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Home My WebLink AboutSDP202000058 Correspondence 2020-11-25 (3)608 Preston Avenue P 434.295.5624 Suite 200 F 434.295.1800 T I M M O N S GROUP Charlottesville, VA 22903 www.timmons.com November 25, 2020 County of Albemarle John Anderson 401 McIntire Rd, Rm. 227 Charlottesville, VA 22902 RE: Crozet ES Addition, Renovation & Site Improvements — Major Site Plan Review — SDP2020-00058 - Comment Response Letter Dear Mr. Anderson: We have reviewed your comments from September 21, 2020 and made the necessary revisions. Please find our responses to the comments below in bold lettering. S D P2020-00058: 1. C0.0: Revise plan title to include SDP202000058. Title has been revised to include County number on Sheet C0.0. 2. C0.1, Note 4: Revise FEMA FIRM effective from Feb. 4, 2005 to May 16, 2016, per code [18-30.3.2]. Note has been revised as requested on Sheet C0.1. 3. C1.3: Provide VDOT IS-1, P13-1, ST-1 details (inlet shaping, pipe bedding, MH steps). Details have been provided on Sheet C1.3. Sheet C4.0: 4. Show permeable paver underdrain connections with pipes/Dis/LIG detention in C7.0, C7.1, whichever these occur. Permeable pavers are no longer being proposed with this project. 5. Label narrowest width dimension typical of 7 curvilinear parking spaces. The narrowest dimension has been labeled; see Sheet C4.0. 6. With project, re-establish buffer with suitable native species (plantings) in areas that are currently managed turf. See 17-600, 17-604.A. Note: proposed design is an improvement over existing managed turf, and over earlier versions of design that showed impervious improvements in the stream buffer. Proposed design proposes only biofilters, and only within the landward fifty -feet (50') of the stream buffer. The plan has been further improved to reduce work within the WPO buffer as one of the two bioretention areas has been removed. The replanting area is mitigation for the work within the WPO buffer and should have a nexus and proportionality to the impact. It is an undue burden to this project to request the whole buffer be replanted especially in areas where there is no impact to the existing WPO buffer. ENGINEERING I DESIGN I TECHNOLOGY Sheet C4.1: 7. Note 1. Ensure Arch/MEP drawings (these are not reviewed by Engineering) provide temporary external containment (if required by USBC) for temporary above -ground oil fuel tank during winter months while construction is ongoing to help mitigate any impact due to accidental loss of oil that, at a school, may go undetected for hours, or days — relevant during possible extended school closure during winter holiday, or closure associated with the pandemic. We have coordinated with the MEP and Architect and the above ground temporary oil fuel tank will have a containment tray/pan at the base to mitigate any spills and/or leaks. The tank with the containment tray the MEP specs will look something like this: 8. Review/revise plan view label / detail caption. Bioretention facility 2C, 4.1, v. biofilter #3, C1.2. Detail has been removed from Sheet C1.2, as the water feature has been removed from the project. 9. (Related), C1.2: Curb cut & biofilter #3 water feature section includes label reading 'exterior stairs without handrail.' Intent seems clear but given C4.1 label/linework that indicate a galvanized handrail is to be positioned at top of steps (feature), provide galvanized handrail detail (openings < 4 in.) to prevent children crossing this railing at the top of biofilter #3. Provide C4.1, plan view ref. label to this handrail detail. Water feature has been removed from project. Sheet C5.0: 10. Revise structure label for structure between storm pipes 139A and 139E from 139E to 1386. Structure naming has been revised as requested. See Sheet C5.0. 11. Pipes 501 / 505 are proposed 18" DIA. An existing pipe between these two pipes at the central -main entrance is 15" DIA. Revise 15" pipe DIA, if needed, to ensure adequate pipe capacity at this location. Design typically avoids smaller diameter downstream conveyance. Culvert computations have been provided on sheet C7.2 for pipes 501 and 505. Both have been decreased in size to a 15" which is more than adequate. 