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HomeMy WebLinkAboutWPO202000015 Calculations 2020-06-08SHIMP ENGINEERING, P.C. Design Focused Engineering June 8', 2020 Emily Cox Civil Engineer II County of Albemarle Department of Community Development 401 McIntire Rd Charlottesville, Virginia 22902 Regarding: Response Letter # 1 for WPO2020-00015 - VSMP Plan Perry Residence (Revision 2) Dear Ms. Cox, Thank you for your review of the VSMP Plan for Perry Residence. We have revised the plans per your most recent comments dated May 22"d, 2020. We have provided below, detailed responses to each of your comments. 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 ESOP, (3) a SWMP, and (4) any TMDL measures necessary. 1. This SWPPP book must be updated with the approved plan sheets at time of approval. Comment acknowledged. 2. Rev 1: Please ensure the correct names are on section IA and VI. It is unclear if they are the same. The correct names are included in sections IA and VI, they are not intended to be the same. Pollution Prevention Plan (PPP) The PPP content requirements can be found in County Code section 17-404. What is the star hatching for? It is unclear in the legend. (Forest & open space, correct?) Comment addressed. EC-2 matting is shown in the legend, but it is not clear where it is used to be on the plan.(appears to be a scaling issue) Comment addressed. 3. Ensure all PPP items are shown on the plan (stockpile, staging area, etc.) 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. The dedicated open space must be in an easement and should be labeled SWM Forest & Open Space. The following note should be on the plan and 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)." Comment addressed. 2. The forest and open space easement must be recorded before plan can be approved. Acknowledged, the Forest and Open Space easement will be recorded. An easement plat has been submitted to the County for review and recordation. 3. SWM maintenance agreement must be recorded before plan approval. Please contact Ana Kilmer (akilmer@albemarle.org or 434-296-5832 ext. 3246) to begin this process. Acknowledged, the SWM maintenance agreement draft has been provided to Ana Kilmer. 4. Please clarify calculations, for example, there are 4 POAs in HydroCAD output, but there are 3 in the plans. It appears DA 2 & 3 go to POA 2 (LS #1). Please ensure the calculations match this. Comment addressed. 5. Please provide culvert design information. Ditch calculations were provided, but not culvert calculations. Comment addressed. 6. Sheet C3] There appears to be work in the VDOT right-of-way. Has this been approved by VDOT? Construction cannot begin until appropriate VDOT permit is acquired. The contractor will apply for the appropriate permit for the extended entrance 7. [Cover Sheet] Provide date topographic information was acquired. Source was listed, but no date. Comment addressed. 8. [Sheet C3] Consider making slope on the NW side of driveway 3:1, not 2:1. Otherwise, special plantings that can withstand that slope must be specified. Comment addressed. 9. [Sheet C4] There appears to be an error in the level spreader detail and table. Dimension should be 3ft, not 3 inches. Also, length should be 36, not 35 ft. Comment addressed. 10. [Sheet C4] Drainage area to level spreaders does not appear to be correct. From calculations booklet, DA 2 & 3 appear to go to LD #1 (5.49AC), and DA 4 to LS#2(3.45AC). Or, if following the ditch drainage areas, LS #1 should have 1.09 AC, not 0.14 AC. Drainage areas have been clarified however the design DA for the level spreaders (on sheet C4) does not appear to be correct. LS #1 should be 5.5. ac and LS #2 should be 3.45 AC based on page 17 in the SWM booklet (post -development drainage areas). The level spreader drainage areas have been corrected on Sheet C4. 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. Please provide the paved CE w/ WR detail from the design standards manual. Comment addressed. Provide silt fence for perimeter controls adjacent to the road. Comment addressed. Provide controls for the culvert at the driveway entrance. Please clearly specify the details for outlet protection (sizing, dimensions, etc.). The outlet protection details have been provided on Sheet C4 and C7. 4. The driveway culvert that outlets into ditch 1 should have outlet protection, not inlet protection. Please specify the details for outlet protection (sizing, dimensions, etc.) The outlet protection details have been provided on Sheet C4 and C7. Provide a location for a stockpile area as well as a construction staging area. Comment addressed. If you have any questions or concerns about these revisions, please feel free to contact me at justin@shimp-en ing eerieg com or by phone at 434-227-5140. Regards, Justin Shimp, P.E Shimp Engineering, P.C.