SW6221004_Stormwater Narrative_20221021

Stormwater Narrative - Automotive Repair Shop Site Development for EEB Holdings, LLC.
EEB Holdings, LLC. intends to develop an automotive repair shop at 3563 Camden Road Fayetteville, NC
28306. The proposed property is 4.98 acres and zoned commercial but the site currently is
undeveloped, wooded land. When NCDOT widened Camden Road around 2017 for the super street
design, they acquired two permanent drainage easements on this parcel in which they placed drop
inlets storm drainage structures within each easement in order to accommodate for future
development, as the street's back of curb elevation was much higher than the site's existing
topography. The intent with this site will be to raise the site's building & parking area via grading it,
implement a storm network to convey the runoff to an infiltration basin stormwater control measure
for treatment. Any flow beyond the 1" treatment volume will be sent towards NCDOT's existing
infrastructure within Camden Road. Upon completion of construction, the intended built upon area
(the site's impervious area) will be 1.275 acres or —25.6% of the entire site's 4.98 acres between the
building, the parking lot area and the various concrete features such as the sidewalk along the front of
the building and the rear concrete delivery pad and potential future impervious areas. The drainage
areas tributary to the stormwater control measure will be 3.74 acres with all of the impervious area
treated by the SCM (1.275 acres) and giving its watershed an impervious percentage of 34.1%. The
remaining areas on the site will be completely grassed and shall continue to drain directly to NCDOT's
existing drainage infrastructure as it did before the site's development.
The site has gentle natural topography that ranges from 1-3% slopes of Lakeland Sand (hydrologic class
A) and falls from the rear towards the frontage along Camden Road — SR1003. A formal soil
investigation has been conducted for the site by a NC licensed soil scientist to determine the in -situ
soils ability to infiltrate (included in this package) and infiltration rates of 3.4 to 8.4 inches per hour
were observed where the intended infiltration basin stormwater control measure will be located.
Additionally, the seasonal high water table was found to be at elevation 205.46 which is over 24"
below the bottom elevation of the intended basin at elevation 208.25. Given the site's sandy nature
and upon analyzing the soils report, it was determined that an infiltration basin would be the most
suitable stormwater control measure for the site.
Attached to this package are the simple method treatment volume calculations, infiltration basin's
drawdown time with stage storage calculations, storm network pipe calculations, the site's
hydrographs, rip rap apron calculation, USGS Quad Map for the site, NCRS Soil Survey as well as the
site's soils investigation report, which was performed by a NC Licensed Soil Scientist. Please review
them and let me know if you have any questions — thank you.
Kenneth Smith Jr., PE PLS
Smith Site Consultants, PLLC. — NC Firm # P-2144
ASmithSite
CONSULTANTS, PLLC