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HomeMy WebLinkAboutWPO201900062 Correspondence 2020-10-26f•�eas 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 October 26, 2020 Matt Wentland Albemarle County Community Dev. 401 McIntire Rd, Rm. 227 Charlottesville, VA 22902 RE: Southwood Redevelopment — Village 1- VSMP Permit Plan Review— WP0201900062 — Rev. 3 Comment Response Letter Dear Mr. Wentland: We have reviewed all of your comments from Rev. 3 dated October 6, 2020 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 signed Registration Form. A signed Registration Form has been included in the SWPPP. Rev. 1 Comment addressed. 2. Provide a signed Certification. A signed Certification has been included in the SWPPP. Rev. 1 Comment addressed. 3. Include the information on impaired waters in Section 7. The TMDL Report for Moores Creek has been included in the SWPPP. Rev. 1 Comment addressed. Revision 1 comments: 4. The proposed area of disturbance is listed differently throughout the SWPPP and plans (12.88 ac. On the Registration Statement, 15.58 ac. In the Nature of Activity, 15.04 ac. In the VRRM not including forest and open space). Please revise to have the same acreage. The proposed area of disturbance has been revised on the plans and throughout the SWPPP. Rev. 2 Comment addressed. ENGINEERING I DESIGN I TECHNOLOGY B. Pollution Prevention Plan (PPP) The PPP content requirements can be found in County Code Section 17-404. 1. he PPP is 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. A FDP permit application and a Flood Study will need to be submitted and approved [18.30.3.12,18.30.3.13]. Acknowledged. A flood plain permit will be submitted/approved prior to the VSMP and final plat approval. Rev. 1 Comment not addressed. A draft of a Flood Study has been attached. However, this outfall has been recently revised. A final Flood Study for the proposed outfall shall be submitted prior to plan approval. Rev. 2 Comment not addressed, response noted. The Flood Study was submitted on July 23. Rev. 3 The FDP is still under review. Acknowledged. 2. This plan cannot be approved until the 1.84lb/yr of nutrient credits have been purchased. Please contact Ana Kilmer prior to purchasing credits. Acknowledged. We have reached out to Ana Kilmer in regard to purchasing nutrient credits. Note that with the revised routing, 1.38 Ib/yr of nutrient credits is required. Rev. 1 Comment not addressed. We have reached out to Ana Kilmer in regard to purchasing nutrient credits. Rev. 2 Comment not addressed, response noted. An affidavit has been sent to Ana Kilmer for the nutrient credits to be purchased. Rev. 3 The credits will need to be purchased before a permit can be issued. Nutrient Credits have been purchased. Proof of purchase has been provided. 3. Please contact Ana Kilmer to complete a Stormwater Management Facilities Maintenance agreement. We have reached out to Ana Kilmer to complete a Stormwater Management Facilities Maintenance agreement. Rev. 1 Comment addressed, the agreement will need to be recorded prior to approval. We have reached out to Ana Kilmer to complete a Stormwater Management Facilities Maintenance Agreement. Rev. 2 Response noted. We have sent Ana Kilmer an Attorney Letter in order to submit a Stormwater Management Facilities Maintenance Agreement. Rev. 3 Comment addressed, recorded in DB 5386 p. 659. 4. The Forest and Open Space Easement, SWIM Facility easements and Mitigation easement will need to be shown on the Final Plat and a Deed of Dedication will need to be signed and recorded for this easement. The Deed will be filled out by the County and forwarded to the applicant when the plat is nearing approval. Acknowledged. Rev. 1 Response noted. S. Show and label all proposed easements on the plans, including facility and access easements. All easements have been shown and labeled on the Grading and Drainage Plan on sheets C4.05-C4.08. Rev. 1 Comment partially addressed. Revise the easement linetype so it shows up clearer. Show easements on the entrance culvert, structure 600 on the entrance road, and on the structures/pipes in the parking lots of the proposed apartment buildings (others may not be listed). Easements have been added at structure 600 and through parking lots at condo buildings. Rev. 2 Comment addressed. 