820229_Lagoon Closure Specifications_20240210

LAGOON CLOSURE SPECIFICATIONS
M Farms Facility #82-229
Site Location: 5394 William R. King Rd
Newton Grove, NC 28365
Sampson County
Prepared By
R. Gregory Swain, P.E.
305 Wendover Lane
Wilmington, NC 28411
[phone]
NC PE License No. 016415
February 12, 2024

1.0 INTRODUCTION
P&1 Farms (Mr. Nelson Porter) Facility ID 82-229, is a former swine farm in Sampson County that has had
no animals populated for considerable time. The purpose of this report is to provide specifications for
closure of the current impoundments (2) for the purposes of animal waste treatment and storage. The
owner wishes to convert the impoundments to fresh water storage.
The information regarding lagoon specifications and cleanout have been provided by Barwick Ag
Services (BAS), certified Technical Specialist. Topographic information was gathered on 2/10/24 during
on -site review of conditions with BAS.
2.0 DESCRIPTION
The impoundments, or lagoons, to be closed are formerly primary treatment/storage lagoons. See
attached aerial view. According to provided dimensions from certified lagoon design documents
provided, along with aerial GIS data, surface areas are approximately:
#1: 43,400 sq. ft. (design document 42,436 sq. ft.)
#2: 38,160 sq. ft. (scaled GIS info closely matches design dimensions)
3.0 GENERAL CRITERIA
All processes and specifications unless otherwise noted shall conform to NRCS Conservation Practice
Standard Code 360 revised October 2023, "WASTE FACILITY CLOSURE". Specifically for the purposes of
this closure, note the following requirements:
1. No additional conveyance of waste into the structure is allowed.
2. Liquid and slurry wastes shall be agitated and pumped according to nutrient and hydraulic
allowable limits established by BAS utilizing the sludge application plan.
3. Agitated slurry must be removed to the maximum extent practicable, adding water as necessary
to facilitate. No more than 12" depth shall be left remaining in bottom.
NOTE: Based on site evaluation of structures and water table, it is not recommended to scrape
sludge from sides or bottom. Particularly Lagoon #1 has steep side slopes (estimated between
1:1 and 2:1), less than standard width top berm. As shown on the attached design drawing,
both seasonal high water table (SHWT) and water level on site visit are considerably above
lagoon bottom elevations, further limiting the use of earth -moving equipment.
4. Final sludge survey must be conducted and recorded by a technical specialist to document
acceptable removal.
5. Disturbed areas (primarily constructed overflow spillway area) shall be vegetated and mulched
to minimize erosion, and shall maintain permanent vegetation post -construction.

6. Once structures are converted to freshwater ponds, they must not be used for fish production,
swimming, or livestock watering until the water quality is adequate for these purposes.
4.0 DESIGN CONSIDERATIONS
As noted, both structures are to be converted to fresh water ponds. A new overflow spillway shall be
constructed along the southeast side of both lagoons, adjacent to existing drainage outlets, as shown in
attached design. The aerial view utilized was sourced from Sampson County GIS. Spillway overflow was
determined to be the most economical and maintenance -free means of impoundment protection. The
area chosen to excavate the spillway is based on limiting the slope and length of slope for outflow to
existing outlets.
As shown in the plan, depth of cut should be based on establishing a bottom elevation in the cut area of
approximately 2.0' below the top of existing berm elevation. This provides spillway depth of 12" below
the design 12" freeboard of the structure. As shown in cross-section detail, the spillway shall be cut to
approximately 15' width at bottom, and side slopes minimum 3:1 to reach existing top of berm.
Additional disturbance of existing berms shall be limited as much as possible.
All disturbed area as well as constructed spillway cut shall be immediately seeded and mulched to
establish permanent vegetation and minimize erosion. The back slope of berm shall be lined with riprap
to original undisturbed grade for all disturbed area, extending minimally 5' in each side beyond the
width of excavated spillway. Riprap shall serve as energy dissipation from fresh water outflow during
storms and further minimizing potential erosion.
Based on previously estimated's u rface area of the impoundment, and utilizing accepted 25 year-24 hour
storm events, estimated outflow estimates are as follows:
Lagoon #1: 43,400 sq.ft. x 7.0" storm event = 25,317 ft3 in storm event =17.6 ft3/min outflow (assuming
structure was at full capacity at start of event). 17.6 ft3/min / 15 ft wide spillway / 0.2 ft flow depth = 5.9
ft/min = 0.1 ft/sec flow velocity. This flow is acceptable to minimize the potential for destructive
velocities in the outflow area with appreciable safety factor.
Lagoon #2: 38,160 sq. ft. x 7.0" storm event = 22,260 ft3 in storm event =15.5 ft3/min outflow (assuming
structure was at full capacity at start of event). 15.5 ft3/min / 12 ft wide spillway / 0.2 ft flow depth = 5.2
ft/min = <0.1 ft/sec flow velocity. This flow is acceptable to minimize the potential for destructive
velocities in the outflow area with appreciable safety factor.

TOP OF BERM UT APPROX. 25' WIDE
AND 24' DEEP SPILLWAY
UT
:
LAN D
3-
1 SIDE SLOPES
-�SIO
41. 3
LOCATION OF SPILLW
AY
RIPRAP Downslope to on inal-9-1—M N,
Seed and mulch ill disturbed areas
/LOCATION OF SPILLWA7
RIPRAP Downslope to *4 inal grade
Seed,'and mulch all disturbed area.
'16
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