|
Some or all of the following activities are
performed during LFG screening monitoring:
- Monitoring in-place probes
- Constructing and monitoring bar hole probes
Table of Contents
In order to conduct adequate screening
monitoring for landfills with or without monitoring systems, the following
equipment may be needed:
- Properly
calibrated infrared detector, combustible gas indicator (CGI), flame ionization
detector (FID) or an equivalent instrument, capable of detecting methane gas at
concentrations of 0.5-100.0 percent by volume in air.
- Bar
hole punch with at least a three foot long clean rod and weighted sliding
handle for driving the rod into the ground.
- Three
foot long, one-and-one-quarter inch diameter, hand-driven, soil auger.
- Plastic
tubing and assorted connectors for ensuring airtight connections when hooking
up the monitoring instrument to probes.
- Auxiliary
air pump (AP)
- Tedlar bags
- Durable
work gloves for using bar hole punch or impact drilling rig.
- Nominal
1/2" plastic PVC pipe cut in 12-18 inch lengths with one end cut off at a 45-degree
angle, for purposes of driving the pipe into the soil.
- Flow meter to measure pumping rate AP.
- Magnehilix
Note:
Training for LFG screening monitoring and for using gas monitoring equipment will
be given on annual basis by the LFG Training Group (please contact Mr.
John Bell at (916) 341-6368 for more information). As a matter of practice, new EA inspectors should be trained in
the proper procedures for screening monitoring of landfill gas upon being hired
and before evaluating a disposal site for compliance with the SMS for landfill
gas by themselves. Additionally, Board
and LEA Staff should attend the annual refresher training on how to conduct
LFG screening monitoring. All staff training should be documented. Maintenance and calibration is documented
for each instrument as recommended by the manufacturer to satisfy quality
assurance/quality control requirements.
Table of Contents
1. Pre-inspection information gathering
Prior to the inspection, the inspector should
obtain and review copies of LFG monitoring reports submitted to the Local
Enforcement Agency (LEA) by the operator for at least one year prior to the
inspection. For existing monitoring
systems, the inspector should identify from the monitoring reports any
particular probes that should be sampled as mentioned in the section on
monitoring sites that have an adequate in-place monitoring system.
Additionally, the inspector should obtain maps and as-built drawings for the
monitoring well system that indicate location, depth and number of perimeter probes,
as well as location of any gas control system or energy extraction system
wells. Any available gas control system drawings and specifications, well
construction details and boring logs would also be useful. This information can help identify probes
that should be sampled during the initial LFG monitoring. The inspector should also consult the LEA to
determine (if applicable) what type of probe fitting/adapter may be used to
connect the gas-monitoring instrument to the probes at a site.
If there is no existing and/or functional LFG monitoring
system, the inspector should review any available documents containing
technical information such as the report of facility information (RFI),
periodic site review (PSR), and any closure documents that may provide the
information needed to establish the best locations for bar hole punch monitoring
as described below.
2. Criteria
for field checking of in-place monitoring systems
Generally, the following should be verified:
- Monitoring Well Probe Design: Probe construction details should generally be included with the
approved gas management plan for a site. A copy of the plan should be obtained
from the LEA and placed in the facility file. When monitoring system plans are
not available, consideration should be given to the types, quantity and depth
of buried wastes, as well as to the proximity of sensitive receptors.
Note: Operators should consider the regular
closure construction standards when designing and placing monitoring well probes. (This is
suggested because all landfills will have to eventually meet these standards at
closure and it is usually more cost effective to meet them sooner rather than
later.)
-
Probe
Functionality.
Monitoring well probes may become plugged up for a variety of reasons. Make sure probes are not
damaged, partially or fully filled with water, covered with dirt or mud, or
otherwise destroyed or contaminated. Additionally, probes should be clearly
marked and include shut off valves and/or terminating caps securely attached to
them. Probes in vaults are less likely to be damaged or plugged, however, they
are more susceptible to flooding). An obstructed probe will result in the LFG
monitor pump laboring noticeably, or even shutting down completely. Checking the latest monitoring records should
help in determining what probes, if any, may not be fully functional. Adequate care should be taken to insure
water or excessive water vapors
is are not drawn into the monitoring
instrument. A hydrophobic filter should
always be used. Additionally, a
comparison with the existing gas monitoring records may show a change from previously
recorded consistent levels of gas to a string of consecutive extremely low or zero
readings.
