520013_Lagoon Repair Plan_20210311

Steve Troxler
Commissioner
North Carolina Department of Agriculture
and Consumer Services
Division of Soil and Water Conservation
Lagoon Repair Plan
DC Mills Farm
Prepared By: Chris Love, PE, NC Division of Soil and Water Conservation
3/11/2021
Contents:
Page 1 — Narrative Description
Page 3 — Cost Estimate
Page 4 — Design Conditions
Page 5 — Details
Page 6 — Soil Report
Narrative Description of Repair
4,
Vernon Cox
Director
The southern dike at the DC Mills Farm in Jones County breached in December 2020. Based on
observations during a site evaluation conducted on 1/12/2021, it was determined that the most likely
cause for this breach was waste flow through cracks in an underlying limestone layer (see Soil Evaluation
Report). There were no other indications that the lagoon's structural integrity was compromised in any
other areas besides the single breach through the southern dike.
Therefore, it is recommended that:
(1) The hole of the breach will be filled in as best as possible with clay and compacted. The
surrounding dike appears to be structurally sound and well compacted clay, so disturbing the
remainder of the dike is not necessary.
MAILING ADDRESS
Division of Soil and Water Conservation
1614 Mail Service Center
Raleigh, NC 27699-1614
Telephone: [phone]
An Equal Opportunity Employer
LOCATION
Old Health Building
216 West Jones Street
Raleigh, NC 27604

(2) The southern portion of the dike will be re -lined with clay, with the addition of bentonite if
necessary. This re -lining will cover the entire inner dike wall and extend 20 feet into the lagoon. A
12-inch layer of clay will be necessary, compacted in 6-inch lifts using a sheepsfoot roller. This
will require the lagoon be drained of liquid waste, with sludge moved to the far end of the
lagoon, and a cofferdam constructed if necessary, to keep the work area dry. To meet the
requirements of the NRCS Waste Treatment Lagoon Standard, the liner must have a hydraulic
conductivity less than 0.003 ft/day (1.25 x 10-6 cm/sec). This can be measured approximately in
the field using a constant head permeameter or using several other instruments and techniques.
The landowner indicated that clay will most likely need to come from off -site as there is not any
clay on the farm. If the clay that is brought in cannot be compacted to meet the hydraulic
conductivity requirement, bentonite will need to be added to the clay outside of the lagoon and
mixed in before being brought into the lagoon to be spread and compacted. Any repairs made to
the lagoon must meet the requirements of NRCS Standards 359 (Waste Treatment Lagoon) and
520 (Pond Sealing or Lining — Compacted Soil Treatment). Requirements regarding bentonite are
found in Standard 520 and will need to be followed if it is determined that the addition of
bentonite to the clay mixture is necessary.
This plan should repair the existing breach in the lagoon and provide some protection against similar
breaches occurring in the future.
Sincerely,
ai
Chris Love, PE
Regional Engineer
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Cost Estimate — DC Mills Lagoon Repair (excluding possible addition of bentonite)
Item
Description of Work
Quantity
Unit
Unit
Price
Amount
1
Mobilization
1
LS
$6,000
$6,000
2
Erosion & Sediment Control
1
LS
$1,000
$1,000
3
Dewatering
1
LS
$1,000
$1,000
4
Clearing & Grubbing
0.5
AC
$5,000
$2,500
5
Backfill - Clay Liner
910
CY
$15
$13,650
6
Seed and Mulch
1
AC
$2,500
$2,500
Total $26,650
d-
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LEGEND
Q CONTROL POINT
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(8" NAIL IN GROUND)
TRAVERSE SURVEY POINT
(4" NAIL IN GROUND)
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NOTES:
1. ALL ELEVATIONS ARE RELATIVE TO NAVD'88
2. REFERENCE MARKS SET BY GPS RTK RAPID STATIC FIELD
OBSERVATIONS AND TOTAL STATION ROBOTIC INSTRUMENT.
3. COORDINATES ARE RELATIVE TO NAD 83 (2011) AND
DISPLAYED AS NORTH CAROLINA STATE PLANE 3200 US
SURVEY FEET.
4. ELEVATION DATA DISPLAYED OUTSIDE SURVEY BOUNDARY IS
DERIVED FROM 2014 NCFMP LIDAR: STATEWIDE NORTH
CAROLINA PHASE 2.
NEW CLAY LINER
12 INCHED TOTAL DEPTH, COMPACTED IN 6 INCH LIFTS
COMPACTED WITH SHEEPSFOOT ROLLER
TOTAL VOLUME 910 CY CLAY
BREACH
FILL IN WITH CLAY AND COMPACT
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DATE
REVISIONS
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TOP OF DYKE EL 65.3 FT
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CURRENT CONDITIONS
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TOP OF DYKE
PROPOSED CONDITIONS
1 FT OF CLAY MIXTURE ADDED TO BOTTOM AND INSIDE SLOPES
ADDED IN 6 INCH LIFTS
COMPACTED WITH SHEEPSFOOT ROLLER
LAGOON BOTTOM RAISED 1 FT
EXTEND 20 FT INTO LAGOON
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NORTH CAROLINA DEPARTMENT OF AGRICULTURE AND CONSUMER SERVICES
REVISIONS
DATE
AFPRDVED
Sheet No 2
of 2

