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Home My WebLink AboutWPO202200032 Correspondence 2023-02-08608 Preston Avenue P 434.295.5624 Suite 200 F 434.295.1800 T I M M O N S GROUP Charlottesville, VA 22903 www.timmons.com February 7, 2023 John Anderson, PE, CFM County of Albemarle Community Development 401 McIntire Rd, North Wing Charlottesville, VA 22902 RE: Berkmar Self Storage — VSMP Plan Review - Comment Response Letter Dear Mr. Anderson: We have reviewed your comments from November 15, 2022, and made the necessary revisions. Please find our responses to the comments below in bold lettering. A. Stormwater Pollution Prevention Plan (SWPPP) 2. Registration Statement, SWPPP Sec. 1 b. Sec. IB: Once Construction Activity Operator named /listed, please include valid email. Once contractor is selected, the section will be completed (understood prior to receiving grading permit). Rev. 1 : Persists. Same response; will be provided prior to approval. 5. Sec. 6.E.: List named individual responsible for PPP. Not required for plan approval but required to receive a grading permit. Once contractor is selected, the section will be completed (understood prior to receiving grading permit). Rev. 1 : Persists. Same response; will be provided prior to grading permit. 6. Sec. 8: List named individual responsible for VESCH /SWPPP compliance inspections. Not required for plan approval but required to receive a grading permit Once contractor is selected, the section will be completed (understood prior to receiving grading permit). Rev. 1 : Persists. ENGINEERING I DESIGN I TECHNOLOGY Same response; will be provided prior to grading permit. B. Pollution Prevention Plan (PPP) No comments. Note: PPP has been updated to reflect recent plan changes. C. Stormwater Management Plan (SWMP) 2. C6.2 a. Revise capacity of pipe 127 such that Q provided > Q required (24.466cfs v. 38.16cfs). We think reviewer means pipe 103 (not 127). Pipe 103 has been upsized. See Sheet C6.2. Rev. 1 : Persists. Please note: Table, C6.2 appears to report identical values for pipe 103 as listed in comment; possible review error. If so, please notify. Storm pipe calculations have been updated to reflect latest layout and grading. All pipes have Q provided > Q required. 3. C6.3 b. Include supplemental narrative in Calc. packet: L Please state: "Albemarle SWM facility database states existing dry detention basin watershed is 61.87 Ac. with 21.37 Ac. impervious. Plan approval date is 11/19/87. Facility is listed in county SWM database (co - owned by) Keglers of Charlottesville and Lowes Investment Corp #341." Proposed development, Berkmar Self -Storage, appears to lack ownership in the facility, or privilege to use it. Applicant parcel is not child to parent subdivision that might assign use rights to Applicant. Applicant should coordinate /execute notarized Agreement with owner to use the existing dry detention basin, and furnish copy to Albemarle. Albemarle would not be party to this Agreement, but relies on prior -recorded instruments — see item iii. If Applicant is aware of an implicit right to rely upon the existing dry detention basin exists (via recorded instrument), please advise Engineering so we may forward document/s to county attorney's office for their review. The supplemental narrative has been added as requested to the calculations packet. The owner/engineer are working with the County regarding legal documentation. Rev. 1 : Need for Agreement persists. Note: Albemarle is not party to the Agreement. Noted. The owner is currently working on preparing all required easement plats and agreements needed to complete the work within the offsite basin. 4. Calculation packet/Additional: c. Separate post-DEV offsite drainage areas into discrete areas since CN / Tc differ for off -site DAs. iii. Notes: 4. To the extent Berkmar Self -Storage relies on off -site dry detention (Keglers) for water quantity compliance, Applicant should furnish notarized Agreement between Berkmar and Keglers. Agreement should outline shared maintenance responsibility for the off -site SWM facility (Ex. detention). Initial WPO plan indicates that the existing detention basin cannot provide detention for Berkmar Self -Storage without structural modification [Stormwater Narrative, sheet C6.31. Applicant will coordinate this item with the County. Rev. 1 : Persists. Note: Agreement is between Berkmar and Keglers, and not Berkmar and Albemarle. Applicant will continue to coordinate the required agreements with adjacent landowners and the County. It is our understanding the basin is currently maintained by the County and it will continue to be maintained by the County long-term. 5. If on -site SWM is required, a recorded SWIM facility /public drainage easement plat (with deeds) is required for VSMP /WPO plan approval. Acknowledged, our intention is to use the offsite detention pond. Rev. 1 : Persists. No on -site SWM is proposed. However, the owner is currently working on preparing all required easement plats and agreements needed to complete the work within the offsite basin. 