SW4240501_Stormwater Narrative_20240819

Hugh Creed Associates, Inc. P.A.
Consulting Engineers & Land Surveyors
1306 W.WENDOVER AVENUE P.O.BOX 9623
GREENSBORO,N.C. 27408 GREENSBORO,N.C. 27429
TELE:[phone] OR(336)275-8084 FIRM LICENSE#C-0551
E-MAIL:[e-mail]
August 16, 2024
Reserve at Old Hollow: Narrative, Calculations and Accompanying
Documents
Table of Contents
1. Stormwater Narrative
2. Stormwater Management Permit Application Form
3. Supplement EZ Form
4. Wet Pond #1 Calculations, Supplement Form
5. Wet Pond #2 Calculations, Supplement Form
6. Hydrographs, Pond Routing
7. Operation & Maintenance Agreements
8. Deed Restrictions & Protective Covenants Form
9. USGS Map
10. Current Deed
11. "YP Walkertown LLC" Annual Report
NOTE: See Construction Plans for additional details

Stormwater Narrative—Reserve at Old Hollow
1. Project Description
This site is a 15.20 acre parcel that is entirely wooded. The parcel contains an existing gravel
drive providing access to an adjacent parcel.
Runoff on the property generally falls to the east and west from a large ridge in the center of
the property. Most of the northern half of the property collects into an existing drainageway
exiting to the east. Runoff to the west drains to roadside swales along NC-66.
100 townhouse units and 4 private roads are proposed for this site.
2. Conveyance of Stormwater
Stormwater runoff will be conveyed by underground stormwater systems to (2) wet detention
ponds. Gutter downspouts will either tie directly into proposed storm pipes, discharge into
swales or onto ground so that flow travels into roadway.
3. Watershed Control Device
Quality Control
The stormwater through each Wet Pond will first enter a forebay to allow sediment to settle
and create non-erosive flows into the main pool. Runoff will then travel into the main pools
where it will be detained until water quality volume requirements are met.
Quantity Control
Reduction of the 1-year, 24-hour storm is required for the site. This analysis was completed as
follows:
Pre-Development Flow:
Drainage area for each pond outlet was delineated in the pre-development condition. The
overlap of the pre-development drainage area of the outlets and the post-development
drainage areas of the wet ponds were compared.
The pre-development drainage area of Wet Pond #1 outlet was directly compared to the
outflow of Wet Pond #1. The pre-development drainage area of Wet Pond #2 was combined
with the pre-development drainage area of Wet Pond #1 and compared to the combination of
Wet Pond #1 and Wet Pond #2 outflows.
CN —Woods, Good Condition, Hydrologic Gorup B Soils = 55
Wet Pond #1: 1-year, 24-hour storm peak flow = 0.245 cfs
Wet Pond #2: 1-year, 24-hour storm peak flow = 0.019 cfs

Combined Pre-Development: 1-year, 24-hour storm peak flow = 0.257 cfs
Post-Development Flows:
1-year, 24-hour storms were routed through each wet pond.
CN — Built-Upon Area = 98
CN —Open Space, Good Condition, Hydrologic Group B = 61
Wet Pond Peak Flows
Pond Runoff into Pond Runoff out of Pond Max. Elevation
Wet Pond #1 6.921 cfs 0.094 cfs 963.67
Wet Pond #2 11.02 cfs 0.179 cfs 944.48
The combined hydrograph flow of both Wet Ponds is 0.273 cfs, less than 10% more than the
0.257 cfs pre-development flow.