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Home My WebLink AboutWPO201500009 Review Comments Stormwater Management Plan 2015-04-08�pF A COUNTY OF ALBEMARLE Department of Community Development 401 McIntire Road, Room 227 Charlottesville, Virginia 22902 -4596 Phone (434) 296 -5832 Fax (434) 972 -4126 VSMP Permit — Amendment Application review Project: Faith Christian Center International Plan preparer: Brian Smith; Brian P. Smith, PE, Civil Engineering [4835 Three Chopt Road, Troy, VA 22974 — bpspe(i�embargmail.com] Owner or rep.: Faith Christian Center International, Inc - Pastor Wayne Frye [pastornfccintl.org; P. O. Box 2306, Charlottesville, VA 22902] Plan received date: 24 Feb 2015 Date of comments: 8 Apr 2015 Reviewer: John Anderson Note— VSMP Application requests to amend SWM plan under WP0201400070, per VAR10 Part II13.1. VPDES Permit VARlOG420 approved 12/10/14 remains valid through June 30, 2019. When approved, SWM Plan under WP0201500009 will replace SWM Plan approval under WP020100070, which will then be void. A. VSMP: SWPPP and Pollution Prevention Plan (WP0201400070/WP0201500009) — §17-405 The SWPPP content requirements can be found in County Code section 17 -405. A SWPPP must contain (1) a PPP, (2) an ESCP, (3) a SWMP, and (4) any TMDL measures necessary. SWPPP as constituted under 17 -405 is unchanged. SWPPP as defined under VAR10 is revised with act of Application requesting design revision for specific elements of prior- approved SWM Plan (WP0201400070). —see Sec. B., below /SWM Plan comments. B. VSMP: SWPPP: Stormwater Management Plan (WP0201500009) VSMP Regulation 9VAC25- 870 -108 requires the VSMP authority to approve or disapprove a SWMP. This plan is disapproved for reasons provided in comments below. The stormwater management plan content requirements can be found in County Code section 17 -403. 1. Include sheet L5.2, which appears to be missing. 2. Revise sheet L5.2: Account for increased buffer impact: WP0201400070, 46,638 sf, WP0201500009, 49,341 sf. —Also, Sec. D., item #2, below. 3. Note: VSMP SWM Plan review does not include review of Retaining Wall. Engineering will comment on revised retaining wall design when submitted with revised site plans. (Rachel Falkenstein, Lead Reviewer) 4. Sheet C7.1: Compare L = 119.41, `Front' Parking Lot Detention with `C' Line Storm Profile dimensions: 56.58' and 68.83'. These values total 125.41' without even considering 6' DIA Manhole. Revise to show consistent length for `C' Line storm detention system, with endpoints clearly discernible, across plan sheets. 5. Sheet C8.0: Revise Channel #1 detail to show 12" min depth consistent with C10.4 ('1 -FOOT DEEP') Engineering Review Comments Page 2 of 4 6. Sheet C8.1: Recommend revise slope of 34.43'24" RCP (Storm D1) between D2 and outlet to limit height of Storm D2 to <12'. Alternatively, provide safety slab for Storm D2 (ht. = 12.23'). 7. Sheet C8.2 /Channel table, Channel #1, Entrance: Revise detail to show D =12" Min, since Q10 Depth =8.5 ". 8. Sheet 8.2: A, B, C Line SWD Profiles, use dash (oval/circle) to represent Tee end sections. Ref `E' Line storm profile (this plan sheet), as example. Revise each profile to show L consistent with 112.00'L shown on C10.2, or revise C10.2 L, consistent with C8.2. Note: C8.0, `C' Line storm profile lengths (56.58/68.83) are inconsistent with both C8.2 and 10.2 — please revise for consistency. (9.29' difference: C10.2, C8.2) 9. Sheet 7.1: Plan view, SW detention control MH E3: revise outline of VDOT DI -3A, to reflect DI -3C (detail below) BI -30. 36. W DETI N JOINT EXPANSION 3' -10" FREE SEE STAA' N 6AR5 G 4' 2" _ BARS C '�ty/%- �� /�]• I 1 l � J I � I IRS F - II 11 AR F u BARS D CR K CONTROL JOINT �A I - VAPIOPo F _ INLET BAR A G�TER FACE OF CURB CRACb PLAN EXPANSION KEYED Jn"T CONST. BARS BACK OF SIDEWALK JOINT, IM11N1NN;IM, SECTION A -A —i r KEYED CANS T. JOINT WARP EED 2. Jt GUTTER A PROACH GTTER 5 G I I } -- BARS F BARS E B N #3" DIAMETER BARS E YMEEP HOLE FRONT ELEVATION DAn F {GUTTER REIAOVEDI 11/x„ 3• -tr^ BENT PLATE n SECTION B -B "R t ¢ TYPE A NOSE DETAIL SHALL BE USED WITH 06-3 & 00-7 STANDARDS. - GRVANIiED TYPE B NOSE DETAIL SHALL BE USED WITH CG-2 6 CG -6 STANDARDS, TYPE A TYPE 8 /p" K W' STUD SHEAR CONNECTOR WELDED GALVANIZED PLATE FOR TYPE A TO BE BENT ON AN ANGLE OF 68.30' TO ANGLE IRON AT 2'C-C. CONNECTORS AND IS TO BE ANCHORED WITH �I /q" X C' STUD SHEAR NOSE DETAILS WELDED 70 ffNT PLATE AT 2' C -C. r- APPR. PAVEMENT 01-3A �, ,� 0I -36 L 0I -3O L I WARPED PAVEMENT FLOW FLOW I FLOW •.