3301_EdgecombeMSWLF_20160506_CAPReport_DIN

S&ME, Inc. | 3201 Spring Forest Road | Raleigh, NC 27616 | p 919.872.2660 | f 919.876.3958 | www.smeinc.com
May 6, 2016
NC Department of Environmental Quality
Division of Waste Management - Solid Waste Section
217 West Jones Street
Raleigh, North Carolina 27603
Attention:Mr. Ervin Lane sent via email:[e-mail]
Compliance Hydrogeologist
Reference:Interim Corrective Action Evaluation Report
Edgecombe County Landfill (Permit No. 33-01)
Tarboro, North Carolina
S&ME Project No. 4305-15-176
Dear Mr. Lane:
On behalf of Edgecombe County, S&ME, Inc. is submit this report documenting the progress of corrective
actions conducted at the Edgecombe County Landfill located in Tarboro, North Carolina in accordance
with the facility’s Corrective Action Plan (CAP), approved by NCDENQ on January 16, 2009 and Corrective
Action Plan Amendment, approved by NCDENQ August 9, 2010.
This report describes the status of implementation of the selected corrective measures, in situ isolation
and monitored natural attenuation (MNA), at the Edgecombe County Landfill including the following:
•Maintaining a consistent contour with pre-1998 waste area;
•Increase slope of the closed MSW area;
•Implementation of a MNA program to address impacted groundwater; and,
•Installation of an upgradient groundwater hydraulic barrier.
If you have any questions about the information presented in this report, please call, or email us.
Sincerely,
S&ME, Inc.
Alexander R. Culpepper, P.G.Samuel P. Watts, P.G.
Project Geologist Senior Project Manager
[e-mail] [e-mail]
Interim Corrective Action Evaluation Report
Edgecombe County Landfill (Permit No. 33-01)
Tarboro, North Carolina
S&ME Project No. 4305-15-176
Prepared for:
Edgecombe County Solid Waste Department
201 St. Andrew Street
PO Box 10
Tarboro, North Carolina
Prepared by:
S&ME, Inc.
3201 Spring Forest Road
Raleigh, NC 27616
May 6, 2016
Interim Corrective Action Evaluation Report
Edgecombe County Landfill (Permit No. 33-01)
Tarboro, North Carolina
S&ME Project No. 4305-15-176
May 6, 2016 ii
Table of Contents
1.0 Site Background.....................................................................................................1
1.1 Regulatory Status.........................................................................................................................1
1.2 Corrective Action Plan................................................................................................................1
1.2.1 In situ Isolation Surface Water ...........................................................................................2
1.2.2 In situ Isolation Groundwater.............................................................................................2
1.2.3 Natural Attenuation Monitoring........................................................................................2
2.0 Aquifer Characteristics.........................................................................................3
2.1 Groundwater Elevations and Flow Direction..........................................................................3
2.2 Groundwater Flow Velocity.......................................................................................................3
3.0 Proposed Corrective Measures ...........................................................................3
4.0 Maintaining a Consistent Contour With Pre-1998 Waste Area....................4
4.1 Description....................................................................................................................................4
4.2 Method of Evaluation..................................................................................................................4
4.3 Status.............................................................................................................................................4
4.4 Proposed Schedule ......................................................................................................................4
4.4.1 Schedule for Completion......................................................................................................4
4.4.2 On-Going Evaluation & Maintenance................................................................................5
5.0 Increase Slope of Closed MSW Area.................................................................5
5.1 Description....................................................................................................................................5
5.2 Method of Evaluation..................................................................................................................5
5.3 Status.............................................................................................................................................6
5.3.1 Tasks Completed..................................................................................................................6
5.3.2 Tasks In-Progress................................................................................................................6
5.4 Proposed Schedule ......................................................................................................................6
5.4.1 Schedule for Completion......................................................................................................6
5.4.2 On-Going Evaluation & Maintenance................................................................................6
6.0 Monitored Natural Attenuation .........................................................................6
6.1 Description....................................................................................................................................6
6.2 Method of Evaluation..................................................................................................................7
6.3 Status.............................................................................................................................................7
6.3.1 Tasks Completed..................................................................................................................7
6.3.2 Tasks In-Progress................................................................................................................8
6.4 Proposed Schedule ......................................................................................................................9
6.4.1 Schedule for Completion......................................................................................................9
6.4.2 On-Going Evaluation & Maintenance................................................................................9
7.0 Installation Of Upgradient Hydraulic Barrier.................................................9
7.1 Description....................................................................................................................................9
7.2 Method of Evaluation................................................................................................................10
7.3 Status.........................................................................................Error! Bookmark not defined.
Interim Corrective Action Evaluation Report
Edgecombe County Landfill (Permit No. 33-01)
Tarboro, North Carolina
S&ME Project No. 4305-15-176
May 6, 2016 iii
7.3.1 Tasks Completed................................................................................................................10
7.3.2 Tasks In-Progress..............................................................................................................11
7.4 Proposed Schedule ....................................................................................................................11
7.4.1 Schedule for Completion....................................................................................................11
7.4.2 On-Going Evaluation & Maintenance..............................................................................11
8.0 Conclusions ..........................................................................................................11
List of Figures
Figure 1 General Site Plan
Figure 2 C&D Waste Placement
Figure 3 Proposed Final Grading
Attachments
Attachment I Photographic Log
Attachment II Visual Landfill Cover Inspection - March 2016, April 21, 2016 (S&ME)
Attachment III Subsurface Exploration & Hydrogeologic Assessment Report, November 20, 2009 (S&ME)
Attachment IV Design Report Former Eagles Property Dam Removal, July 20, 2011 (S&ME)
Attachment V Notice of Exemption, dated July 27, 2011 (LQS)
Interim Corrective Action Evaluation Report
Edgecombe County Landfill (Permit No. 33-01)
Tarboro, North Carolina
S&ME Project No. 4305-15-176
May 6, 2016 1
1.0 Site Background
1.1 Regulatory Status
Edgecombe County currently operates a solid waste facility on a tract of land located off of Colonial Road
(S.R. 1601) in Edgecombe County, south of Tarboro, North Carolina (Figure 1). In general, the solid waste
facility includes a municipal solid waste (MSW) transfer facility; a construction & demolition (C&D) debris
landfill unit; white goods and pallets storage area; soil borrow pits; and various operational buildings. The
C&D landfill unit is operated over an existing closed MSW landfill, in accordance with North Carolina
Department of Environmental Quality, Division of Waste Management (NCDENQ-DWM) Permit No. 33-01.
On behalf of Edgecombe County, S&ME completed a Corrective Action Plan (CAP), dated June 30, 2008
for the landfill in accordance with Solid Waste Rules defined under 15A NCAC 13B .1636 and .1637. The
CAP included the selection of in situ isolation combined with monitored natural attenuation (MNA) as the
remedial alternatives for groundwater impacted with cobalt, petroleum constituents and chlorinated
compounds. In situ isolation was selected because the site conceptual model indicated that surface water
and groundwater management issues are the primary mechanism for addressing the release and
migration of the constituents of concern at the landfill. MNA has been incorporated into the facility’s
updated (January, 2010) Water Quality Monitoring Plan (WQMP) to monitor and evaluate the
effectiveness of the remedial measures.
The CAP was submitted on behalf of Edgecombe County to the NCDEQ - DWM, Solid Waste Section
(Section) and approved for implementation by the Section in a letter dated January 16, 2009. The CAP
and the WQMP were submitted as part of the C&D Landfill permit application approved by the Solid
Waste Section on March 31, 2010 by the renewal of the C&D landfill Permit to Operate (PTO). After the
CAP was submitted to the Solid Waste Section, S&ME collected additional information on the site geology
and hydrogeology in the vicinity of the proposed hydraulic barrier as part of the design and
implementation process. Additionally, the County purchased the property immediately adjacent to the
southern property boundary of the landfill facility (former Eagles Farm, LLC). S&ME reviewed the original
design presented in the CAP, considering the additional space available to the south of the landfill and
the newly obtained geologic and hydrogeologic information. Based on that review, S&ME prepared a
Corrective Action Plan Amendment, report dated July 27, 2010 describing the revised design for
implementing the proposed up-gradient hydraulic barrier. The revised design presented in the Corrective
Action Plan Amendment uses the same concept as the approved CAP, with minor revisions of the
hydraulic barrier. The revised design was intended to reduce capital cost for implementation, minimize
future maintenance, and more effectively divert groundwater flow around or away from landfill waste.
The Corrective Action Plan Amendment was approved by NCDEQ August 9, 2010.
1.2 Corrective Action Plan
The CAP proposes corrective measures focused on “in situ isolation” of the landfill from surface water and
groundwater sources that may enter or pass through the waste mass. In situ isolation system will
minimize water exposure to the buried waste mass limiting the release of contaminants to the water and
to the environment. The CAP corrective measures have three components: 1) management of surface
water infiltration and discharge, 2) management of groundwater infiltration and discharge, and 3)
monitoring the naturally occurring chemical and biological degradation of constituents.
Interim Corrective Action Evaluation Report
Edgecombe County Landfill (Permit No. 33-01)
Tarboro, North Carolina
S&ME Project No. 4305-15-176
May 6, 2016 2
1.2.1 In situ Isolation Surface Water
The focus of an in situ isolation system for surface water is to reduce infiltration of surface water from
storm events and to manage the stormwater drainage discharged from the landfill site. The engineered
design to address surface water infiltration includes a grading plan to improve stormwater drainage from
the surface of the landfill and reduce surface water infiltration into the waste. The grading plan includes:
1) removing soil berms that were installed on the surface of the landfill as erosion control measures
during landfill construction; 2) re-grading and shaping some portions of the landfill cap to increase the
percent slope on filled areas to maintain consistent contours with the pre-1998 waste area; 3) increasing
the slope of the closed MSW area to facilitate improved surface drainage; and, 4) excavating, stabilizing,
and extending the drainage ditch located on the south side of the landfill waste boundary from the west
end of the groundwater hydraulic barrier around to the southern and western perimeter of the landfill.
The drainage routes for stormwater shed from the landfill will flow to the north to stormwater
sedimentation basins lined with low permeability material to manage the stormwater discharged to
surface water features. Surface water and groundwater intercepted by the hydraulic barrier to the south
of the landfill will flow through the former location of the Eagles Farm pond and will discharge to Jerry’s
Creek east of the landfill.
1.2.2 In situ Isolation Groundwater
The in situ isolation of the landfill waste from groundwater requires an engineered design to reduce
infiltration of groundwater from upgradient and lateral sources that allow groundwater flow through the
subsurface toward the landfill waste. The engineered design will divert upgradient and lateral
groundwater flow around or away from the landfill waste using a hydraulic barrier to reduce the volume
of horizontal groundwater flow into the landfill. The engineered design will manage lateral groundwater
flow toward the landfill waste and will discharge groundwater diverted from entry into the landfill waste
