SW6191205_2019.12.10 Narrative for NC DEQ _12/18/2019

PROJECT: SPECIAL OPERATIONS FORCES DINING FACILITY
ABERDEEN TRAINING FACILITY, FORT BRAGG, NC
ABSTRACT
A dining facility, consisting of a single -story concrete slab -on -grade building, is proposed for the
Ft. Bragg Arbedeen Training Dining Facility located in Hoke County within Arbedeen, NC. In
addition to the proposed building, other improvements are proposed to include a new service
driveway, pedestrian access and storm water management facilities. The project site consists of
approximately 1.07 acres. The site is south of Rockfish Creek on the west of King Rd and
northeast of Memory Lane. The streets to the north and south are not named. The site is roughly
1.3 miles away from Lake McPhaul. A location map is included below for reference.
Aberdeen
Cake Park
Aberdeen
E5
x+ea
0 and
inn
Project Location
EXISTING CONDITIONS
An asphalt parking lot and a concrete dumpster pad surrounded by a fence exists on the site.
Several utilities run through the site as well. Both the above and below grade improvements will
be removed or relocated for the proposed building footprint. Un-named roads exist north and
south of the proposed building. A grade break exists along the northerly side of the parking lot,
leading to Swale along the northerly limits of the site. An aerial photograph of the existing site is
provided on the following page.
Woolpert Arbedeen Training DFAC
Design Narrative Hoke County, North Carolina

PROPOSED CONDITIONS
An overall site plan is included within the Construction Plans. The road that exists on the
northern side of the building must have a section of the concrete curb removed for the proposed
driveway connection. A service drive will connect to the existing road south of the proposed
building. East of the existing asphalt parking lot is a concrete sidewalk which also must be
removed as part of the redevelopment. The proposed building displaces the existing parking lot.
Runoff from the site is directed into three detention and infiltration systems. In general, the site
and the storm water management system benefit from excellent hydraulic conductivity of the
soils consistent with the site location. The infiltration rate is based upon field testing performed
by the geotechnical engineer. The conductivity is a key factor as both the basis of design and in
meeting the requirement of the Energy and Independence Security Act.
The first detention and infiltration system, located along the northerly limits of the site, consists
of an infiltration area with an overflow structure connected to the existing conveyance system.
Runoff from the flat, central section of the building roof will drain through a combination of
rooftop drains leading to the northerly infiltration area. The sloped portion of the roof will be
conveyed via downspouts to splashpads located around the building.
The second detention and infiltration area is located in the northwest portion of the site, receiving
runoff from the proposed service driveway via a concrete flume. This detention and infiltration
area, which has less capacity than the other two areas, also serves to capture "debris" that may
unintentionally wash from the adjacent dumpster. Thus, service members and maintenance
personnel may be required to periodically remove said debris from the area for aesthetic and
functional purposes.
The northwest infiltration is connected via a 15" storm pipe to an underground detention and
exfiltration system located within the southwest portion of the site. Runoff is also conveyed to
Woolpert Arbedeen Training DFAC
Design Narrative Hoke County, North Carolina

this area via overland swales and a piped connection from the east. The underground detention
system consists of perforated pipe with open graded stone encapsulated in a geotextile to promote
infiltration. Excess runoff is directed to an existing storm drain to the southwest of the site.
A summary of the drainage areas is shown below:
SUMMARY (TOTAL) OF DRAINAGE AREAS
Post -developed Total Area 46,775 Sq. Ft.
Post -developed Impervious Area 28,503 Sq. Ft.
Post -developed Pervious Area 18,272Sq. Ft.
Post -Developed Percent Impervious 60.9 %
The maximum allowable discharge rate is equal to or less than that of the existing conditions.
The comparative computation is performed using Pondpack by Haested Methods. The analysis is
based on the SCS method for comparison of the existing against post developed flow rates.
The allowable and summation of the computed rate of discharge is as follows:
1 Year,1 day storm event —1.10 cfs (allowable) / 0.00 cfs (computed)
10 Year,1 day storm event — 3.62 cfs (allowable) / 0.77 cfs (computed)
25 Year,1 day storm event — 4.86 cfs (allowable) / 2.65 cfs (computed)
The design makes excellent use of the hydraulic conductivity found both in the region and
specific to the site, resulting in a net reduction of the runoff from the existing site.
G:\DE\Clients\Norfolk A-E 2017\7853C - Ft. Bragg ATF JSOC DFAC\9.0 Disciplines\1.0 Civil\Eng\Storm Design\Stormwat., management
report\2019.12.10 Narrative for NC DEQ .d"
Woolpert Arbedeen Training DFAC
Design Narrative Hoke County, North Carolina