• •� I 1 1 DETAIL WHEN USED FOR JSE ON CRAPES ADJACENT TO CURB FOR USE IN SAGS WITHOUT GUTTER BOTH SIDES TO BE SYMMETRICAL 1VOOT SPEC"ATION ROAD AND BRIDGE STANDARDS STANDARD CURB DROP INLET REFERENCE SHEET 1 OF 2 1 REVISION DATE 12" - 30" PIPE: MAXIMUM DEPTH IH] • 8' 233 "", Dam ..A DEPARTLENT OF TRANSPORTATION 302 10. C10.2/C12.0: Provide design/spot Elevations at Church Entrance to ensure drainage to Filterra units #1, #6 to avoid ponding which may occur without precise elevations. Include schematic arrows. (Image, below) Engineering Review Comments Page 3 of 4 Z —, 11. Sheet C10.6 /C11.1: Revise SHORT VERSION BMP coMpuTATiONS values. Decrease 1. 93 91 ac. value by 0.1979 ac., since areas (Ac. slightly less than) A2 /B2 route to Filterra units #9, #10 (0. 0748, 0.1231 Ac) and should be excluded from 0.3907 ac. pavement value /C11.1. Report Tot. AREA = 1.7412 acres. Then, 1.5484/1.7412=0.89. Then, 0.74 X 0.89=0.66. Then 0.66 > 0.25. TOT I_ post develop impervipus AR = Tot . /AREA 9391 ' res . (1. 484 ac Werra 003907 ac pavernA6 impervious a� 1..9391 =0 0.74 0.7259 0. � 0.25 12. C11.1: Revise hatching to include (stair /phased) areas at NE corner of Church; these areas are not routed through detention. (Images, below). pi 1 1 k ES 1 f IPA 'oil ;I w� w L , . �� GT Engineering Review Comments Page 4 of 4 13. Note: Although calculations support design, eliminating Filterra units and associated inlets forces 0.4974 Ac. to Filterra #1 and 0.3300 Ac. to unit #2. Spread, inlet E3, increases from 8.88' to 11.73' and 10 -yr Q, from 2.616 cfs to 4.930 cfs (int = 6.5 "). Rear parking SW quality control depends on 2 Filterra units rather than 5. An 8' DI -3C (E3) replaces initial inlet design: 2.5' DI -3A (E2). Eliminating 3 Filterra units invites uncertainty should remaining units or DI -3C experience performance issues. More units rather than less and additional points of connection between paved surface and rear stormwater detention provide inherent reliability (seen in initial design). Additional units on south and east sides of the rear parking lot would help ensure system reliability, and are recommended but are not required. 14. Strongly recommend consider future expansion, and revise rear SW detention capacity to accommodate Q2 /Qi0 routing under phased future expansion scenarios. May require only modest additional length. 15. Strongly recommend: In addition to changes outlined in #11, above, recommend revise SHORT VERSION BMP COMPUTATIONS, C10.6, to include future impervious surface runoff from Phase 2 construction. Additional future construction is not exempt from the VSMP since part of a common plan of development (Church). This means water quality requirements apply to future expansion. Design will be evaluated against Part IIB technical criteria (9VAC25- 870 -65, VaRRM .xls). The SHORT VERSION BMP COMPUTATIONS .xls (now discontinued, but useful in this case/Part IIC) may be revised to include walks, roof, stairs, or paved impervious areas to show future quality compliance. For example, if estimate 6,000 SF future impervious area, current design may cover future expansion. Math (see #11, above): Report Tot. AREA = 1.7412 acres + 6,000 sf, or 1.8789 acres. Then, 1.5484/1.88 =0.82. Then, 0.74 X 0.82 =0.61. Then 0.61 > 0.25 C. VSMP: SWPPP: Erosion Control Plan (WPO201500009 and WPO201400070) — §17-402 Virginia Code §62.1- 44.15:55 requires the VESCP authority to approve or disapprove an ESCP. This plan is approved, ref comment, below. The erosion control plan content requirements can be found in County Code section 17 -402. Design unchanged from initial ESCP, WPO201400070 /Initial remains approved. D. VSMP: Mitigation Plan (WP0201400070) — §17-406 1. Restore sheet L5.2. —Also, item # B.1. above 2. Stream buffer impact has increased from 46,638 sf to 49,341, or 2,703 sf. Mitigation at 2 X impact =5,406 sf. Propose Mitigation for additional impact. A suitable proposal would be to restore 2 of 3 Filterra units eliminated with revised design for the rear parking lot, with additional (inlet) connection to rear detention system. Development lies within 150 ft. of Shadwell Creek. Stream water quality and mitigating elements of design are a priority. Please note that if two Filterra units are restored, 4 smaller units could be used; that is, units 1 and 2 would be smaller, and additional units may be relatively small. This alleviates concern relating to system performance or SWM compliance issues. —Items # B.2./13., above. The VSMP permit Amendment application and plans may be resubmitted for approval when all comments have been satisfactorily addressed. Please provide 2 copies of the complete permit package with a completed application form. Engineering plan review staff is available 2 -4 PM on Thursdays, should you require a meeting to discuss this review. Plan reviewer is available at 434.296 -5832 -x3069 should you have any questions. de: WI'0201500009 I-CCI 040815