SW4201101_Post_Construction_Stormwater_Cover_Letter_20201124

DocuSign Envelope ID: 73DF71321-A286-472A-A975-FCA4AEF4C149
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November 14, 2020
Division of Energy, Mineral & Land Resources
Stormwater Program
1612 Mail Service Center
512 North Salisbury Street
Raleigh, NC 27699-1612
RE: POST CONSTRUCTION STORMWATER PERMIT FOR HERITAGE OAKS SEC II
This narrative is provided for background and additional information on the post construction
stormwater submission for Heritage Oaks, Sec 11 residential subdivision.
BACKGROUND
The site is located in Forsyth county at the terminus of Heritage Oaks Lane, a residential
subdivision developed in the late 1980's. This site is zoned residential single family (RS-9) and
the developer/owner has a home within the tract to be developed. Forsyth County/Winston Salem
planning board approved a site plan for the extension of Heritage Oaks Lane and an
accompanying major subdivision on May 10, 2018 and further revised a minor change for lots
44-45 on February 10, 2020.
The development plan indicates 27 lots with less than 24% impervious coverage and 1.7 lots per
acre for low density development. The site permitting for erosion control, streets, and public
water and sewer utilities has been completed and the first section of infrastructure has been
installed. At the time of plat review for the first phase of 10 lots it was discovered the post
construction stormwater permit has been overlooked. This submission is to ensure the remainder
of permitting is completed prior to platting and conveying any lots.
The pre -constructed site is a combination of open grassed areas and mature tree stands. The
post -constructed site is planned to minimize grading of lot areas and removal of existing trees to
the maximum extent practical.
STORMWATER CONVEYANCE
The undeveloped areas of the site outside of the planned right of way area are covered in mature
grass and trees. Stormwater outside of the right of way is planned for existing surface flows to
remain the maximum extent practical.
The stub street to the site and the site itself is 20' ribbon pavement streets with side ditches.
Water is conveyed across intersections and periodically from ditch lines between lots using open
throat catch basins and pipe. The pipe runs are limited with the primary method of conveyance
being performed via grassed ditch lines.
PO Box 669 Walkertown, NC 27051 336-748-0071

DocuSign Envelope ID: 73DF71321-A286-472A-A975-FCA4AEF4C149
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STORMWATER CONVEYANCE (Cont'd)
Where street grades exceed 5% and erosive velocities are calculated in the ditch line, an
appropriately specified matting (Excelsior 11) is planned to protect underlying soils from erosion.
At the end of piped outlets, wide ditch lines/swales are planned also with specified outlet
protection and channel matting.
Sheet C-4.0 outlines the drainage areas and shows 10yr storm event calculations for expected
ditch line volume, velocity and stability/matting needed throughout the street and conveyance
system. The first 400' of street/ditch line entering the site has 6-8.75% grades. The remainder of
the street/ditch line grades are 1-1.25%.
The grassed conveyance system within the right of way and the existing site conditions outside
of the right of way provide for the maximum extent practical length of conveyance for cleaning
water prior to reaching the site boundaries.
Best Regards ,.�```��. •• s s•,�
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Alex Carter, PE c
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11/14/2020
PO Box 669 Walkertown, NC 27051 336-748-0071