SW6101104_Stormwater Narrative_20121221

Stonnwater Narrative
TUAS Support Facility
Fort Bragg, NC
The proposed TUAS Support Facility at Fort Bragg consists of an 11,250 square foot
training facility and an 870 square foot wash bay with associated parking and driveways.
The 6.35-acre site is located on the northern side of Pratt Street, approximately 1100 feet
east of the intersection of Pratt Street and Lewis Street, in Fort Bragg military base. The
site is currently lightly wooded with very gentle grades. Soils are sandy and very
permeable. Stonnwater runoff flows to Tank Creek to the east of the site.
The proposed stormwater system will incorporate grassed drainage swales around the
majority of the perimeter of the disturbed area and bioretention areas to promote
Qp infiltration, as we dry detention basiy , educe peak flow discharge. The proposed
disturbed area �s 3.14 cres and is rough 56% )mpervious. The majority of the
stormwater fro disturbed area will be ected into the grassed swales and
discharge to the large bioretention area. Overflow runoff from the bioretention pond will
be routed through the dry detention basin, and then discharged into the existing
underground storm drainage system.
The system was routed using Hydraflow software. The results for the 2 year, 10 year,
and 100 year storms are included in the stormwater calculations. The resulting peak
outflows (efs) are shown below:
1-Fear
Predevelopment 0.089
Postdevelopment 0.063
2-year 10-year 100-year
0.363 2.294 7.780
0.235 2.190. 11.16
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Notes for TUAS Support Facility Stormwater Certification
Noted Deviations:
1. The following plant species were used in the biorctention areas:
Shrubs - clethra alnifolia
iteavirginica
ilex verticiltata
Herbaceous - Baptisia australis ( false indigo)
chasmanthium latifolium (river oats)
coreopsis verticiltata ( moonbeam)
Supplemental Notes for Certification Requirements:
4. per the approved plans, the roof drains on the front of the building discharge into
an irrigation reservoir tank. All others are directed into the system.
7. No significant trash/debris is expected from the drainage area, therefore, no trash
racks were proposed.