NC0072575_Report_19941201 (2)

157
Evaluation of Drainage
Modifications on the
Overland Flow
Land Application System
Prepared for
Golden Poultry Co., Inc.
Sanford, NC
December 1994
ERM-Southeast, Inc.
300 Chastain Center Blvd.
Suite 375
Kennesaw, GA 30144

MCgGRovND AND OBJEC77VEs
A site inspection of the overland flow land application system at Golden Poultry Co., Inc'in
Sanford, NC was made on October 19 and 20, 1994. The purpose of the evaluation was to
review the storm water drainage patterns on the overland flow system and to provide
recommendations for the elimination of excess drainage through the effluent monitoring
station, where practical. For this exercise, excess drainage is defined as any storm water
which does not fall directly on any of the overland flow terraces or drainage channels'evaluation was conducted by comparing existing field conditions with construction drawingss
taking measurements where necessary, and examining erosion patterns. The attached figure
shows the existing overland flow terraces and drainage Patterns.
OBSMZVA77ONS
The overland flow system is surrounded by a perimeter road. Except for occasional flooding
by the Deep River, no storm water runoff appears to overflow the perimeter road into the
overland flow system. The area within the perimeter road is approximately 139.3 acres.
The overland flow terraces occupy 129.6 acres of this area. The internal road across the
system occupies approximately 0.4 acre and is included in this area as it was designed and
constructed as a part of terraces 9 and 10. The drainage channels and roadside slopes
external to the terraces, but draining into the overland flow system, occupy approximately
5.5 acres. Approximately 3.2 acres are occupied by triangular areas external to the terraces,
but draining within the system. In addition, approximately 1.0 acre of the triangular areas
and roadside slopes external to the terraces drain outward across the perimeter road rather
than into the overland flow drainage system. In summary, 138.3 acres of the 139.3 acres
within the perimeter road drain through the effluent monitoring station and all but 3.2 of
those acres, or a total of 135.1 acres within the perimeter road are a necessary part of the
overland flow system.
Four external sources of storm water also exist which enter the overland flow effluent
monitoring station. Up to approximately 2.0 acres of the perimeter road may contribute
drainage to the system. This area of road, varying from 10 to 15 feet in width, either slopes
toward the overland flow system or has no cross slope. The second source of external storm
water entering the effluent monitoring station enters the overland flow drainage channel
between the effluent monitoring station and the perimeter road to the north. Thick weeds,
brush, and trees prevented a determination of the area draining to this location, but the depth
of the stabilized erosion channel indicates it may occupy several acres; a very rough estimate
is less than 5 acres. The third source of external storm water going to the overland
system is from an approximately 0.8 acre area surrounding the smaller of the flow
ponds. The fourth source of storm water is approximately 5 acres of storage storage
Therefore, there is a total of roughly 10 to 12 acres of external storm water drainage
pond.
currently flows through the discharge monitoring station. In summary, a drainage which
150.3 acres drain through the effluent monitoring station, of which 140 total of 148.3 to
approximately 94 percent, are a necessary.1 acres, or
part of the overland flow system.

DISCUSSION AND RECOABMWA77ONS
Seven different areas compose the 3.2 acres of triangular area external to the overland flow
terraces which drain to the overland flow system. These areas very from less than 0.1 acre
to 1.1 acres. These areas are relatively insignificant, comprising approximately 2.3 percent
of the area within the perimeter road. Two of these areas, those at the south ends of terraces
10 and 11, comprise approximately 1.1 acres combined, provide a wetlands treatment
environment as well as surge storage for storm runoff. While it is physically possible to
externalize the flow from the larger of the triangular areas, it is not practical because of the
lack of gradient. For example, to externally drain the largest 1.1 acre area would require
approximately 1,100 feet of underground pipe or 350 feet of underground pipe if a discharge
to Deep River is used.
It is practical to divert the storm water from the portion of the perimeter road that drains
through the overland flow system and that entering north of the effluent monitoring station to
external drainage. However, this diversion is less than 5 percent of the area draining
through the effluent monitoring station. This diversion would be primarily a simple process
of using a motor grader to reshape the road to an 8 percent (1 inch in 12 inches) cross slope
so that storm water will drain away from the overland flow system. Ditching alongside the
road will also be needed at some locations and two road corners will require some buildup.
In giving locations of road areas needing regrading, the number will refer to the terrace, the
letter N or S refers to the north or south end of the terrace, the letter E or W refers to the
east or west projection of the north or south end of the terrace if such exists. For example,
3S-E refers to the east side of the south end of terrace 3. The following road locations could
be regraded: 3S-E, 4S, 5S9 10S, 11S, 1259 13S9 17N, 15N, 14N-E, 14N, 13N, 12N9 11N,
ION, 7N9 6N, 5N, and 1N. In addition to regrading the road to drain outward along terrace
13S through 17S, a shallow ditch could be cut along the outside of the road. The ditch could
have periodic turnouts to carry the storm water to a lower ground level in the woods for
discharge. This ditch could also divert the storm drainage entering the overland flow
drainage channel north of the effluent monitoring station so that it enters the channel to the
south of the station. The road corner at the northeast corner of terrace 17 and at the
northeast corner of terrace 16 needs buildup to assure outward drainage. Road grading and
some ditching would be needed along terrace 16N to carry storm drainage away from the
system. A shallow ditch is also needed north of the road and the road regraded from
approximately 70 feet east and 70 feet west of the intersection of terrace IN and terrace 2N.
The road west of terrace 1 from approximately 280 feet south of the northwest corner to
approximately 470 feet north of the southwest corner needs regarding to drain away from the
system. The drainage ditch alongside this section of roadway also needs cleaned out as it is
badly clogged with sediment, vegetation, and organic debris.
The shallow drainage channel west of the smaller storage pond could be cleaned out,
regraded, and extended around the north end of the pond. A uniform bottom slope would be
suggested for the regraded channel from the existing discharge point to the upper terminal
point with the depth of 0.5 feet at the terminal point. The material removed in the cleanout
and regrading of the channel could be used to increase the slope from the edge of the smaller
ERM-SOUTHEAST INC. 2 4631

storage pond to the regraded channel. It is impractical to attempt to divert storm water from
the 10 feet wide divider between the two ponds.
SUMDIARY
In summary, a total of approximately 150.3 acres drain through the effluent monitoring
station, of which 140.1 acres or approximately 94 percent are a necessary part of the
overland flow system. The overland flow terraces occupy 129.6 acres of the total 150.3
acres drained through the effluent monitoring station. Based upon this evaluation, less than
10 acres which currently drain through the effluent monitoring station could be reshaped and
the drainage patterns rerouted to bypass the monitoring station. However, it will only be
cost-effective to reshape approximately 5 acres, those being in the area between the effluent
monitoring station and the perimeter road to the north. All other areas (i.e. roadways and
small, unused triangular areas) are so small that the cost to reshape and redrain them do not
appear to be worth the benefit to be gained. While the drainage from the 5 acres identified
above could be redirected, 5 acres is less than 4 percent of the total 140.1 acres which are
necessary for the overland flow system. Therefore, it is unlikely that this effort will have a
significant impact on final effluent volume or quality. It is recommended that no regrading
or drainage redirection be initiated until the evaluation of treatment system alternatives has
been completed and reviewed by the North Carolina Department of Environmental
Management.
ERM-MUM" INC 4651