using an improved perimeter drainage system. Retaining and/or diverting the groundwater from flowing
through the waste in the landfill is intended to reduce the volume of water available for the production of
leachate in the landfill. Therefore, the transport of leachate from the landfill would be reduced. The
reduction of groundwater flow beneath the landfill is also intended to lower groundwater levels in the
landfill, thereby minimizing contact of groundwater with waste and/or leachate contained in the landfill.
1.2.3 Natural Attenuation Monitoring
The monitored natural attenuation (MNA) program described in the CAP is necessary to review the
performance of the engineered controls that will be implemented to reduce surface water and
groundwater infiltration into the waste at the landfill. The monitoring network at the landfill is comprised
of monitor wells and piezometers that are measured for water elevations and or sampled on a semiannual
schedule. During each semiannual monitoring event, groundwater flow directions and concentrations of
target constituents in surface water and groundwater are monitored. The MNA network will be used to
evaluate performance of the CAP, specifically change in hydraulic head from upgradient to downgradient
of control measures and collecting groundwater geochemical parameters indicating the biological activity
occurring in the natural attenuation process.
Interim Corrective Action Evaluation Report
Edgecombe County Landfill (Permit No. 33-01)
Tarboro, North Carolina
S&ME Project No. 4305-15-176
May 6, 2016 3
2.0 Aquifer Characteristics
2.1 Groundwater Elevations and Flow Direction
The uppermost aquifer at the site is unconfined and is found in the surficial Sunderland Formation,
Pleistocene-age marine, silty sands. This aquifer is recharged by inflow from up-gradient areas and by
precipitation infiltration. The uppermost aquifer underlying the landfill is expected to discharge to the
local surface water features including Jerry’s Creek and the drainage features in the active landfill area.
During flood conditions, the southwest perimeter trench and the farm pond located in the southeast
corner of the site may recharge the aquifer. A massive marine clay layer (Yorktown Formation) underlies
the surficial aquifer at depths ranging from approximately 8 to 24 feet below the original ground surface
acts. This clay layer acts as an aquitard and confining layer below the landfill.
Based upon the groundwater potentiometric surface elevations, groundwater flow direction beneath the
landfill is estimated to be to the north-northeast. The average horizontal hydraulic gradient from two
three point solutions using well sets MW-3B, MW-7A, and MW-5, and P-1, MW-7A and MW-5 is
estimated to be 0.0218 ft/ft.
2.2 Groundwater Flow Velocity
Aquifer rising and falling head tests were previously performed at the site by Law Engineering Company
and by S&ME. The aquifer test data were used to estimate the hydraulic conductivity of the sediments in
the surficial aquifer intersected by the screened intervals of the monitor wells tested. The aquifer test data
(provided in previous reports) were analyzed by the Bouwer and Rice Method.
The hydraulic conductivity, K, values previously measured at the site ranged from 1.29x10-5 centimeters
per second (cm/sec) to 3.65x10-4 cm/sec. An average hydraulic conductivity value of 5.95x10-5 cm/sec
was used for calculating the site-wide flow velocity. The average hydraulic gradient of 0.0224 ft/ft,
calculated from the three point solution described above was used as the site-wide average gradient. An
effective soil porosity, n, of 15% was used as the site-wide average.
The average groundwater flow velocity, V, for the site, using the equation and input values above, was
estimated at 8.96 ft/yr.
3.0 Proposed Corrective Measures
The implementation of the selected corrective measures, in situ isolation and MNA, at the Edgecombe
County Landfill includes the following:
♦Maintaining a consistent contour with pre-1998 waste area;
♦Increase slope of the closed MSW area;
♦Implementation of a MNA program to address impacted groundwater; and,
♦Installation of an upgradient groundwater hydraulic barrier.
Interim Corrective Action Evaluation Report
Edgecombe County Landfill (Permit No. 33-01)
Tarboro, North Carolina
S&ME Project No. 4305-15-176
May 6, 2016 4
The following sections detail the progress of the above corrective measure activities that have been
conducted at the County’s landfill in accordance with the facility’s Corrective Action Plan (CAP), approved
by NCDEQ on January 16, 2009 and Corrective Action Plan Amendment, approved by NCDEQ August 9,
2010.
4.0 Maintaining a Consistent Contour with Pre-1998 Waste Area
4.1 Description
Maintaining consistent contour elevations across the waste disposal unit where C&D waste is not
currently being placed (western portion of waste disposal unit) will reduce groundwater contamination by
reducing vertical percolation of pounded rain water into the waste mass which can produce leaching.
Maintaining a consistent contour entails some initial grading operations to remove or regrade existing
stormwater slope diversion berms on the landfill cap and maintenance to those areas where ditches,
slumps, and sinkholes have formed from waste decomposition. Maintaining a consistent contour would
involve a continuous process of inspection and backfilling on a quarterly basis for existing or potential
surface water collection locations followed by timely addition of backfill soil and reseeding.
4.2 Method of Evaluation
Visual inspection is the method for evaluating consistent contour elevations across the closed MSW
disposal unit. Edgecombe County employees perform non-routine inspections of the landfill cover system
during mowing, while relocating slope drains and while performing operation and maintenance (O&M) on
the landfill gas (LFG) collection system. Additionally, Edgecombe County has contracted S&ME to
perform an annual inspection of the landfill cover system during performance of the facility quarterly
methane monitoring. S&ME summarizes the findings of the annual landfill cover inspection in a letter
report to Edgecombe County’s landfill manager.
The cover system is examined for signs of settlement, erosion, vector damage, brown or bare vegetation,
bulging areas, standing water, deep-rooted or woody vegetation, and signs of gas leakage such as
distressed vegetation or fissures. The condition of the landfill gas extraction wells was also inspected
while onsite.
4.3 Status
Removal and regrading of existing stormwater slope diversion berms on the landfill cap was completed in
2008 (See Photos 1-9,Attachment I).
4.4 Proposed Schedule
4.4.1 Schedule for Completion
None. This corrective measure has been fully implemented.
Interim Corrective Action Evaluation Report
Edgecombe County Landfill (Permit No. 33-01)
Tarboro, North Carolina
S&ME Project No. 4305-15-176
May 6, 2016 5
4.4.2 On-Going Evaluation & Maintenance
Annually from 2009 to 2016, S&ME has completed landfill cover inspections and reported the findings to
the Edgecombe County landfill manager. S&ME’s most recent landfill cover inspection was performed on
March 17, 2016. S&ME’s findings and recommendations from the were provided in a letter report titled
Visual Landfill Cover Inspection - March 2016, dated April 21, 2016 (Attachment II). In summary, S&ME’s
report recommended Edgecombe County perform the following maintenance activities:
♦Repair leachate seepage areas observed on the landfill cap;
♦The slope drains in the northern central area of the landfill should be re-connected to provide
appropriate drainage;
♦Continue regular mowing on the landfill cap and perimeter to promote healthy growth of grass,
and to minimize growth of weeds or tall vegetation with a tendency for deep root penetration;
♦Continue to monitor steep slopes for signs of erosion and continue using flexible down-drains to
intercept and direct surface water away from areas that have not been stabilized;
♦Continue inspection and backfilling of existing or potential surface water collection locations
Edgecombe County shall continue to perform visual inspections and perform maintenance to those areas
where pipes, roads, ditches, berms or subsidence are causing ponding of surface water over the waste
mass.
5.0 Increase Slope of Closed MSW Area
5.1 Description
Increasing the slope of the landfill cover will decrease the infiltration of stormwater into the MSW waste
and reduce the potential for groundwater contamination. The eastern portion of the waste disposal unit
is where the current C&D waste disposal is being conducted. The C&D waste has been placed over the
existing MSW landfill and has increased the slope in this area.
The slopes in the western portion of the MSW landfill are relatively flat with a majority of the area at a
slope of approximately 5 to 6 percent. Increasing the slope in this area would involve moving the current
C&D waste placement operations from the eastern portion of the waste disposal unit to the western
portion. The C&D waste placement would increase the slope in this area and also provides an additional
barrier to stormwater infiltrating into the MSW landfill.
5.2 Method of Evaluation
Visual inspection and topographic survey is the method for evaluating increased slope of the closed MSW
disposal unit. As the active working face of the C&D placement operations advances from east to west,
the slope of the existing MSW landfill cap increases.Figure 2 shows the location of active working face of
the C&D placement operations as of Mid-2015 relative to the proposed area of future waste placement.
Where C&D waste has been placed over the existing MSW landfill cap, the slope of the ground surface
has increased.
Interim Corrective Action Evaluation Report
Edgecombe County Landfill (Permit No. 33-01)
Tarboro, North Carolina
S&ME Project No. 4305-15-176
May 6, 2016 6
5.3 Status
5.3.1 Tasks Completed
Figure 2 shows the location of active working face of the C&D placement operations as of June 2015.
Where C&D waste has been placed over the closed MSW landfill unit, the slope of the ground surface has
increased. From June 2007 to June 2015, Edgecombe County has placed 416,841 tons of C&D waste on
top of the closed MSW landfill unit, covering an area of approximately 61,650 square feet. As of June
2015, approximately 37,045 square feet of the closed MSW landfill unit has been covered with C&D waste
representing approximately 61 % of the total area to be covered with C&D waste.
5.3.2 Tasks In-Progress
Edgecombe County continues to place C&D waste on the western portion of the closed MSW waste unit.
5.4 Proposed Schedule
5.4.1 Schedule for Completion
The current C&D waste placement operation continues to move from the eastern portion of the waste
disposal unit to the western portion. As the active working face of the C&D placement operations
advances from east to west, the slope of the landfill cover increases.
In the 2010, Permit Application, Section A–Facility Plan outlines the 5-year development plans through 35
years show C&D continuing to be placed over the existing MSW landfill cap from the eastern to the
western portion of the MSW landfill.Figure 3 shows the proposed final grading plan following the
completion of C&D disposal operations. Based on the phasing presented in the facility operation plan,
the schedule for completing implementation of this corrective measure is as follows:
♦2024 (year) – Complete placement of base footprint of C&D waste (Phases 1-4)
♦2055 (year) – Complete final placement of C&D waste (Phases 5-9)
5.4.2 On-Going Evaluation & Maintenance
Annually, Edgecombe County shall perform a topographic survey of the active C&D landfill and evaluate
the placement of C&D waste.
6.0 Monitored Natural Attenuation
6.1 Description
The COCs in groundwater at the landfill include the organic parameters: vinyl chloride, benzene, cis-1,2-
dichloroethene, trichloroethene, and 1,4-dichlorobenzene, and the inorganic constituent: cobalt.
Following construction of the corrective measures presented above, surface water and groundwater
coming in contact with waste materials in the waste disposal unit will be minimized. Waste material
leachate coming into contact with groundwater will then be minimized. The COCs in groundwater are
Interim Corrective Action Evaluation Report
Edgecombe County Landfill (Permit No. 33-01)
Tarboro, North Carolina
S&ME Project No. 4305-15-176
May 6, 2016 7
then expected to naturally attenuate and trend toward cleanup goals. MNA will be implemented as the
corrective measure for impacted groundwater.
Based on the years of groundwater monitoring, analytical data coupled with the various studies
throughout the groundwater monitoring history of the facility, including the previously discussed NES, the
primary substrate at the facility should contain a sufficient quantity of anthropogenic organic carbon to
support biodegradation of the chlorinated solvent COCs. In addition, there is likely native organic carbon
in trace amounts which will further enhance biodegradation rates of these constituents.
6.2 Method of Evaluation
For the Edgecombe County Landfill, it has not yet been determined if the contaminant plume is still in a
growth phase, stable phase, or if the plume has already reached its peak and is now a shrinking plume. At
a time of one to three years following implementation of the isolation and water management correction
measures presented above, the groundwater plume status at the facility would be determined during the
MNA process.
This process would involve sampling the appropriate property boundary groundwater monitoring wells
for the constituents found exceeding their respective 2L Standards/GWPST. After an appropriate amount
of samples have been taken, assumptions may be drawn concerning the constituent magnitude
concentration trend (increasing, decreasing, or static) in order to re-evaluate the dispersion and natural
attenuation process effectiveness. The objectives for a MNA groundwater remediation program include
the following:
♦Demonstrate that natural attenuation is occurring;
♦Be protective of human health and the environment;
♦Monitor natural attenuation and environmental impact; and,
♦Restore groundwater at the edges of the plume to below the 2L Standard and GWPST.
The existing monitoring network, plus additional monitor wells to be installed, will be used to monitor
groundwater quality and trends. Monitoring wells MW-3B, MW-4, and MW-9, the upgradient wells,
would allow determination of geochemical conditions in the groundwater prior to entering the source
area. Monitoring well MW-5 is located in the plume and will be utilized to collect data for bioremediation
rate calculations. Additional wells will be installed along the downgradient facility boundary to define the
