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Home My WebLink AboutWPO201500062 Approval - County 2016-03-31COUNTY 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 plan review —Approved Project: Glenmore Leake K2 Lots 24-27 & 29 Amendment Plan Plan preparer: Graham Murray, Collins Engineering [200 Garrett St., Suite K, Charlottesville, VA 22902, graham(&collins-en ing eerieg com, scott(&collins-en ine eerieg com] Owner or rep.: Neal Sansovich, Central Virginia Real Estate Ventures LLC 2325 Grey Heron Rd, Keswick, VA 22947 Plan received date: 27 Aug 2015 (Rev. 1) 20 Jan 2016 (Rev. 2) 31 Mar 2016 (.PDF/e-review) Date of comments: 24 Sep 2015 (Rev. 1) 6 Mar 2016 (Rev. 2) 31 Mar 2016 —Approved Reviewer: John Anderson A. Stormwater Pollution Prevention Plan (SWPPP) The SWPPP content requirements can be found in County Code section 17-405. A SWPPP must contain (1) a PPP, (2) an ESOP, (3) a SWMP, and (4) any TMDL measures necessary. Provide SWPPP Exhibit. May use details from WP0201300015 ESC plan, if relevant. A SWPPP is not requested, but rather Exhibit showing PPP measures. PE -seal (signature/date) is required. Alternatively, provide a complete SWPPP. Note: A SWPPP has been required by the Virginia VPDES permit program for projects disturbing an acre or more since 2009, at least. Request solicits material that should exist for WP0201300015, but I regret late request for an Exhibit. (Rev. 2) Addressed. B. VSMP: SWPPP: Stormwater Management Plan (WP0201500062 /Amends WP0201300015) VSMP Regulation 9VAC25-870-108 requires the VSMP authority to approve or disapprove a SWMP. This plan is approved. 1. Identify WPO Plan Number and Title being amended. Revise Title, sheet 1, to include WPO Plan number and title being amended. (Rev. 1) Addressed. Remaining comments, sheet 2: 2. Provide SWM Facility Access. (ACDSM.5.BMP for SWM) (Rev. 1) Partially Addressed. As follow-up: Ref. photos 1, 2 [county; 9/24/15]: Access/guardrail conflict. Provide opening. Reference/adopt VDOT guardrail specifications in design (GR -2, 2A). Show guardrail in both plan view images, sheet 2. Engineering Review Comments Page 2 of 3 Photo I/view south —Farringdon Rd. (removed —shown with prior comments) Photo 2/view north —Farringdon Rd. (removed —ref prior comments) Please provide VDOT guardrail details/design[VDOT R&B SpecNol. I -GR-2, 2A; sheets 1 and 2; rev. date 7/111 (Rev. 2) Addressed. Label road (provide name). (Rev. 1) Addressed. Furnish Approved basin 2-, 10-, 100 -yr routings for comparison. (Rev. 1) Addressed. As follow-up: WP0201300015: (Apr 17, 2013 routings / peak cfs) Q2 =17.07 Qlo =29.98 Qioo =64.02 WP0201500062/Amendment (peak cfs): Q2 =7.59, ok, <Apr 17 2013 routings Qlo =42.83 Qioo =76.70 WP0201500062 Qlo > WP0201300015 Qlo. DEQ has advised that a Part IIC facility that proposes to increase rate of discharge forfeits Part IIC eligibility, writing: "Your summary of our telephone conversation (below) is correct. "Grandfathered" projects that are subsequently amended or modified resulting in an increase in the amount of TP leaving each point of discharge, or resulting in an increase in the volume or rate of runoff are no longer considered "grandfathered" under Section 48 of the VSMP regulations. As a result, the amended or modified project must be designed to comply with the new Part IIB technical criteria. [Andrew Hammond, VDEQ —email: 12/15/2015 5:42 PM] Please revise design to provide Qlo < Apr 17, 2013 Qlo. (Rev. 2) Follow-up Addressed. OUTPUT: Routing method: storage -indication tiydrograph a Routing summary of Peaks: 2 -yr 24 -hr Peak scs storm inflow (cfs) 23.062 at 11.98 (hrs) discharge (cfs) 15.919 at 12.10 (hrs) water level (ft) 348.951 at 12.10 (hrs) storage (cy) 738.266 nydrograph 1 Routing summary of Peaks: 10 -yr 24 -hr Peak scs storm inflow (cfs) 48.G79 at 11.98 (hrs) discharge (cfs) 24.846 at 12.14 (hrs) water level (ft) 351.551 at 12.14 (hrs) storage (cy) 1427.889 nydrograph 2 Routing summary of Peaks: 160 -yr 24 -hr Peak scs Storm inflow (cfs) 106.565 at 11.98 (hrs) discharge (cfs) 81.120 at 12.06 (hrs) waterlevel (ft) 353.332 at 12.06 (hrs) storage (cy) 2112.510 Identify Approved basin type consistent with 9VAC25-870-96.C. Table 1, or DEQ BMP Clearinghouse nomenclature (basin is non-specific). (Rev. 1) Addressed. Multiple references to As -built are inconsistent with site inspection, 24 -Sep 2015 (discussed briefly with Scott, 24 -Sep). Correct existing grade to reflect As -built grades. In places, grade is 1:4, near vertical. Steepest existing grade on WPO Plan Amendment is 1:1. Accuracy is critical. Avoid inaccurate grades which may have contributed to conditions that required this plan amendment. (Rev. 1) Addressed — Appreciate response: "The extended detention basin's topography and spot shots shown reflect asbuilt data provided to Collins Engineering by Commonwealth Land Surveying, LLC. The September 24, 2015 comments reference a site visit where County Engineering observed grades of 1:4. This is in contrast to the licensed land surveyor's topography which triangulates grades of 1:1.33 in the vicinity of the basin's steeper areas. In both cases though, the steeper grades to the east are mitigated with the proposed grading modifications. The proposed grading changes consist of filling the lower 6' and shrinking the bottom footprint's length slightly. To offset this minor shortening of the basin floor, it was expanded in width. Raising the facility 6' now allows the contractor to catch grade more easily while burying steep side slopes. Shrinking the footprint's length also allows the contractor to grade back to the 350' contour from the new basin floor elevation of 342' over a greater horizontal length. It is the applicant's hope that the paid 31 Engineering Review Comments Page 3 of 3 party survey, coupled with the proposed modifications, resolves County Engineering's concerns regarding the proposed side slopes of the extended detention basin." [Last pp.: 24 -Sep 2015 site photos] 7. Specify means of sealing existing low -flow orifice, and three 12" DIA mid -flow orifices. This requires engineering, not flexibility. Specify materials, products, etc. Specify with level of detail to ensure orifices are watertight. Alternatively, specify which sections of existing 42" DIA concrete riser must be replaced. (Rev. 1) Addressed. 8. Revise profile description `to be sealed.' Revise to reference details, narrative, notes, specifications. See item #7. (Rev. 1) Addressed. 9. Delete reference to `Equivalent trash rack' (Hanson typical, bottom margin); `Contractor may elect to install a different trash rack.' Design cannot leave this degree of unapproved plan change to a contractor's discretion. (Rev. 1) Addressed. 10. Specify Hanson Anti -vortex frame and grate. Grate access to 42" DIA riser is essential. Design must specify precast Hanson Anti -vortex device with frame and grate, or alternative device. (Rev. 1) Addressed. 11. Provide field survey As -built Exhibit (not just spot shots) to accompany Plan Amendment, an exhibit based on field survey data obtained after today. (Rev. 1) Addressed. 12. Note: A number of photos support comments, and are available. [pp. following] (Rev. 2) Acknowledged. C. VSMP: SWPPP: Erosion Control Plan (WP0201500062) Virginia Code §62.1-44.15:55 requires the VESCP authority to approve or disapprove an ESCP. This plan is approved. Provide Exhibit that provides ESC measure details including storm runoff bypass/diversion during period of constructed modifications to facility. This is not request for a complete ESCP, but is essentially equivalent. Required for SWM Plan Amendment Approval. Focus on practical measures and potential for downstream impact since bypass of storm events during period of construction would appear essential. May revive WP0201300015 ESC plan sheet/s to show ESC measures, if helpful. (Rev. 2) Addressed. Please submit four (4) copies of the WPO/VSMP plan for Approval. Please also provide 2 copies of SWPPP exhibit, and 2 copies of revised ESCP/VSMP SWPPP inserts (11" x 8.5"). Thank you. File: WP0201500062_Glenmore Leake K2 Lots 24-27 & 29—SWM Amendment Plan_033116rev2 Approval.doc