SW4230701_Stormwater Narrative_20231107

DocuSign Envelope ID:32FDAAC7-F690-40D1-8649-072F4B5B7F8A
111110 BEESOO BCRRTER, PR.
CIVIL ENGINEERS LAND SURVEYORS
LAND PLANNING
April 12, 2023
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 HIGH MEADOWS, SEC II
This narrative is provided for background and additional information on the post construction
stormwater submission for High Meadows, Sec II residential subdivision.
BACKGROUND
The site is located in Stokes county at the terminus of Maverick Trail Drive, a residential
subdivision developed in the late 1980's thru late 1990's in various sections and phases. This
site is zoned residential single family(RS-20) through the City of King, NC and the
developer/owner has a site plan approved in January of 2022 by King Planning Board for the
final phase of work.
The development plan indicates 20 lots with less than 24% impervious coverage and 1.3 lots per
acre for low density development. The site permitting for streets,public water and sewer
utilities, erosion control and stream crossing permits (404/401) is under review.
The pre-constructed site is mature tree stands. The post-constructed site is planned to minimize
grading and removal of existing trees to the maximum extent practical.
STORMWATER CONVEYANCE
Stormwater for the public right-of-way is planned to be conveyed via vegetated side ditch
conveyances to the maximum extent practical. These side ditch profiles are planned for 3:1
minimum side slopes. Ditch line storm water will be conveyed at periodic intervals using piped
conveyance between lots to reduce the possibility of erosion due to excessive flows. Piped
conveyances will utilize designed stone aprons for outlet protection from erosion and to reduce
the velocities prior to entering vegetated conveyances with a maximum slope of 5% and a
minimum length of 100' prior to entering any stream. All conveyances are designed for a
minimum bottom width of 2' and maximum side slope of 3:1. The design of the conveyances is
to disperse the flows prior to the existing stream through the middle of the site.
The streets are designed as 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:32FDAAC7-F690-40D1-8649-072F4B5B7F8A
isi_110 BEESOO BCRRTER, PR.
CIVIL ENGINEERS LAND SURVEYORS
LAND PLANNING
STORMWATER CONVEYANCE (Cont'd)
Where street grades exceed 5% and erosive velocities are calculated in the ditch line, an
appropriately specified matting (Excelsior II or riprap) 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 l0yr storm event calculations for expected
ditch line volume, velocity and stability/matting needed throughout the street and conveyance
system. The majority of street and ditch profiles are under 3% grades. The street tie-in crossing
over the stream area has been designed to minimize grades to the maximum extent practical and
still meet required vertical profile design requirements for NCDOT and King,NC. Grades
around the stream crossing will exceed 10% and utilize riprap over filter fabric to protect ditch
lines from erosion.
The grassed conveyance system within the right of way and 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, o� .oF• E S s,o•• 2
',,9� •
• NG I"E �•••
Alex Carter, PE
....... un ��0
4/12/2023
PO Box 669 Walkertown, NC 27051 336-748-0071