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Home My WebLink AboutWPO202100046 Correspondence 2023-02-07� •s 608 Preston Avenue P 434.295.5624 Suite F434.295.1800 TIMMONS GROUP Charlottesville, VA 22903 www.timmons.com January 20, 2023 David James County of Albemarle Dept. of Community Development 401 McIntire Rd, North Wing Charlottesville, VA 22902 RE: Barnes Lumber — VSMP Permit Plan Review — WP0202100046 - Comment Response Letter Dear Mr. James: We have reviewed all of your comments from October 4, 2022, (Rev. 1), 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. Please complete the Registration Statement. The Registration Statement will be completed when the individual responsible for SWPPP implementation is known. Rev. 1): Not addressed. Acknowledged, please complete prior to approval. The Registration Statement will be completed prior to approval once the individual responsible for SWPPP implementation is known. 2. Section 2 — Insert copy of DEQ letter when obtained. The DEQ letter will be in inserted when it is obtained. Rev. 1): Acknowledged, please complete prior to pre -con request. Acknowledged. The DEQ will be inserted when obtained prior to pre -con request. 3. Section 7 —Name the impaired waterway and list TMDL. The impaired waterway TMDL action plan has been added to section 7. Rev. 1): Addressed. ENGINEERING I DESIGN I TECHNOLOGY 4. Section 9 — Sign & date Signed Certification. The certification will be completed when the individual responsible for SWPPP implementation is known. Rev. 1): Not addressed. Acknowledged, please complete prior to approval. The certification will be completed prior to approval once the individual responsible for SWPPP implementation is known 5. Section 10 — Complete if delegating authority. This section will be completed if authority is delegated. Rev. 1): Acknowledged, please complete prior to pre -con request. This section will be completed prior to pre -con request if authority is delegated. B. Pollution Prevention Plan (PPP) The PPP content requirements can be found in County Code Section 17-404. 1. Update with revision changes. Erosion and Sediment control sheets have been updated with all revisions Rev. 1): Acknowledged. 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. Provide pre -/post- land cover map showing percentage of each land cover. Land cover tables have been added to Sheets 7(1) and 7(2). Rev. 1): Addressed. 2. Address potential drainage issue: The low point has been removed. Rev. 1): Addressed. 3. There are a few long ditches created please identify & provide ditch design (table). a. Show drainage area, slope/profile, cross-section showing geometry, 2-/10-yr levels, liner type needed/provided. A calculation summary table has been provided on sheet 7(3) as well as a typical cross section. The 2-yr velocities are all below the thresholds provided in the VAESCH for grass lined channels. The channels also provide capacity for the 10yr depth. Detailed calculations are provided in the calculation book. Channel labels have been provided on Sheets 4A and 4B that match the names in the design table. Rev. 1 : Addressed. 4. Sheet 7(1) — Longer flow paths that should be considered that begin at the upper elevation of drainage area. Longer flow paths were considered. Due to the impervious surface in DA1, the Tc is not longer than 6 minutes even with the longer path so a minimum Tc of 6 minutes is still used. a. The drainage areas, CN values, etc. need to match those shown in the calcs, vice -versa. All drainage areas, CN values, and Tc have been updated. Rev. 1 : Addressed. 5. Sheet 7(3)- a. Provide slope, length & type information of barrel. This information is provided on sheet 8(1). b. Provide trash rack and detail over bottom orifice. A trash rack and detail has been added over the bottom orifice. See Sheet 7(3). Rev. 1 : Addressed. 6. Design Calculations - a. Verify NOAA 24-hr precipitation values are correct. The NOAA 24-hr precipitation values have been updated. The NOAA table is now provided in the appendix. b. Provide post -development map of these areas. Do these areas match up with what's shown on Sheet 7(2)? Pre- and post -development areas have been updated. The design calculations match the drainage area maps in the plan. Rev. 1 : Addressed. 