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HomeMy WebLinkAboutWPO202100004 Correspondence 2021-09-23f 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 September 23, 2021 Matt Wentland County of Albemarle Community Development 401 McIntire Rd, North Wing Charlottesville, VA 22902 RE: Southwood Phase 1 Blocks 9, 10, & 11— VSMP Permit Plan Review — W PO-2021-00004 - Comment Response Letter Dear Mr. Wentland: We have reviewed your comments from (Rev.1) August 26, 2021 and made the necessary revisions. Please find our responses to the comments below in bold lettering. 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 ESCP, (3) a SWMP, and (4) any TMDL measures necessary. 1. Provide a completed and signed DEQ registration statement. This will be a modification if the existing permit will be used. The signed registration statement will be provided once obtained. It is our understanding the technical review of the plan can be completed to reach an approval with this being a requirement of permit issuance. Rev. 1): Unless the contractor is applying for a new DEQ permit, the Registration Statement should be provided at this time. A signed copy of the DEQ registration statement is now included in the SWPPP. 2. Provide a signed certification. The signed certification will be provided once contractor has been selected. It is our understanding the technical review of the plan can be completed to reach an approval with this being a requirement of permit issuance. Rev. 1): Comment not addressed. The certification should be signed by the owner. A signed copy of the certification is now included in the SWPPP. ENGINEERING I DESIGN I TECHNOLOGY B. Pollution Prevention Plan (PPP) The PPP content requirements can be found in County Code Section 17-404. 1. The PPP appears to be acceptable at this time. Acknowledged. 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. The underground storage facility A will need to be removed from beneath the parking and travelway in front of Lots 71 and 72 and relocated outside of any travelways or where its repair/replacement will affect a travelway/entrance to a building. Engineering recommends it be moved to behind lots like SWM B. The storage facility has been relocated and redesigned accordingly. The new location is located outside of the travelway and would not impede access to the buildings in the event of major maintenance. Further the system is outside of the ACSA easement as well so as not to impede their maintenance. This location is the best available location to provide for vehicular access for typical maintenance without impact or limitation to the site should major maintenance ever be required. Rev. 1): Comment partially addressed. SWM A and pipe 107 will need to be moved away from the building. The easements for SWM A and pipe 107 should not overlap the building and should provide 10' between the building and the storm structures to ensure repair/replacement will not affect the building. The location relative to the parking and travelway is acceptable. Pipe 107 has been adjusted such that the easement does not overlap the building footprint and allows for access and maintenance. The underground detention system (SWM A) has also been revisited and improved to pull the system further away from the building. We found an opportunity to lower the underdrain and capture unused storage and thus eliminate a section per row of the arch system to shrink the facility footprint. Capturing the previously unused storage volume at the base of the system actually increased the overall storage volume. The calc book has been updated and facility rerouted for the small change in the stage storage curve and minor tweaks were made to the control structure accordingly. Further we have included an impermeable liner around SWM A to eliminate any seepage towards the building foundations or adjacent slopes. All easements have been adjusted accordingly and are now approximately 4 feet off of the building providing ample space and construction tolerance. 2. Provide a chart showing the overall nutrient credit requirements for the development (currently this plan and WPO201900062). Include the amounts for what has been treated on -site and what has been purchased. After the post -construction phosphorus control requirement reaches 10 lbs. /yr., VAC25-870-69(B)3 will need to be met. An overall phosphorous removal tabulation has been provided on Sheet C6.2 for this development, WPO201900062, and subsequently submitted Southwood PHA Blocks 11 and 12 (WPO202100022). This table will be provided with future WPO submissions associated with the approved rezoning. Please consider this a living document and guidance to demonstrate our intent and ability to provide the minimum 75% treatment credit on site. Rev. 1 : Comment addressed. 3. This plan cannot be approved until the 4441.85 lbs./yr. of nutrient credits have been purchased. Verify this meets 9VAC25-870-69 Section B and contact Ana Kilmer prior to purchasing credits. Acknowledged. This will be coordinated with Ana Kilmer and proof of nutrient credit purchase will be provided once the purchase has occurred. In addition, the plans and calc book have been revised to appropriately account for and document the 0.63 TP credit for treating 2.91 acres of off -site area as part of 9-11. This area has been hatched and included on the legend on Sheet 6.0. Because this area is being treated by the 9-11 storm system, it reduces the nutrient credit purchase from 1.85 Ib/yr to 1.22 Ib/yr for the site. This has been better documented in the plans and calc book in this submittal than in the previous version of the documents. Rev. 1 : Response noted. Since this project drains to impacted streams, the credits will need to be purchased from the Ivy Creek credit bank. Revise Sheet C6.2 and the narrative in the calculations package to match. Sheet C6.2 has been revised to match the stormwater narrative. Availability letter for the Ivy Creek credit bank has been provided on the plan. 4. The outlet from SWM B will need to be released into an adequate channel. Currently it appears to release on the slope above the existing road ditch. The outlet location has been adjusted to better align with the existing channel. Updated field collected topographic data has been added to better depict the existing drainage swale to the ex 30" culvert. Rev. 1 : Comment addressed. 5. Label the steepness of the slopes and include a note that the maximum steepness is 2:1. This includes the slope around steps. Slope labels, as well as the requested note, have been provided on Sheets C5.3 — C5.5. No slopes exceed 2:1. Rev. 1 : Comment addressed. 6. Provide a level area adjacent to parking (such as on Alley 1) so residents are not exiting their vehicle directly onto a slope. A 5' wide level area has been provided adjacent to New Leaf Drive. Rev. 1): Comment addressed. 7. Provide more detail on SWM A and SWM B, including on the outlet structures (particularly for SWM A, as the flow is split). Underground detention details have been provided on Sheets C6.6-6.8. Rev. 1): Comment addressed. 8. Provide details for the Contech Jellyfish system. Details have been provided on Sheets C6.9 and the jellyfish has been revised to a Hydro International upflow filter. Rev. 1): Comment addressed. 9. The landscaping plan is not being reviewed or approved with these plans, only the locations relative to the storm system. The proposed trees should not be located directly next to inlets (such as on Road 1). Acknowledged. Tree locations have been adjusted to provide more space between inlets and trees. Tree locations over top of SWM B have been coordinated with the manufacturer and deemed acceptable. Adequate soil depth for the selected species is provided see note on sheet 1-1.2 at the top of the sheet. Rev. 1): This will be reviewed on the site plan submittal. Acknowledged. 10. After talking with Megan, we'd like you to include the conservation plan checklist on the VSMP plans in regards to the undisturbed preserved trees. Also show this area on Sheet C2.0, since that sheet shows all the vegetation being removed. The conservation plan checklist has been moved to Sheet C3.1 as requested. The tree preservation area has been shown on Sheet C2.0 as well. 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 approved, 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. Show the trap needed for the wash rack on the Construction Entrance. Wash racks have been shown on all Construction Entrances. See Sheets C3.2 — C3.4. All runoff from vehicle washing at the Entrances is directed to downstream traps and basins via diversion dikes. An additional area for a small trap has been illustrated adjacent to the construction entrances. Rev. 1 : Comment addressed. 2. Include a detail for a Paved Construction Entrance. A Paved Construction Entrance detail has been provided on Sheet C3.1 and is shown in E&SC Phase II, Sheets C3.5-C3.7. Rev. 1 : Comment addressed. 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 434.295.5624 or email at bryan.cichocki@timmons.com . Sincerely, Bryan Cichocki, PE Project Manager