SW3221004_Stormwater Narrative_20221012

PROJECT: MOUNT PLEASANT HIGH SCHOOL TURF FIELD
NARRATIVE
Proposed project is the installation of a synthetic turf field inside the existing running
track at Mount Pleasant High School off Walker Rd in Mount Pleasant NC (Cabarrus
County).
The area of work is primarily limited to the natural grass field inside the track perimeter.
The turf field scope of work includes installation of silt fence, inlet protection, removal of
existing organics and soil, compaction of subgrade, installation of perimeter curbing,
stone base, and synthetic turf. Scope of work also includes construction of new concrete
pole vault runway and landing pad outside the track.
High Jump Pad and Long Jump/Pole Vault runways to be reconstructed and surfaced
with synthetic track surfacing.
All spoils to be hauled to designated area on -site.
The total disturbed acreage for this project is 2.50 acres.
Based on USDA Web Soil Survey data the area soils primarily classify as MeD
(Mecklenburg), a loamy soil indicative of hydraulic group C.
STORMWATER NARRATIVE
Project is proposed as LOW DENSITY for the entire site. Total property area is 100.9
ac. There is 1.86 ac of surface water on the property resulting in a total site project area
of 99.04 ac. The existing BUA on the property is 18.80 ac based on aerial data. BUA to
be removed from within the proposed field area is 0.13 ac. The new BUA (Turf Field) to
be added is 2.35 ac for a net increase of 2.22 ac. The new BUA of the overall property
after the project is 21.22% [(18.80-0.13+2.35)/99.04] which is less than 24%.
New BUA will be dispersed into existing field drainage system and site conveyances
with no changes outside of the existing turf field. Artificial turf fields typically provide
reduced peak flows from that of typical impervious surfaces due to increased time of
concentrations. Post time of concentrations are often higher than that of pre -developed
Tc's. The turf system is typically modeled as porous pavement with the flow through the
stone base media as a function of Darcy's equation resulting in a reduction of peak flows
at outlets. This results in negligible peak flow impact to the existing drainage system and
conveyances.
Stream and wetland delineation was provided by Isaac Hinson PWS 91866.