6301_MooreCounty_MSWLF_CDLF_WorkPlan_FID1827340_20240201

January 30, 2024
NCDEQ-DWM-SWS
2090 US Highway 70
Swannanoa, NC 28778
Attention: Ms. Jaclynne Drummond
Reference: Work Plan- Additional Surface Water Assessment and Additional Passive Gas Vent Wells
Moore County Landfill - Permit # 63-01
Aberdeen, Moore County, North Carolina
S&ME Project No. 4358-20-043E
Dear Ms. Drummond:
S&ME, Inc. (S&ME), on behalf of our client, Moore County, is submitting this Work Plan to describe proposed
additional surface water sampling and the installation of additional passive gas vent wells at the Moore County
Landfill located in Aberdeen, NC (Permit # 63-01). This work plan discusses the proposed activities. Please contact
us at your convenience if there are any questions regarding the information contained in this document.
Task A: Additional Surface Water Assessment
Background
As stated in S&ME's Corrective Action Plan Evaluation Report (CAER), dated June 15, 2023, the sample size for the
groundwater analytical data set for 1,4-Dioxane at the subject site is relatively small. Given an anticipated relatively
low attenuation rate for 1,4-Dioxane in groundwater, the need for long-term groundwater monitoring data is
essential. Additional monitoring data is needed to perform an adequate evaluation of MNA and other options as
effective remedies for 1,4-Dioxane. The NCDEQ letter dated August 24, 2023, was in response to S&ME's CAER
report, dated June 15, 2023. The letter concludes that NCDEQ is requiring additional corrective measures be taken
for the 7,4-Dioxane exceedances for protection of human health and the environment. One key data gap for the
pending evaluation of potential corrective measures options for 1,4-Dioxane, is the absence of a sufficiently
detailed understanding of the 1,4-Dioxane distribution in surface water. To begin to close this data gap, S&ME
recommends additional surface water sample points to better define the extent of stream impacts.
Existing site drawings depicted the tributary immediately south of the C&D landfill, to extend eastward to the
closed Municipal Solid Waste Landfill (MSW), a detail that prompted S&ME to conduct an informal review of this
tributary. During a site visit on January 19, 2024, S&ME staff walked the tributary immediately south of the C&D
landfill. S&ME observations suggested that the tributary likely originates near the sediment basin south of C&D
landfill Cell 6, rather than near the MSW landfill. The blue line for this tributary east of Cell 6, was dry during our
site visit, thus this portion of the map blue line likely represents a natural drainage way, rather than a stream.
S&ME observations are supported by depths to groundwater typically on the order of 11-12 feet below grade at
well MW-13SR, while there is less than 10 feet of elevation change between well MW-13SR and the blueline
S&ME, Inc. 13201 Spring Forest Road I Raleigh, NC 276161 p 919.872.2660 1 www.smeinc.com