edge of the plume and act as sentinel wells. These wells would be monitored and evaluated to determine
if bioremediation is working as well as to determine if re-evaluation triggers have been exceeded.
6.3 Status
6.3.1 Tasks Completed
The following tasks have been completed for the MNA corrective action:
♦January 19, 2010 – Groundwater samples collected and analyzed for geochemical parameters
necessary to evaluate monitored natural attenuation (MNA) in addition to the Appendix I
constituents for Detection Monitoring (constituents listed in 40 CFR 258).
♦July 20, 2010 – Groundwater samples collected and analyzed for geochemical parameters
necessary to evaluate monitored natural attenuation (MNA) in addition to the Appendix I
constituents for Detection Monitoring (constituents listed in 40 CFR 258).
Interim Corrective Action Evaluation Report
Edgecombe County Landfill (Permit No. 33-01)
Tarboro, North Carolina
S&ME Project No. 4305-15-176
May 6, 2016 8
♦January 18, 2011 – Groundwater samples collected and analyzed for geochemical parameters
necessary to evaluate monitored natural attenuation (MNA) in addition to the Appendix I
constituents for Detection Monitoring (constituents listed in 40 CFR 258).
♦July 27, 2011 – Groundwater samples collected and analyzed for geochemical parameters
necessary to evaluate monitored natural attenuation (MNA) in addition to the Appendix I
constituents for Detection Monitoring (constituents listed in 40 CFR 258).
♦July 2012 – S&ME submitted the Baseline Water Quality and Monitored Natural Attenuation (MNA)
Report, dated July 19, 2012. The Baseline MNA Report concluded that natural attenuation is
occurring on site by one of more reductive processes. S&ME recommended:
1)modifying the SAP to discontinue sampling for several MNA parameters used to evaluate
aerobic microbiological activity (volatile fatty acids, biochemical oxygen demand, chemical
oxygen demand, and hydrogen);
2)discontinuing sampling for geochemical/MNA parameters be in all monitor wells, until
corrective measures have been implemented at the site;
3)geochemical/MNA parameters be measured every 18 months, once corrective measures are
in place, to allow the parameters to be measured during alternating seasons.
♦September 17, 2012 – In a letter dated September 17, 2012, the Section acknowledged receipt
and review of the Baseline MNA Report. The Section did not approve elimination of ant of the
MNA parameters. The Section did approve Edgecombe County discontinuing MNA monitoring
until the corrective measures described in the CAP were implemented and approved sampling for
MNA parameters every 18 months thereafter.
♦January 2013 – S&ME personnel, on behalf of Edgecombe County, met with the Section to discuss
approved modifications to the Sampling and Analysis Plan (SAP) for the Edgecombe County
landfill. The agreed-upon revisions to the SAP were summarized in a letter to the Section dated
April 19, 2013, and the Section confirmed the revisions in an email from Mr. Ervin Lane, of the
Section, dated May 1, 2013.
6.3.2 Tasks In-Progress
Edgecombe County implemented MNA monitoring on January 19, 2010 as part of the facility semiannual
water quality monitoring. On January 18, 2013, S&ME personnel met with the Section to discuss changes
to the SAP. During the meeting, the Section approved modifications to the SAP, in which MNA and
Geochemical parameters were to be temporarily discontinued until the corrective measures were
implemented. Once the corrective measures are in place, the revised SAP for MNA and geochemical
parameters will be implemented.
Edgecombe County continues to perform semi-annual water quality monitoring. Geochemical parameters
indicative of MNA are collected in accordance within the WQMP. Monitor wells MW-5, MW-12, and MW-
15 were selected to provide information on the MNA processes in conjunction with the Appendix I
analytical data. MNA parameters include the following performance parameters as required by the
NCDEQ DWM: chloride, sulfate, alkalinity, biochemical oxygen demand, chemical oxygen demand, total
organic carbon, nitrate as N, nitrate/nitrite as N, sulfide, total dissolved solids, iron, manganese, carbon
dioxide, ethane, ethene, methane, volatile fatty acids, and hydrogen.
Interim Corrective Action Evaluation Report
Edgecombe County Landfill (Permit No. 33-01)
Tarboro, North Carolina
S&ME Project No. 4305-15-176
May 6, 2016 9
6.4 Proposed Schedule
6.4.1 Schedule for Completion
None. This corrective measure has been fully implemented.
6.4.2 On-Going Evaluation & Maintenance
MNA parameters sampling and statistical analysis was allowed to be temporarily suspended until the
hydraulic barrier construction was complete. MNA monitoring was last completed in 2012; based on the
partial implementation of corrective measures, S&ME recommends resuming collection of MNA
parameters in compliance monitoring wells MW-5, MW-12, MW-15, and MW-16 beginning in June 2016,
and every 18 months thereafter over the next three years (June 2016, December 2017 and, June 2019).
This schedule will allow the parameters to be measured during alternating seasons, thus facilitating a
more representative analysis of conditions at the site. Evaluation of MNA should also include a USEPA
approved MNA screening model every 18 months to simulate the groundwater remediation at the facility
and determine the mass flux and mass balance starting in June 2016.
7.0 Installation of Upgradient Hydraulic Barrier
7.1 Description
The conceptual in situ isolation plan in the CAP involves the construction of a barrier to intercept and
divert groundwater flowing beneath the landfill. This proposed hydraulic barrier is to extend along the
southern (upgradient) boundary of the landfill. Diverting the upgradient groundwater flowing on top of
the Yorktown marine clay toward the landfill should 1) reduce the volume of water that contributing to
the production of leachate and 2) lower groundwater levels, thereby increasing the vertical separation
between the groundwater table and the bottom of the buried waste mass. The reduced volume of water
and the reduced groundwater flow velocity has the intended purpose of decreasing the migration of
contaminants of concern and keeping them “in situ.”
S&ME performed a subsurface investigation and hydrogeologic assessment for use in designing the
hydraulic barrier and stormwater drainage system components necessary to implement the corrective
measures selected in the CAP. This information was included in S&ME’s report Subsurface Exploration &
Hydrogeologic Assessment Report, dated November 20, 2009. A copy of this report is included as
Attachment III.
Based on the site specific information obtained from the Subsurface Exploration & Hydrogeologic
Assessment, S&ME prepared revised design for the implementation of the hydraulic barrier. The revised
design was submitted to the Section in S&ME’s report Corrective Action Plan Amendment, dated July 27,
2010. The revised design presented in the Corrective Action Plan Amendment used the same concept as
the approved CAP, with minor revisions of the hydraulic barrier. The revised design was intended to
reduce capital cost for implementation, minimize future maintenance, and more effectively divert
groundwater flow around or away from landfill waste. Significant design features included:
Interim Corrective Action Evaluation Report
Edgecombe County Landfill (Permit No. 33-01)
Tarboro, North Carolina
S&ME Project No. 4305-15-176
May 6, 2016 10
♦Re-design the outfall structure that regulates the flow through the ponds or remove the dam to
the pond located on the southeast corner of the facility;
♦Install 1,150 linear feet of groundwater barrier trench drain on the former Eagles Farm LLC
property to direct groundwater to the existing pond to the east and/or drainage ditch to the west.
The location of the proposed hydraulic barrier system is presented in the Corrective Action Plan
Amendment, dated July 27, 2010. The CAP Amendment also presents a profile that depicts the ground
surface; the top of the Yorktown Formation; the proposed groundwater barrier trench invert, and
construction details for the hydraulic barrier trench.
7.2 Method of Evaluation
Changes in groundwater elevation within the waste disposal unit, and reduction in groundwater flow
beneath the landfill are the methods for evaluating the effectiveness of the in-situ isolation. In-situ
isolation is proposed as part of the corrective measures in this report. However, there are currently no in-
situ isolation structures in-place at the landfill facility. Groundwater elevation data will be collected from
the facility’s water quality monitoring network on a quarterly basis.
7.2.1 Tasks Completed
♦October 2008 through March 2009 – S&ME performed additional assessment necessary to
develop design specifications for the hydraulic barrier. The findings were summarized in S&ME’s
report titled Subsurface Exploration and Hydrogeologic Assessment Report, dated November 20,
2009. A copy of this report is provided as Attachment III.
♦August 2009 – Edgecombe County purchased the adjoining Eagles Farm LLC property to the
south of the landfill.
♦July, 2010 – S&ME submitted Corrective Action Plan Amendment, dated July 27, 2010, with a
revised design for the implementation of the hydraulic barrier.
♦August 9, 2010 – The Solid Waste Section approved the Corrective Action Plan Amendment.
♦March 11, 2009 – S&ME submitted a revised Erosion and Sedimentation Control Plan (E&SC)to
Land Quality Section (LQS) to obtain a permit for land disturbance for the construction of the
proposed corrective measures.
♦May 20. 2009 – LQS issued a final Letter of Approval with Modifications to E&SC Permit.
♦July 20, 2011 – S&ME submitted a dam removal application to NCDEQ LQS for removal of the
dam impounding surface water in the former Eagles Farm pond located in the southeast corner of
the facility. (Attachment IV).
♦July 27, 2011 – LQS, State Dam Safety Engineer issued a letter acknowledging receipt of S&ME’s
application. LQS determined the former Eagles Farm pond dam to be classified low hazard, and
issued a Notice of Exemption for the removal of the dam (not requiring approval from LQS). A
copy of the Notice of Exemption is provided as Attachment V.
♦June 2011 through April 2012 – Edgecombe County lowering the water level in the former Eagles
Farm pond located in the southeast corner of the facility by dismantling the concrete block
riser/outlet structure.(Photos 10 through 15, Attachment I)When the riser was dismantled to
its lowest point, the outlet (two corrugated metal pipes) was still approximately 10 feet above the
bottom of the pond.
Interim Corrective Action Evaluation Report
Edgecombe County Landfill (Permit No. 33-01)
Tarboro, North Carolina
S&ME Project No. 4305-15-176
May 6, 2016 11
♦May 11, 2012 through May 15, 2012 – Edgecombe County mechanically dewatered the pond with
a large agriculture pump and removed/relocated viable fish. (Photos 16 through 19,
Attachment I)
♦May 2013 – S&ME completed preparation of construction specifications for the site grading and
corrective measures installation for the in situ isolation.
♦August 17, 2015 - Edgecombe County completed final removal of the former Eagles Farm pond
dam (Photos 20 and 21, Attachment I).
7.2.2 Tasks In-Progress
♦The land disturbance permit issued by LQS has expired. S&ME is updating the E&SC plan to
apply for a new land disturbance permit for the construction corrective measures associated with
the in situ corrective measures.
♦S&ME is revising the final construction specifications for corrective measures installation.
♦S&ME is measuring groundwater elevations, and evaluating the effect of draining the pond on
the up gradient hydrogeology.
7.3 Proposed Schedule
A proposed schedule of dewatering the existing drainage ditch and pond features and installing a
groundwater barrier trench drain activities is as follows:
7.3.1 Schedule for Completion
August 2016 – November 2016
♦Re-submit Erosion and Sedimentation Control Plan (E&SC) to LQS to obtain a new land
disturbance permit for the construction areas of the landfill corrective measures
♦Review and update the construction specifications for corrective measures installation.
♦Continue collection of quarterly groundwater elevation data.
December 2016 – March 2017
♦Corrective measures grading project let for bid
♦Selection of Contractor to install corrective measures
May 2017 - December 2017
♦Construction of in situ isolation system -- improve diversion ditches, install up gradient hydraulic
barrier, install additional monitor wells and place low permeability fill in sedimentation ponds.
7.3.2 On-Going Evaluation & Maintenance
On a quarterly basis, Edgecombe County shall collect water levels and evaluate in-situ isolation.
8.0 Conclusions
The CAP for the Edgecombe County Landfill proposes corrective measures focused on “in situ isolation” of
the landfill from surface water and groundwater sources that may enter or pass through the waste mass.
Interim Corrective Action Evaluation Report
Edgecombe County Landfill (Permit No. 33-01)
Tarboro, North Carolina
S&ME Project No. 4305-15-176
May 6, 2016 12
In situ isolation system will minimize water exposure to the buried waste mass limiting the release of
contaminants to the water and to the environment.
Edgecombe County has begun implementing the corrective measures. Some of the corrective measures
have been fully implemented and some of the corrective measures are still in the process of being
implemented. Edgecombe County has begun are in the ongoing evaluation and maintenance of the
implemented corrective measures. Below is a summary of the implementation of the selected corrective
measures, in situ isolation and MNA, at the Edgecombe County Landfill:
Corrective
Measure
Implementation
Begun
Implementation
Complete
Date
Implementation
Complete
Evaluation
Schedule
Maintaining consistent
contour with pre-1998
waste area
x x 2008 Annually
(Started in 2008)
Increase slope of the
closed MSW area
x 2024
(estimate Phase 4
filling complete)
Annually
(Started in 2007)
Monitored Natural
Attenuation (MNA)
x x June 2011
(baseline MNA)
Every 18 Months
(Started June
2016)
Install upgradient
groundwater hydraulic
barrier x December 2017
(estimated)
Quarterly
(Start March 2018)
Figures
Q:\PROJECTS\2015\4305-15-174\CAD\D1435.dwg, FIG1, 5/6/2016 3:59:36 PM, 1:1
C
H
E
C
K
E
D
B
Y
:
D
R
A
W
N
B
Y
:
A
P
P
R
O
V
E
D
B
Y
:
D
E
S
I
G
N
E
D
B
Y
:
P
R
O
J
E
C
T
N
U
M
B
E
R
:
S
C
A
L
E
:
D
A
T
E
:
O
F
:
D
R
A
W
I
N
G
:
BYDESCRIPTIONDATENO.
WWW.SMEINC.COM
D
R
A
W
I
N
G
N
U
M
B
E
R
:
3201 SPRING FOREST ROAD, RALEIGH, NC 27616
NC ENG. LICENSE #F-0176 PHONE: [phone]
D
-
1
4
3
5
B
T
R
M
A
Y
2
0
1
6
1
"
=
2
0
0
'
4
3
0
5
-
1
5
-
1
7
5
GENERAL SITE PLAN
1
EDGECOMBE COUNTY LANDFILL
TARBORO, NORTH CAROLINA
C
H
E
C
K
E
D