7. Provide inlet shaping (IS-1) in any drainage inlet structure with 4' or greater drop. Inlet shaping has been added. See sheet 8(1)-8(3). Rev. 1 : Addressed. 8. Provide safety slab (SL-1) in any drainage structure taller than 12'. Safety slabs are called out to be required in any drainage structures taller than 12'. See sheets 8(1)-8(3). Rev. 1 : Addressed. 9. Sheet 8(1) — Provide end wall (EW-1) for 48" dia. Pipe. The structure has been updated to be an EW-2 for the 48" dia. pipe. Rev. 1 : Addressed. 10. Show the HGL in the storm profiles. The HGL has been added to the storm profiles. Rev. 1 : Addressed. See comment #15. 11. Retaining wall must be located outside of SWM facility easement. A retaining wall is no longer proposed. The easement is now provided for only the underground detention. Rev. 1 : Acknowledged; N/A 12. Provide forebays/gabion weir for detention pond. A detention pond is no longer proposed. Rev. 1 : Acknowledged; N/A 13. There appears to be disturbance in the 100' stream buffer that will need to be mitigated. Mitigation plan has been included with this submission. See sheet 7(6). Rev. 1 : Acknowledged. 14. Please provide approval/acceptance by VDOT if this pond is to be maintained by VDOT and not with the County. The pond has been replaced by an underground detention system that will be maintained by the county. A label for the easement has been included on sheet 4B which reads, "Proposed permanent drainage easement for county maintenance." Rev. 1 : Acknowledged; N/A. 15. (Rev. 1) Sheet 8(1)— a. Add a note or callout(s) to provide water -tight fittings at pipe joint connections where the HGL is above the pipes (i.e. under pressure). A note has been added (0) on sheets 8(1)-8(3). b. Add note or callout(s) to provide water -tight fittings where pipes of dissimilar materials connect. A note has been added (#4) on sheets 8(1)-8(3). D. Mitigation Plan (MP) The mitigation plan requirements can be found in County Code Chapter 17-406. 1. Submit plan for review. A mitigation plan has been included with this submission on sheet 7(6). Rev. 1 : Addressed. 2. Rev. 1): The mitigation area is 100' from the edge of stream (50' shown), see County GIS. The 100'stream buffer has been shown. E. 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. Please add the WPO# to title sheet. WPO number has been added to the cover sheet. Rev. 1): Addressed. 2. Sheets 2 through can be removed. Keep the notes. Sheets 2A and 2B have been removed. Rev. 1): Acknowledged. 3. Existing Conditions Sheets —Show the 100' stream buffer accurately. The stream buffer has been updated. Rev. 1): Not addressed. Its 100' from the stream edge. Refer to County GIS. The 100' stream buffer has been shown. 4. E&SC Sheets — a. Please include all demo activities in your limits of disturbance. All demo activities are included in the LOD Rev. 1): Acknowledged. b. Provide CRS (VADEQ E&SC Spec. No. 3.03) or DC (VADEQ E&SC Spec. No. 3.39) for the roads. DC is provided throughout the LOD. Rev. 1 : Acknowledged. c. Show OP symbol at barrel end outfall. OP symbol has been added at barrel end outfall. Rev. 1 : Acknowledged. d. Provide CIP & OP here: CIP and OP has been added. Rev. 1 : Acknowledged. e. Add TP or adjust LOD line: LOD and TP has been adjusted. i. Identify area (landscaping?) Rev. 1 : Acknowledged. f. Add a baffle for phase II Sediment Basin to prevent short-circuiting. A baffle has been added to phase I sediment basin. Rev. 1 : Acknowledged. 5. Determine if anti -vortex is needed for SIB and if so, provide detail. The sediment basin design has been updated to a temporary sediment basin only and is no longer to be converted into a stormwater management pond. The outlet structure will also be temporary and will include an anti -vortex device. Rev. 1 : Acknowledged. 6. Please correct the amount disturbed in your LOD. 18.10 ac & 18.64 ac are shown on the plans. The plan has been revised and is no longer including rough grading some of the parcels with this phase. The LOD has been updated to 10.49 ac. in all areas. Rev. 1 : Acknowledged. 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