. Y (Y or N) OK Y (Y or N) OK Y (Y or N) OK Y (Y or N) OK ft/sec N (Y or N) OK N (Y or N) OK Y (Y or N) OK X OK Form SW401-Bioretention-Rev.8 Parts I and ll. Design Summary, July 30, 2009 Information Revised 12-9-09 per DWQ comments Page 2 of 2 5outhweSt Elevation 5'-0" ~ 8" flood de h ~ a ~ ~ ~'d ~ 385.0 )n Plan 385.12 Ito oflev of mle [ ~ ~ } ~ ei Spreader ~ ~ ` r top ade i ~ level5pre outlet level Spreader _ .I ~ (See inset) ariance. _ overFlow outlet ~ level s reader i I - ~ io p ~ ° intcr~rr , ~.!r asin ~ `~~A . '°~..A ~v. downs out , im-,~~oion. ~ - ~ p t 3 - '1~, , ~ ~ ~ z ~ ' ® ~ 8 i 1 lee, ~ ~ ader ~ i f ~ ~ ~ q.. , 1 ° i Pe t~ ~ t~ ~ ~ i s ire "~E~ ~~,.o ve~5p ~ f inlet rowlock = ~ ~ ~ ~ [ ~f,, ad of le ? ~.1 h'1 {~bl ~Ir e~~ ~P ~ level s reader ~ ill; [ ~ ~ _ downs out outlet , w 22'-5 s p , ..w ~ ~a. ~ ~,~-~s.o _ p _ _ to inlet level Spreader - _ See inset ~ ~ . ~ ~ , , y, ~ s ' . , ,A . ~ ) ` ~ r,,,.~,.~.>F , i. ~ ° ~ 24" Sand/soil ~ 'ij Arive -.,.~~,~t - mix layer 12 x 12 Inlet Bax ~ ~%i wl 6 pVC drain pipe ~ ~ v ~r;,;i ~ ~ ~ , ~ ~ - ~ ; ~tur ~r~.1~;. Note: - 11 ' Entire bioretention ~ i Date: 10 N®vember 2009 12 Sand la er 9 basin iS brick masonry Y 9 ' construction on concrete ~ ~ e~><se: 9 ece bey 2009 r Dw J per DWQ comments L ~ ~I footings-to match 3'-4" 9 ~ Q i I 1:~-~ l i 1 ~~(~ii..~ I I;II.[I `9 ti iiGJ i i ,i founda an wa interior width exiStin heat um li ~ , , ~ _ I g p p ~ ~ 1~ r ~:cJ ~ ~ ,i n~~i,~ l~ ~i~i : „~n ~ ~ r . f,~i U, ~ .~i~ie'' '1 ~ _ 2-A~ WG erforated 2' - si~~ p t - e out et drains, wrapped ~ Isometric ~ . r ~ ~ ~ ~ Sra ~a1°a~, 3t. Durham, NC 27705 :exi5tin hau5e= 9caie:l°=2-0" ~~/0 in iter a ric. ~1,~ ~ - ; F axo 919-286-6638 a ~y , ~ plan enter emen~G _ ~ ? ~ ~ ~ r r ~ iti _i1~i ) .r' secondary downspout ~ _ - IF i S rl f'L r ~v k 1 f _.Zu ~.t aP~- 6"_~ from pond side eave ~ .i'~ zma~i:~st~rm~ Wit: sfjiiii~v-orks@ti-nug.org - - w,. downspout e~~,~ 4a~~rat~~ii~u~a~~G 6~~~aa~ - ~,®~~¢®u't ~a~ I-~.~=:: ~~~as~~a~~~ ~ F rwo d 15 al miti anon- re x a ition iemove sod, and till Sourwood 2 Oxydendrum arboreum Sou o g g t native soil, prior to Serviceber 1 Amelanchierx randiflora 'Autumn Brilliance` 'Autumn Brilliance' Serviceber 15 al miti anon-tre to -385.0 lacin sand la er J. 'Cayman`s Gra ' 20 Juncus atens 'Cayman's Gra ' California Gra Rush #32 bioretention p p g Y y ® p y y Filterfabric finer, all sides P. orientate 16 Pennisetum orientate 'Kerley Rose' 'Karl2y Rose' Oriental Fountain Grass #18 bioretention top= 355.12 i weep hoies,- P. K,Rose 10 Penn~setum onentale Oriental Founta n Grass #32 bioretention 16 o.c. , Grasses available from Hoffman Nurse , Rou emont, NC 800-203-8590• www.hoffmannurse .coin ~ Overflow Dissi ator- a°overfiow plantln Schedule 5 in. de th #57 Stone =y y~' = 2"mulch layer+ w/ 2"-4" river