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HomeMy WebLinkAboutWPO202200033 Correspondence 2023-03-17SHIMP ENGINEERING, P.C. Design Focused Engineering March 15, 2023 Mr. David James dlames2 kalbemarle.ora Albemarle County Building 401 McIntire Rd Charlottesville, VA 22911 Regarding: WP0202200033 —LOT A-13 BUN DORAN FARM Comments & Responses #2 Dear Mr. James, Thank you for your review the VSMP Plan for Lot A-13 Bundoran Farm. We have revised the plans per your most recent comments. Please see below for a detailed response to each of your comments. A. Stormwater Pollution Prevention Plan (SWPPP) The SWPPP content requirements can be found in County Code section 17AO5. A SWPPP must contain (1) a PPP, (2) an ESCP, (3) a SWMP, and (4) any TMDL measures necessary. 1. You are only required to complete the SF SWPPP. View template here. https://www.albemarle.org/home/showpublisheddocument/2662/6378655379265000 (Rev.1) Update with approved plan. Noted. B. Pollution Prevention Plan (PPP) The PPP content requirements can be found in County Code section 17AO4. 1. Provide PPP measures. ' I Appears complete, update to match approved plan. Noted. 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. 'over: Add WPO# to title. (Rev. 1) Addressed. 1. Level spreaders: Ensure design meets water quantity standards per BMP Spec. 92, Sec. 6.3. Including but not limited to: a. A bypass/overflow to pipe/channel will be necessary for design flows greater than the 1-in/hr storm or consider an alternate (LS) design. b. Provide a minimum 6' channel width from c/1 to lip. IRav 1) 1 aval znronrlor Hoc innc annaarfn ha arlaniiafa Prnvirla I S mainfannnra nInn A level spreader maintenance plan has been provided on sheet C5. See attached Exhibit A in this comment response. 2. Level .,,......... r C should be relocated outside of the stream buffer. Provide justifica...,., (Of reasonable use) to keep it there otherwise. (Rev. 1) Addressed. 3. Sheet C3, etc.: Ensure fill disturbance will be no more than 30 LF of stream. [17-604 C(3)] Acknowledged. More information about the installation is requested, see comment D.3. Acknowledged. 4 Q1, ')(, rz,,,.;— I noticed the 10-yr ditch velocities are lower than the 2-yr. (Rev. 1) Acknowledged. 5. Provide analysis of ditches specifically 4 &5: It is preferable to use more current and conservative rainfall values for ditch design and wondering how you arrived at those (Rev. 1) Addressed. 6. (Rev. 1) Provide predevelopment land cover information (Not shown on plans or with calcs). Need predevelopment information to make evaluation of how much increase in postdevopement runoff. After discussion with Justin Shimp, we understand this comment has been withdrawn as this is subject to a Stormwater Management Agreement For Single Family Residence Construction. (Rev. 1) Provide postdevelopment land cover with percentages of each cover type. After discussion with Justin Shimp, we understand this comment has been withdrawn as this is subject to a Stormwater Management Agreement For Single Family Residence Construction. 8. (Rev. 1) Water quality requirements will need to be met. After discussion with Justin Shimp, we understand this comment has been withdrawn as this is subject to a Stormwater Management Agreement For Single Family Residence Construction. 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. Provide county's paved construction entrance detail per ACDSM, p. 9. Construction entrance detail has been added on Sheet C9 (Rev. 1) Not addressed. — Details has been shown on Sheet C9. Provide culvert inlet trap design (DA>lac) & detail. [VESC HB, 3.08] (Rev.1) The DA received to the CIP is a bit high. Please provide check dams along ditches 2 & 4. Check dams along ditches 2 & 4 have been provided. Provide utility stream crossing (USC), VSS, SSS for culvert installation and bank Utility stream crossing detail is not provided because the stream is not going to be disturbed, the proposed pipe will be installed next to the existing pipe. (Rev.1) Not fully addressed. Provide more information about the culvert installation. What will prevent culvert from moving if not embedded? Provide photos of stream bank & ex. culvert. Cofferdam is mentioned in USC specs. Provide that installation and stabilization are met per the spec. More information about the culvert crossing expansion has been provided. See attachment to this comment response for recent site photos of the existing crossing. The new culvert will also be imbedded but not countersunk, it is added to provide conveyance for stormwater runoff, not seasonal baseflow. Thus, it will be installed outside of the existing stream waters, with an invert 0.2' higher than the existing culvert. This will then be backfilled. The new banks (only on the disturbed side, nearer to the property entrance) will be stabilized with rip -rap. The Sandbag Cofferdams are going to help to hold back water and allows a work area to be dewatered so that crews can excavate and install the new culvert. Notes preventing disturbance of stream waters are now added to the plans. stabilization & details. [VESC HB, 3.22, 3.23, 3.25] As noted above, no stream disturbance will occur. (Rev.1) Provide photos with measurements of existing crossing width and rock cover diameter. The existing crossing should meet the minimum specifications of 3.24 (SC) for construction vehicles. The current crossing is sufficient to meet the specs of 3.24 (SC) for construction vehicles. -The weir width should be 6 x D.A. (12.42-ft). A & C elevations should (Rev.1) Addressed. table. [VESC HB, 3.13] (Rev.1) Addressed. 7. (Rev.1) Sheet C2: Show existing treeline. Existing treeline has been shown in existing sheet C2. 8. (Rev.1) Note: Disturbance is over an acre and prior to land disturbance will need a DEQ SF CGP, SF SWPPP approved, EF ''PO plan approved, SW AGM- ,igned, and posted bonds. https://www.albemarle.org/home/showpublisheddocumeny2710/637867521357670 000 - SW AGMT Application has been signed. - Bonds have been provided in this application. See attached documents in this comment responses. F. Mitigation Plan (MP) itc but may need to be revised to address all comments. (Rev.1) Acknowledged. If you have any questions, please do not hesitate to contact me at odria@shimp-engineering.com, or you may contact Justin Shimp at Justin@shimp-engineering.com or by phone at (434)-227-5140. Best Regards, Odri Barefoot -Diaz Shimp Engineering, P.C.