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Home My WebLink AboutWPO202200005 Correspondence 2022-07-22 (2)608 Preston Avenue P 434.295.5624 Suite Zoo IF434.295.1800 T I M M O N S GROUP Charlottesville, VA 22903 www.timmons.com July 21, 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 June 22, 2022 (Rev. 1) 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/engi neeri ng-a ppl ications/vsm p. Submitted. Rev. 1): Addressed. 2. Rev. 1): Include WPC# and project name on SWPPP cover. Added to SWPPP cover. 3. Rev. 1): Complete & Sign Registration Statement. Acknowledged. Will follow up with signed form. ENGINEERING I DESIGN I TECHNOLOGY a. Sec. II I. — Change: The 6Ih order HUC is JR15 or 020802040402 and downstream receiving water is Cow Branch. Revised. 4. Rev. 1): Sec. 4 & 5 — Update with the approved versions. Updated. 5. Rev. 1): Sec. 8 —Complete prior to preconstruction meeting. Acknowledged. Will follow up with signed form. 6. Rev. 1): Sec. 9 —Complete prior to approval. Acknowledged. Will follow up with signed form. 7. Rev. 1): Sec. 10—Complete prior to preconstruction meeting. Acknowledged. Will follow up with signed form. 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. (Rev. 1): Addressed. 2. Rev. 1): Provide a detail of the concrete washout, mortar mixing station, and fuel station. Namely of the containment area that could be site specific. Added more detailed callouts and concrete washout detail per 7/6/22 email correspondence. 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. Rev. 1 : Acknowledged; You can add a note/callout in the detail to provide for trashrack over weir plate orifices. Added on sheet C1.2 and sheet C6.2. 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. Rev. 1 : Partially addressed. Please provide the necessary cover for the 5' diameter pipes. Cover has been revised to 2.5'. b. Show HGL. HGL added to profiles on Sheet C7.1. Rev. 1 : Addressed. 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. i. 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. Rev. 1 : Acknowledged; Not currently addressed. See sheets C1.2-C3.3 for detention system details. d. Rev. 1 : Verify / Correct structure labeling (highlighted). Corrected profile names. 3. Provide water -tight fitting where pipes of dissimilar materials connect. Added beneath pipe table on sheet C7.1. Rev. 1 : Addressed. 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. Rev. 1 : Please show MH access in the profiles. Include maintenance access ladder and detail. MH access is shown in profiles on sheet C5.2. Sheets C1.2-C3.3 include the maintenance access ladder and riser details. 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. Rev. 1 : Addressed. 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". Rev. 1 : Addressed. a. Rev. 1 : Provide 15" for pipe 323, as well. Pipe 323 is now 15". i. Rev. 1 : Provide pipe anchor blocks (every other pipe joint at a minimum, >16%). Revised so that no pipes are greater than 16%. 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. Rev. 1 : Addressed. 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. Rev. 1 : Addressed. 9. Rev. 1 : Please provide any manufacture specific installation & long-term maintenance requirements for the UD system. See sheet C1.2-C1.3 for installation and maintenance notes. 10. Rev. 1 : Please contact Ana Kilmer (akilmer@albemarle.org) prior to nutrient credit purchase. Purchase needed prior to permit issuance. -Currently, 1.98 Ib/yr TP are needed. Acknowledged. Will contact Ana prior to purchase. Note: SWM plan amends W13O200600002. 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 "WPO202200009" under title. b. Signature panel can be removed. Removed. Rev. 1 : Addressed. 2. Sheet 2.1/2.2: Show footprint and label existing BMP/SWM facilities. Footprint and labels added. (Rev. 1): Addressed. 3. Sheet 2.4/2.5: Show label for the removal of the bioretention facility and SWM pond. Add note ...'as shown on WPO200600002'. Added label that denotes removal and references previous plan. Rev. 1 : Addressed. 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. Rev. 1 : Addressed. 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. Rev. 1 : Addressed. c. Show staging area, stockpile area (protected with silt fence). Added to PPP. Rev. 1 : Addressed. 5. Sheet 3.3: a. Show SB symbol. SB still in place for ph.ii until upstream area is fully stabilized. SB symbol added. Rev. 1 : Addressed. b. Show IP symbol at curb cuts and OP symbol at basin. IP symbol added to curb cuts and OP symbol at basin. Rev. 1 : Acknowledged; the OP is shown from end of 15" pipe into basin. Moved OP symbol to end of 15" pipe. 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. Rev. 1 : N/A; Acknowledged. 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. Rev. 1 : 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 clint.shifflettC@timmons.com . Sincerely, Clint Shifflett, PE Project Manager