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Home My WebLink AboutSDP200500045 Request of Modification, Variance, Waiver Minor Amendment 2005-10-17 Brown Auto Park Brown Subaru Site Plan—Minor Amendment Stormwater Management & Water Protection Summary October 17, 2005 The Subaru building will be located in an undeveloped portion of the Brown Auto Park. The approved site plan for the Brown Auto Park provides water quality treatment for the parking lots and travelways through the use of Filterra boxes. The proposed Subaru facility will include some reconfiguration of curb around the new building, creating some new drainage patterns. As a result,two new Filterra boxes are proposed to ensure that the previously approved and installed Filterra boxes will not be overburdened by the revised drainage patterns. The maximum allowable contributing drainage area for a 6x6 Filterra is 0.25 acres. The revised drainage areas to the 6x6 Filterra boxes do not exceed this amount. The maximum allowable contributing drainage area for a 4x6 Filterra is 0.17 acres. The drainage area to the 4x6 Filterra box does not exceed this amount. The maximum allowable contributing drainage area for a 8x4 Filterra is 0.22 acres. The drainage area to the 8x4 Filterra box does not exceed this amount. The building roof runoff is directed to the curb along the west side of the building. The roof drains are located at points that allow sufficient distance for the outfall to achieve sheet flow prior to entering a Filterra box. rif'T 1 8 "15 y. --, 443'71 1.=r -414?.91 f .. ii9.643I SfiO, ,+sCt <9-. + ?:3 r, - -, 44F.94 k 39 • j 1 A 7 x i it - 6 F L -� ITN. : ' 44r t y'�*""{ " . �' 491, � ILTE�, fi.Y -wr..--r �, tti � 1 I d4r:4449 . Ins � � ""° � : :3i>1 ... -_. : Y r ' 4 ,,..A1F44, .. ---"' 4 .4.-• 7- - „4.4 „.*: ' t 1 .69 ,7aP ,�4 #:tiBYr �v I , : /' f • t 6Gt i444fim 4SL ' • f r -.. y1 p 'wi4� 43?S$ _ 43245.- 4 9 ri �' 4tF, $. fra --"-- Ili( ',%r. ' 1y1' a3"Y�'.�">y, 2. 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FC .E II.S$ 4 .50 ;I- *�� ;' ti';`,-- 028 AC. (ROOFS711 ',_:',;:i..e:::1:4 -,:.:4:: ,r► t rr e• + iJr_ _, �� ii, fl 111t zt r 4 >-, f:11611 - 1,, -,.:1:: , 1 r 1 1102717 _..4?X 3 4 *428-44 ..._ - i .1* * I --'w4IP;.4-i-mod Ilk 4 92 i' ,. r.+ 426 fi4.� __ i��I � " I (. 4 i4i.23 $4 a2.'J + Sty„t 42e 34 s263a 4a5;2 I t I i I i ' j e — y, ai f 4s sr" ar ! I s \e` `T 1 ` On, $ WATEFS . +Yi 4 982 f *12492 t` ▪1 1 3 4 .10 41 51+ R',:, I 4 F�` RT4ii `r. f 4?3 33 }t D 6' .. 1I1 \ 1 \_,4'A'11,/ , :, lip : ' R4" MbPE I i DRAINAGE AREAS - SCALE: 1" =40' October 17, 2005 Clark Gathright Daggett & Grigg Architects/Planners 1001 East Market St, Suite 200 Charlottesville, VA 22902 Dear Sirs: Subject: SDP 2005-045 Brown Auto Phase II, Filterra® Units Following receipt of a copy of a comment letter from Albemarle County, dated October 12, 2005, I have re-reviewed the revised planned layout and sizing of the Filterra® units located adjacent to the new proposed building (email drawing file dated 10-14-05). The four Filterra® structures were studied for; • Planned Filterra®box size • Filterra® contributing drainage area meeting project's regional sizing specification • Spot elevations (TC) for Filterra® and bypass relief • The bypass is lower than the Filterra® elevation (spot elevations) • The grading pattern encourages cross linear flow and not head-on flow • The Filterra® outlet drain pipe is sized correctly and exits perpendicular to the wall The plan review concluded that the Filterra® structures listed above were sited and sized appropriately to treat stormwater to our published specifications. It is common and quite acceptable for Filterra® units to be bypass structures for other Filterra® units. It is also common for relief (as opposed to a specific structure) to function as the bypass for a Filterra®unit. One other note about the comments is that I have seen a number of plans where the Filterra® effluent pipe is run for a hundred feet or more as 4" or 6" PVC pipe. This may be due to the fact that the stormwater effluent is filtered and all larger particle sizes removed. More water volume cannot enter this effluent pipe since the media material is the flow limiting factor of the system. When this rate is exceeded, excess flow results in a surface bypass. Please do not hesitate to contact me for any further information. Yours sincerely Edward Kay, Filterra® Operations Manager a • • • • * • i +�• e a •�► + r • 1 •is ■■�, r•■■•ons ma mum warns DAGGETT & GRIGG ARCHITECTS PC William B.Daggett,Jr. AIA,NCARB James P.Gngg October 17, 2005 AIA Steve Tugwell Department of Community Development County of Albemarle 401 McIntire Road Charlottesville, VA 22902 Re: SDP 2005-045 Brown Auto Park-Minor Site Plan Amendment (WPO-2005-00054) Please find attached copies of the revised site plan. A. Final Site Plan comments: 1. All existing and proposed curb radii are now labeled. 2. The curb type is now labeled. 3. The grades are sloped to direct water away from the building. 4. No response required. B. Stormwater Management comments: 5. The SWM plan, application and fee were submitted on June 28, 2005. On August 1, 2005, I requested deferral of the plan review. I am not aware of any approval for the plan submitted on June 28th. The plan was re-submitted with some minor revisions on Sept. 23, 2005 with a re-dated copy of the Application Form. Let me know if an additional fee is required. 6. There is no biofilter on the current site plan. 7. The Filterra boxes are located upstream from curb inlets. Filterra 1 is upstream form inlet F-1.,Filterras 2 and 3 are upstream of G-2. 100 10th Street NE,Suite 200•Charlottesville,VA 22902•Voice-(434)971-8848•FAX—(434)296-3040 See attached letter from Americast regarding this matter. Note that the Filterra sizes, locations and drainage areas are revised from the previous submittal. 8. The flume is widened to 30". 9. The effluent pipes from the Filterra boxes are sized to match the discharge pipe. It should be noted that the effluent from the Filterra boxes is highly filtered and is not subject to clogging by branches or other storm-borne debris. The County's minimum required pipe size does not apply to this type of application. It should be noted that the currently approved site plan shows Call me if you have any questions, 971-8848 ext. 224. Respectfully submitted, Clark Gathright 100 10th Street NE,Suite 200•Charlottesville,VA 22902•Voice-(434)971-8848•FAX—(434)296-3040