6301_MooreCounty_MSWLF_LFGWorkPlan_FID1678531_20220524

May 24, 2022
NCDEQ-DWM-SWS
2090 US Highway 70
Swannanoa, NC 28778
Attention: Ms. Jaclynne Drummond transmitted by email to: [e-mail]
Reference: Work Plan — Landfill Pilot
Moore County Landfill — Permit # 63-01
Aberdeen, Moore County, North Carolina
S&ME Project No. 4358-20-043B
Dear Ms. Drummond:
On behalf of Moore County, S&ME, Inc. (S&ME) conducted certain data gathering activities to advance our
understanding of site conditions, essential to the development of an alternate landfill gas remedy. This Work Plan
serves to provide a brief summary of data recently collected and proposed activities for additional assessment.
Background
In November 2018, Golder Associates installed a landfill gas cut-off trench to address concentrations of methane
greater than the lower explosive limit (LEL) at compliance point GP-18 (formerly well MW-15), located close to the
northern property line. On -going routine monitoring of compliance point GP-18 indicates that the cut-off trench
has not resulted in compliant LEL concentrations at this property boundary monitoring location. In 2021, Moore
County renewed dialog with the adjacent landowner to the north, exploring the option to purchase additional
land north of the Municipal Solid Waste (MSW) landfill to provide for a greater distance between the limits of
waste and the property boundary. If successful, the land acquisition would have positioned points of compliance
further to the north. Moore County reported that the adjacent property owner was not receptive to a sale of their
land.
As a related matter, groundwater quality impacts have been documented down -gradient of the MSW landfill and
corrective measures have been implemented. It is well recognized that enhanced landfill gas management could
also provide indirect benefits in the form of reduced volatile organic compound (VOC) concentrations in shallow
groundwater down -gradient of the MSW landfill. Gas migrating under pressure vertically downward to
groundwater can result in VOCs in gas, partitioning into the groundwater. Figure 1 depicts groundwater
monitoring wells, gas probe monitoring points and other essential site features.
To advance our understanding of subsurface site conditions for further analysis of alternate landfill gas remedies,
additional information was necessary. Information regarding thickness of the cover system, cover system soil
characteristics, and how waste may have been historically placed were valuable to development of a conceptual
model for gas migration, to be utilized to evaluate remedies for gas management for compliance.
The following tasks were completed in 2021 or are currently underway:
S&ME, Inc. 1 646 W. Market Street, Suite 10S I Greensboro, NC 274091 p 336.288.7180 1 www.smeinc.com

Work Plan — Landfill Pilot
Moore County Landfill — Permit # 63-01
Aberdeen, Moore County, North Carolina s
S&ME Project No. 4358-20-043B III i
S&ME is reviewing LIDAR topographic data for the MSW landfill, examining the data for evidence of
settlement and opportunities to fill low areas to improve positive surface drainage. This task is underway.
A reduction in infiltration of water through the cover system may reduce gas generation.
A Frequency Domain Electromagnetic (FDEM) geophysical survey was performed to re-examine the
horizontal extent of waste, estimate thickness of waste, and detect indication of historic trench fill waste
placement verse monofil waste placement in older units making up the closed MSW Landfill. A review of
the survey data suggests natural earth partitions likely exist between some of the closed waste MSW
landfill units, which is depicted on Figure 2. Noteworthy is the inferred presence of a natural earthen
partition between two landfill units, near gas monitoring point GP-18. The inferred existence of this
feature is consistent the apparent gap between separate historic MSW units, as depicted on Exhibit A.
Considering that local soils tend to be coarser -grained and more gas permeable when compared with the
adjacent landfill unit, our conceptual model predicts that the earthen partition may function as a primary
conduit for local horizontal gas migration to the north toward monitoring point GP-18. It is S&ME's
opinion that this earthen partition is important to explore as a migration conduit. If validated, the conduit
could be exploited to provide improvement to landfill gas concentrations at points along the northern
property boundary.
A direct -push drill rig was used to assess the thickness of the closed MSW landfill cover system soils, with
a focus on the older sections of the landfill where no final cover data existed. Multiple shallow (less than 4
foot deep) soil borings were performed along a series of transects (see Exhibit B). In general, the landfill
soil cover system was found to be composed of 3 or more feet of soil, overlying the waste. Based on soil
textures observed, the soil was likely locally derived.
A drill rig was utilized to install two gas monitoring points at locations near the northern property
boundary for the closed MSW landfill. Monitoring point GP-20 was installed west of the gas cut-off trench
and existing gas monitoring point GP-18 (see Figures 1 & 2). Monitoring point GP-21 was installed east
of monitoring point GP-18. These monitoring points were originally installed exclusively for a pilot test
intended to examine the feasibility of converting the passive landfill gas cut-off trench into an active gas
collection point. However, landfill gas measurements obtained indicated elevated methane concentrations
at GP-20 and high non -compliant methane readings at GP-21 (see Table 1). These findings indicated that
the horizontal extent of methane gas concentrations in the vicinity of the gas cut-off trench, exceeded
best -case estimates for landfill gas capture, achievable with application of active gas extraction to the gas
cut-off trench. This finding negated the potential value of the active gas extraction pilot test, which was
not performed.
Common options to achieve landfill gas compliance include but are not limited to 1) installing additional landfill
gas vents and applying active gas extraction (applying a vacuum, piping the gas to a central location, and
managing the recovered gasses), 2) installing additional landfill gas extraction points functioning as passive gas
vents, and 3) implementing other measures aimed at reducing the generation of landfill gases.
Given the complex and heterogeneous nature of landfill waste, design of landfill gas mitigation systems is not an
exact science. The apparent gap in waste between two of the closed landfill units coupled with the current
May 24, 2022

