7901_RockinghamMSWLF_ March2024LFGRemediationPlan_FID1832128_20240319

March 11, 2024

Mr. Ervin Lane
Compliance Hydrogeologist
North Carolina Department of Environmental Quality
Solid Waste Section
1646 Mail Service Center
Raleigh, NC 27699-1646
Via Email: [e-mail]

RE: Landfill Gas Remediation Activity Update and Remediation Plan
Rockingham County Solid Waste Management Facility – Area III
Solid Waste Section Permit No. 79-01
LaBella Project No. 2233671, Phase 02

Dear Mr. Lane:

On behalf of Rockingham County, LaBella Associates (LaBella) is submitting this update on recent
landfill gas remediation activities at Area III of the closed pre-Subtitle D landfill (Solid Waste Permit No.
(SSPN) 79-01) at the Rockingham County Solid Waste Management Facility, which operates under
SSPNs 79-01 & 79-04. The update also presents plans for ongoing landfill gas remediation in Area
III.

Background
The Rockingham County Landfill facility is located in the west-central portion of Rockingham County,
North Carolina, between the towns of Wentworth and Madison. The site is located on a property totaling
approximately 230 acres; 82 acres of which were approved for municipal solid waste (MSW) disposal
by the North Carolina Department of Environmental Quality (NCDEQ). The site includes six discrete
landfills: Closed Areas I through V, and the Subtitle D Landfill (Phases 1 through 4). Wall Recycling,
LLC (Wall) currently operates the active Subtitle D landfill (SSPN 79-04) and is responsible for
environmental monitoring and reporting for that part of the facility; while the County is responsible for 
environmental monitoring and reporting for the closed pre-subtitle D landfill areas (SSPN 79-01).

Recent and historical landfill gas monitoring at boundary probes M-5 and M-12, located north of the
closed Area III, has indicated consistent exceedances of the lower explosive limit (LEL) for methane.
There is minimal distance between the northern end of the Area III waste unit and the property
boundary; therefore, these probes are located in close proximity to the waste. Gas probe M-5 is
completed to a depth of approximately 40 feet below ground surface (bgs), with a screened interval
estimated to be 5-40 feet bgs. Gas probe M-12 is screened from 5-30 feet bgs. The locations of these
gas probes and other pertinent site features are shown on Drawing 1 (attached).

Previous Remedial Activity
A Landfill Gas Remediation Plan (LGRP) was submitted to NCDEQ in December 2018 to address
multiple gas issues at the facility, including methane exceedances in the vicinity of closed Area III.
Specifically, it addressed exceedances in probe M-12, which was installed in May 2018. The 2018
LGRP recommended installation of additional passive gas vents in the Area III waste unit. As a result,

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gas vents GV3-10 and GV3-11 were installed in February 2019. The gas vents were converted to
extraction wells and connected to the active gas extraction system and flare.

In accordance with the New Source Performance Standards (NSPS) XXX requirements and the facility’s
approved Gas Collection and Control System (GCCS) Design Plan, four additional gas wells (GV-3-12
through GV3-15) were installed in Area III in June 2021. As part of the approved GCCS Design Plan, a
new flare (Control Device No. 3, (CD-3)) consisting of a small flare rated at 150 standard cubic feet
per minute (scfm) that combusts landfill gas collected from Area III was simultaneously installed in
2021. The flare became operational in November 2021. Prior to the startup of CD-3, landfill gas
collected from Area III was routed to CD-2, a large subtitle D rated at 1,000 scfm.

Following the installation of CD-3, and in continuing efforts to reduce the methane concentrations in
M-12, and later M-5, the facility focused on adjustments to the vacuum and flow in the active gas
extraction system in Area III.

On January 17, 2024, representatives of Rockingham County, LaBella Associates, and NCDEQ Solid
Waste Section (SWS) met on site at the Rockingham County Landfill to discuss the methane
exceedances north of Area III. The recommendation at the time was to install a gas intercept trench
between the edge of waste and probes M-5 and M-12. It was agreed that plans for the trench
installation would be submitted to NCDEQ-SWS within 60 days.

Historical Review
LaBella researched available drawings for Area III, depths of gas vent and gas probe installations, etc.,
to facilitate remedial design. Based on the depth of waste and the depth of gas probes M-5 and M-
12, concern was raised whether a gas intercept trench could be installed with sufficient depth to
intercept migrating landfill gas. If a significant amount of methane is migrating at depths greater than
15-20 feet, vertical soil gas vents may be more effective than an intercept trench.

