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HomeMy WebLinkAboutWPO202000010 Correspondence 2020-06-08 (3)SHIMP ENGINEERING, P.C. Design Focused Engineering June 4t", 2020 Emily Cox, County of Albemarle Department of Community Development 401 McIntire Road, Room 227. Charlottesville, Virginia 22902 Regarding: WPO2020-00010 - Stoudt Property — VSMP Comment Response (Revision 3) Dear Ms. Cox, Thank you for your review of the latest revision of the VSMP Plan for the Stoudt Property. We have reviewed and revised the plan per the your most recent comments dated June 41h, 2020. See below for detailed responses to each of your comments. 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 ESOP, (3) a SWMP, and (4) any TMDL measures necessary. 1. What is the correct title for this project? It was listed as Lithic property, Stoudt property and Lithic Stoudt Handy on all different documents. Rev. 1: Comment addressed. 2. Rev. 1: Section 9, signed certification, must be signed. Rev. 2: Comment Addressed B. Pollution Prevention Plan (PPP) The PPP content requirements can be found in County Code section 17-404. Please double check the PPP provided in the SWPPP book to ensure all items apply to this site. Also, a lot of items note that they are shown on the plan, but they are not currently shown on the plan. Rev. 1: Comment addressed. 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. Proposed open space should be labeled as "SWM Forest & Open Space." Any Forest and Open Space used in the VRRM worksheet will need to be shown on an Easement Plat and labeled as 'SWM Forest and Open Space'. Land disturbance permit cannot be issued until the plat is recorded. Easement plat application can be found here: http://www.albemarle.org/upload/images/forms center/departm ents/Communitv_Development/forms/Subdivision_ Applications/E asement Plat & Checklist. Rev. 1: Comment response says credits will be purchased, but section 5 of the SWPPP says that open space will be used and Sheet C5 and calculations packet narrative says that nutrient reduction will be achieved by the vegetated filter strip. Please clarify. Rev. 2: Comment addressed. 2. The following note will need to be placed on both the VSMP plan and the Easement Plat: "The SWM Forest and Open Space Easement is subject to the guidance set forth by DEQ in the Virginia Stormwater Management Program. The areas will remain undisturbed in a natural, vegetated state, except for activities as approved by the local program authority, such as forest management, control of invasive species, replanting and revegetating, passive recreation (e.g., trails), and limited bush hogging to maintain desired vegetative community (but no more than four times a year)." Rev. 1: Comment response says credits will be purchased, but section 5 of the SWPPP says that open space will be used and Sheet C5 and calculations packet narrative says that nutrient reduction will be achieved by the vegetated filter strip. Please clarify. - Ref: Response 1 above. - Rev. 2: Comment addressed. [Sheet C2 and cover sheet] Existing contour elevations do not appear to match County GIS. Please check the information and provide a date the topographic information was obtained or field verified. Rev. 1: Comment not addressed. County GIS shows elevation of 612 surrounding the house, your contours are in the 400's. 4. [Sheet C2] Please show the 100ft WPO buffer. The stream is. This survey was done using an assumed data benchmark. The benchmark assumed elevation is at 500.0. See cover sheet for Surveyor Information. 4. [Sheet C2] Please show the 100ft WPO buffer. The stream is shown. Rev. 1: Comment addressed. 5. Rev. 1: Sheet C2 should not show the proposed buffer since it is existing conditions. Sheet C2 has been revised accordingly, the proposed buffer is not shown now. Rev. 2: Comment addressed. 6. Rev. 1: Ensure appropriate grading is used and shown for drainage area maps (for example, proposed grades should be used for the post-dev drainage area maps. This has been shown for drainage area maps. Rev. 2: Comment addressed. 7. Rev. 1: Provide all required design information for the vegetated filter strip per Practice 2 in the BMP clearing house: https://www.swbmp.vwrrc.vt.edu/ Table 2.3 (Filter Strip Design Criteria) of the VIRGINIA DEQ STORMWATER DESIGN SPECIFICATION No. 2 Handbook has been added on the sheet C4. Rev. 2: Comment not addressed. Table 2.3 was provided on the plans, but specifications were not met (length of filter strip, slope, soil amendments). Was an exception request submitted? Rev. 3: The design did not meet specifications and the waiver/exception was denied. Response: The vegetated filter strip is no longer proposed as a means of water quality management. The 0.25 lbs/yr of required reduction has been addressed through the purchase of nutrient credits. The Nutrient Credit Availability Letter has been included in the SWM Packet. Rev. 1: Ensure maintenance requirements for the filter strip are shown on the plans. Section 9.1 of the VIRGINIA DEQ STORMWATER DESIG SPECIFICATION No 2 Handbook has been added on the cover sheet. Rev. 3: Comment addressed C. 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. [Sheet C3] The landscape buffer is outside the limits of disturbance. Will this land need to be cleared for planting? Please add a note so the contractor knows not to disturb the area. Rev. 1: Comment addressed. 2. [Sheet C5] Please provide the paved wash rack detail from the design standards manual, page Rev. 1: Comment addressed. 3. [Sheet C6] Please show that the DA to the silt fence complies with requirement of/a ac per 100 ft of silt fence. Rev. 1: Comment not addressed. Plan shows 0.3lacres/100 ft, when only 0.25 (1/4 ac per 100 ft) acres is allowed. Based on the silt fence length of 255 ft, only 0.64 acres of Drainage is allowed. There is 0.78 currently shown. Rev. 2: Comment addressed. 4. [Sheet C6] Ensure the diversion has an adequate outfall. VESCH 3.12 says, Outlet Diversions shall have adequate outlets which will convey concentrated runoff without erosion. Acceptable outlets include STORMWATER CONVEYANCE CHANNEL (Std. & Spec. 3.17); LEVEL SPREADER (Std. & Spec. 3.21); OUTLET PROTECTION (Std. & Spec. 3.18); and PAVED FLUME (Std. & Spec. 3.16). Rev. 1: Comment not addressed. Silt fence cannot be the outfall of a diversion channel. Rev.2: Comment addressed. 5. Rev. 1: VDOT permission will be necessary for the construction entrance. Rev. 2: Comment addressed. Please note that various correspondence has occurred regarding this project that is not encompassed by the comment responses provided above. Most importantly, the Vegetated Filter Strip is no longer proposed as a means of addressing Stormwater Quality Requirements. The requirements are now met through the purchase of 0.25 nutrient credits. The pervious berm and gravel filter strip have been removed from the plans, leaving the vegetated landscaping strip area as originally proposed. The Stormwater Quantity has been addressed throughout the plans by describing both the increased volumes of sheetflow to the strip, how the strip will affect the sheetflow and the potential for impact of downstream properties from the increased sheetflow. Please see summary of stormwater management plan on Sheet C5 of the VSMP. If you have any questions or concerns about these revisions, please feel free to contact me at michael@shimp-engineering.com or at 434-227-5140 and we can discuss any questions that you may have in further detail. Regards, Michael Chandler Project Engineer Shimp Engineering, P.C.