6. Clearly shown and label how the bioretention will be accessed for maintenance. An access easement has been added in the vicinity of pipe 201. Rev. 1 Comment partially addressed. The maximum slope for a grassed access is 20%, please revise. [Design Standards Manual]. Grading has been revised to 20% maximum for 10' wide access path. Rev. 2 Comment not addressed, scaling the contours shows a 25% slope. Grading has been revised to 20% maximum slope. Rev. 3 Comment addressed. 7. Include the bioretention maintenance and inspection schedules from DEQ BMP Spec. 9 on the plans. DEQ BMP Spec. 9 maintenance and inspection schedules have been added to the Stormwater Summary on sheet C6.01. Rev. 1 Comment addressed. 8. Include the planting plans for the bioretention. A planting plan has been added for the bioretention. See sheet 1-1.01 and 1-1.02. Rev. 1 Comment partially addressed. Only one biofilter shows any plantings on the landscape plan. Provide separate details/tables for the biofilter plantings following the requirements in DEQ BMP Spec. 9 sections 6.8 and 6.9. Plantings for both biofilters have been shown on sheets 1.3.01 and 1-3.02. Rev. 2 Comment not addressed, separate biofilter requirements and proposed landscaping were not found on the landscape sheets. Biofilter 1 does not show up fully on the sheets. Biofilter landscape has been shown on sheet L1.04. Rev. 3 Comment addressed. 9. Provide the routing calculations for the bioretention. Bioretention routing calculations have been included in the calculation book. Rev. 1 Comment addressed. 10. Show and label the pre-treatment requirements for the level 2 bioretention on the plans. Gabion basket forebay wall details have been added to sheet C6.00. Rev. 1 Comment partially addressed. Show and label both of the two required pre - treatments for each Level 2 biofilter. Include the size of the pre-treatment cells. [DEQ BMP Spec. 9, Table 9.3 and Section 6.4] Per Table 9.4, pre-treatment cell and gravel diaphragm have been provided at each bioretention basin. Riprap-lined pre-treatment cell has been added to detail for additional clarity. Rev. 2 Comment partially addressed, I did not see the size of the cells on the plans. The size of the pre-treatment cells has been added to C6.01 Bioretention Facility Details. Rev. 3 Comment addressed. 11. Provide more detail on the path through bioretention 2. Bioretention 2 has been relocated and revised. Rev. 1 Comment addressed. 12. Include the County As -built requirements on the plans. The As -built Road Plan policy has been added to the Notes and Details on Sheet C3.00. Rev. 1 Comment not addressed. Include the VSMP As -built requirements. The VSMP As -Built requirements have been added to sheet C1.00. Rev. 2 Comment addressed. 13. On Sheet C6.0, include a breakdown of the proposed and conceptual impervious areas in each biofilter drainage area. The proposed and conceptual impervious areas have been labeled for each drainage area on sheet C6.00. Rev. 1 Comment addressed. 14. Show more detail for the outfall into the stream. Include the stream banks, as it will need to outfall directly in the stream to not use energy balance. Include a drainage area map for the stream to show the 1% is being met. Outfall location has been revised. 1% drainage area map has been added to plans on sheet C6.02. Rev. 1 The provided DA map appears to be incorrect. Areas are included that enter the stream below the proposed outfall and areas that drain to the other side of the Interstate. I've attached a printout from County GIS showing the drainage area at the pipe outfall. Stormwater management approach has been revised to include an oversized storage pipe to meet energy balance requirements. See sheet C6.00 for additional information. Rev. 2 See comments below. Acknowledged. 