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Location: Buffalo Lake Road, Harnett County, NC
Owner: Allied Development, Inc.
E. Frank Weaver, 1H - President
350 Wagoner, Drive
Fayetteville, NC 28303
Phone: 910 -433 -0888
Consultant: Chandler Engineering, PA
Jim Chandler, PE
309 S. Fuquay Avenue
Fuquay- Varina, NC 27526
Phone: 919- 390 -4227
Project Description and !Narrative:
The proposed project is inside Harnett County's jurisdictional limits and is located along Buffalo
Lake Road, approximately 1.7 miles south of the intersection of Buffalo Lake Road and NC Hwy 27.
The site is immediately adjacent to the Food Lion grocery store located at 1655 Buffalo Lake Road.
The scope of this project will include the construction of a 8,250 sf Family Dollar Store. The overall
design and permitting for this project is being completed by Dan Miller of Withers & Ravenel. They
are coordinating the required planning approvals through Harnett County and erosion control
approvals through NCDENR Land Quality Section. Copies of their appropriate sheets are included in
the plan sets. Our firm is responsible for handling the permanent stormwater management design for
this project and its placement on the adjoining tract owned by our client noted above. The reason for
this is that the balance of the tract, +/- 300 acres, owed by Allied Development, Inc. is currently being
master planned by our office as a PUD submittal to Harnett County to develop +/- 8 acres of further
commercial area, +/- 100 apartment units and +/- 200 single - family residential lots. This will be
designed to County standards to include curb and gutter and thus will require a high density permit.
At this time the stormwater management will be dealt with regionally and will include the current
development of the Family Dollar Store by Withers & Ravenel. Until such time, it is the intent to
develop a temporary, acting as permanent, device to handle their immediate needs. Amanda Bader,
Stormwater Administrator for Harnett County, is aware of our plans and has approved this approach.
The site is comprised of 1.19 aces but also includes an off -site driveway extension that comprises
another 0.47 acres creating a total drainage area of 1.66 acres which has been accounted for in our
design. The site discharges by three methods, a driveway stub for future connection, a pipe system
discharge and a proposed roadside swale. We account for collecting and treating all drainage into one
elongated infiltration basin.
There are no known wetlands, endangered species or flood plain located on this site. A copy of the
USGS map is included that shows the site drains to an un -named tributary to Mire Branch Creek, a
part of the Cape Fear River Basin. Also included is a letter from a licensed soil scientist confirming
that no wetlands exist.
The Natural Resources Conservation Service (MRCS) web based soils report has been used to identify
that the onsite soil types are Lakeland Sand which is a Hydrologic Soil Group type "A ". A copy of
this mapping is included. This has also been verified by the soil scientist that performed the
infiltration testing on site. A copy of their report is also attached.
The portion of the site being treated drains via slight sheet flow from north to south. A drainage area
delineation is included on the plan sheet. Since the site area is so small, a Tc of 5 minutes has been
assumed.
An infiltration basin will be used to treat the new impervious area added to the Family Dollar site and
the off -site driveway extension. Dewatering calculations are provided to demonstrate that the basin
will completely drain within 5 -days.
The bottom surface area of the proposed basin will be 1,885 sf so only (1) infiltration test is required.
However due to the length of the proposed basin, two (2) on site infiltration tests were performed.
The results from these tests provided infiltration rates of 8.07 in/hr and 8.65 in/hr. The high number
was thrown out and 8.07 in/hour was used for the routing calculations. The testing also reported that
the SHWT elevation was not encountered within 12 -feet of existing grade. Therefore, a separation of
more than 2 -feet is being provided.
Since this will be a temporary, acting as permanent, device, we wanted to avoid the implementation of
a bypass system or a vegetative filter strip so the basin has been design to handle the 10 -year event
using half of the tested infiltration rate.
The County, due to downstream concerns in this area, also requires that the 100 year event be
managed and reduced. Precipitation values were obtained the NOAA web site and are included.
Pond Pack software was used to calculate the HGL rates using the SCS Method. A report of all the
calculations is included and construction details are shown on the plan sheet.