Work Plan — Landfill Pilot
Moore County Landfill — Permit # 63-01
Aberdeen, Moore County, North Carolina I I
S&ME Project No. 4358-20-043B
conceptual model for gas migration presents a practical opportunity to verify the existence of this feature, which
represents a target to improve gas venting at the northern end of the landfill. If this feature is a dominant local
conduit for gases migrating out of the adjacent waste units, then migrating northward; installing vent wells within
this conduit should relieve gas pressure and lessen the northward migration of landfill gases.
S&ME recommends a limited assessment and passive landfill gas venting pilot study focused on the earthen
partition between the two closed MSW landfill units, and the impact venting of this partition may have on gas
concentrations measured at point GP-18. The information gathered from this assessment would supplement the
data gathered and being gathered to assess alternate landfill gas remedies. Use of passive gas vents is preferred
over active gas extraction. Passive gas mitigation methods avoid higher initial capital costs and higher long-term
operations and maintenance costs associated with active gas collection systems.
Work Plan - Gas Vent Well Installation
Install two passive gas vent wells in the apparent earthen berm between two landfill units, approximate locations
are shown on Figure 2. Each passive gas vent well will be constructed of 4-inch diameter PVC casing and well
screen, completed to an estimated total depth of 35 feet below grade, and fitted with a candy cane style passive
vent surface completion. A staff professional will document subsurface conditions encountered and the
installation of each well. Following well installation, well locations will be recorded using a handheld GPS unit. If
waste is discovered during drilling, the borehole will be abandoned with bentonite. One or more off -set boring
may be attempted to verify the presence of the earthen berm.
A GEM2000 landfill gas meter or equivalent will be used to measure landfill gases (methane, CO2, 02, and balance
gas) emitted from the wells, following well installation and during each subsequent routine quarterly gas
monitoring event conducted during 2022. The same suite of landfill gases will be monitored at existing monitoring
points GP-18, GP-19, and GP-20, along with existing gas vents GV-33 and GV-34 connected with the landfill gas
cut-off trench located in the vicinity of GP-18.
A letter report will be prepared to document the well installation, data collected, conclusions, and opinions
regarding actual or potential effects of the new gas vent wells on landfill gas non-compliance at gas monitoring
point GP-18. The augmented gas monitoring data set will provide valuable input into future analysis and selection
of an alternate landfill gas remedy, if required.
Schedule
Based on subcontract drill rig availability, well installation is tentatively scheduled for June of 2022. Landfill gas
monitoring will occur after well installation, then during the subsequent routine quarterly monitoring events for
2022.
May 24, 2022

