4407_Haywood_WhiteOakMSW_LFGMonitoringPlanPhase1-5_DIN26973_20161103

Explosive Gas Monitoring Plan
White Oak MSWLF
Haywood County, North Carolina
November 2016
1100 Crescent Green Drive, Suite 208
Cary, North Carolina 27518 • O: 919-792-1900 • F: 866-311-7206
NC FIRM C-2910
Explosive Gas Monitoring Plan
White Oak MSWLF
TOC 1
Contents
Introduction ............................................................................................................... 1
Permanent Landfill Gas Monitoring Wells ................................................................. 1
Landfill Gas Monitoring Locations ............................................................................. 1
Landfill Gas Monitoring Equipment............................................................................ 2
Landfill Gas Detection in Wells .................................................................................. 2
Landfill Gas Detection in Structures .......................................................................... 2
Landfill Gas Monitoring Observations ........................................................................ 3
Figures
Figure 1 – Landfill Gas Monitoring Well Detail
Figure 2 - Explosive Gas Monitoring Plan Monitoring Locations
Forms
Landfill Gas Measurements Field Worksheet, White Oak MSW Landfill, Haywood
County, North Carolina

Explosive Gas Monitoring Plan
White Oak MSWLF
Page 1
1.0 Introduction
The Haywood County White Oak MSWLF will monitor quarterly for methane and other
explosive landfill gases within the landfill structures and at the landfill gas monitoring
wells.
2.0 Permanent Landfill Gas Monitoring Wells
The permanent landfill gas monitoring wells (monitoring well) will consist of a plastic stand
pipe similar to a piezometer used for groundwater detection. A typical permanent landfill
gas monitoring well is detailed in the attached Figure 1. The permanent probe will be
constructed at a minimum depth of six (6) feet. A minimum 6" diameter hole will contain
a one (1) inch slotted PVC pipe. The bottom two (2) feet will be backfilled with non-
carbonate pea gravel with a bentonite seal one (1) foot thick above it. The remaining three
(3) feet will be backfilled with in situ soils. The one (1) inch PVC pipe will be approximately
three (3) feet above the existing grade. The PVC pipe will be capped with a one (I) inch
PVC cap, one quarter (1/4) inch NPT hose barb, and 1" tubing, plugged or capped to
prevent contamination. A minimum four inch (4”) diameter schedule 40 PVC sleeve or
aluminum/steel prefabricated well cover will be placed over the one inch (1”) pipe and
filled with clean masonry sand to within four inches (4”) of the one inch (1”) schedule 40
PVC cap. The top of the PVC pipe sleeve or prefabricated well cover will be secured with
a removable water tight cap. Where necessary, a marker post will be placed in close
proximity to the landfill gas monitoring well. A permanent well I.D. will be placed/painted
on the marker post or the well cover.
3.0 Landfill Gas Monitoring Locations
The migration of methane and other explosive landfill gases (landfill gas) is induced by
pressure gradients. The landfill gases will move from areas of high pressure to those of
low pressure following the path of least resistance. Landfill gas will generally migrate
vertically until it reaches the landfill surface where it may begin to flow horizontally until it
finds a pathway out through the permeable in situ soils or a landfill gas venting/extraction
system. Given that Haywood County’s landfill is designed with a synthetic membrane
base liner system there should be no landfill gas migration into or through the subsurface
permeable in situ soils. The final cap system, once designed and installed, will also
contain a synthetic membrane liner system with a landfill gas venting/extraction system.
This type of cap system will also prevent the migration of landfill gas into or through the
surrounding permeable in situ soils.
Since methane, a component of landfill gas, is lighter than air, it wants to escape into the
atmosphere. Experience has shown that whenever gas is migrating no matter what the
spacing or depth of the monitoring probes, the gas will fill the void created by the
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White Oak MSWLF
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monitoring well and an explosive gas detection meter will monitor the level of
concentration. The six foot depth of the monitoring wells is to ensure a stable monitoring
point. The only time a shallow monitoring well has not worked is in a very heavy,
impermeable clay layer that acts as a seal to the migration of the gas. If a clay layer is
encountered during the construction of a monitoring well, it will either be moved beyond