15. Contact the Army Corp and provide correspondence allowing the outfall into the stream. We have reached out to the Army Corp pertaining to the outfall into the stream. Rev. 1 Comment not addressed, response noted. We are in communication with the Army Corp on the revised outfall and will provide correspondence in future submittals. Rev. 2 Comment not addressed, response noted. We have emailed with Vinny Pero at the Army Corps of Engineers. He has stated that this project qualifies for a non -reporting Nationwide Permit No. 18. Rev. 3 Comment addressed. Revision 2 comments: 16. The 1-yr flows on the table on sheet C6.00 do not add up to what is shown for the total (it looks like the 0.32 should be 0.23). Calculations on sheet C6.00 have been verified to match HydroCAD calculations. Due to routing formulas, combined flows occasionally differ from simple addition. Refer to calculation book for additional details. Rev. 3 Comment addressed. 17. Provide the 10-yr routing for the storage pipe and for the whole system. The 10-yr routing has been provided in the Design Calculations and Narrative. Rev. 3 Comment addressed. 18. Provide more detail on the storage pipe, such as a detail of the weir wall. Ensure maintenance access to both sides of the weir wall, at the weir wall. A storage pipe weir wall detail has been added to sheet C6.01. Rev. 3 Comment addressed. 19. The storage pipe easement may need to be greater than 20' Use the calculation from the Design Standards Manual to determine the easement width (Width = Pipe Diameter + 2' (Depth to bottom of pipe — 5') + 10'). The easement over the pipe should also be labelled as a Stormwater Facility Easement, as it's addressing the DEQ quantity requirement. The storage pipe easement has been revised to be 32.5' and 42.5' wide dependent on depth. The easement has been called out as a Stormwater Facility Easement. See sheet C4.09. Rev. 3 Comment addressed. 20. After considering the larger than usual drainage area to Bioretention #1, provide a flow splitter prior to the outlet to allow only the Treatment Volume to enter the facility (and any additional amount in order to meet Energy Balance). [DEQ BMP Spec. 9, Section 6.5]. The BMP clearinghouse includes a recommendation for a 2.5 acre maximum drainage area and allows up to 5 acres. Bioretention Facility #1 currently captures 4.39 acres of runoff, although only 2.55 acres of that is impervious land cover. Bioretention Facility #2 captures 1.69 acres of runoff. The facilities are currently designed to capture the amount of runoff necessary to meet the energy balance equation. Any reduction in runoff sent to the facilities would result in a site outflow that would not meet the energy balance equation. Bioretention Facility #1 has maximized the area available and providing two bioretention facilities in this area is not feasible due to site constraints and the proximity of the floodplain. Please also note, stone rip -rap and a forebay with gabion basket weir structure have been provided to mitigate the larger flow. Rev. 3 Comment addressed. 21. Provide more separation between Pipe 201 and Pipe 105/Structure 104. 10' is preferred. 10' separation has been provided between Pipe 201 and Pipe 105/Structure 104. See Sheet C4.10. Rev. 3 Comment addressed. 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 ESG p9Ftl9.. appeaFS ptahlp at thig tl.. e Acknowledged. Revision 1 Comments: 2. Provide a sediment trap for the grading on the northeast side of the entrance. The final grading should also be revised to direct the runoff to the culvert instead of having channelized runoff flowing into the road. Sediment Trap #3 has been added. Ditch has been added in the proposed condition to direct runoff to culvert. Note that storm pipes along Road 1 have been sized for future development by others on this parcel with approximately 80% impervious surface. (Rev. 2) Comment addressed. Revision 2 Comments: 3. It appears the outlet pipe for Sediment Basin 1 is shown going under Old Lynchburg Road. Please revise to stay out of the public road and show the existing road more clearly on the plans. Sediment Basin 1 outlet pipe has been revised. Old Lynchburg Road has been labeled close to the Sediment Basin 1 outlet pipe in order to clarify the location of the existing road. Rev. 3 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 email me at clint.shifflett@timmons.com . Sincerely, Clint Shifflett, PE Project Manager