Work Plan — Landfill Pilot
Moore County Landfill — Permit # 63-01
Aberdeen, Moore County, North Carolina s
S&ME Project No. 4358-20-043B III i
Closure
S&ME appreciates the opportunity your support of this matter. If you have any questions regarding the Work Plan,
please do not hesitate to contact the Project Manager, Edmund Henriques.
Sincerely,
5&ME, Inc.
all f
1
Edmund Henriques, L.G.
Senior Project Manager/Senior Geologist
[e-mail]
Attachments:
Figures
Tables
Wayne H. Watterson, PE
Senior Engineer
[e-mail]
May 24, 2022 4

Attachments

REFERENCE:
<�� } GOOGLE EARTH PRO AERIAL PHOTOGRAPH
\N (DATED SEPTEMBER 30, 2018)
III
LEGEND
Approximate Passive Gas Vent Location
Interpreted Extent of Possible Landfill Material
Conceptual Gas Migration Directions
SCALE:
AS SHOWN
DATE:
3/29/2022
PROJECT NUMBER
4358-20-043C
FIGURE NO
Approximate proposed locations for two new passive gas vent wells Figure 2

Exhibit A -Sits Plan Depicting Separate Historic_MSW Units ,
I 2 I 1
D
C
LEGEND
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1 W,� LOCATION OF GddJ WASTE
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MONITORING WELL
SURFACE WATER SAMPLE LOCATION
PROPERTY LINE
CONTOUR LINE'
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CLOSED.. PLC AREA
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_ pRp�P �\ vi APPROX. 10 ACRES) PA6,ouS
�FA��OLLLIII LpppLCCCAAA110N ` \.,, �� \ MANTENANCE APPii07I, IOGAiICfY OF 1
FAC(A>1' STYE EXISTING FIRE HYDRANT T
" CITIZEN"
♦ \ / �� � _,__�, ��_�� PROPOSED 6` WAVER LINE
♦ w � _ 1
`SCALE &
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♦ FAtgNt\-jJ//.n.6/ gig ,,�j� SC ALEHOUSE
CLOFILL EADRRELCID
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♦`
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�♦ -� �\ _ �..� ���y`� NOTES
♦\-`�~ -�\ \\ ! 1. DRAVANG BASED ON SURVEY BY PIEDMONT AERIAL SURVEYS, INC. OCTOBER 1985.
2. MONIYERING WELLS SURVEYED 4/5/95 AND UPDATED 9/39/96 8Y NOR
♦ \ \ ���'"=��;_yl- .` \� J� ENGINEER?N:0
♦ \\\ -- 3. THE TOPD
F FOR F1.fi ACRES OF MSW CLOSED IN 1994 IS BAS£p ON A FIELD
SURVEY BY NDR PRIOR TD CLOSURE.
X. PROPERTY LANE .METES AND BOUNDS FROM DRAWINGS PREPARED BY; PIEDuENT
1732. 7.3' T _ _ �1 AERIAi, SURVEYS INC. LANDFILL SiIE NO. 3 DATER FEU. 197A (EASTERN PARCEL): AND HOBBS, UPC14URCH AND ASSOC. PA. SHEET t OF 2 REVISEO DEMOLITION
DISPOSAL AREAS -DATED MARCH 1991 (WESTERN PARCEL)
5. MAINTENANCE FACILITY LOCATION BASED ON INFORMATION PROVIDED BY MOORE
COUNTY 8/1/96. SEE ALSO "D-2"
6. OFFSITE HOUSE AND BARN LOCATIOKS APPROXIMATED FROM ORTHOPHOTE MAP
PREPARED BY L. ROBERT NIMBALL & ASSOC, (1989).
- r- — - F_� E A ^ P.C.
WATER QUALITY
(_ I � F_ � �� SAMPLING LOCATIONS
f i MOORE COUNTY I_ANDFiL
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Exhibit B - Cover System Soil Assessment Boring Layout
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Table 1
Summary of 2020 & 2022 Methane Gas Readings
Moore County Landfill (Permit 63-01)
Moore County, North Carolina
