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Home My WebLink AboutWPO201700023 Review Comments As-Built Reviews 2023-03-31John Anderson From: John Anderson Sent: Friday, March 31, 2023 3A8 PM To: Steve Edwards Cc: Jonney Otto; Dan Ratzlaff, Emily Cox Subject: Planning Application Review for WPO201700023 Oakleigh. [ As-bult review ] The Review for the following application has been completed: Application Number= WPO201700023, As -built drawing review Reviewer = John Anderson Review Status = Requested Changes Completed Date = 03/31/2023 This email was sent from County View Production. Hi, Steve, Thanks for your patience. Please accept As -built drawingreview eview comments (also in CV): `update, janderson2 3/31/2023 3:46 PM: 1. Provide stormwater routings for underground detention system to ensure compliance with SWM quantity requirements since two weir plate orifices (6" x 6" ; 25"(w) x 4"(h)) and concrete baffle wall (weir wall) are all constructed lower than design, by 0.92', 0.75', and 1.40' respectively. Ref. sheet 1 Const. Record Drawings (As -built) for VSMP, item C.8 (significant deviations), and submit computations. Note: With As -built baffle wall ht.=546.80', it appears the system does not detain /contain the 10-yr event, as designed, since 10-yr WSL=548.15'. Baffle wall (weir wall top) design elev.=548.20'. If UG system does not meet design SWM performance standards or requirements, please propose remedy. 2. Please provide labels at plan view of UG detention to indicate that surface paving is incomplete, and that at present not all storm runoff designed to reach the unit (for detention /water quality treatment) is reaching the unit. 3. Provide SWM Narrative that discusses partial detention (item 2) and lack of water quality treatment at UG detention, since sheet 13 Stormfilter Standard Detail labels indicate stormfilter cartridges have not been installed as of survey. Although labels are accurate reflection of As -built condition, narrative is required to substantiate effect of partial installation of approved SWM system. 4. Sheet 3: Provide deed bk.-pg. reference to recorded SWM and public (proposed) drainage easements. Ref. sheet 1 Const. Record Drawings (As -built) for VSMP, item C.10. Deed bk-pg ref. is sufficient, but this ref. should appear on the As -built drawing. for example: SWM deed of easement: DB-PG 5230/688. Note: Applicant furnished .PDF copies of recorded easements via download a -link, 2/24/23. Note: Applicant is encouraged to submit As -built of ACSA utilities -- 5. Sheet 13: UG Detention SWM A - outlet structure A4 detail (prior to WPO plan bond release): BTM=542.65' while 15" HDPE pipe INV IN =543.05'. Provide remedy to eliminate 0.4' pooled water in floor of structure (for example: place 0.4' depth flowable grout in floor of structure). 6. Capture and report WPO2017-00023 Amendment #1 (approved 3/26/18), sheet 11, SWM Plan -post-development drainage area map impervious and permeable pavement areas that route to either SWM facility (biofilter, or UG Detention). Compare as -built areas with Amendment #1 design, and furnish SWM narrative calcs. as needed, to provide compliance demonstration, or context. 7. Compare As -built SWM facility phosphorus removal with WPO201700023 Amendment #1, sheet 12, SWM Plan - SWM Quality/BMP map label, which reads: 'BMP #1 and #2 provide 3.78 lbs/yr phosphorus removal > 3.27 Ibs/yr required.' 8. List biofilter area provided; same ref: Sheet 12, Amendment #1. 9. Provide bioretention basin section detail (details: elevs., matrix, stone depth, fabric, R-tank dimensions, etc.): Ref. WPO201700023, Amendment #2, approved 6/5/19, sheet 14, SWM Plan - SWM B details. 