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WPO201700029 Plan - As-built WPO VSMP 2019-10-22
PROJA CIVIL ECT ME LAND PLANNING ENGINEERING August 19th, 2019 John Anderson Civil Engineer II Albemarle County Department of Community Development 401 McIntire Road Charlottesville, VA 22902 Regarding: Hillbrook Subdivision— SWM Certification Letter WPO 201500033 - Amendment Dear Mr. Anderson, I have performed the necessary surveys and inspections on the stormwater management systems at the Hillbrook Subdivision. I can confirm that the system has been installed in a manner that meets the overall goal of the SWM Plan for this development. An as-built analysis has determined the revisions to the approved site plan, detailed in the SWM As-Built Analysis Letter attached, have been installed correctly and operate in a manner that meets the approved site runoff and VRRM requirements. We have completed final inspections of the site and request that the full VSMP bond amount be released. If you have any questions please email me at justin@shimp-engineering.com or you may call our office at 434- 227-5140. APPROVED test Reg.rds, by the Albemarle County Community Deve pme t Department Date Q(2-7 ( File nh,J70/�600 vdPo z-D/t d da � Justi imp, P.E. A)� 6 2 D �d/7 0 (9 Shi Engineering, P.C. RECEIVED AU6 2 6 2019 COMMUNITY DEVELOPMENT PROJECT MANAGEMENT SHIMP CIVIL ENGINEERING LAND PLANNING ENGINEERING August 26th, 2019 APPROVED John Anderson by the Albemarle County Albemarle Count ent Department y Community Dev lop Department of Community Development Date !a Z - Engineering Department File c► vi Regarding: WPO 201500033 Hillbrook Subdivision SWM As-Built Analysis Dear Mr. Anderson, Please find attached a summary of the SWM Plan for the As-Built storm system at Hillbrook Subdivision. Revisions from approved SWM plan: 1. Revision to the undetained sheet flow area to the east of the site: the area of sheet flow has been increased in the northeastern portion of the site near lots 2 & 3 because the ditch in the back of lot 3 was not installed. Instead of being routed to the underground detention, this undetained area sheetflows to the wooded area at the rear of the lot. This is shown as Drainage Area B and includes 0.03 acres of impervious disconnection within this area. The SWM Maps, HydroCAD calculations, and the VRRM spreadsheet have been updated to reflect this revised drainage. 2. Revision to the underground detention at the east of the site near lot 3: This detention now has a 3" drain that outlets into the open space parcel for the subdivision. This drain outlets to a level spreader, thereby maintaining the sheet flow condition originally proposed for this BMP. Items that have not changed, and still comply with the approved SWM plan: 1. The concentrated runoff that flows to the northwest of the site: the as-built condition of this concentrated runoff still complies with the energy balance equation 2. Simple disconnection where specified in the original plan: downspouts where simple disconnection was specified have simple disconnection. Please note that it is the individual lot owners responsibility to maintain this simple disconnection per SWM maintenance agreements 3. The function of the detention pipes at the northwest portion of the site: the detention system functions as designed. 