S&ME Project No. 4358-20-043A
Location Scale- house
g Point Type •
7
02/17/20 0.0%
Maintena
Shop
•
0.0%
Station
•
0.0%
Blake
Crawlspace
•V,f,
0.0%
GP-9
0.0%
r
footn tel.
18.7%
WUFMl!
not installed
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
See
footnote#2
0.0%
0.0%
0.0%
0.0%
See
footnote#1
11.9%
Al
28.1%
not installed
r
See
footnote#4
not installed
NEGEMEM
See
footnote#4
not installed
04/07/20
0.0%
0.0%
0.0%
0.0%
0.0%
32.2%
not installed
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.0%
0.4%
23.6%
59.9%
not installed
not installed
not installed
09/15/20
0.1%
0.0%
0.0%
0.0%
0.1%
abandoned
0.0%
0.0%
0.0%
abandoned
0.0%
abandoned
0.0%
abandoned
0.0%
0.0%
0.0%
0.0%
22.5%
0.0%
not installed
not installed
12/14/20
0.0%
0.0%
0.0%
0.1%
0.1%
abandoned
0.0%
0.0%
0.0%
abandoned
0.0%
abandoned
0.0%
abandoned
0.0%
0.0%
0.5%
9.6%
61.3%
0.0%
not installed
not installed
02/24/21
0.0%
0.0%
0.0%
NM
0.0%
abandoned
0.0%
0.0%
0.0%
abandoned
0.0%
abandoned
0.0%
abandoned
0.0%
0.0%
1.4%
28.7%
67.9%
0.0%
not installed
not installed
04/12/21
0.0%
0.0%
0.0%
0.0%
0.0%
abandoned
0.0%
0.0%
0.0%
abandoned
0.0%
abandoned
0.0%
abandoned
0.0%
0.0%
1.2%
2.0%
21.8 %
0.0%
not installed
not installed
09/29/21
0.0%
0.0%
0.0%
0.0%
0.0%
abandoned
0.0%
0.0%
0.0%
abandoned
0.0%
abandoned
0.0%
abandoned
0.0%
0.0%
1.0%
19.5%
57.5%
0.0%
not installed
not installed
12/17/21
0.0%
0.0%
0.0%
0.0%
1 0.0%
abandoned
0.0%
0.0%
0.0%
abandoned
0.0%
abandoned
0.0%
abandoned
0.0%
0.0%
0.0%
13.8%
27.8%
0.0%
10.1%
57.0%
03/25/22
0.0%
0.0%
0.0%
0.0%
1 0.0%
abandonedl
0.0%
0.0%
0.0%
abandonedl
0.0%
abandoned
0.0%
abandonedl
0.0%
0.0%
0.0%
29.1%
54.7%
1 0.0%
1 28.1%
56.4%
Notes:
Monitoring Point Types: PB = Property Boundary, ONSS = On Site Structure, OFFSS = Off -site Structure
Footnote#1 = MW-6 was replace by GP-19 as the property boundary compliance point. MW-6 is approximately 150 feet inside the property boundary and not a compliance point.
Footnote#2 = GP-10 was replaced by GP-10R, GP-13 replaced by GP-13R, GP-14 replaced by GP-14R, GP-15 replaced by GP-15R
Footnote#3 = Groundwater monitoring well MW-15 converted to gas monitoring point now identified as GP-18, which is a property boundary compliance point.
Footnote#4 = Gas monitoring points installed for a cancelled active gas extraction pilot test. A new passive venting pilot test has been proposed.
all measurements recorded in percent methane by volume
Lower explosive limit of methane gas: 5%
Upper explosive limit of methane gas: 15%
Data recorded prior to 9/15/20 obtained by Golder
not installed = Well not installed at the time of monitoring
Yellow highlight cells and values in bold print indicate methane percent by volume greater than or equal to 5% at property boundary monitoring point
Orange highlight cells and values in bold print indicate methane percent by volume greater than or equal to 1.25% inside structures.
TAENV\Projects\2020W5&20-A -- County Routine 1. a WQ..-ring\Phase. Qu-,MM-Monitoring 2021-2022\-R-mgs-1I,-Charts IN-RESS 1. 5/24/2022