rock at surface _ 2a-"Soil/sand mix ,,y'%;~, - , _ 2 5and~.,/SIO eat %~~ti. ~ ~ \ ~\bioretention, x ® ® ~ ~ . i I'ropo5eddrainagearea: i ~ \ ~ ~ oed drainage area: sa. ft. 5outhwrest%,;~, ~ ~ , ~ , ; 4 ~z ,extend drains ~ i ~ ~ • ~ (1,50+ 5~. ft. impervious) i sq. ft. impervious) ~ ~~``.v throu ~h brickwalG% ti~i,~~ y~~,~'~~ ' ~ ~ exi5tin drama e area: ~,:Elevat~on f , g, ~ \ Y • ~ ~ Pro o5ed drama e area i5 F \ ~ , g ~ drainage area io to existing drainage area, 5,9255 .ft. ~'Scale:l =5-0" /`r.\\Y ~ ~ ~ . ti,,r\, ~ ` t identical toexi5tingdra(nag ® °~u , , ~ ~ . a1~3 x {with higher imperviau5 pert ti- 1217 5 . ft. im ervioue . her impervious percentage) ting conditions . o ~ ~ ° a p ~ ~G t1~ d~ ~ -see existing conditions ~ ~ '~77,,}} F4t~S. , ~5`I ~~,.t~ l`~ y~ ,,1 ,~~z, ~ 8-~. orienta[e 8-~. onentale ~ ~ ~ ~ ~ FS` , r ~ --4 .A ~ s ® ~:A. ~ ~ sbpeat ® e`a «o o , Pro c~~ed dope at r;~ ® ~ e ~ ~ '~~rret~nrlon - ~ ~ 5~~ bioretention 'w ~ '~:+.vu' tG't~'GkE-rx ~a (vre (Jetaii) ~ o sioretention :15.2% . ~ _ ~ pal fi of r gv2 ~ f98T~ ?Oy5 ` r'`~ r° ~ _ time r s $ 1~97~t ,~aa , `a. s;" co icrsntr. 4, b E'' ` m 20-J CarmanSGray ~ r' ' ~ , o , Z-5ourwood ,y ~ ; ~"'1.~G~,t t,,~ ran ~ ~ 10 o,c. (ty) The soil mix should be uniform and free of stones, stumps, ~ f0F 7~ s S" tl`: ; ~ $fJ(iTflX;4Sliir"t`J Ct't7 . ~ ® roots or other similar material reater than 2 inches. It ; s ~ ` z ~b ~ ' =3,a ~ ccr ..vx~ 3/8~ OF ~f17 ?8 ~3/:C` ~HtXV 7+~E ~ x - ~ r a ~~~,p ~ should be a homo enous soil mix of 85-88 percent by ~.z2 oeres ~ . ~ , ~`v + Ld~Y f Vr'. , j`i~~. ~y L. u F ; d-~^am ~ ~Ri7t. a ~1.2'R l ~ ~ ~t 'P ~ ~ ~ „~r~ ~ weight sand (USD Soil Textural Classifiication), 8 to 12 f, ~ y i 1~~1.y;? :r-~, ,rte , r- D , t ~ ~ ~"s; percent fines (silt and clay), and 3 to 5 percent or ante ~ ~ ~ ~ 1 r , a, - ~ matter such as eat moss shall be used. Soil mex Phos 1 3`~ 19',4 ~~1 _ horns [ndex s all be be sari 10-30. ' ~4. ~ ~s~. ~ ~ r ~ ~ ~ Bioretent~ n . e D ~ ~ ~A.~ plantin ha out ,_;E~ _ ,r , , ~ , ,q- ii ~ ~ 'fir ' d-- •'P~ ~ 1~1 f, ~ _ ^v ' ~ YY " A 4 Tai l_sr n:': r,~SY;a ryJ / `~~p~ ,y ` l i ,,u ~ , „~n, ,r~ t~F~ ~ s~ ' ~ e n i, ~ ~ ; 7] 1 ~ ~ ~ ~ _ P , P3 . ~ 'hit- - - u . ~~m _,:z ~ s~;' ,~:4„ Cc in , ~ R ~ , s' " f'rC' ~0 ` jar ;s' ~ q f-. Y:~~. - _ 1~.\ - F i s \ s ~ Site at 3v < , - - - _ ~ : ,,r ~ - z~ 219 Kirldield Dr. ~ ~ - ~ R -ice - ~ \ ~ ~ - 1-5e ; ~ ~ . v ~o: ~ 0 n _.o.y~ - - \ ! 1-5erviceberry dT _ r ~y \ do - e J _ ~t'. - ~~~~tt _ ; r ~ '1 ~ s~~ _ _ _ t ~ . r ~ 3 y ~ • . d , I' > I_-~r ~ rd~ . . ` . _ _ w . 9~ ~ ~ tr l Eli C*` - rte 1~1,_ - g . , _ A s „ r ~ . , 11065 „ • ~ , . r, to i n _ _ ~ t. , t~; ~ ~ ~ " ~ ' ~ r ~ eAge otveyetntion d , ~ r ~ - ~ E«tin Condit'on~ N ~ Q ,a za ~ 3 • ~al~: L =2Q~ Vlcin it ~a ~„f~a SCALE:1 IA! = 20 Ff. ;c _ ~s~~~~a-~ Yt~ „