the clay or excavated to a depth that is in the conductive zone below the clay.
The location and spacing of the landfill gas monitoring wells as well as the on-site
structures include the Maintenance Building and the Scale House are shown on Figure
2.
4.0 Landfill Gas Monitoring Equipment
The landfill gas can be detected by use of an instrument that reports the percent of lower
explosive limit (% LEL) and the methane gas concentration (% CH4). The instrument
being used is the LandGEM 2000.
5.0 Landfill Gas Detection in Wells
Quarterly the Haywood County landfill will monitor for methane and other explosive landfill
gases at the landfill gas monitoring wells as shown on attached Figure 2. If landfill gas is
present and the level is detected at or above the lower explosive limit (100% LEL), it must
then be determined if the landfill gas is migrating or has migrated beyond that particular
monitoring well. If it is determined that explosive landfill gas has or may have migrated
beyond the particular monitoring well then additional steps may be implemented to
delineate the extent of any suspected landfill gas migration. If it is determined that
explosive landfill gas has or may have migrated across the landfill boundary then the
facility will immediately take all necessary steps to ensure protection of human health.
The North Carolina Department of Environment Quality (NCDEQ) will be notified. Within
seven (7) days of detection, the methane gas levels detected and a description of the
steps taken to protect human health will be placed in the operating record. Within 60
days of the detection of suspected landfill gas migration at or beyond the landfill boundary,
the County will prepare and implement a remediation plan for the suspected landfill gas
releases. A copy of the remediation plan will be placed in the operating record and the
NCDEQ will be notified that the plan has been implemented. Resampling of the affected
landfill gas monitoring wells will be performed as necessary to evaluate the effectiveness
of the approved remediation plan.
6.0 Landfill Gas Detection in Structures
Quarterly the Haywood County landfill will monitor for methane and other explosive landfill
gases at on-site structures. Currently, the on-site structures include the Maintenance
Building and the Scale House as shown on attached Figure 2. Each structure will be
Explosive Gas Monitoring Plan
White Oak MSWLF
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monitored for explosive landfill gas using the following general protocol:
1. All crawl spaces will be monitored;
2. All corners in the structure will be monitored;
3. Any observed holes, cracks and/or pipe penetrations through the foundation
will be monitored;
If methane gas is detected above 25% of its lower explosive limit (25% LEL) in any
structure, excluding gas control or gas recovery system components, the monitoring
technician will verify the field calibration of the detection instrument in accordance with
the manufacturer’s instructions and the structure will be resampled. If the reading is still
above 25% LEL, evacuate the building and take all steps necessary to protect human
health. NCDEQ will be notified as well as the Haywood County Solid Waste Director.
Within seven (7) days of initial detection, the methane gas levels detected and a
description of the steps taken to protect human health will be placed in the operating
record. Upon taking the necessary safety precautions, attempt to determine the source
of the explosive gas. If the source is found, initiate repairs to prevent re-infiltration of the
landfill gas or remove the source. If the source of the landfill gas infiltration cannot be
easily determined and/or promptly corrected then the structure must be closed and
marked to prevent further occupancy. The County will then prepare and implement a
remediation plan for the suspected landfill gas releases within sixty (60) days of initial
detection. A copy of the remediation plan will be placed in the operating record and the
NCDEQ will be notified that the plan has been implemented. The structure will remain
closed for occupancy until such time as the repairs and/or remediation plan have been
implemented and the structure retested for the presence of landfill gas concentrations.
The structure will be reopened for occupancy once the landfill gas concentrations are
below the 25% LEL concentration.
7.0 Landfill Gas Monitoring Observations
Observations for the landfill gas monitoring wells AND for the on-site structures will be
recorded on the attached form titled “Landfill Gas Measurements Field Worksheet, White
Oak MSW Landfill, Haywood County, North Carolina”.

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Figure 1 – Landfill Gas Monitoring Well Detail