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HomeMy WebLinkAboutWPO202100022 Correspondence 2021-08-20TIMMONS GROUP August 20, 2021 Matt Wentland County of Albemarle Community Development 401 McIntire Rd Charlottesville, VA 22902 608 Preston Avenue P 434.295.5624 Suite 200 F 434.295.1800 Charlottesville, VA 22903 www.timmons.com RE: Southwood PHA Blocks 11 & 12 —VSMP Permit Plan Review— WPO-2021-00022 - Comment Response Letter Dear Mr. Wentland: We have reviewed your comments from June 3, 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) and ESCP, (3) a SWMP, and (4) any TMDL measures necessary. 1. The existing DEQ permit may need to be modified as it appears the limits of disturbance has been increased from previous plans. The DEQ Permit is proposed to be separate from other Southwood phases/projects. See Sheet C2.2 for Overall Phasing Plan. 2. Provide a signed Certification. The signed Certification will be provided once the 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. B. Pollution Prevention Plan (PPP) The PPP content requirements can be found in County Code Section 17-404. 1. The PPP appears acceptable at this time. PPPs have been revised per E&S updates and provided within the SWPPP. 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. ENGINEERING I DESIGN I TECHNOLOGY 1. This plan cannot be approved until the additional 0.94 Ib/yr and 0.76 Ib/yr of nutrient credits have been purchased or the reduction provided on -site. Please contact Ana Kilmer prior to purchasing credits. Once the total load reduction required reaches 10 Ib.yr between this project and all others on the property, 75% of the reductions will need to be achieved on -site (9VAC25-870-69(B)3). Please provide a table detailing the reduction required and the reduction provided on site for the project as a whole to determine if credits can still be purchased. DEQ has also updated their credit purchasing requirements, located in 9VAC25-900-91(B)3). Since this project drains to impacted streams, the credits will need to be purchased from a bank located in the same 8-digit HUC. The process goes upstream, then HUC12, HUC10, and HUC8, at which point the Ivy Creek credit bank is in the same HUC8. The overall phosphorus reduction table has been added to Sheet C6.1. 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. 2. Other than the forebay, list the other pre-treatment used that is required for Level 2 Bioretention (BMP Spec. 9, sect. 6.4). In addition to the pretreatment cell (forebay), a gravel flow spreader has been incorporated at each curb cut prior to flowing into the pretreatment cell. 3. It is stated that the water quantity will be handled by the approved WPO201900062 plans, however that plan states that it accounts for an additional 1.10 acres of impervious while this plan proposes an additional 2.84 acres. This plan also appears to have larger drainage areas than what is shown on WPO201900062. Please clarify and provide more detail on this plan as to how that will be achieved, including updated drainage area maps of the overall development. A table showing the approved and proposed numbers from each plan may be helpful. First to clarify the 1.10 acres of impervious on WPO201900062 was allocated as a place holder for the empty lots on the plan at that time. The current amendment to the Village 1 plan (WPO202100019) provides water quantity for the future development of block 12. The Village 1 amendment provides partial water quality for block 12 for the transition from forest to managed turf. Drainage from Block 12 goes to Horizon Road, which is accounted for in the Village 1 plan (WPO202100019). The Village 1 plan captures all of the Block 12 drainage and accounts for 2.14 acres of impervious area. This plan proposes 1.97 acres of impervious area on Block 12 which will be adequately served by the pond to be installed with Village 1. Drainage from Block 11 is incorporated in Blocks 9-11 plan (WPO202100004). The Blocks 9-11 plan accounts for 1.34 acres (0.83 acres impervious) of drainage from the development of block 11 with this plan. This plan proposes 0.83 acres of impervious area which will be adequately captured and served by the downstream detention system to be installed with the Blocks 9-11 plan. This response has been added as a note to the plan sheets C6.0 & C6.1 for documentation. The numbers listed above are documented by the VRRM spreadsheets on each of these pages for the two discrete areas of land disturbance with this plan. 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. The trap outlets may need to be adjusted at the time of construction depending on the construction of improvements shown on other plans. The sediment trap (ST2) has been adjusted based on updates to Blocks 9-11 site plans. A note has been added for the trap to be coordination with construction of W PO202100004. 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