12. C5.1: Compare plan view of pipes 303, 305 on C5.1 with C7.1, Storm Sewer Profile (images, below). a. Provide sufficient cover for pipe 303 its entire length. Crown of pipe is exposed in profile view. Sufficient cover has been provided over pipe 303. See Sheet C7.1. b. Provide fine grade lines and spot elevations at Str. 304 to ensure runoff capture at this location. Fine grade lines and a spot elevation have been provided for Str. 304. However, all Nyloplasts in the 300 series are solid covers, so runoff capture is not the intention at this point. c. Show and label 4" solid HDPE that intersects pipe 305, in profile view. The 4" solid HDPE pipe has been shown on Sheet C7.1. d. Show fine grade lines and spot elevations at other (grate) inlets to ensure runoff is captured. All rims have been labeled as requested on Sheets C5.0 — C5.1. e. Reposition pipe 303 end section (Str. 302) to align with pipe. ES is not a flow - redirecting structure. Structure 302 has been repositioned as requested. 13. Provide runoff capture (DI) prior to CG-12 ramp at approx. contour 692.75' in bus loop parking, else ramp receives concentrated runoff. It is not very practical to place a structure at this location on the curve of the curb line and so close to the sanitary sewer easement. This curb ramp does not serve any accessible parking spaces and is provided as a convenience for wheeling anything into the rear entrance. 14. General (VSMP-related): Recommend Note on Site Plan that bioretention basins may not be constructed until all contributing drainage areas are stabilized, and that Note also require bioretention construction in accord with WPO202000039 plan. The VSMP plan will likely include similar note, requiring contributing drainage area stabilization prior to biofilter construction. A note has been provided as recommended on Sheets C4.0 and C4.1. 15. C5.3: Provide trench drain or similar for basketball court to minimize risk of ice on asphalt walk during winter. Court drains NW to SE. This expanse of impervious area (basketball court) will sheet rain or snowmelt to an asphalt walk. Proposed grade, 0.5%, is relatively flat. Debris trapped against chain link serves as a dam to drainage. A C1.1 detail to supplement outdoor basketball court layout may eliminate need for trench drain if 5' chain link fence detail is included and shows -6" gap at the bottom edge to allow debris to be swept or blown through the gap. Experience with debris dam at chain link fence at Sutherland MS tennis courts advises this comment. The grading of the basketball court has been revised to provide more slope (see Sheet C5.1). Additionally, the chain link fence has been removed. Therefore, we do not believe an additional trench drain is needed in this location. 16. C1.1: a. Outdoor basketball court layout: Revise court gates, consistent with C4.1 plan view, where gates open onto asphalt walk. Gates have been eliminated from the plan. b. Outdoor basketball court layout: Revise label to read 5' sideline to edge of pavement to read 5' sideline to chain link fence, since asphalt continues beyond fence, as asphalt walk. Chain link fence has been removed from the plan; detail has been revised accordingly on Sheet CIA. c. Recommend light duty asphalt pavement section specify % slope to ensure adequate drainage from basketball court, across walk. Basketball court grading has been revised to increase slope and ensure adequate drainage. Slope labels have been added to Sheet C5.1. 17. C5.4: a. Recommend Note or label to reference WPO202000039. In the future, this sheet will only be submitted with the WPO submission. Therefore, a reference to the WPO plan is not necessary. b. Recommend label each SWM facility'SWM facility'. Labels have been provided on Sheets C5.0 and C5.1. Sheet C7.0: 18. Revise structure label for structure between storm pipes 139A and 139B from 139B to 138B in profile captioned UG Detention — Pipe 141 (@Sta. 10+94.99). Structure has been renamed as requested. 19. Str- 126 MH-1 with splitter weir: provide small scale plan / profile relevant details, notes, labels, and elevations for pipe inverts, MH floor, weir elevation/s such that split flow is discernable, and ladder, weir, pipe entry / exit conflicts are avoided. Likely submitted with WPO, but also required for site plan. Due to stormwater changes, this structure is no longer proposed with this project. 20. C7.2: Supplement (or replace) storm sewer tables with VDOT LD-204 and LD-229 stormwater inlet and storm sewer design computations (tables). Additional review comments possible. Tables on Sheet C7.2 have been replaced with the requested formatting 21. Note: WPO plan approval is required prior to Major Site Plan Amendment approval (WPO202000039 has been submitted, review pending.) Acknowledged. We have included PDF copies of the plans and calculations for your review. If you have any questions or comments, please feel free to give me a call at 434.327.5380 or email me at bryan.cichocki@timmons.com. Sincerely, Bryan Cichocki Project Manager