B
Y
:
D
R
A
W
N

B
Y
:
A
P
P
R
O
V
E
D

B
Y
:
D
E
S
I
G
N
E
D

B
Y
:
P
R
O
J
E
C
T

N
U
M
B
E
R
:
S
C
A
L
E
:
D
A
T
E
:
O
F
:
D
R
A
W
I
N
G
:
BYDESCRIPTIONDATENO.
WWW.SMEINC.COM
D
R
A
W
I
N
G

N
U
M
B
E
R
:
3201 SPRING FOREST ROAD, RALEIGH, NC 27616
NC ENG. LICENSE #F-0176 PHONE: [phone]
D
-
1
4
3
5
B
T
R
M
A
Y

2
0
1
6
1
"

=

1
0
0
'
4
3
0
5
-
1
5
-
1
7
5
C&D WASTE PLACEMENT
2
EDGECOMBE COUNTY LANDFILL
TARBORO, NORTH CAROLINA
CHECKED BY:DRAWN BY:
APPROVED BY:DESIGNED BY:
PROJECT NUMBER:
SCALE:DATE:
OF:DRAWING:
BY
DE
S
C
R
I
P
T
I
O
N
DA
T
E
NO
.
WW
W
.
S
M
E
I
N
C
.
C
O
M
DRAWING NUMBER:
32
0
1

S
P
R
I
N
G

F
O
R
E
S
T

R
O
A
D
,

R
A
L
E
I
G
H
,

N
C

2
7
6
1
6

NC

E
N
G
.

L
I
C
E
N
S
E

#
F
-
0
1
7
6

P
H
O
N
E
:

(
9
1
9
)

8
7
2
-
2
6
6
0
D-1437
BTR
MAY 20161" = 100'
4305-15-175
PR
O
P
O
S
E
D

F
I
N
A
L

G
R
A
D
I
N
G
3
ED
G
E
C
O
M
B
E

C
O
U
N
T
Y

L
A
N
D
F
I
L
L
TA
R
B
O
R
O
,

N
O
R
T
H

C
A
R
O
L
I
N
A
Attachment I
Edgecombe County Landfill
Interim Corrective Action Evaluation Report
S&ME Project #: 4305-15-175
3201 Spring Forest Road
Raleigh, North Carolina 27616
D a t e :
1 0 -2 0 -0 8
P h o t o g r a p h e r :
S .
W a t t s
1
Location / Orientation Landfill Cap
Remarks Removal and regrading of existing stormwater slope diversion berms
D a t e :
1 0 -2 0 -0 8
P h o t o g r a p h e r :
S .
W a t t s
2
Location / Orientation Landfill Cap
Remarks Removal and regrading of existing stormwater slope diversion berms
Edgecombe County Landfill
Interim Corrective Action Evaluation Report
S&ME Project #: 4305-15-175
3201 Spring Forest Road
Raleigh, North Carolina 27616
D a t e :
1 0 -2 0 -1 6
P h o t o g r a p h e r :
S .
W a t t s
3
Location / Orientation Landfill Cap
Remarks Removal and regrading of existing stormwater slope diversion berms
D a t e :1 0 -2 0 -0 8
P h o t o g r a p h e r :
S .
W a t t s
4
Location / Orientation Landfill Cap
Remarks Removal and regrading of existing stormwater slope diversion berms
Edgecombe County Landfill
Interim Corrective Action Evaluation Report
S&ME Project #: 4305-15-175
3201 Spring Forest Road
Raleigh, North Carolina 27616
D a t e :
1 0 -2 0 -0 8
P h o t o g r a p h e r :
S .
W a t t s
5
Location / Orientation Landfill Cap
Remarks Removal and regrading of existing stormwater slope diversion berms
D a t e :
1 0 -2 0 -0 8
P h o t o g r a p h e r :
S .
W a t t s
6
Location / Orientation Landfill Cap
Remarks Removal and regrading of existing stormwater slope diversion berms
Edgecombe County Landfill
Interim Corrective Action Evaluation Report
S&ME Project #: 4305-15-175
3201 Spring Forest Road
Raleigh, North Carolina 27616
D a t e :
2 0 0 8
P h o t o g r a p h e r :
S .
W a t t s
6 Location / Orientation Landfill Cap
Remarks Removal and regrading of existing stormwater slope diversion berms
D a t e :
2 0 0 8
P h o t o g r a p h e r :
S .
W a t t s
7
Location / Orientation Landfill Cap
Remarks Removal and regrading of existing stormwater slope diversion berms
Edgecombe County Landfill
Interim Corrective Action Evaluation Report
S&ME Project #: 4305-15-175
3201 Spring Forest Road
Raleigh, North Carolina 27616
D a t e :
2 0 0 8
P h o t o g r a p h e r :
S .
W a t t s
8
Location / Orientation Landfill Cap
Remarks Removal and regrading of existing stormwater slope diversion berms
D a t e :
1 0 -2 0 -0 8
P h o t o g r a p h e r :
S .
W a t t s
9
Location / Orientation Landfill Cap
Remarks Removal and regrading of existing stormwater slope diversion berms
Edgecombe County Landfill
Interim Corrective Action Evaluation Report
S&ME Project #: 4305-15-175
3201 Spring Forest Road
Raleigh, North Carolina 27616
D a t e :
0 1 -0 8 -0 9
P h o t o g r a p h e r :
M .
L o g u t
10
Location / Orientation Pond south of the landfill (former Eagles farm), looking north
Remarks Representative photo of pond surface water elevation prior to
dewatering
D a t e :
0 1 -0 8 -0 9
P h o t o g r a p h e r :
M .
L o g u t
11 Location / Orientation View of the riser/outlet structure for the former Eagles farm pond.
Remarks The lid of the riser has been removed to evaluate the structure prior to
dewatering the pond.
Edgecombe County Landfill
Interim Corrective Action Evaluation Report
S&ME Project #: 4305-15-175
3201 Spring Forest Road
Raleigh, North Carolina 27616
D a t e :
0 1 -0 8 -0 9
P h o t o g r a p h e r :
M .
L o g u t
12 Location / Orientation
Two metal corrugated pipes discharging water through the dam the on
the former Eagles farm pond.
Remarks Prior to dewatering the pond.
D a t e :
0 6 -2 4 -1 1
P h o t o g r a p h e r :
M .
L o g u t
13 Location / Orientation View of the riser/outlet structure for the former Eagles farm pond.
Remarks Four courses of concrete blocks have been removed, lowering the
water level approximately three feet below the original pool level.
Edgecombe County Landfill
Interim Corrective Action Evaluation Report
S&ME Project #: 4305-15-175
3201 Spring Forest Road
Raleigh, North Carolina 27616
D a t e :
0 6 -2 4 -1 1
P h o t o g r a p h e r :
M .
L o g u t
10
Location / Orientation Former Eagles farm pond. Looking south.
Remarks View of the pond after lowering the water level approximately three
feet below the original pool level.
D a t e :
0 6 -2 4 -1 1
P h o t o g r a p h e r :
M .
L o g u t
11 Location / Orientation Former Eagles farm pond. Looking west
Remarks View of the pond after lowering the water level approximately three
feet below the original pool level.
Edgecombe County Landfill
Interim Corrective Action Evaluation Report
S&ME Project #: 4305-15-175
3201 Spring Forest Road
Raleigh, North Carolina 27616
D a t e :
0 1 -0 8 -0 9
P h o t o g r a p h e r :
M .
L o g u t
12
Location /
Orientation View of the riser/outlet for the former Eagles farm pond.
Remarks The riser has been partially deconstructed, lowering the water
level in the pond approximately six feet.
D a t e :
0 6 -2 4 -1 2
P h o t o g r a p h e r :
U n k n o w n
13
Location / Orientation Former Eagles farm pond. Looking south.
Remarks View of the pond after lowering the water level approximately
three feet below the original pool level.
Edgecombe County Landfill
Interim Corrective Action Evaluation Report
S&ME Project #: 4305-15-175
3201 Spring Forest Road
Raleigh, North Carolina 27616
D a t e :0 3 -1 3 -1 2
P h o t o g r a p h e r :
W .
R a w l s
14 Location / Orientation Former Eagles farm pond. Looking south.
Remarks View of the pond after lowering the water level approximately three
feet below the original pool level.
D a t e :
0 4 -1 0 -1 2
P h o t o g r a p h e r :
S .
W a t t s
15 Location / Orientation View of the riser/outlet for the former Eagles farm pond.
Remarks The riser has been deconstructed, down to the bottom, lowering the
water level in the pond approximately 10 feet below original pool.
Edgecombe County Landfill
Interim Corrective Action Evaluation Report
S&ME Project #: 4305-15-175
3201 Spring Forest Road
Raleigh, North Carolina 27616
D a t e :0 4 -1 0 -1 2
P h o t o g r a p h e r :
S .
W a t t s
14 Location / Orientation Former Eagles farm pond. Looking south.
Remarks View of the pond after lowering the water level approximately 10 feet
below the original pool level.
D a t e :
0 4 -1 0 -1 2
P h o t o g r a p h e r :
S .
W a t t s
16 Location / Orientation Former Eagles farm pond. Looking east.
Remarks View of the pond after lowering the water level approximately 10 feet
below the original pool level.
Edgecombe County Landfill
Interim Corrective Action Evaluation Report
S&ME Project #: 4305-15-175
3201 Spring Forest Road
Raleigh, North Carolina 27616
D a t e :
5 -1 5 -1 2
P h o t o g r a p h e r :
S .
W a t t s
17
Location / Orientation Former Eagles farm pond. Looking east.
Remarks Water being pumped out.
D a t e :
5 -1 5 -1 2
P h o t o g r a p h e r :
S .
W a t t s
18
Location / Orientation Former Eagles farm pond. Looking southeast.
Remarks Water pumped out for fish removal
Edgecombe County Landfill
Interim Corrective Action Evaluation Report
S&ME Project #: 4305-15-175
3201 Spring Forest Road
Raleigh, North Carolina 27616
D a t e :
5 -1 5 -1 2
P h o t o g r a p h e r :
A .
W a t t s
19
Location / Orientation Former Eagles farm pond. Looking south.
Remarks Fish Removal
D a t e :
8 -2 5 -1 5
P h o t o g r a p h e r :
A .
C u l p e p p e r
20
Location / Orientation Former Eagles farm pond. Looking west.
Remarks Breach in dam.
Edgecombe County Landfill
Interim Corrective Action Evaluation Report
S&ME Project #: 4305-15-175
3201 Spring Forest Road
Raleigh, North Carolina 27616
D a t e :
8 -2 5 -1 5
P h o t o g r a p h e r :
A .
C u l p e p p e r
21
Location / Orientation Former Eagles farm pond. Looking south.
Remarks View of the pond after the dam was breached, lowering the water level
approximately 20 feet below the original pool level.
Attachment II

