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Home My WebLink AboutWPO201700073 Correspondence 2018-02-22 (2)Y . + Dewberry Engineers Inc. 804.290.7957 Dewberry �.� y 4805 Lake Brook Drive, Suite 060 www.dewberry.com fax Glen Allen, VA 23060 www.dewberry.com February 12, 2018 David James County of Albemarle Planning Services 401 McIntire Road Charlottesville, VA 22902 RE: Boar's Head Inn Lobby Renovation and Parking Relocation (SDP20170oo65) Dear David James, In response to your engineering comments via comment letter dated December 7, 2017 we offer the following responses: A. Stormwater Pollution Prevention Plan 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. 1. Insert a copy of General Permit coverage when obtained. Dewberry Response: General Permit will be added to the SWPPP when obtained. B. Pollution Prevention Plan (PPP) The PPP content requirements can be found in County Code section 17-404. (PPP requirements have been adequately addressed) C. Stormwater Management Plan (SWMP) VSMP Regulation 9VAC25-870-108 requires the VSMP authority to approve or disapprove a SWMP. This plan is disapproved, and the reasons are provided in the comments below. The stormwater management plan content requirements can be found in County Code section 17 403. 1. Cover — Please remove the SDP number in title and add the WPO number. Dewberry Response: The WPO number has been added on Sheet T1.o1 to replace the SDP number. 2. Show SWM easements over all permeable pavement, and underground detention system. Dewberry Response: SWM easements have been added over all permeable pavement and underground detention and have been shown on Sheet C3.01. 3. Please label proposed drainage structures & corresponding design related details. Dewberry Response: Structures have been labeled on the Sheets C3.03 and C3.04 as well as on the profiles on C4.o1 and C4.02. Details have been added to C5.03 and C5.o6. David James Boar's Head Inn Lobby Renovation and Parking Relocation SDP20170oo65 February 12, 2018 Page 2 of 5 4. Provide drainage computations with DA map. Dewberry Response: Drainage Areas and computations can be seen on Sheet C6.03. Additional drainage area information can be found on Sheet C6.oi. 5. Provide proposed stormwater drainage profiles. Dewberry Response: Stormwater drainage profiles have been added as Sheets C4.oi and C4.02. 6. Permeable Pavement (VADEQ SW Design Spec. 7) a. Underdrain — Show perforated pipe installed for the full length of the permeable pavement cell, and non perforated pipe, as needed, is used to connect with the storm drain system. Dewberry Response: Perforated underdrains have been added through the permeable pavement areas, and connecting to proposed stormwater structures. b. Field -verified infiltration tests required, 1-2 per facility. Dewberry Response: The contractor will be required to complete the 1- 2 field verified infiltration tests, and will report to the Engineer is there are any issues. c. Confirm the depth to seasonal high groundwater table and bedrock (minimum 2 ft. below the design bottom of the facility). Dewberry Response: Geotechnical report will be completed, and the County will be notified if this is an issue. d. Show underdrain at 0.5% min slope. Dewberry Response: A note has been added to the underdrain detail on Sheet C5.04. e. Use an impermeable liner along the sides closest to the `Boars Head Inn' building. Dewberry Response: A note has been added to the underdrain detail on Sheet C5.04. f. Located loo'from any water supply well and 35'from any septic system. Dewberry Response: A note has been added to the underdrain detail on Sheet C5.04. g. The owner should be informed of the routine long and short term maintenance actions. Dewberry Response: The owner is aware of the maintenance required. h. Plan landscaping to limit the amount of soil, mulch, grass clippings, leaves, nuts and fruit that may inadvertently clog the paving surface. Dewberry Response: Landscaping will limit the amount of the materials that could potentially clog the pavers. i. Include the construction sequence and installation notes from section 8.2 and 8.3 Construction inspection notes in the plan. Dewberry Response: The construction sequence and installation notes from section 8.2 and 8.3 have been added to Sheet C6.03. 7. Please identify each practice and show each CDA on a separate sheet. Looks like there may be 8 individual cells. Page 2 of 5 `�pe. Dewberry�.� David James Boar's Head Inn Lobby Renovation and Parking Relocation SDP20170oo65 February 12, 2018 Page 3 of 5 Dewberry Response: Paver area and contributing drainage areas have been shown on Sheet C6.05. 8. Show/provide Rv calcs. Dewberry Response: Rv calculations for pre and post conditions have been broken down and shown on Sheet C6.05. 9. Provide storm pipe & inlet design calcs. Dewberry Response: Storm Schedule has been added to Sheet C6.05. lo. Please show pipe flow direction arrows. Dewberry Response: Pipe flow direction arrows have been added to Sheet C3.o3. 