SW4230601_Stormwater Narrative_20230911

Stormwater Treatment and
Management Narrative
Brentwood Park — Phase 9
Forsyth County, NC
JEG Job No. 20090
June, 2023
Brentwood Park Phase 9 is a single-family detached subdivision located near Rural Hall
in Forsyth County. The proposed 36 lot subdivision is owned by Brentwood RH, LLC, and
is located on 23.9 acres within Brentwood Park. Entrances to the site will be provided off
of Brentwood Park Lane, Brentwood Park Place, and Spruce Pine Court. The site is
located in the Roanoke River Basin. Trick-urn Creek and several unnamed tributaries are
located on the site. The NCDEQ-DWR has classified Trick-urn Creek as Class C waters.
The site is located within a NPDES Phase II area. With a density of 1.5 dwelling units per
acre, and a built-upon area of 22.0%, Brentwood Park Phase 9 is a low-density
development.
The roadway system consists of 22-ft wide ribbon paved roads with vegetated side
ditches designed to North Carolina Department of Transportation standard for future
acceptance into their system. The proposed water system is designed to Winston
Salem/Forsyth County system public standards and consists of 6-inch and 8-inch D.I.
water lines with hydrants, valves, and water services. Sewer service will be provided by
individual private septic and ground absorption systems on each lot.
Site grading on the 23.9-acre site has been limited to 6.4 acres within the roadway limits
and areas required for three temporary sediment basins. There are indications that
grading at the site was initiated at some time in the past as evidenced by partial road
grading and remnants of sediment basins. A stream and wetland determination was
conducted by Pilot Environmental, Inc. at the site. A copy of the report is attached for
reference, which includes soil information/maps, and a USGS location map. Construction
of new homes and roads will take place on higher ground, resulting in no impacts to
stream or wetlands identified in the report. 30-ft undisturbed buffers have been proposed
along all perennial and intermittent streams identified in the report.
Vegetated roadside ditches are utilized along all roadways. A bottom width of 1 .0-foot
with side slopes of 3:1 is utilized on each side of the ditches. Calculations are included
that show no erosion should occur during the 10-year storm event.
Riprap stormwater outlets have been engineered to prevent downslope erosion at all
discharge points while also creating dispersed flow.
All built upon areas within this development discharge into vegetated swales of varying
lengths from 100 to over 400 feet. Due to the size of the drainage areas. storm inlets and
additional piping is required to provide for shallower flows and reduce the potential for
future soil erosion. Since the piping is in excess of what is typically considered incidental
piping, we have added two curb outlet systems at the larger storm discharge locations.
The combination of the vegetated swales and curb outlet systems should provide for
equal or better-quality runoff than if the site had only incidental storm piping.