S&ME, Inc. | 3201 Spring Forest Road | Raleigh, NC 27616 | p 919.872.2660 | f 919.876.3958 | www.smeinc.com

April 21, 2016
Edgecombe County Landfill
Administration Building, Box 10
Tarboro, North Carolina 27886
Attention: Mr. Larry Moore
Landfill Supervisor
Reference: Visual Landfill Cover Inspection - March 2016
Edgecombe County Landfill, Tarboro, North Carolina
Facility Permit No. 33-01
S&ME Project No. 4305-15-172
Dear Mr. Moore:
S&ME, Inc. (S&ME) is pleased to submit this letter report documenting our inspection of the landfill cover
on March 17, 2016 at the Edgecombe County Landfill located in Tarboro, North Carolina. Our services
were performed under our existing contract with Edgecombe County (S&ME Proposal No. 43-1500497,
dated August 27, 2015) based on directives from the North Carolina Department of Environment and
Natural Resources (NCDENR), Division of Waste Management (DWM) on May 16, 2001, and to assist
Edgecombe County comply with Section .1626(4) of 15A NCAC 13B (Solid Waste Rules).
 Project Background
Edgecombe County currently operates a solid waste facility on a tract of land located south of Tarboro,
North Carolina at 2872 Colonial Road (Figure 1). The County operates a construction & demolition (C&D)
landfill unit that rests over an existing closed municipal solid waste (MSW) landfill. The landfill is operated
in general accordance with North Carolina Department of Environment and Natural Resources (NCDENR)
Permit No. 33-01.
On behalf of Edgecombe County, S&ME has performed methane monitoring and visual evaluation
services on a quarterly basis in the effort to comply with the facility permits operational requirements and
Section .0544 (d) and .1626 (4) of the Solid Waste Management Rules. S&ME has previously transmitted
the methane monitoring results for the structures and gas monitor wells to the county by email.
 Visual Inspection Of Landfill Cover
A visual evaluation of the landfill cover and the landfill gas and groundwater monitoring wells was
completed at the Edgecombe County Landfill by Sam Watts, P.G. of S&ME on March 17, 2016. The landfill
cover system was examined for signs of settlement, erosion, vector damage, brown or bare vegetation,
bulging areas, standing water, deep-rooted or woody vegetation, and signs of gas leakage such as
distressed vegetation or fissures. The condition of the landfill gas extraction wells was also inspected
while onsite.
Visual Landfill Cover Inspection - March 2016
Edgecombe County Landfill, Tarboro, North Carolina
Facility Permit No. 33-01
S&ME Project No. 4305-15-172

April 21, 2016 2

Representative photographs of the observed site conditions are attached. The location of the photograph
and the observations are shown on Figure 1. In summary, S&ME personnel observed the following:
 Grass on the landfill cover was mowed and generally the coverage of the landfill in grass was
good (Photos 1).
 Leachate seepage was observed along southwestern portion of the landfill cap (Photo 2).
 Leachate seepage was also observed across the road on the north side of the landfill (Photo 3).
 Areas of wet grass and a seep area were observed along the northeastern side of the landfill
(Photos 4 and 5).
 A localized wet area within an area of sedge grass is located in the northwestern portion of the
landfill (Photo 6).
 Other areas of small leachate seeps were in the southeast edge of the landfill and in the northern
central area of the landfill.
 Active C&D filling of the landfill was observed as wells as new cover soil being placed over the
waste at the top (crown) of the landfill (Photo 7).
 Some of the slope drains in the northern central area of the landfill were cutoff or disconnected.
The observed leachate seeps were all contained within the facility boundary. S&ME personnel did not
observe any other additional maintenance requirements for the final cover system, erosion control
structures, landfill gas monitoring wells, or groundwater monitoring wells.
 Recommendations
Based upon the above observations, S&ME recommends Edgecombe County perform the following:
 Repair leachate seepage areas observed on the landfill cap (see the attached steps to repair a
leachate breakout);

 The slope drains in the northern central area of the landfill should be re-connected to provide
appropriate drainage;

 Continue regular mowing on the landfill cap and perimeter to promote healthy growth of grass,
and to minimize growth of weeds or tall vegetation with a tendency for deep root penetration;

 Continue to monitor steep slopes for signs of erosion and continue using flexible down-drains to
intercept and direct surface water away from areas that have not been stabilized;

 Continue methane monitoring at the facility in accordance with the facility closure plan; and,

 Place a copy of this report in the facility operating record.

Visual Landfill Cover Inspection - March 2016
Edgecombe County Landfill, Tarboro, North Carolina
Facility Permit No. 33-01
S&ME Project No. 4305-15-172

April 21, 2016 3
 CLOSING
Please call us at [phone] if you have any questions about the information presented in this letter,
or if we can be of further assistance.
Sincerely,
S&ME, Inc.

Claudia Irvin, E.I.T. Samuel P. Watts, P.G.
Environmental Scientist Senior Project Manager

Attachments: Figure 1 – Landfill Cover Inspection Observations
Photograph Log
Leachate Breakout Repair Process
cc: Jimmy Price, Edgecombe County Interim Solid Waste Director

Visual Landfill Cover Inspection - Edgecombe County Landfill
Tarboro, North Carolina S&ME Project No. 4305-15-172
Taken by: S. Watts Date Taken: 3/17/2016
1

1 View looking northwest at C&D landfill from entrance road.
Overall, grass looks established.
2 Leachate seep located in the southwestern portion of the
landfill.

3 Leachate seep across access road on north side of
landfill.
4

An area of wet in the grassed area to the left of the access
road located on the north side of the landfill.

Visual Landfill Cover Inspection - Edgecombe County Landfill
Tarboro, North Carolina S&ME Project No. 4305-15-172
Taken by: S. Watts Date Taken: 3/17/2016
2

5 Leachate seep area located on the south side of the north
access road.
6 Wet area and sedge grass located in the northwestern
portion of the landfill.
7 Looking southwest from the northern access road. New
cover soil is visible to the left.

Visual Landfill Cover Inspection - March 2016
Edgecombe County Landfill, Tarboro, North Carolina
Facility Permit No. 33-01
S&ME Project No. 4305-15-172

April 21, 2016

LEACHATE BREAKOUT REPAIR
At locations where leachate breakout repair is required, the following steps shall be taken:
Step 1:
The surrounding grade elevation and boundary of the leachate breakout shall be established by surveying
or string-lining and marked by staking as necessary.
Step 2:
An impervious and heavy duty tarp or heavy mil plastic sheet shall be set close to the excavation areas
and shall be used for the stockpiling of excavated material.
Step 3:
Soil within 3 feet of the marked edge of the leachate breakout shall be excavated. Excavated material
down-slope of the leachate breakout shall be disposed of as waste. Excavated material up-slope of the
leachate breakout shall be stockpiled as Topsoil (for the top 9 inches) or General Fill (for soil between the
top 9 inches and the waste).
Step 4:
Once waste material is reached, excavation shall proceed further until four feet of waste is excavated.
Drainage aggregate shall then be placed to within 2.5 feet of existing grade.
Step 5:
Above the drainage aggregate, General Fill shall be placed in loose lifts not exceeding 6 inches in
thickness. The fill shall be moisture conditioned and compacted. Dry bentonite powder shall be spread
over each compacted lift at a rate of 2.5 lbs. per square foot. Lifts shall be placed in this manner to a
depth from existing grade of 8 inches.
Step 6:
The stockpiled Topsoil shall be combined with imported Topsoil and placed evenly back into the
excavated area such that the elevation of the final surface of the excavated area is now approximately at
the existing grade elevation. The exposed Topsoil layer shall be fertilized, seeded, and matted. It is
expected that the 1-inch height difference will even out to desired elevation over time.
Step 7:
Dispose of any remaining excavated waste in a MSW landfill. Remove the tarp or heavy mil plastic sheet
and uncover any grass covered by repair activities.