10. Provide permeable paver and pavement as -built details (paver type, bedding depth, slope, underdrain, etc.): Ref. WP0201700023, Amendment #2, approved 6/5/19, sheet 15, SWM Plan - SWM B details.' As -built drawing, sheet 13 REINFORCED CONCRE I BAFFLE WALL SECURED TO STRUCT�IRE WALLS TW= � 60' CMP PIPE (PERFORATED) Additional Additional MANHOLE RISER ACCESS RIM ELEV. 551.05 VDOT STD. STA STEPS I i 25"(W) x 4"(H) ORIFICE W/TRASH RACK — — INV. 545.60 2-YR ELEV. 546.55i,11_ _ 6" z 6" ORIFICE _ — W/ TRASH RACK INV. 543.70 V ELEV. 544.62_a_ _ 2,520 CUBIC FT F543.05 INV. 5432p INV. BT—M= ^ �y 15" HDPE PIPE r 6" PVC PIPI J J TO STORM FII 6" PVC SECTION It 543.20 OUTLET STRUCTURE A4 WPO201700023, Amendment #1, sheet 11 POST DEVELOPMENT RUNOFF AT POINT OF = 5.37 Acres (modeled as 3 sub areas in Hydrocad) (Includes 1.49 Acres of Permeable Paver) Dev. Area w/o SWIM = 0.65 Acres (6S) - Shown as hatch CN = see SW Model Printout Q21P-0 = 1.76 cfs < Q2(Pro) = 2.28 cfs (no change) Q,oiP�> = 7.77 cfs < Q101Pre� = 8.84 cfs (no change) Sub Watershed to Bio-Retention D.A. = 4.72 Acres (-.04 SWM FACILIT EASEMENT AROUND Impervious rea= .8 cres PAVER PAI Permeable Paver Area = 1.49 Acres Dev. Open/Landscape Area = 1.16 Acres (-.04) oods! rass Combo rea = 0.2 cres Tc = 5.00 mins. 1,Z) Sub Watershed to 60" HDPE _..-.. ! D.A. = 3.19 Acres (+.04 + .34) Impervious Area = 1.39 Acres (+.01 + 0.30) Permeable Paver Area = 0.84 Acres (+.07) ev. pen Lan scape Area = 0. Acres 4 +. 41) Woods/Grass Combo Area = 0.25 Acre Tc = 5.00 mins. POST DEVELOPMENT RUNOFF AT POINT OF AKIAI void rno AMMA A D.A. = 3.93 Acres (modeled as 4 sub areas in Hydrocad) (+.04 + 0.34) Dev. Area to 60" HDPE = 3.19 Acres (2S) & (3S*) & (14S) (+.04 + 0.30) *Includes 0.84 Acres of Permeable Paver Area (+.071 CN = see SW Model Printout = 0 i Q2(Post) = 2.55 cfs < Q2(pm) = 2.57 cfs Q10(posp = 8.76 cfs < a10(w) = 8.90 cfs WP0201700023, Amendment 41, sheet 12 BMP #1 BIO-RETENTION D.A. = 4.72 Acres (-.04) 79,511 sf of Impervious Area (+34 sf) r11 x 2.5" = 1,988 sf Biofilter Area Req. (+1 sf) RinflIter Area Provided = 217fi sf ovoia]----I 3 BMP#2 STORMFILTER 8'x6' Vault StormFilter w/ 50% RR E§CULW_T97-Mffea1es1 60,480 sf (1.39 ac.) of Impervious Area (+13,535 sf) 60,480 sf x 1/2 in. rain = 2,520 cf WQV (+564 cf) 2,520 cf of Detention routed through Stormfilter @ 0.25 cfs = 10 Cartridges (OK) (BMP #1 D.A. includes 36,613 sf of permeable pavers) (+3,072 sf) BM #1 & #2 provide 3.78 Ibs/yr Phosphorous Removal > 3.27 Ibs/yr required WP0201700023, Amendment 42, sheet 14 SO MM SOLIDER PERIMETER BANDING COURSE NO.8 AGGREGATE IN OPENINGS EAGLE BAY AQUA BRICH CONCRETE PAVERS 3 k MIN. THICK 2- NO.8 AGGREGATE 4- NO. 57 STONE 12- NO.3 STONE COMPACTED \ SUBGRADE \ ` ASPHALTICONCRETE PAVING SECTION 'I "I FLUSH CURBIEDGE RESTRAINT VDOT2IA GRAVEL BASE FILTERFABRIC OT21A DE R-35 GRAVEL L 8' PERFORATED SDR-35 RAIN SECTION ABUTTING PAVING GRAVEL STOUNDRM R DRAINS) BASE (TIE TO STORM DRAINS) PERMEABLE INTERLOCKING PAVERS SECTION ASPHALTICONCRETE 1 & PAM-9.5 POROUS PAVING SECTION ASPHALTSURFACE 2)V PAM-19 POROUS ASPHALT BASE 'I I CLASS A3 CONCRETE 1` NO.8 AGGREGATE FLUSH CURBIEDGE COMPACTED RESTRAINT 4- NO.67 STONE COMPACTED 8' NO. 3 STONE COMPACTED COMPACTED — SUBGRADE VDOT2IA GRAVEL BASE FILTER FABRIC OE r'a, VOOT T21A 2IA 8'PERFORATED SOft-95 SECTION ABUTTING PAVING GRAVEL UNDERDRAIN BASE mETOSTORM DRAINS) PERMEABLE ASPHALT - ALTERNATIVE TO PCIP SECTION Thanks, again best, J. Anderson John E. Anderson, PE I Civil Engineer 11 Department of Community Development I County of Albemarle, Virginia 401 McIntire Road I Charlottesville, VA 22902 434.296.5832 ext. 3069 VDOT STD CG-6 NO.8 AGGREGATE IN OPENINGS — EAGLE BAY AQUA I CONCRETE PAVER 31` MIN. THICK 2- NO.8 AGGRE 4` NO.57 STONE 12- NO. 3 STONE � COMPACTED SECTION ABUTT Ir111OE1W.1n01W1� t 1 TJ TJ I J J J I � COMPACTED SUBGRADE SECTION ABUTTING CU 6