4. The required total phosphorous reduction: the original plan required treatment for 1.02 lbs TP. This amount was met with a nutrient credit purchase. The as-built VRRM requirements remain the same. The as-built SWM analysis methodology has been kept from the original SWM Plan. The rear portion of the site which outlets into woods had been designed to sheetflow in compliance with 9VAC25-870-66-D. The as-built conditions achieve this design strategy. The as-built 10-yr runoff to the wooded area is less than the pre-development 10-yr runoff. Thus, flood protection requirements have been met. The as-built 1-yr runoff to the wooded area is 0.21 cfs more than the pre-development 1-yr runoff. This increase in runoff is acceptable because the runoff is entirely sheet flow and does not concentrate within the wooded area. This runoff will not cause erosion due to the even slopes and heavy groundcover over which the runoff sheetflows. Since flood protection requirements have been met, and since the physical condition of the site ensure sheetflow, this 0.21 cfs increase in sheetflow runoff from the 1-yr storm is acceptable per standards set forth in 9VAC25-870-66-D. Therefore the as-built conditions meet the approved design requirements for SWM analysis. Sheetflow Runoff Flow Rates 1-yr(cfs) 10-yr(cfs) Pre- Post- Pre- Post- Dev Dev Dev Dev 0.32 0.53 3.29 2.62 If you have any questions please do not hesitate to contact me at michael@shimp-engineering.com or you may contact Justin Shimp at Justin@shimp-engineering.com or by phone at 434-227-5140. Best Regard , Michael Chandler Shimp Engineering, P.C. 8/26/2019 Dropbox-Hillbrook Court SWM Facility Inspection-Simplify your life Gr/(-Je e,C;/...r. )0 < Z•Z Hillbrook SWM Fa...n.pdf ••• EX ROUDABUSH, GALE &ASSOCIATES, INC. A A PROFESSIONAL CORPORATION g t LAM)SURVEYING Serving Virgnnia Since 1956 ENGINEERING LAND PIA.NNING LM;INLLR1M DLPARIMENT SCRYLY DLPARTMLN I 172 SOUTH PANTOPS DRIVE,STE.A 914 MONTI('El LO ROAD JIMI..IALx1ARI.P.E. CHARLO1TESVILLF VA22911 ('HARL.OTTFSVILLE,VA 22902 WILI.IAM J.L.EDBF ITF.R,L.S. DON FRANCY),P.E. PHONE(434)9794121 PHONE(434)977.0205 BRIAN D.JAMISON.L.S. DAV ID M.ROBINSON.P.E. FAX(434)979.1681 FAX(434)296.5220 (RISTOPHER C WINTERS,L.S. AMMY M.GEORGE,PLA INF(YaROUDABUSI LCOM Date: 13 August 2019 Subject: Hillbrook Detention Facility Inspection Roudabush Pipe Inspection Services conducted a video inspection of an underground Stormwater Detention facility on Hillbrook Court in Albemarle County.The facility consisted of approximately 75 feet of Stormtech MC-4500 Arch style pipe with detention stone base.The arch pipe is approximately 5 feet wide by 4 feet tall The pipe was accessed through a plastic structure within the pre- treatment cell between lots 3 and 4 z ' a•, Image I.Inspection Access Point There pipe appeared to be in good condition with no obvious cracks,joint separations.or visual deformities.The arch-type pipe made inspecting for deformation or collapse difficult,but a visual inspection did not identify any issues. 