Attachment III
SUBSURFACE EXPLORATION & HYDROGEOLOGIC ASSESSMENT REPORT EDGECOMBE COUNTY LANDFILL TARBORO, NORTH CAROLINA
S&ME Project No. 1054-07-241A

Prepared for:
Edgecombe County
P.O. Box 10
Tarboro, North Carolina 27886

Prepared by:

S&ME, Inc.
3201 Spring Forest Road
Raleigh, North Carolina 27616

November 2009

Subsurface Exploration & Hydrogeologic Assessment Report S&ME Project No. 1054-07-241A
Edgecombe County Landfill, Tarboro, NC November 20, 2009

i
TABLE OF CONTENTS
1. INTRODUCTION ..................................................................................................... 1
2. PROJECT DESCRIPTION...................................................................................... 2
3. SUBSURFACE EXPLORATION............................................................................ 3
3.1 Test Pit Excavations............................................................................................ 3
3.2 Standard Penetration Test (SPT) Borings ........................................................... 4
3.3 Interpretation of Lithology for Barrier Design ................................................... 4
3.3.1 Open Ditch – Hydraulic Barrier Corrective Measure Option............. 4
3.3.2 Sedimentation Basin SB-3 .................................................................. 5
3.3.3 Subsurface Barrier Wall - Hydraulic Barrier Corrective Measure
Option 6
3.4 Laboratory Testing.............................................................................................. 7
3.4.1 Soil Boring Sample Data .................................................................... 7
3.4.2 Test Pit Bulk Sample Data.................................................................. 7
3.5 Findings Subsurface Exploration ........................................................................ 8
4. Hydrogeologic Study ................................................................................................. 9
4.1 Soil Borings, Piezometers, and Site Measurements............................................ 9
4.2 Hydraulic Monitoring and Groundwater/Surface Water Interaction ................ 10
4.3 Pond Discharge Test ......................................................................................... 11
4.4 Pond Study Results ........................................................................................... 11
5. CONCLUSIONS...................................................................................................... 12

TABLES
Table 1 Soil Boring Test Results
Table 2 Test Pit Sample Test Results
Table 3 Standard Proctor Test Pit Data
Table 4 Pond Study Water Level Data

FIGURES
Figure 1 Site Plan
Figure 2 Cross Section of Study Area

APPENDICIES
Appendix I Summary of Test Pit Data Records
Appendix II SPT Boring Logs
Appendix III Laboratory Test Records
Appendix IV Pond Study Measurements and Calculations
Subsurface Exploration & Hydrogeologic Assessment Report S&ME Project No. 1054-07-241A
Edgecombe County Landfill, Tarboro, NC November 20, 2009

1
1. INTRODUCTION
Edgecombe County currently operates a construction and demolition (C&D) debris
landfill on top of a closed municipal solid waste (MSW) landfill on a tract of land located
off of Colonial Road (State Road 1601) in Edgecombe County, south of Tarboro, North
Carolina. S&ME has previously assisted the County with environmental and engineering
services for the landfill facility as required by the North Carolina Solid Waste
Management Rules (15A NCAC 13B).

As a part of those services, S&ME completed a Corrective Action Plan (CAP) for the
landfill in accordance with Solid Waste Rules defined under 15A NCAC 13B .1636 and
.1637. That CAP (dated June 30, 2008) was submitted on behalf of Edgecombe County
to the North Carolina Department and Natural Resources (NCDENR) Division of Waste
Management (DWM). The CAP included the selection of In-situ Isolation combined
with monitored natural attenuation (MNA) as the remedial alternatives for groundwater
impacted with cobalt, petroleum constituents and chlorinated compounds. In-situ
Isolation was selected because the site conceptual model indicates that surface water and
groundwater management issues are the primary mechanism for addressing the release
and migration of the constituents of concern at the landfill. MNA has been incorporated
into the facility’s updated (August, 2009) water quality monitoring plan (WQMP) to
monitor and evaluate the effectiveness of the remedial measures.

This report was prepared to present the findings of the subsurface investigation and
hydrogeologic assessment. The data from the subsurface investigation and
hydrogeologic assessment was collected for use in designing the hydraulic barrier and
stormwater drainage system components necessary to implement the corrective measures
selected in the CAP. The findings from these investigations may also be used to review
corrective measures alternatives that may be well suited to meet the Edgecombe County
long-term objectives for the landfill facility.
Subsurface Exploration & Hydrogeologic Assessment Report S&ME Project No. 1054-07-241A
Edgecombe County Landfill, Tarboro, NC November 20, 2009

2
2. PROJECT DESCRIPTION
The implementation of the selected corrective measures, In-situ Isolation and MNA, as
the proposed remedies at the Edgecombe County Landfill will involve the following:

• Installation of an upgradient groundwater hydraulic barrier;
• Maintaining a consistent contour with the pre-1998 waste area;
• Increase slope of the closed MSW area;
• Stormwater improvements on the western half of the landfill; and,
• Implementation of a MNA program to address impacted groundwater.

The proposed design and installation of the hydraulic barrier on the upgradient south side
of the landfill and the stormwater drainage improvements proposed for the west side of
the landfill required a more thorough understanding of subsurface soil and groundwater
conditions in those specific areas of the site to prepare an engineered design. Subsurface
exploration was performed to review the lithologic sequence and soil engineering
properties for the geotechnical engineering component of the corrective measure design.
The barrier wall on the upgradient side of the landfill and the stormwater improvements
also required both conceptual and design engineering services. A hydraulic stress test
using the pond as a discharge point was performed to review the aquifer response and
effects of dewatering for use in the review of cost effective barrier system options to be
selected for a design. S&ME utilized test pits and soil borings and performed a
hydrogeologic evaluation to collect site-specific data to support the engineered CAP
design.

Improvements to the landfill cap drainage system involved a review of existing site
drainage conditions. Material volume estimates were required and sources for suitable
soil from accessible locations for landfill cap system grading modifications were
reviewed.

A meeting was held on March 12, 2009 with Mr. Lorenzo Carmon and Mr. Danny
Bagley of Edgecombe County and Mr. Sam Watts and Mr. David Wells of S&ME, Inc.
During this meeting, Mr. Carmon indicated that Edgecombe County was considering the
option to purchase the adjoining property to the south of the landfill. The purchase plan
would expand the property boundary to the south so that the acquired land could be
utilized to construct a collection trench, instead of a barrier wall, and to utilize dewatering
of the existing pond and drainage features associated with the property to the south to
form the hydraulic barrier on the south side of the landfill.

As a result of this meeting, S&ME has prepared a separate feasibility evaluation report
that compares alternatives for the hydraulic barrier system that may be used in the
corrective measures system. The report compares the approved proposed design
described in the 2008 CAP and two alternatives based on the findings of this subsurface
exploration and hydrogeologic assessment. The feasibility report presents conceptual
models for the alternatives with estimated installation costs compared to the corrective
measures described in the approved CAP. The options presented in the feasibility
evaluation report are for review and/or approval by Edgecombe County.
Subsurface Exploration & Hydrogeologic Assessment Report S&ME Project No. 1054-07-241A
Edgecombe County Landfill, Tarboro, NC November 20, 2009

3
3. SUBSURFACE EXPLORATION
3.1 Test Pit Excavations
A representative of S&ME was present at the site on October 7, 2008 to observe test pit
excavations conducted using a rubber tire backhoe. Seven test pits were excavated by
Edgecombe County Landfill personnel at locations and depths determined by S&ME in
the field based on encountered soil conditions. The test pits were performed to review
soil properties that would be encountered by future grading activities for the corrective
measures.

Test pit locations:
• TP-1, TP-2, TP-3, TP-4, and TP-5 were positioned near the proposed
location of the open ditch near the south and west boundary of the site.
• TP-6 was located within the limits of the proposed Sedimentation Pond
SB-3 near the northwest corner of the site.
• TP-7 was centrally located on the site east of the proposed ditch line near
the south property boundary.

Soil descriptions for the lithologic sequence were documented on test pit data log forms.
Approximate test pit locations are shown on the Site Plan, Figure 1.

Test pits were excavated to depths that ranged from approximately eight to ten feet below
ground surface (bgs). Test pit TP-7 encountered buried waste materials at an
approximate depth of three feet bgs and was terminated at that depth. Encountered soils
were visually classified in the field by an S&ME representative in general accordance
with Unified Classification System (USCS) guidelines. If groundwater was observed in a
test pit, the groundwater level from below the ground surface was measured in the test pit
after its completion. Summaries of subsurface conditions encountered in test pits are
presented in Appendix I, Summary of Test Pit Data logs.

Approximately three inches of grass and topsoil was encountered at the ground surface at
test pit locations TP-3, TP-4, TP-5, and TP-7. Beneath the surface materials, natural soils
were typically encountered to test pit termination depths. Natural soils consist of clayey
and silty sands (SP-SC, SC, SM), sandy and clayey silts (ML), and sandy and silty clays
(CL). The typical profile consists of near surface silty and clayey sands to approximate
depths of three to five feet bgs underlain by silts and clays. The majority of the
excavated materials were visually observed as wet of their optimum moisture content.
Test pit TP-1 was excavated to a depth of approximately eight feet below the land
surface. Water was encountered in test pit TP-1. The depth to water in test pit TP-1
approximately two hours after excavation completion was approximately four feet bgs.
Note that test pit TP-1 is located in the ditch on the southwestern portion of the site. At
the time of the excavation, the backhoe became stuck in the ditch at test pit TP-1.
Therefore, the other test pit locations were offset to locations topographically higher than
the ditch. After up to 1.75 hours of test pit completion, no accumulated groundwater was
observed in the excavation bottoms at test pit locations TP-2 through TP-7. Figure 1
shows test pit locations along with site topography.
Subsurface Exploration & Hydrogeologic Assessment Report S&ME Project No. 1054-07-241A
Edgecombe County Landfill, Tarboro, NC November 20, 2009

4
3.2 Standard Penetration Test (SPT) Borings
S&ME personnel were present at the site on February 13 and 17, 2009 to observe
standard penetration test (SPT) borings conducted using hollow stem auger drilling
procedures with S&ME’s CME-550 drill mounted on an all terrain vehicle. Thirteen SPT
borings were completed by S&ME personnel at locations along the proposed open
drainage ditch or barrier wall near the southeastern property boundary. Approximate
SPT boring locations are shown on the Site Plan, Figure 1. SPT boring logs are
presented in Appendix II.

SPT borings were performed to depths ranging from approximately 15 to 30 feet bgs.
Within each boring, samples were collected at 2.5-foot intervals with a split-spoon
sampler, with the exception of borings B-11 and B-13. SPT borings B-11 and B-13 were
sampled at five-foot intervals with a split-spoon sampler. Standard penetration tests were
conducted in conjunction with split-spoon sampling in general accordance with ASTM D
1586. Soils were classified in the field during drilling operations by S&ME personnel.
Borings were backfilled with soil cuttings mixed with bentonite.

The typical SPT boring profile consists of near surface sand, silty sand, and clayey sand
underlain by silts and clays. The subsurface exploration identified a marine clay
(Yorktown Formation), underlying the near surface soils at the landfill site at depths
ranging from nine feet bgs in boring B-3 to 24.5 feet bgs in boring B-11. Figure 1 shows
SPT boring locations.
3.3 Interpretation of Lithology for Barrier Design
The boring locations were positioned to correlate with proposed corrective measures
locations including the open drainage ditch, the barrier wall, or the French drain that will
be used to implement controls on surface water and/or groundwater flowing toward the
landfill. The summary of the test pit and boring lithology and the target layers
encountered in the sample locations that influence the engineered design for corrective
measure options is presented below. Figure 2 presents a cross-section of the assessment
area.
3.3.1 Open Ditch – Hydraulic Barrier Corrective Measure Option
Grading and excavation were proposed to construct an open drainage ditch that would act
as a hydraulic barrier and groundwater diversion from the central portion of the south
property boundary toward the southwest corner of the property and parallel to the west
property boundary to the north toward Jerry’s Creek. Test Pits TP-1 through TP-5 and
soil borings B-1 through B-4 were drilled to review the soil types present for the purpose
of ditch design as well as to review the potential re-use of excavated material that will be
removed to construct the ditch. Boring depths were targeted to terminate in the marine
clay. The lithology from the soil borings and test pits presented in order from east to
west to north in the area of the proposed open ditch is summarized below.