6. If on -site SWM required, please include Construction Record Drawings As -built for VSMP on the plans, as well as practice -specific SWIM installation, periodic inspection /maintenance information on the plans. Acknowledged, our intention is to use the offsite detention pond. Rev. 1 : Not addressed, unless overlooked. Please direct reviewer to location/sheet # of .PDF on plans. No onsite SWM is proposed. However, the .PDF has been added to sheet C1.1 and is referenced on sheet C6.3. 9. New: Unless discharge at Str. 100 is to a manmade channel, EB applies at Str. 100. Please make provision to extend manmade channel from Str. 100 to dry detention basin which straddles Kegler's and Lowe's parcels. This plan does not meet EB requirements at Str. 100, but appears to meet EB at outfall of dry detention basin. Between Str. 100 and the detention basin, please show compliance with state stormwater channel protection requirements for storm runoff release to a manmade channel (riprap ditch); 9VAC25-870-66.B.1. Improvements have been shown within the channel noted and additional description has been added into the stormwater narrative. ADDITIONAL COMMENTS FROM 12/15/2022 EMAIL • Greg Harper /Water Resources approval is paramount. WR maintains facility. Noted. We will continue to work with you on an agreeable solution. • (photo A) Avoid replacing 18" DIA pipe, since this pipe is 12'-14' below grade. The ex. extended detention basin is stable at pipe inlet; replacing 18" w/ 15" DIA will likely de- stabilize. Can achieve same or better effect with Alt. design (riser w/floor at 18" inlet). The design has been updated to avoid replacing the ex. 18" pipe. • (photo B) Alt. design: MH-sec. riser with low -flow /mid -flow orifice, or weir plate, with trash rack top, to achieve energy balance /10-yr flood protection downstream of Ex. basin. The design has been updated in general accordance with what is described here. • Please report 100-yr WSE in ex. basin —if routing is overlooked in calc. packet, please direct me to it (.PDF p. #). 100-year WSE, 478.14', has been added to the plans and calculations. The project causes a rise in the 100 -year storm where two -feet of freeboard is no longer available. The berm has been proposed to be raised to maintain two -feet of freeboard. • (photo C) Albemarle requests evaluation of slope embankment stability upslope of Playful Learners. SWM detention basin has no overland relief. A geotechnical evaluation is being conducted and will be provided prior to approval, but is not included with this submittal. • (photo D) Facility currently does not stage; rather watershed runoff simply transits existing detention basin (Kegler's) with marginal /no detention. It was noted in follow-up conversations the basin hasn't been observed during heavy rainfall so staging is really unknown. • Confirm design is based upon actual As -built field survey of Kegler's. Confirmed. Volumes used are based on as -built information. • (photo E) Provide riprap throughout existing incised channel/s, within basin. Riprap has been added to the channel as discussed. • (photo F) Preserve /protect slope, stone /bedrock in vicinity of 18" pipe inlet. Noted; design has been updated based on additional conversations. • (photo G) Provide riprap from Kegler's to point of discharge from Berkmar self -storage parcel, TMP 04500-00-00-11200; it must be a manmade channel all the way. Riprap has been added to the channel as discussed. • (photo B) Improved trash collection; example: 'kennel' chain link enclosure, concrete slab with downturn to limit heavy debris collection typ. of this facility (plastic, bottles, debris). Trash collection has been improved based on follow-up email on 1/31/23. • Improved access to ex. detention basin interior. The previous low point is proposed to be backfilled to eliminate the steep slopes down to the outfall pipe as per follow-up discussions. D. Erosion and Sediment Control Plan (ESCP) No remaining comments. Note: Revisions to the ESC plans and narrative have been made to reflect the latest plans. 'Next Steps' after WPO plan approval Thanks for the reminders on next steps. We will begin to get ready to complete nutrient credit purchase and easement plats so they are ready when no comments are left on the plans. We have included PDF copies of the plans for your review. If you have any questions or comments, please feel free to give me a call at 434.295.5624 or email campbell.boltonPtimmons.com. Sincerely, Empbel�, PE — Project Manager