Work Plan- Additional Surface Water Assessment and Additional Passive Gas Vent Wells January 30, 2024
NCDEQ-DWM-SWS Page 2
shown to the south on Figure 1. The blue line shown east of the landfill access road, between the C&D and MSW
landfills, is also likely a drainage way rather than a stream. Depths to groundwater observed at MW-7, MW-8, and
MW-14, typically exceed 14 feet below grade, indicated a much deeper water table in this area. These informal
stream assessment findings were used as a guide to the selection of new surface water sample locations proposed
in this Work Plan.
Scope of Work
S&ME proposes seven new surface water sampling locations, at points along tributaries to Horse Creek, which
flank the C&D and MSW landfills. S&ME will collect surface water samples at seven new locations and three
existing sample locations SW-1, SW-3, and SW-4 during February 2024. Samples will be collected from the seven
new sample points again during the routine spring 2024, water quality monitoring event. The new sample
locations will be recorded with a hand-held, non -survey grade GPS, and marked in the field with flagging and/or a
PVC pipe. The samples will be submitted for analysis by Method 8260 for Volatile Organic Compounds and
Method 8260 SIM for 1,4-Dioxane. The results for each of the two monitoring events will be incorporated into the
routine Spring 2024 water quality monitoring report. Figure 1 depicts approximate locations for the seven new
surface sample locations and the four routine monitoring surface water sample points. Some field adjustment of
the proposed locations may be necessary based on actual site conditions.
Limitations
The segment of Horse Creek immediately down -gradient of the C&D landfill is not on land owned by Moore
County; therefore, 1,4-Dioxane impacts to Horse Creek will not be evaluated at this time. The potential Hope -
Wilson land swap Moore County is working on may result in Moore County owning land containing the segment
of Horse Creek, immediately down -gradient of the C&D landfill.
Task B: Install Additional Passive Gas Vent Wells
Background
Based on persistently elevated levels of methane at compliance monitoring probe GP-18, Moore County installed
an LFG cut -off -trench during November 2018, in an area between the closed MSW landfill and property line
monitoring probe GP-18, to the north. Following installation of the LFG cut-off trench, LFG monitoring data
continued to document property line conditions, which require corrective measures, for offsite LFG migration.
In June 2022, S&ME initiated a pilot test involving installation and monitoring of two new passive LFG vents that
tapped into transmissive sandy sediments forming a narrow partition between two MSW landfill units. Although
substantial LFG levels are being emitted by the new vents, the monitoring data set does not suggest that the two
additional wells may not result in compliant conditions at property line monitoring probe GP-18.
Traditional remedies for landfill gas migration control rely upon LFG vents (passive or active) installed within the
waste to provide venting the gases and for the reduction of gas pressures inside the waste. LFG vent well
separation distances are often on the order of one well every 200 feet, throughout a landfill unit. Installation of
LFG vents within the waste are substantially more expensive when compared with LFG vents installed outside of
the waste. Since the property line north of the MSW landfill is the area where non -compliant LFG conditions exist,
Moore County has elected to install LFG vents outside of the waste, in the vicinity of the property line, in an effort
to mitigate the non -compliant LFG condition.
S&ME, Inc.

Work Plan- Additional Surface Water Assessment and Additional Passive Gas Vent Wells January 30, 2024
NCDEQ-DWM-SWS Page 3
Scope of Work
Moore County will mark the location of the property line in the vicinity of the proposed well sites. S&ME will
subcontract drilling and installation of five 4-inch diameter passive gas vent wells. The wells will be installed
outside of the waste at approximate locations shown on Figure 2. Each vent well will be constructed of 4-inch
diameter PVC casing and well screen, completed to just above the groundwater surface, an estimated total depth
of 50 feet below grade. S&ME will observe and document subsurface conditions encountered during drilling, and
well installation details. Following installation, each vent well location will be recorded using a handheld GPS unit.
A GEM2000 landfill gas meter or equivalent will be used to measure landfill gases (methane, CO2, 02, and balance
gas) emitted from the vent wells, following well installation. Monitoring of these new passive LFG vents will be
incorporated into each subsequent routine quarterly gas monitoring event conducted during 2024.
A Well Installation Data Report will be prepared to document the installation of the wells, and the initial LFG
readings obtained following installation.
Schedule
Based on subcontract drill rig availability, well installation is tentatively scheduled for March of 2024. Landfill gas
monitoring will commence after installation, then during the routine quarterly monitoring events for 2024.
Sincerely,
S&ME, Inc.
�A� 02 .�(:��
Edmund Henriques, L.G.
Senior Project Manager/ Senior Geologist
[e-mail]
Cody McMechen, L.G.
Project Geologist
[e-mail]
S&ME, Inc.

SOURCE: 2017 AERIAL PHOTOGRAPH OBTAINED FROM NC ONEMAP

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DATE:
JAN. 2021
PROJECT NUMBER
4358-20-043
FIGURE NO.
2
SOURCE: 2017 AERIAL PHOTOGRAPH OBTAINED FROM NC ONEMAP