• Boring B-4 – encountered silty sand, silty clay, and clayey silt, clayey sands
resting over marine clay at a depth of 21 feet bgs. The bottom of the ditch
could correspond to the elevation of the top of the marine clay.

Subsurface Exploration & Hydrogeologic Assessment Report S&ME Project No. 1054-07-241A
Edgecombe County Landfill, Tarboro, NC November 20, 2009

5
• Boring B-3 – encountered silty and clayey sands and wet sandy clay resting
over marine clay at a depth of nine feet. The bottom of the ditch could
correspond to the elevation of the top of the marine clay.

• Boring B-2 – encountered silt, silty sand, silty clay, and clayey sands resting
over marine clay at a depth of ten feet bgs. Soft clay and sandy silt over the
marine clay indicate that the bottom of the ditch could correspond to the
elevation of the top of the marine clay.

• Boring B-1 – encountered silty and clayey sands resting over marine clay at a
depth of 11 feet bgs. No significant clay was present above marine clay from
this boring. For design purposes, the bottom of the ditch could correspond to
the elevation of the top of the marine clay.

• TP-1 – encountered approximately five feet of poorly sorted wet to saturated
sand to clayey sand that was resting over saturated clay.

• TP-2 – encountered approximately two feet of wet silty clay that was present
over two feet of wet silty sand that rests over wet silty clay.

• TP-3 – encountered approximately five feet of sandy silt that was present over
wet silty clay;.

• TP-4 – encountered approximately five feet of wet silty sand that was present
over wet clayey silt.

• TP-5 – encountered approximately one foot of wet silty sand resting on three
feet of clayey fine sand that was resting over wet clayey silt.

The soil borings and test pits performed to assess the proposed open ditch location
indicate that a marine clay (Yorktown Formation) encountered on the south boundary of
the facility was at elevation of approximately 61 feet msl (feet relative to mean sea level).
The surface of the marine clay appears to be generally flat with little undulation west of
soil boring B-3 and slopes downward to the south toward Jerry’s Creek. The soil material
observed in the test pits was moist to saturated.
3.3.2 Sedimentation Basin SB-3
The outfall from the proposed open ditch will be designed to discharge into a proposed
sedimentation basin located near the northwest corner of the facility. A significant
quantity of material will likely be excavated from this area to construct the sedimentation
basin. Test pit TP-6 was located near the middle in an area likely to be excavated to the
greatest depth of the proposed sedimentation basin. The findings from test pit TP-6 are as
follows:

• TP-6 – encountered approximately 3.5 feet of moist silty fine sand resting
over approximately 3.5 feet of wet clayey silt that both over lay wet silty sand.

Subsurface Exploration & Hydrogeologic Assessment Report S&ME Project No. 1054-07-241A
Edgecombe County Landfill, Tarboro, NC November 20, 2009

6
Based on the lithology from test pit TP-6, the material excavated during construction for
the sedimentation basin will likely be suitable for daily cover material at the C&D
landfill.
3.3.3 Subsurface Barrier Wall - Hydraulic Barrier Corrective Measure Option
The proposed hydraulic barrier options may include a barrier wall or a French drain for
groundwater diversion from the central south property boundary to the east corner of the
landfill property. Test pit TP-7 and soil borings B-5 through B-13 were performed to
review the soil types present for the proposed barrier wall design as well as to review the
depth and thickness of water bearing units for designing a French drain that would divert
groundwater and bypass the landfill. The samples were also used to review the potential
re-use of excavated material that will be removed to construct the barrier system. Boring
depths were targeted to terminate in the marine clay. The lithology from the soil borings
and test pit presented in order from west to east in the area of the proposed hydraulic
barrier is summarized below.

• Boring B-7 – encountered sandy clay, silty sand, and sandy clay resting over
marine clay at a depth of 19 feet bgs. The sandy clay was soft at 11.5 feet
bgs. Therefore the barrier bottom may target the marine clay top elevation.

• Boring B-5 – was performed to a depth of three feet bgs and then off-set to
the south since waste materials were encountered between three and 8.5 feet
bgs. Silty sand, sandy silt and sandy clay to sandy silt were observed over the
top of a blue gray marine clay at a depth of 17 feet bgs. The bottom of the
barrier could correspond to the elevation of the top of the marine clay.

• Boring B-8 – encountered sand, sandy clay, and sandy clay to clayey sand
layers resting over the top of marine clay at a depth of 21 feet bgs. The bottom
of the barrier could correspond to the elevation of the top of the marine clay.

• TP-7 – encountered approximately one foot of silty sand resting
approximately one half foot of gravel that was resting on moist silty sand.

• Boring B-6 – encountered silty sand resting over waste material at a depth of
five feet bgs where it was terminated.

• Boring B-9 – encountered silty sand, silty clay, sand, sandy clay, silty sand,
wet clay and clayey sand resting over the top of marine clay at a depth of 22
feet bgs. The bottom of the barrier could correspond to the elevation of the top
of the marine clay.

• Boring B-10 – encountered sand, silty clay, and sandy clay to clayey sand
resting over marine clay at a depth of 21 feet bgs. The bottom of the barrier
could correspond to the elevation of the top of the marine clay.

• Boring B-11 – encountered sandy silty clay, sand, clay, and coarse sand
resting over the top of marine clay at a depth of approximately 24.5 feet bgs.
Subsurface Exploration & Hydrogeologic Assessment Report S&ME Project No. 1054-07-241A
Edgecombe County Landfill, Tarboro, NC November 20, 2009

7
The barrier bottom could target the marine clay at approximately 24.5 feet
bgs.

• Boring B-12 – encountered sand resting over black silty clay present from
three to 15 feet.

• Boring B-13 – encountered sandy and silty clay resting over the top of marine
clay at a depth of 18 feet bgs. The silty clay was soft at 15 feet bgs. The
bottom of the barrier could correspond to the elevation of the top of the
marine clay.

The soil borings performed to assess the proposed barrier system location indicate that a
marine clay (Yorktown Formation) was encountered at elevations ranging from
approximately 45 feet msl to 62 feet msl. An apparent ridge in the clay (62 feet msl) was
indicated by the boring data from boring location B-5 near the south boundary of the
facility. The surface of the marine clay appears generally flat with some undulation west
of the ridge and slopes more steeply down from the ridge to east with some undulation.
The borings east of the ridge indicate that the marine clay slopes more steeply downward
to the east toward the pond.
3.4 Laboratory Testing
Soil samples were submitted to the laboratory for testing to determine natural moisture
content, grain size distribution, plasticity indices (Atterberg Limits), moisture density
standard proctor curves, or soil permeability rates. Tests were performed on split spoon
samples collected from selected soil borings as well as selected bulk samples obtained
from the test pits. The soil permeability (hydraulic conductivity) tests were performed on
re-compacted bulk samples. The laboratory testing was performed in general accordance
with applicable ASTM standards.
3.4.1 Soil Boring Sample Data
Grain size analysis testing (ASTM D 422) was performed on soil samples obtained from
soil borings B-1, B-3, B-5, B-8, B-9, B-12, and B-13. The results of the soil grain size
distribution tests, natural moisture content, and Atterberg Limits are summarized in
Table 1.
3.4.2 Test Pit Bulk Sample Data
Grain size analysis testing (ASTM D 422) was performed on bulk samples obtained from
test pits TP-1, TP-2, TP-3, and TP-6. The results of the soil grain size distribution tests
incorporated with the test pit log indicated the following:

Atterberg limits testing (ASTM D 4318) was performed on bulk samples obtained from
test pits TP-2 and TP-3. Results of Atterberg limits tests indicate liquid limits (LL)
between 34 and 47 percent, plastic limits between 15 and 25 percent, and plasticity
indices (PI) between 13 and 22 percent. Testing indicates that the tested soils have low
plasticity indicative of sandy clay, and moderate plasticity characteristics typical of silty
clay. The results of the soil grain size distribution tests, natural moisture content, and
Atterberg Limits from the Test Pit samples are summarized in Table 2.
Subsurface Exploration & Hydrogeologic Assessment Report S&ME Project No. 1054-07-241A
Edgecombe County Landfill, Tarboro, NC November 20, 2009

8

Standard Proctor compaction tests (ASTM D 698) were performed on bulk samples
obtained from test pits TP-1, TP-2, and TP-3. The Standard Proctor compaction tests
results are summarized in Table 3. The natural moisture contents of the bulk samples
ranged from approximately 15.7 to 65.4 percent. Natural moisture content testing
indicates a majority of the tested soils are well above their optimum moisture.

Hydraulic conductivity testing (ASTM D 5084) was performed on five recompacted bulk
samples to review the potential for re-use of excavated material in the design and
construction phase of corrective measures at the landfill. The samples were recompacted
to approximately 95 percent of their Standard Proctor maximum dry density near their
corresponding optimum moisture content. The permeability values (k) in centimeters per
second (cm/s) are summarized below from the re-compacted samples tested:

TP-1 five to six feet bgs 2.29x10-6;
TP-2 surface to two feet bgs 1.01x10-6;
TP-2 four to five ft bgs 6.41x10-7;
TP-3 surface to two feet bgs7.22x10-7;
TP-3 six to eight feet bgs 4.60x10-7.

The k values measured by the permeability tests indicate that material with low
permeability soil (approximately 10-6 cm/s and 10-7 cm/s) is present on site.

Laboratory tests were conducted in general accordance with applicable ASTM test
procedures. Dry density and optimum moisture contents from the Standard Proctor Tests
are summarized in Table 3. A tabular summary of laboratory testing and individual
laboratory test data sheets are presented in Appendix III.
3.5 Findings Subsurface Exploration
In general, the results of the subsurface exploration indicated that soils encountered
within the test pits and soil test borings are suitable for use as general site fill (i.e. raising
grades in landfill area, daily cover for the C&D waste operations, and vegetative cover).
However, soils encountered at ground surface at some test pit locations contain organic
material which will require removal prior to use as fill. Significant portions of the soil
materials encountered in the test pits are wet and will require extensive drying prior to re-
use as fill. Tests performed on clay material from test pit bulk samples indicate that low
permeability soils (k values less than 10-5 cm/s) were present on site. Low permeability
soil is required for landfill cap material and can also be used as liner material for
sedimentation basins.

The soil borings performed to assess the proposed barrier system location indicate that a
marine clay (Yorktown Formation) was encountered at elevations ranging from
approximately 45 feet msl to 62 feet msl. An apparent ridge in the clay (62 feet msl) was
indicated by the boring data from boring location B-5 near the south boundary of the
facility. The surface of the marine clay appears generally flat with some undulation west
of the ridge and slopes more steeply down from the ridge to east with some undulation
Subsurface Exploration & Hydrogeologic Assessment Report S&ME Project No. 1054-07-241A
Edgecombe County Landfill, Tarboro, NC November 20, 2009

9
4. HYDROGEOLOGIC STUDY
A hydraulic study was performed to collect data that was used to review potential options
and configurations for a groundwater barrier to implement the “in-situ isolation”
corrective measures plan.

