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Home My WebLink AboutWPO202100071 Correspondence 2022-10-05Dewberry® October 5, 2022 Dewberry Engineers Inc. 804.290.7967 4806 Lake Brook Drive, Suite 200 804.290.7928 fax Glen Allen, VA 23060-9278 I www.dewberry.com County of Albemarle Community Development Department Attn: David James, Engineering 401 McIntire Road, North Wing Charlottesville, VA 22902-4579 RE: WPO202100071 ACSA Avon Maintenance Yard Dear Mr. James, Please see comment responses below. 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 submit the SWPPP for review. Dewberry: SWPPP included with Final Site Plan submission. B. Pollution Prevention Plan (PPP) The PPP content requirements can be found in County Code section 17-404. 1. Please submit PPP exhibit sheet for review. Dewberry: PPP sheet included. 2. Provide concrete washout detail. Dewberry: Concrete washout detail added to sheet C5.02. 3. Fuel/Chemical areas will need to be covered under a separate permit if discharging to drainageways that will leave site. Provide locations of any stormwater treatment and/or separator system to be used. Dewberry: Note added to PPP. The fueling/chemical areas are contained onsite during construction. 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. Ditches/Channels — a. Provide callout/label for each. Dewberry: Callouts provided on sheets C4.13-C4.17. b. Show grading and centerline. Dewberry: Grading and centerline shown on sheets C4.13-C4.17. Page 1 of 4 Mr. David James ACSA Avon Maintenance Yard WP0202100071 October 5, 2022 C. Show stationing at 50' intervals. Dewberry: Stationing provided on sheets C4.13-C4.17. d. Provide cross-section details and determine 2-yr velocity and lining requirements. Dewberry: Cross sections provided on sheets C4.13-C4.17. Velocities and lining requirements provided on sheet C4.18. e. Provide ditch design worksheet. See VDOT drainage manual for guidance. Dewberry: Ditch design worksheets provided on sheet C4.18. f. Provide profiles in cases where the channel slope varies or connects to a drainage structure. Dewberry: Profiles provided on C4.13-C4.17. 2. C4.06/4.07/4.08: a. Show the HGL in the profiles. Dewberry: HGL added to the profiles b. Revise: The minimum pipe size diameter is 8" for STM 13-14-12, STM 19-20. Dewberry: Pipe size has been increased to a minimum of 8". 3. C6.01 - Your SWIM narrative mentions three outfalls. Your Water Quantity only shows energy balance for A02. What about the other outfalls how do they meet Quantity? Dewberry: All three outfalls have been shown on the plans. 4. C6.06 — Show Tc path for A03; seems low. Dewberry: The Tc Path shown and stated as 5min is just for the 0.29 ac of site area that drains to AO 3 through existing the existing storm sewer system along Founders Place. 5. Provide the inlet design for STM 18. Provide half -clogged design per VDOT drainage manual. Ensure existing drainage system along Founders Place is designed adequately to handle the additional flow. Dewberry: Inlet computations have been updated to be 50% clogged. 6. Provide half -clogged design for STM 6 & STM 16 per VDOT DM. Dewberry: Inlet computations have been updated to be 50% clogged. 7. Provide letter of availability from offsite nutrient credit provider on the plans. Dewberry: Letter provided. 8. Include this checklist in the plan set. http://www. al bema rle. org/upload/images/forms_center/departments/Commu nity_De ve lop ment/forms/Eng i neeri ng_and_WPO_FormsNVPO_V SM P_C onstructi on_Record _D rawings_Policy_23May2014.pdf Dewberry: Checklist added to sheet C6.01. Dewberry® Page 2 of Mr. David James ACSA Avon Maintenance Yard WP0202100071 October 5, 2022 g. Show the SWIM facility and access easement(s). Easements should be recorded with plat prior to grading permit issuance. Dewberry: SWIM facility and access easements have been added. Please see sheet C3.02. Easements will be recorded prior to grading permit. 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. Sheets C5.01, 5.03-5.06 can be removed from the WPO plan set. Dewberry: Sheets removed from WPO plan set. 2. Cover: Please add the WPO# under title. Dewberry: WPO number added to cover sheet. 3. C1.01-.03: Show all existing utilities and easements with deed book references. Dewberry: Existing utilities and easements shown. 4. Please correct grading here to be 2:1 or less. Dewberry: Grading corrected. 5. C2.04: Provide TS, B/M on back of sed. basin slope. Where grade is 3:1 and over, use B/M. [VADEQ ESC HB, Spec. 3.31, 3.35, 3.36] Dewberry: TS and B/M provided. 6. C2.04/2.04: Show location of sediment trapping device at CEs. Dewberry: Location of sediment trapping device shown at construction entrances. 7. C2.05/2.06: a. Provide CRS for the access roads. [VADEQ ESC HB, Spec. 3.03] Dewberry: Construction Road Stabilization provided. b. Provide MU/PS on slopes. Where slopes are 3:1 and greater use B/M. [VADEQ ESC HB, Spec. 3.31, 3.35, 3.36] Dewberry: MU, PS, and B/M provided on slopes as needed. c. Provide mix or type of low -maintenance ground cover (not grass) to be used on slopes 3:1 and greater. Dewberry: SlopemasterTM clover blend or equivalent low -maintenance clover blend will be used. Note added to C2.05-C2.06. g. C2.06: Provide callout to a detail of type of IP to be provided here. [VADEQ ESC HB, Spec. 3.07] Dewberry: Addressed. Dewberry-- Page 3 of 4 Mr. David James ACSA Avon Maintenance Yard WP0202100071 October 5, 2022 9. C6.09: a. Show anti -seep collar placement along barrel. Dewberry: Anti -seep collar placement along barrel has been added. See sheet C6.08 for sediment basin detail. b. Show the 4' min. depth cut-off trench placement under embankment. Dewberry: Note has been added to sheet C608 (Note 2). 10. Revise: STM 3 exceeds 1-acre minimum drainage area. [VADEQ ESC HB, Spec. 3.07] Dewberry: An additional storm inlet with inlet protection will be added to the proposed storm sewer system. 11. Need to show the length of OP along with the OP calcs to determine minimum length and also show the graded receiving channel from OP. Dewberry: Graded channel shown. Outlet protection length and material added. 12. Show graded receiving channel from barrel. What is the velocity out of barrel? 90 degrees is the minimum skew angle to receiving channel consider adjusting angle or depending on velocity provide solution to prevent scour. Dewberry: Graded channel from barrel shown. Manhole added to decrease the angle of the outflow. 13. Revise: Concentrated discharge must be contained and not cut down slope, i.e., STM 21. [MS-8] Dewberry: PVC pipe has been lengthened to channel as well as riprap channeling to the outfall of STM 21. 14. Constructed channels/ditches on slopes. Unless these channels are properly designed it might be best to consider Temp. Slope Drains (TSD). [VADEQ ESC HB, Spec. 3.15] Dewberry: Specifications and E&SC measures address contractor requirements for compaction, construction methods, and maintenance responsibilities to ensure the channels are constructed and maintained properly. 15. Provide conversion details for the sed. basin to permanent facility. a. Notify/Coordinate with ESC inspector on the start of embankment construction. A geotech engineer should be present during and after construction to monitor, report and verify stability and compaction of dam. Dewberry: Sequence of construction for the sediment basin to permanent facility are detailed on C608. A note to coordinate with ESC inspector at the start of embankment construction has been added to C608 (Note 1). Sincerely, Kevin Pennock Associate, Senior Project Manager IM.." Dewberry-- Page 4of4