North Carolina Division of Soil and Water Conservation
Technical Services Section, Soil Interpretive Services
Soils Evaluation Report
Date of Evaluation: 1-12-2021 Report Date: 1-14-2021
Project: Lagoon Repair at farm 52-13 Client: Donnie Mills
Objective of Soils Evaluation: To evaluate soils used in the construction of an anerobic lagoon
that has developed a leak.
Soil Scientists: Edward Stephens, Soil Scientist, NCDA&CS DSWC
Other Participants: Martin McLawhorn, Environmental Specialist, NCDA&CS DSWC
Marlene Salyer, NCDENR DWR
Chris Love, Engineer, NCDA&CS DSWC
Kevin Weston, Smithfield Foods
Donnie Mills, Farm Owner
Location: The farm is near Hargett's Crossroads on Lee Mills Road in Jones County. Coordinates
recorded in decimal degrees are: 35.012769, -77.614509.
Geology/Topography: The lagoon is built on an upland landscape position on soil mapped as
Goldsboro loamy sand, 0-2% slope. Tuckahoe Creek flows near the lagoon. A soil map is attached to
this report.
Field Work: A large tracked excavator with an operator was on site to assist with the soil evaluation.
Two pits were excavated and then filled in after evaluation. Elevation and depth measurement data was
collected with a Topcon laser construction level and should be considered preliminary. A site map
showing the lagoon and approximate locations of the conveyance is attached.
General Observations:
1. The lagoon was completed in 1994. The construction checklist has a hand-written note that
mentions a geotextile liner that was covered by 1' of "good plastic material". This note does not specify
the type of geotextile or the USCS classification of the soil installed as a liner. Mr. Mills stated that clay
for the lagoon liner and dike wall core was trucked in form Pink Hill, NC.
2. The lagoon structure appeared to be well maintained. The structure was free of trees and was
covered in grass.
3. A hole over 8' deep and 3-4' in diameter was observed on the toe slope of the lagoon on the outside
bordered by Tuckahoe Creek. A photograph of the hole is included as Figure 1. The hole had been
created by the flow of effluent under pressure from the lagoon. A hole approximately 3' in diameter
1