Also, during our research, LaBella discovered that there was, at one time, a road that bisected the
Area III waste unit that was apparently later covered by waste. This old road led directly to the location
of M-5, raising speculation that this road could be a conduit for gas migration from the waste to M-5.

Proposed Soil Gas Vents
LaBella will supervise the installation of six soil gas vents, three near M-5 and three near M-12, at the
approximate locations shown on Drawing 1. The distance between vents in each 3-vent set will be
approximately 50 feet. The exact locations of the vents may be adjusted in the field based on
accessibility or other site features.

Borings for the soil gas vents will have a 10-12-inch diameter and will be advanced to depths equal to
the total depth of the nearest gas probe, auger refusal, or groundwater, whichever is encountered first.
The vents will be constructed with four-to-six-inch diameter PVC screen from approximately 5 ft-bgs to
total depth, with pea gravel in the annular space to a depth of one-foot above the screen, a two-foot
bentonite seal, and soil cuttings to ground surface.

Each vent will be connected to the header pipe for the existing utility flare (CD-3), currently operational
for the closed landfill, so that no free methane will be vented to the atmosphere as required by the
facility’s Title V Air Permit. Valves will be installed to allow adjustment of flow at each vent in order
attain an optimum balance between capturing enough of the methane to remedy the probe
exceedances, but not flood the gas extraction system with unnecessary oxygen. Adjustments will be

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made as frequently as deemed necessary and practical to maintain the balance, but at a minimum on
a quarterly schedule.

Monitoring and Reporting
The landfill gas boundary probes, including M-5 and M-12, will continue to be monitored on a quarterly
schedule. The new soil gas vents will also be monitored during each quarterly event after they are
installed. After four consecutive quarterly monitoring events after the soil gas vents are installed, the
results will be evaluated, and an update report will be submitted to NCDEQ. If additional steps are
needed, an updated Landfill Gas Remediation Plan will be submitted.

Schedule
 Installation of the soil gas vents will be completed within 90 days of NCDEQ approval of this
plan, pending driller availability; and
 A landfill gas remediation update and, if needed, an updated Landfill Gas Remediation Plan
will be submitted to NCDEQ within 60 days of completing the fourth quarterly monitoring event
after the soil gas vents are installed.

If you have any questions regarding these plans for landfill gas remediation at the Rockingham County
Solid Waste Management Facility, please contact me at [phone].

Respectfully submitted,
LaBella Associates

Van Burtbach, PhD, PG
Senior Technical Geologist

Drawing 1 – Area III Proposed Landfill Gas Vents
cc: Robert Pike, NCDEQ
Ronnie Tate, Rockingham County
Chris Gustin, Wall Recycling
Charlie Jarboe, Wall Recycling
Dan Jarboe, Wall Recycling

WHITE GOODS
(APPROVED BY DEQ)
OLD SHOP
M-4
M-5
CONCRETE AND
BRICK STORAGE
M-12
68
0
69
0
71
0
66
0
64
0
62
0
72
0
70
0
68
0
68
0
66
0
GV3-10
GV3-11
GV3-12
GV3-8
GV3-5
GV3-4
GV3-3 GV3-2
GV3-6
GV3-7
GV3-1
GV3-9
GV3-16
GV3-17
GV3-14
GV3-15
GV3-13
CLOSED
AREA III
(PERMIT 7901)
PROPERTY LINE (TYP)
670
690
710
730
670
63
0
73
0
730700
65
0
PROPOSED SOIL
GAS VENT (TYP)
APPROXIMATE
LIMITS OF WASTE
EXISTING GAS
WELL (TYP)
EXISTING GAS PROBE (TYP)
71
0
69
0
66
0
64
0
62
0
720
700730
710
690
64
0
61
0
660
670
62
0
63
0 64
0
620
64
0
690
670
650
0
(FEET)
GRAPHIC SCALE
1005025
Revisions
NO:DATE:DESCRIPTION:
DRAWING NAME:
6/
3
/
2
0
1
0

8
:
4
7
:
5
6

A
M
DRAWING NUMBER:
DATE:
ISSUED FOR:
DRAWN BY:
REVIEWED BY:
PROJECT NUMBER:
© 2024 LaBella Associates
12-D OAK BRANCH DRIVE
GREENSBORO, NC.
[phone]
labellapc.com
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AREA III PROPOSED
LANDFILL GAS VENTS
ROCKINGHAM COUNTY
WENTWORTH, NORTH CAROLINA
ROCKINGHAM COUNTY LANDFILL
MADISON, NORTH CAROLINA
2233671.02
REVIEW
03/07/24