2 of 2 https.//www.dropbox.com/sh/2noux7ft9nskijy/AACvg0xco52NYW68-VQs7WgHa?d1=0&preview=Hillbrook+SWM+Facility+Inspection.pdf 1/1 V5MF AS -BUILT PLAN f0K H I LL15 ROOK WFO 2015-00033 TMF OG200-00-00-12GOO RIO DISTRICT, ALt5EMAKLE COUNTY, VIKGINIA VICINITY MAP SCALE: 1 "=2,000' r t } � fat nE a. i { ' : aygp [i 1 Cry) yy}nnr,�) C4 1 r V Li' f=:�r{i(Y. p? i Efi�A11 Ili f4amrr.W �1GE t8y t yy t �1 �`�','� dd i Lq IMAGE PROVIDED BY GOOGLE MAPS SHEET INDEX C I - COVERSHEET C2 - AS -BUILT PLAN C3 - SWM DETAILS C4 - STORM PROFILES PROPERTY INFORMATION 0WNER: HILLTOP PARTNERS, LLC P.O. BOX 645 CHARLOTTESVILLE, VA 22902 DEVELOPER: RED DIRT DEVELOPMENT, LLC P.Q. BOX 645 CHARLOTTESVILLE, VA 22902 LEGAL REFERENCE: DB 4722 PG 405-419 (414-418 PLAT) DB 4562 PG 266 TAX MAP 61 PARCEL 126 (2.63 AC TOTAL) EASEMENT PLAT: DB 5227 PG 146-154 SOURCE OF AS -BUILT As —Built Survey Provided to Shimp Engineering, P.C. on 10/28/2016 By: Lincoln Surveying APPROVED by the Albemarle County Community evelop ent Department Date i Q 12 File �v'i �ol� - Q b '3'� JU ' 'IN 1Y1. SHIiVIP ic. Nc . 45183 ,6,,5 DAM NOT REQI SOIL REWO TO I P INTO PRE 7.1'X6.9' PRETREATMENT CELL 6"X6" TREATED LUMBER PROP. INV=494.60 W/ J57 STONE & FILTER FABRICI DAIS NOT REQUIRED W146 1#64416N 166— —1 PROP. GRADE ABR GRADE EX. GRADE " [ II A I 1 „A„ CBE — — — — EX. GRADEI-I' I i i— r1 24"X15" HDPE TEE p r-r--r 15' HDPE O 0.86x � cp Ilnnr ra °-1 ° °- �, 0MIt i III I -�� GRATED TOP — VO9�-- I =I I STORMTEC MC-4500 r EO-TEXTILE FABRIC =—_ _ ° ..3 STORMTEC MC-4500 DETENTION STONE na rnlm I (I- nR Fnurjut L VDOT 7.1'X6.9' PRETREATMENT CELL ffwJ57 STONE do FILTER FABRIC 'ENT GE I ELEV=496.3 F114FR --:.,;,�;;—, DETENTION PLAN AND CROSS-SECTION 1 "=5' X 48 ORIFlffl 10-YR WSE=493.39 = " 1-YR WSE=491.99 v— . —8R.- III„�_.90 3* nnlnnr ORIFICE :II'.ELI'ilK�' ' S'YJF•�i � �I, ` , FROM STM 3A TO STM 2 'l:l+lil:: PROFILE VC ('--2NNLET 3 DETAIL C3 1"=10' PRE-TREATMENT CELL WAS NOT REQUIRED TO BE INSTALLED 1LULn Iln�n�= 7IIIm 6''""()T #5. I IAI�T_L [�11 Lm! vH TrofL fLT r�T "pT70R ELEV=50235 of HDPE INFLOW MH-1 FLAT TOP PROFILE VIEW 3' TALL WEIR PLATE — 15" HDPE " bk+E0 0.86% 45, "BPE TO STM 6 498.17 rI r'rr+-i 196.0 WIRE MESH SCREEN 10-YR WSE=498.' 1-YR WSE=497.17 7 i5! I Innr @ —` Q-62% FRO4 15" HDPE STM 4 0 0.= 0 Lo hZ z FE NW � ^z d� z w '`I © = a b z z r - F D N O �y N N 1 lil V) J �W =0 w� N Q "-1 oI U 4�� 1�Q q U JUS I NI. HLAP L' '. No. 45183 o � sstONAL 7fGaWI nn NFORGE _iEE YiE'R PEAfE STEEL WEIR PLATE 15" HDPE 0 1.20% � �R I Innr ra STM 5A ftE'd=*#96-e 496.23 W14H WIRE MESH SCREEN 3"H X 24"W ORIFICE ('--3STR 5 VAULT DETAIL C3 . 1= Q X Z 0 W J Q W m J Q Date 04 16 2019 Scale 1 "= 20' Sheet No. C3 OF 4 mmio 13.029 510 505 500 495 490 485 480 475 470 10+00 11 +00 12+00 13+00 14+00 STORM SEWER PROFILE X4-7 C4 Scale: 1"=20' Horizontal, 1"=10' Vertical STORM SEWER 2 PROFILE 3-3A C4 Scale: 1°=20' Horiz., 1"= Vert. STORM SEWER 3 PROFILE 5-5A C4 Scale: 1"=20' Horiz., 1"=10' Vert. 510 505 500 495 490 485 480 475 470 U J 1V1. SHIMP ;P. L c. T0. ' 5183 �SSIONAL. E