SW4240203_Stormwater Narrative_20240515

DocuSign Envelope ID: 1F253CF5-32A9-4537-AAED-29CB1A82CD80
BEESOO BCRRTER, PR.
I !!1_ 10 CIVIL ENGINEERS LAND SURVEYORS
LAND PLANNING
February 14, 2024
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 HIDDEN WOODS VILLAGE
This narrative is provided for background and additional information on the post construction
stormwater submission for Hidden Woods Village residential subdivision.
BACKGROUND
The site is located in Forsyth County on Stanleyville Road(SR1920) across from Brookhill Park
Drive (SR4517). This site is zoned residential single family(RS-20) through the City of Winston
Salem,NC. The developer received a major subdivision approval for 25 lots by the City-County
Planning Board on June 17, 2008 and subsequently received site permitting and installed the
streets and water main from 2008 into 2009. The site then became dormant due to the economic
depression of that time. The site plan was recently revised to 20 lots by planning staff approval
to better match the existing septic soils available on site. The street configuration remains the
same as the pavement was installed in or around 2009.
The current site plan indicates 20 lots with less than 24% impervious coverage and 1.2 lots per
acre for low density development.
Based on historical aerial imagery, the site was timbered in 2006 and has now grown back in
thick, small stands of undergrowth, hardwoods and pines. The site areas for home building and
septic fields will be cleared of this thick re-growth. The post-constructed site is planned to
minimize grading and removal of existing trees to the maximum extent practical for home and
septic field construction.
STORMWATER CONVEYANCE
The streets are designed as 20' ribbon pavement streets with side ditches. The only intersection
is flat and has no cross piping installed from the 2008-2009 construction. The existing side
ditches will be fine graded to achieve a 3:1 minimum side slope where possible to maintain the
required NCDOT shoulder width against the pavement section. A 48" RCP pipe with concrete
headwalls was installed in a drainage area during the street construction in 2008-2009.
Stormwater for the public right-of-way is planned to be conveyed via vegetated side ditch
conveyances to the maximum extent practical. There is no existing or planned piping from the
side ditches. The ditch outlets will follow natural contours and be returned to sheet flows as
PO Box 669 Walkertown, NC 27051 336-748-0071

DocuSign Envelope ID: 1F253CF5-32A9-4537-AAED-29CB1A82CD80
BEESOO BCRRTER, PR.
CIVIL ENGINEERS LAND SURVEYORS
LAND PLANNING
quickly as possible. Piped conveyances will be utilized at some lots for driveway connections
crossing over ditch sections.
The drainage areas into the existing side ditches is limited to approximately 60-65' from the
street centerline into the side ditches. While some grading for driveway connections will occur,
it will have minimal impact on the drainage areas. The calculated velocities in all four existing
side ditches is under 5 FPS and erosion is not indicated for mature vegetated conveyance.
Sheet C-4.0 outlines the drainage areas. The l0yr storm event calculations provided as a
separate document indicate the velocities for all four existing side ditches are between 1.5 and
3.9 FPS. It is expected the side ditches will be cleared and fine graded for 4:1 fore slopes and
3:1 back slopes into a"V" shaped road side ditch section to meet NCDOT standards. The
ditches will be vegetated using permanent grass(es) to prevent erosion once mature vegetation is
established.
The grassed conveyance system within the right of way and outside of the right of ways are all
planned to be vegetated with grass to provide for cleaning and infiltration of stormwater to the
maximum extent practical.
0
Best Regards, ,�`'oe-`.. ' �//.
S AL
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•
Alex Carter, PE % � '• Nc i N E�..
/'"'in,unI III IIINN""
2/14/2024
PO Box 669 Walkertown, NC 27051 336-748-0071