SW3230601_Stormwater Narrative_20230626

Denver Fitness Facility
PROJECT NARRATIVE
Project Description
The purpose of this project is to develop a commercial fitness facility.The site is being designed with a
proposed sand filter SCM per the NC DEQ Post Construction Stormwater Section design manual
guidelines.Approximately 4.1 acres will be disturbed during this construction period.The site is 3.568
acres located on N. NC Hwy. 16 Business in Denver, NC and Lincoln County(See Vicinity Map).
Site Description
The site has minimal rolling topography with slopes from 2 to 6%with a ridge line running through the
middle of the property from south to the north and ending prior to the northern property line.The site
is a vacant commercial lot with existing developed commercial properties surrounding the property with
grassed field and heavily wooded cover on the lot.The site drains to the north and west of the parcel
with the drainage flow eventually to Forney Creek to the west of the project site.
Post Construction Stormwater
The property has two sections of stormwater treatment requirements.They are the WS-IV/P for
Watershed Areas by the County and a Post Construction Stormwater Area by the NC DEQ. See proposed
plans for delineation line shown for these areas. With both areas of regulation,the project designer has
chosen to submit a plan inclusive of both areas to NCDEQ for review and compliance with the use of a
single Sand Filter with the smaller project site. Drainage from the site and the additional off-site
drainage area is being diverted by catch basins around the building to the sand filter forebay. In
addition, a drainage swale near the northern property line diverts the remaining flow to a catch basin
that flows under the entrance drive to the sand filter forebay.The Stormwater Drainage Sheet C-5
delineates the Drainage Area with the additional area of impervious surface that is not able to flow to
the sand filter for treatment.This was a recommendation by the NCDEQ review(Jim Farkas) for extra
treatment volume in the sand filter for compensation of the untreated impervious area. After the
treatment volume reaches the sand filter it is first treated in the forebay for sediment retention and
then is diverted through a perforated riser to the sand filter chamber for final treatment by infiltration
through the sand filter. Bypass flow(Q10)will be diverted through an emergency overflow spillway
(vegetated) and a primary open weir box for smaller storm events and better connection for the
underdrain system.
Soils
See following sheets for Web Soil Survey information and location on tract.Also,see the soil site soils
report by Catawba Valley Engineering&Testing for detail information.