The conceptual In-situ Isolation plan in the CAP involves the construction of a barrier to
block and divert groundwater flow on top of the Yorktown marine clay from flowing
beneath the landfill. This proposed hydraulic barrier is to extend along the southern
(upgradient) boundary of the landfill. By retaining and diverting the upgradient
groundwater flow toward the landfill, the volume of water that could contribute to the
production of leachate and for the transport of leachate that is generated will likely be
reduced. The reduction of groundwater flow beneath the landfill will likely result in
reduced contaminant concentrations in the groundwater over time and lower groundwater
table levels below the landfill resulting in an increased vertical separation between the
bottom of the buried waste and the remaining groundwater above the clay.

The hydrogeologic study used data from soil borings described in Section 3.3, the test
pits discussed in Section 3.4 as well as soil borings, temporary piezometers, and
monitored dewatering of the surface water impoundments located on the southeast
boundary of the landfill site. The surface water impoundments (Study Ponds), shown on
Figure 2, are near Storage 1 and Break Trailer 2.
4.1 Soil Borings, Piezometers, and Site Measurements
Three shallow soil borings with temporary piezometers were installed on January 8,
2009. Borings Pond 1, Pond 2 and Pond 3 were completed to 12 feet bgs, 11 feet bgs and
6.5 feet bgs, respectively. The borings with piezometers were installed to review the
lithology and groundwater levels in the vicinity of two surface water features located near
the southeast corner of the Edgecombe County facility west of Colonial Road. The three
borings were positioned on the facility. The surface water features are two retention
ponds that are connected by a small stream channel. The southernmost pond is entirely
located off-site south of the facility. The primary pond reviewed by the study is the pond
that is located partially on the facility and partially off-site. Figure 1 shows the locations
of the piezometers and the study ponds.

Soil boring Pond 1 was located south of the break trailer on the facility approximately
26 feet from the north edge of the pond at full pool, and approximately 35 feet from the
pond outfall structure. The boring for Pond 1 encountered silty sand, gravel, clayey silt,
and silty sand over silty clay at a depth of 3.5 feet. There was organic layer within the
silty clay was present at 4.5 feet and soils were wet at approximately 5 feet bgs. The silty
clay rested on sandy silt present between 5 and 7.5 feet bgs. Gray silty clay was observed
from 7.5 feet to the termination of the boring at 12 feet bgs. A two-inch diameter PVC
well screen and casing were installed into the borehole. The well screen was ten feet
long and terminated at a depth of approximately 12 feet below the ground surface. Sand
was placed around the well screen to approximately one foot above the screen interval.
Bentonite was placed in the annular space of the boring around the riser pipe from the top
of the sand pack to the ground surface to seal the temporary well. Approximately three
feet of riser pipe stuck up above the ground surface.
Subsurface Exploration & Hydrogeologic Assessment Report S&ME Project No. 1054-07-241A
Edgecombe County Landfill, Tarboro, NC November 20, 2009

10

Soil boring Pond 2 was positioned approximately 105 feet west of soil boring Pond 1
and was approximately 35 feet from the north edge of the pond at full pool. The boring
for Pond 2 encountered silty gravel, sandy clay, silty sand, that rest on the top of silty
clay present from 4.5 feet bgs to 5.5 feet bgs. The silty clay rests on clayey sand at a
depth of 5.5 feet. The clayey sand rested on sandy silt observed between 7 feet bgs and
the termination of the boring at 11 feet bgs. A two-inch diameter PVC well screen and
casing were installed into the borehole. The well screen was five feet long and
terminated at a depth of approximately 11 feet below the ground surface. Sand was
placed around the well screen to approximately two feet above the screen interval.
Bentonite was placed in the annular space of the boring around the riser pipe from the top
of the sand pack to the ground surface to seal the temporary well. Approximately one foot
of riser pipe stuck up above the ground surface.

Soil boring Pond 3 was approximately 400 feet west-southwest of the outfall to the
northern pond, and was positioned between the off-site pond and the facility pond.
Boring Pond 3 encountered roots, silty clay, sandy silt, clayey silt, and silty sand resting
over sandy clay from 5 feet bgs to the termination of the boring at 6.5 feet bgs. The soils
reviewed in the boring were wet at approximately two feet bgs. A two-inch diameter
PVC well screen and casing were installed into the borehole. The well screen was five
feet long and terminated at a depth of approximately 6.5 feet below the ground surface.
Sand was placed around the well screen to approximately one foot above the screen
interval. Bentonite was placed in the annular space of the boring around the riser pipe
from the top of the sand pack to the ground surface to seal the temporary well.
Approximately 3.5 feet of riser pipe stuck up above the ground surface.

S&ME measured the elevations of the top of the piezometers using a tripod, level, and
rod marked in feet in 1/100th of a foot increments. The top of casing (TOC) elevations
for piezometers Pond 1 and Pond 2 and the elevation of the top of the outfall to the
Edgecombe County pond were measured on January 8, 2009. The top of casing for
piezometer Pond 3 was measured on January 13, 2009. The elevation measurements
were made relative to the well casing elevation at monitor well MW-4. Groundwater
levels were monitored from Pond 1, Pond 2, Pond 3, MW-4, GW-4, MW-3B, GW-2R
GW-1R, and P-1. The pond pool elevation was monitored by measurements made from
the measuring point on the top of the outfall. Initial groundwater level measurements
while the pond was at full pool were recorded January 8, 2009 from the monitoring
points.
4.2 Hydraulic Monitoring and Groundwater/Surface Water Interaction
The January 8, 2009 groundwater level measurements from the piezometer and monitor
well TOCs in the pond study monitoring network (Pond 1, Pond 2, Pond 3, MW-4, GW-
4, MW-3B, GW-2R GW-1R, and P-1) and the pond pool elevation measured from the
point on the top of the outfall in the pond were compared. The elevations indicate that
the pond elevation is higher than the groundwater levels in the piezometers and monitor
wells located adjacent to the pond. Therefore, the pond is acting as a recharge feature of
surface water to the groundwater aquifer while the pond elevation is at full pool.

Subsurface Exploration & Hydrogeologic Assessment Report S&ME Project No. 1054-07-241A
Edgecombe County Landfill, Tarboro, NC November 20, 2009

11
Since the pond was a man-made surface water feature, a study was performed to review
the impact of dewatering the pond. While surface water was released from the pond to
lower the pool elevation, the pond study monitoring network of points was monitored to
review the groundwater level changes in the adjacent monitor wells.
4.3 Pond Discharge Test
A continuous discharge from the pond was established using a siphon system where
surface water was discharged from the pond outfall structure. The flow rate was initially
approximately 60 gallons per minute. Since the flow was the result of a siphon system,
the discharge rate decreased slightly as the head in the pond pool elevation was lowered.

The discharge commenced on February 13, 2009. Groundwater and surface water levels
were monitored for the network on February 13, 2009 and on February 17, 2009.
Continuous water level data was collected using pressure transducers in piezometers
Pond 1, Pond 2 and in monitor well MW-4. The water level data was reviewed and
analysis was performed using water level measurements at start up and immediately
before the discharge from the siphon was stopped on February 17, 2009.
4.4 Pond Study Results
The hydrogeologic study was performed to assess the interaction of the surface water in
the facility pond located on the southeast corned of the facility property. The study
indicated that the pond acts as a recharge feature to the water table while the pond is at
full pool elevation. The water levels measured during the discharge test indicated that a
partial reversal in the recharge affect to the aquifer from the pond would occur when the
pond level was lowered approximately 7.5 feet below the January 8, 2009 full pool
elevation. At the point that the pond level is lowered approximately eight feet (elevation
of ~56 feet-msl) below the top of the outfall structure, the pond becomes a discharge
feature and groundwater from the aquifer will flow toward the pond. Selected
groundwater elevation data is presented in Table 4 to show this relationship. The
elevations of the temporary piezometers (Pond 1 through Pond 3) and the top of the
outfall structure to the pond were measured relative to the top of casing elevation
reported by Spruill and Associates September 4, 2007 for monitor well MW-4. Elevation
measurements of the points used for the hydrogeologic assessment by S&ME and a copy
of the drawdown analysis made from the groundwater and surface water elevations for
the pond study are located in Appendix IV.

The analysis of the interaction of groundwater and surface water elevation data during
dewatering of the pond indicates that lowering the pond elevation by eight feet below the
current pool elevation controlled by the outfall structure would impose a hydraulic barrier
on the upgradient (southeastern) corner of the landfill. Lowering the surface water level
in the ponds is an alternative that the County may review to use as a component to the
hydraulic barrier described in the CAP.

Subsurface Exploration & Hydrogeologic Assessment Report S&ME Project No. 1054-07-241A
Edgecombe County Landfill, Tarboro, NC November 20, 2009

12
5. CONCLUSIONS
The results of the subsurface exploration assisted in defining the depth to the Yorktown
Formation marine clay and describing the lithology in locations for the proposed
hydraulic barrier and stormwater drainage system described in the 2008 CAP. The
elevations of the marine clay surface will be used to prepare the designs and grading
plans for the subsurface drainage and stormwater improvements for the hydraulic barrier
system.

The soil borings performed to assess the proposed barrier system location indicate that
the Yorktown Formation marine clay was encountered at elevations ranging from
approximately 45 feet msl to 62 feet msl. The subsurface exploration obtained sufficient
depth and elevation data for the top of the marine clay to prepare a design for a hydraulic
barrier that penetrates the surface of the marine clay layer.

In general, the subsurface exploration found that the soils are suitable for use as general
site fill (i.e. raising grades in landfill area, daily cover for the C&D waste operations, and
vegetative cover). Organic material that was encountered at the ground surface at some
test pit locations may be used for the vegetative cover layer over the low permeable soil
in the landfill cap. The soil materials encountered in the test pits are wet and will require
extensive drying prior to re-use as fill material. Testing performed on clay material from
test pit bulk samples indicate that low permeability soils (k values less than 10-5 cm/s)
were present on site. Low permeability soil is required for landfill cap material and may
also be used as liner material for sedimentation basins.

The hydrogeologic study was performed to assess the interaction of the surface water in
the facility pond located on the southeast corned of the facility property. The study
indicated that the pond acts as a recharge feature to the water table while the pond is at
full pool elevation. The drawdown analysis of water levels measured during a pond
discharge test predicts that the pond will reverses from a recharge feature to a discharge
feature when to pool elevation is lowered approximately 8 feet below the current full pool
elevation controlled at the outfall structure.

The pond study indicates that lowering the pond elevation by eight feet below the current
pool elevation controlled by the outfall structure would impose a hydraulic barrier on the
upgradient (southeastern) corner of the landfill. Lowering the surface water level in the
pond is an alternative that the County may review to use as a component to the hydraulic
barrier described in the CAP.
6. RECOMMENDATIONS
S&ME recommends that the information presented in this subsurface exploration report
be used to evaluate alternatives for hydraulic barrier systems and the respective costs for
these alternatives. Based on this feasibility study of the corrective measures alternatives,
Edgecombe County may select the most cost effective alternative that meets the objective
of the corrective measure and the long term goal of the County.

Attachment IV
Attachment V