11. Sheet C3.02 — Storm pipe shown connecting two inlets, where does stormwater go from there? Dewberry Response: The existing inlet continues west, towards the existing service road. An approximate location of existing pipe has been shown on Sheet C3.o4. 12. Sheet C3.o3 a. Add a manhole over 12"pipe outfall at connection with stormwater vault. Dewberry Response: The configuration of the underground stormwater system has changed. No manhole is needed. b. Consider relocating DI-3B (TOP=559.92') a bit further downstream. Dewberry Response: The location of this structure, now a DI-3C has been shifted. 13. Sheet C5.03 — UD Vault details a. Add Upstream or Downstream for the vault detail titles. Dewberry Response: The configuration of the underground stormwater system has changed. There is only one vault detail. b. Show the pavement/CG cover/Finished grade Dewberry Response: Finished grade has been labeled on the vault detail as well as the culvert box detail. c. Show that maintenance access will be provided to downstream/outlet side of weir. Dewberry Response: Access manholes have been shown in plan on Sheet C3.03, and in the details on Sheet C5.03. d. Section B is shown incorrectly (opposite direction of arrows) downstream. Dewberry Response: The detail has been revised. e. The 9"H shown in the 9x36 orifice doesn't match the model/calcs of 6"H on sheet C6.o6. Dewberry Response: The orifices have changed and have been labeled on the detail on Sheet C5.03, consistently with the calculations shown on Sheet C6.o6. f. Is the box culvert 2" thick? Dewberry Response: The slab is a minimum 8" thick as stated in the detail on Sheet C5.03. g. Show the weir height and clearance dimensions. Page 3 of 5 `� -"F Dewberry �. David James Boar's Head Inn Lobby Renovation and Parking Relocation SDP20170oo65 February 12, 2018 Page 4 of 5 Dewberry Response: The weir height and dimensions have been shown on the detail on Sheet C5.03. 14. Sheet C6.o1 — Show in SWM narrative computations that your SWM design meets Part II(B) requirements. Show that Energy Balance, or channel/flood protection to the limits of analysis is met. Dewberry Response: A statement stating that we've met Channel protection and Flood protection has been added to Sheet C6.o1, including calculations. 15. Sheet C6.o6 a. Confirm if 12" outfall pipe of UD vault system is the primary outfall in the post development routing calcs. If not, please include. Dewberry Response: The outfall of the underground detention system is the primary outfall in the routing calculations. b. Confirm if o.97ac is t00% impervious. Dewberry Response: The curve numbers used in AutoCAD were pulled from the spreadsheet shown on Sheet C6.oi or from the VRRM Spreadsheet summary shown on Sheet C6.03. 16. Sheet L3 — Please identify PO, what type of tree? Dewberry Response: Landscaping sheets have been revised for clarity. See Sheet L3 for designation. D. Erosion and Sediment Control Plan (ESCP) Virginia Code §62.1-44.15:55 requires the VESCP authority to approve or disapprove an ESCP. This plan is disapproved, and the reasons are provided in the comments below. The erosion control plan content requirements can be found in County Code section 17-402. 1. Please show callouts for proposed structures & E&S controls to a detail sheet. Use leaders/extend arrows/shading for clarity where needed. Dewberry Response: Proposed structures and E&S controls are shown on Sheets C2.01, C2.02, C3.05, and C3.o6. Details can be found on Sheet C5.01. 2. There are managed slopes near the parking lot. Please show the managed slopes on the existing site conditions sheet(s). Dewberry Response: The managed slopes on the existing site have been hatched on Sheet C1.02. 3. Provide low maintenance ground cover where grades are steeper than 3:1, see sheet C3.04. Dewberry Response: Low maintenance ground cover where grades are steeper than 3:1 will be provided as needed. 4. Sheet C2.o1/C3.o5 a. Provide `sediment control logs' or similar at the entranceways of the existing parking lots. Dewberry Response: Additional sediment control devices and notes have been added to ensure sediment will not travel offsite. See notes and details on Sheets C2.01, C2.02, C2.03, C2.04, C3.05, C3.o6, C5.01. b. Fix leader should point to the concrete washout. Dewberry Response: This leader has been revised. Page 4 of 5 `� -"F Dewberry �. David James Boar's Head Inn Lobby Renovation and Parking Relocation SDP20170oo65 February 12, 2018 Page 5 of 5 5. Provide concrete washout details. Is hay bale acceptable? Dewberry Response: Concrete washout detail has been added to Sheet C5.05. 6. Sheet C3.o6 — Provide `sediment control log' along parking lot entranceway. Dewberry Response: Additional sediment control devices and notes have been added to ensure sediment will not travel offsite. See notes and details on Sheets C2.01, C2.02, C2.03, C2.04, C3.05, C3.o6, C5.01. 7. Sheet C5.o1 — Add CE symbol to `Paved wash rack' detail. Dewberry Response: This detail has been removed. Thank you for your attention in this matter. Please contact me with any questions or concerns at (804) 205-3321 or email Reeler (&dewberry. com Sincerely, Devin Keeler, P.E. Dewberry Page 5 of 5 `�-' Dewberry�.