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Home My WebLink AboutWPO202100038 Correspondence 2022-04-04S� 608 Preston Avenue P 434.295.5624 Suite F434.295.1800 TIMMONS GROUP Charlottesville, VA 22903 www.timmons.com April 4, 2022 Matt Wentland County of Albemarle Community Development 401 McIntire Rd, North Wing Charlottesville, VA 22902 RE: Southwood Village 2 — VSMP Permit Plan Review — WPO-2021-00038 - Comment Response Letter Dear Mr. Wentland: We have reviewed all of your comments from Rev. 1 January 14, 2022 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. Will the existing DEQ permit be used to cover this area? If so, please provide a completed and signed DEQ Registration Statement modification if the area increased from the original permit, or a new Registration Statement modification if the area increased from the original permit, or a new Registration Statement with Village 2's information if not. A new registration statement for Village 2 has been provided. Rev. 1): Comment addressed. 2. Provide a signed certification. A signed certification has been provided. Rev. 1): Comment addressed. B. Pollution Prevention Plan (PPP) The PPP content requirements can be found in County Code Section 17-404. 1. The PPP is acceptable at this time. Acknowledged. 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 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. This plan cannot be approved until the 1.48 Ib/yr of nutrient credits have been purchased. Please contact Ana Kilmer prior to purchasing credits. Since this project drains to impacted streams, the credits will need to be purchased from the Ivy Creek credit bank. Ana Kilmer has been contacted per the proposed 1.48 lb/year of nutrient credits. Rev. 1): Comment not addressed; response noted. Acknowledged. Nutrient credits will be purchased prior to plan approval. Coordination with Ana Kilmer is underway. 2. Show the SWM Forest & Open Space from the Village 1 plans on these plans. No improvements are allowed in this area (including stone dust trails) and any grading will require DEQ BMP Spec. 4 Soil Amendments to be used. This may require changes to the Village 1 amendment. The SWM Forest & Open Space from the Village 1 plans has been shown. No improvements are proposed in this area. Rev. 1): Comment partially addressed. Provide a more detailed exhibit showing the F&OS, the new mitigation area, and the limits of disturbance. It appears everything is outside of the area, but it is difficult to tell. An additional Open Space Plan has been added at a more detailed scale. See sheet C4.04. The maximum side slopes allowed by the County inside a basin is 3:1. The basin should also be moved out of the buffer as much as possible. Slopes of SWM A have been revised to 3:1. Due to proximity of adjacent house lots, location is as far out of the buffer as feasible. Rev. 1): Comment addressed. 4. Due to the pond's drainage area being less than 10 acres, provide a water balance calculation (DEQ BMP Spec. 14, Section 6.2). A water balance calculation has been provided on sheet C6.01. Rev. 1): Comment addressed. 5. Provide more detail on the pretreatment forebays. DEQ BMP Spec. 14, section 6.4 requires forebays to be at least 4 feet deep with an aquatic bench. Show how the forebays meet all items in this section. Forebay Sizing Detail (SWM A), including volume calculations, has been added to sheet C6.01. Gabion Basket Forebay Wall Detail (SWM A) on sheet C6.01 has been updated accordingly. Per email dated 12/2/2021, aquatic benches are not required per DEQ's 2013 Specification 14, Section 6.3 and Appendix D, due to the depth of water and the small pond and forebay sizes. Due to limited space available around the wet pond, aquatic benches are not proposed. We understand that the County's discussion of the requirements is ongoing at the time of this submittal. Rev. 1 : Comment not addressed. The forebays will need to meet the section 6.4 design requirements for pretreatment forebays. 4' wide aquatic bench with 25% slope has been provided all the way around the pond, including in the forebays. 6. Provide a landscaping plan for the basin per Section 6.7. A landscape plan for the basin has been provided on sheet C6.00. Rev. 1 : Comment addressed. 7. Show the maintenance access to all elements of the basin and how it meets Section 6.8 (slope, width, etc.). This will need to be in an easement. The maintenance access easement and its slope and width have been labeled on sheet C4.04. Rev. 1 : Comment not addressed. It appears there is a retaining wall running through the access easement and it is still unclear how it will loop around the pond while avoiding the areas that are not to be disturbed. Stormwater access easement has been revised to pass through the trail connector open space at the cul-de-sac and follow the 200-series pipes to the pond. 8. Include the maintenance requirements from Section 9 on the plans. The Inspections and Ongoing Maintenance Tasks for VA DEQ Stormwater Design Specification No. 14 has been added to sheet C6.01. Rev. 1 : Comment addressed. 9. The buffer disturbance from the basin will require a mitigation plan. A Mitigation Plan has been added on sheet C6.03. Rev. 1 : Comment addressed. Please note that this area will need to be vegetated and undisturbed at bond release. Acknowledged. Note #2 has been added to sheet C6.03. 10. Provide fence and or railing around the proposed pond, as it is located close to backyards and adjacent to the proposed trail. A 3-board safety fence has been added around the proposed pond. See sheet C4.01. Rev. 1 : Comment not addressed. Sheet C4.01 was not in the plan set. Also include a detail of the fence. Board fence label has been added to Grading and Drainage Plan; see sheet C4.05. Detail was included in previous submittal, and remains in this submittal; see sheet C1.01. 11. Provide more detail on the storm sewer behind the cul-de-sac lots (elevations, profile, etc.) and how run-off will reach the system. The drainage area map shows all the run-off above the storm sewer being collected, but the grading appears to show its sheet flowing and bypassing the inlets. The storm sewer should also be moved outside of the buffer. The storm sewer has been moved outside of the stream buffer. Profiles have been provided for the storm sewer behind the cul-de-sac lots. See sheet C7.01. Additionally, the drainage map has been revised on sheet C6.02 to accurately reflect the grading. Rev. 1 : Comment partially addressed. These pipes are no longer showing on the plans (like the layer is off). See sheet C4.05 for storm pipe layout behind the cul-de-sac lots. The profiles are shown on sheet C7.01. 12. Per the Code of Development, residential lots are to be located outside of stream buffers, preserved slopes, and floodplains. Grading for the lots should also be outside the buffer. Grading has been revised to not impact stream buffer. Rev. 1 : Comment addressed. 13. Private drainage easements should be a minimum of 10' wide. The easement width calculation from the Design Standards Manual should still be used for pipes not at minimum depth. The private drainage easements have been revised to all be a minimum of 10' wide. Rev. 1 : Comment addressed. 14. Drainage easements that are not a constant width should be labelled as variable width. Some of the other easement widths appear to be incorrectly labelled (such as the 10' label on the easement for pipe 101). Drainage easement labels have been revised accordingly. Rev. 1 : 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 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. Some of the ESC measures appear to slightly overlap the preserved slopes. Relocate these items so the slopes are not disturbed. All ESC measures have been relocated to be out of the preserved slopes. 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 clint.shifflett@timmons.com . Sincerely, Clint Shifflett, PE Project Manager