Loading...
HomeMy WebLinkAboutSW6230703_Response To Comments_20231030 c, 4Dsite October 30, 2023 civil engineering I land surveying NCDEQ Division of Water Quality Attn: Brianna Holland 512 N. Salisbury Street Raleigh, NC 27604 RE: Storm water resubmittal, Brayden Preserve Subdivision, Cumberland County, North Carolina Brianna; We received the review comments dated October 3, 2023. The comments have been addressed as noted below. 1. Drainage Area a. For a low-density project like this, the "drainage area" of the low-density area is equal to the project area and excludes the surface water area. Please revise the Basin Information Table in Section IV, 10 of the Application, Supplement-EZ Cover Line 2, and Supplement-EZ Drainage Areas Lines 5-6 accordingly. See 15A NCAC 2H .1003(1)(c)(i). Updates made is requested 2. Supplement-EZ a. Drainage Areas, Line 18: Please provide. 3. Calculations a. Outlets must be stable per 15A NCAC 02H .1003(5). Riprap calculations were provided at discharge points with culverts, but stability must be demonstrated at all stormwater outlets. Provide engineering calculations exhibiting that where vegetated conveyance ends, the exit velocity for the design flow is nonerosive for the existing field conditions. Guidance for this can be found in the NC Erosion and Sediment Control Planning and Design Manual Chapter 6. https://www.deq.nc.gov/about/divisions/energy-mineral-andland- resources/erosionand-sediment-control/erosion-and-sediment-control- planning-anddesign-manual i. There are 2 storm outlet locations for the development. These are ditches 9 and 12. Calculations for both of these ditches were included in the original submittal. Both ditches are lined with a temporary erosion control matting. The velocity for Ditch #9 in permanent state is 2.64 fps and the same velocity for Ditch #12 is 1.93 fps. The velocities are less than the maximum allowable 409 Chicago Drive, Suite 112,Fayetteville. NC 28306 office I 910-426-6777 fax 910-426-5777 On time,every time. www.4Dsitesolutions.corn velocity. Unless I am missing something, these outlet ditches are stable and no additional work is required to satisfy this comment. Please provide electronic copies of the USGS topographic map of the site, NRCS soils map, the signed & sealed cover page for the calculations, the storm drainage/hydraulic grade line calculations and the property deeds. These items were provided in the hard copy submission but were not uploaded electronically. Please ensure that the electronic repository is complete. Items have been uploaded as requested 5. Provide PDFs of all revisions, 2 hardcopies of revised plan sheets, 1 hardcopy of other documents, and a response to comments letter briefly describing how the comments have been addressed. Done. No plan sheet modifications were required based on responses to comments. I look forward to working with you on this project. If you have any questions or concerns, please contact me at your earliest convenience. Sincerely, 4D Site Solutions, Inc Scott Brown, PE sbrown@4dsitesolutions.com Enclosure 2