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Home My WebLink AboutWPO202200009 Correspondence 2022-05-20f 608 Preston Avenue P 434.295.5624 Suite 200 IF434.295.1800 T I M M O N S GROUP Charlottesville, VA 22903 www.timmons.com May 20, 2022 David James County of Albemarle Community Development 401 McIntire Rd, North Wing Charlottesville, VA 22902 RE: Mountain View Elementary School — VSMP Permit Plan Review — Comment Response Letter Dear Mr. James: We have reviewed all of your comments from April 22, 2022 and made the necessary revisions. Please find our responses to the comments below in bold lettering. County Code section 17-410 and Virginia Code §62.1-44.15:34 requires the VSMP authority to act on any VSMP permit by issuing a project approval or denial. This project is denied/approved. The rationale is given in the comments below. The VSMP application content requirements can be found in County Code section 17-401. 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. Submit a SWPPP. Template https://www.albemarle.org/government/communitvdevelopment/apply- for/engineering-applications/vsmp. Submitted. B. Pollution Prevention Plan (PPP) The PPP content requirements can be found in County Code section 17-404. 1. Provide a PPP for review. Provided. ENGINEERING I DESIGN I TECHNOLOGY C. Stormwater Management Plan (SWMP) VSMP Regulation 9VAC25-870-108 requires the VSMP authority to approve or disapprove a SWMP. This plan is denied, 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. Sheet 6.2: a. Verify/Correct diameter - 48" versus 6' per details. Corrected the dimension to match the title of the detail. b. Provide secured trash rack over orifices. Acknowledged. Trash rack over orifices will be provided when the detention systems are spec'd. 2. Sheet 7.1: a. Revise: The height of cover over detention pipe system shall be 2' or diameter whichever is greater. All detention pipes systems have a minimum of 2' cover or''/: the diameter. b. Show HGL. HGL added to profiles on Sheet C7.1. c. Provide profile of detention pipe system: Show invert, slope, size, length, material, weir, access. Profile of detention systems are located on Sheet C7.1 More details will be provided when the systems are spec'd. Provide maintenance access above weir. Maintenance access shown above weirs on plan sheets. ii. Provide access ladder & detail. Acknowledged. Access ladder detail will be provided when the detention systems are spec'd. 3. Add note to provide water -tight fitting where pipes of dissimilar materials connect. Added beneath pipe table on sheet C7.1. 4. Sheet 5.2, etc.: Show MH accesses above weir plate locations for the CMP detentions. MH access is provided above the weir plate locations. 5. Provide trash rack secured to spillway barrel of det. pond. Added note to profile on Sheet C7.1. StormRax trash rack by Contech or approved equal will be provided. 6. Provide additional MH access (every 50' of length) for storm pipes 307, 317, 319, 418. Alternatively, additional MH access not required if pipe size is 15". Storm pipes revised to be 15". 7. Sheet 6.4: Nutrient bank availability: The first assessed waterway downstream of the LDA with an impairment is Cows Branch, as shown on the DEQ NPS Nutrient Trading Dataviewer. According to the hierarchy credits should be purchased within the same 8- digit HUC (02080204). It appears that there are two banks available, The Rivanna River NPS bank and Ivy Creek NPS bank to purchase from. Revised. See sheet C6.4 for Rivanna River NPS bank availability letter. 8. Hydro Calcs — Please provide Post Dev summary sheets like the Pre Dev (on pages 10, 22, 34) given. Verify total DA match Pre -/Post-. Revised. Total DA in Pre and Post is 7 AC. 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. Cover: a. Add WPO# under title. Added "WP0202200009" under title. b. Signature panel can be removed. Removed. 2. Sheet 2.1/2.2: Show footprint and label existing BMP/SWM facilities. Footprint and labels added. 3. Sheet 2.4/2.5: Show label for the removal of the bioretention facility and SWIM pond. Add note ...'as shown on WP0200600002'. Added label that denotes removal and references previous plan. 4. Sheet 3.2/3.3: a. Revise construction entrance (CE). Centrally place or provide additional construction entrance. There's grading shown not just at the current CE location. If trucks are hauling earth, then there should be connected paths between areas shown to get to the CE. Two additional paved construction entrances are denoted on Sheet 3.2/3.3. b. Show sediment trapping device location at CE. Diversion dike added from paved construction entrance to sediment basin. The two new additional paved construction entrances drain to inlet protection. c. Show staging area, stockpile area (protected with silt fence). Added to PPP. 5. Sheet 3.3: a. Show SB symbol. SB still in place for ph.ii until upstream area is fully stabilized. SB symbol added. b. Show IP symbol at curb cuts and OP symbol at basin. IP symbol added to curb cuts and OP symbol at basin. c. Grading over 2:1 here. Revise to be 2:1 or flatter. The slope in this location is 3:1. The screen shot provided (below), indicates a drop 3' vertically, over approximately 9' horizontally. / 411 i \ SF Nm n I P3 \ vm Mu d. Provide type of low -maintenance ground cover (not grass) for slopes over 3:1. Slopes steeper than 3:1 are not proposed. We are happy to provide CAD files for reviewers to confirm slopes. Bluebeam PDF measurements provided by reviewer seem to be slightly off our CAD model. 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 clint.shifflett(@timmons.com . Sincerely, Clint Shifflett, PE Project Manager