was observed on the inside of the lagoon on the inner slope. The hole was the inlet to the conveyance
and had been temporarily diked with soil from the top of the structure.
4. The hole on the inside of the lagoon was enlarged with the excavator to provide access to the clay
core. The core appeared to be constructed of cohesive soil that was compacted. The inlet hole was
nearly vertical and is not thought to penetrate through the core. The hole was filled in and tamped with
the excavator bucket to serve as a temporary repair to prevent effluent discharge.
5. The hole on the outside of the lagoon was enlarged to determine how effluent was leaving the
lagoon. At a depth of approximately 8.5' a layer of hard sedimentary rock or marl was observed. The
excavator could not continue digging past the top of that layer. The soil that was excavated around the
outlet hole was native, coarse textured soil with some silt and clay content. The excavated soil was
returned to the pit and was compacted with the excavator bucket.
6. Effluent was observed entering the outlet hole/excavated pit from the Tuckahoe Creek side instead of
the lagoon side. The volume of the flow was similar to a 6" irrigation pipe with very low pressure, the
effluent bubbled into the pit from an unseen opening in the sedimentary rock.
6. According to Mr. Mills, Tuckahoe Creek has exceeded its banks several times recently due to heavy
rains associated with hurricanes. Flood waters from Tuckahoe Creek have encroached on the toe slope
of the lagoon structure before receding.
Results:
Based on observations of the effluent conveyance it seems likely that the clay liner has
failed and allowed effluent to discharge from the lagoon structure. A localized repair of the
liner in the conveyance and adjacent area should be sufficient to repair the structure. Clay
from a local clay mine or bentonite should be considered. The core of the lagoon structure is
thought to be in good repair since the discharge was not attributed to an overtop event or high
levels of effluent and the dike wall remains in place.
A possible cause of the liner failure is the amount of water that has been absorbed,
discharged or transmitted through the soil and fractured sedimentary rock adjacent to and
under the lagoon structure. Due to the recent hurricanes and tropical weather systems that
have passed through southeastern North Carolina the water table has been at or above the
surface for extended periods. Recent temporary changes to the hydrology could have allowed
soil and rock to shift. A weak spot in the lagoon liner may have allowed the flow of effluent
down through the sedimentary rock and back to the surface on the outside toe slope of the
lagoon structure.
2

For questions or comments, contact Edward Stephens at 910-585-3792 (email:
[e-mail]).
Edward Stephens
Soil Scientist
N.C. Division of Soil and Water Conservation
RERERENCES:
Daniels, R.B., Buol, S. W., Kleiss, H.J., Ditzler, C.A. 1999. Soil Systems in North Carolina, Technical Bulletin 314. North Carolina State University,
Soil Science Department. Raleigh, North Carolina 27695-7619.
Natural Resources Conservation Service, National Soil Survey Center. 1998. Field Book for Describing and Sampling Soils. United States
Department of Agriculture. Lincoln, Nebraska.
North Carolina Agricultural Research Service. 1992. Redoximorphic Features for Identifying Aquic Conditions. North Carolina State University
Technical Bulletin 301. 33 pages.
Soil Survey Division Staff. 1993. Soil survey manual. Soil Conservation Service. U.S. Department of Agriculture Handbook 18. (Last modified
March 28, 2011)
Soil Survey Staff. Soil Survey of Jones County, North Carolina. Natural Resources Conservation Service. U.S. Department of Agriculture
https://websoilsurvey.sc.egov.usda.gov/App/WebSoilSurvey.aspx retrieved 1-14-2021
Soil Survey Staff. 2014. Keys to Soil Taxonomy, Twelfth Edition. Natural Resources Conservation Service. U.S. Department of Agriculture.--
U. S. Department of Agriculture, Natural Resources Conservation Service. 1997. Agricultural Handbook Number 590: Ponds —Planning, Design,
Construction. Washington, DC.
3

D. C. Mills Farm Lagoon
1-14-2021
No Scale
Locations are approximate
Site Map
4
N
A

Soil Map
Selected Soil Series Labels
Go
Goldsboro
Mk
Muckalee
NoB
Norfolk
M-W
Misc. Water
5

Photo of the outlet hole
Courtesy of David May, NCDENR
Figure 1
6