- Please note that not all of the
landfill gas issues may be resolved employing the screening process during an
initial inspection. If necessary, upon
return from the inspection, EA inspector may consider consulting the appropriate
technical staff at the Board for further assistance in determining the
functionality of plugged probes and to discuss the need for supplemental
enhanced monitoring.
- Generally monitoring wells are adequately placed
if they are: At or near (within 2 ft. of the permitted boundary of the disposal facility)
facility property boundary if the landfill has no permit. If the operator has
chosen to install a well inside the permitted facility boundary closer to
waste, and the inspector finds more than 5 percent LFG in a probe, then the
operator will have to either install another well closer to the permitted facility
boundary, or control LFG at that point to a level below 5 percent. A point of compliance may be chosen at any
monitoring well designated by the operator to meet 27 CCR Section 20919.5.
If a methane concentration above 5 percent is found in a compliance probe
located toward the interior of a disposal site, this would indicate the need
for further monitoring closer to the boundary. In such a case, a violation can also
be given for an inadequate monitoring system.
Placed outside of the zone of
influence of an active LFG control system outer gas extraction wells. Probes
placed directly opposite of extraction wells generally tend to have lower LFG
readings than wells placed between extraction wells, however, this should be
verified through direct probe measurements using a vacuum gauge.
Placed every 1,000 feet or less,
or at least one for each linear side of the facility perimeter boundary, (whichever
can provide more coverage), for landfills that are subject to 27 CCR 20919.5.
In some cases, exceptions from these guidelines may be allowed. (Additional
probes may be required if there is a significant amount of landfill gas being
generated within the site and there are no natural barriers to prevent off site
LFG migration).
Placed
adjacent to receptors (structures, orchards, crops, etc.) that are within 1,000
feet of the site regulatory boundary.
Note: If possible, conduct a visual inspection to compare the system
layout indicated in the available construction plans with the current field
situation.
Note: The above recommendations and guidelines are
not intended as absolute criteria in evaluating the adequacy of the LFG
monitoring system and program implemented by the operator but are rather
designed to assist the inspector in determining whether to monitor and, if
necessary, where to conduct additional monitoring by employing bar hole probes.
3. Results of field checking
Monitoring system
evaluation will result in one of the following conclusions:
a. Monitoring system is adequate
- Based upon determination by
inspector
- Based upon verification of in-place monitoring system constructed
according to approved design.
b. There is no monitoring system in place
c. The monitoring system is
inadequate
- Determined by inspector with or without
approved plan
- Determined by review of plans by appropriate technical staff prior
to field inspection and verified by inspector.
- Based on key probes being
partially or fully nonfunctional during screening monitoring.
Table of Contents
The following sections show where and how
screening monitoring should be conducted for facilities that have (1) an
adequate monitoring system, (2) no monitoring system, or (3) an inadequate
monitoring system. After evaluating the monitoring system using the criteria in
the previous section:
1. If the monitoring system is adequate:
Monitor selected in-place perimeter wells.
Wells that have one or more of the following
characteristics should be selected for monitoring:
- Well
has a documented history of elevated readings.
- Well at
the perimeter of a waste unit without an active control system, or that has a control
system that is malfunctioning, disconnected, or has a recent history of
unreliable operation.
- Well is
close to off-site receptors (within 1,000 ft.)- Receptors include buildings, agricultural
crops and public gathering locations, such as schools, playgrounds, parks and
golf courses. If multi-depth probes
meet any one of the above criteria, all depths should be monitored.
2. If
there is no monitoring system:
Conduct screening monitoring using a bar-hole
punch. Bar holes should be placed at appropriate locations on the perimeter of
a site based upon the following criteria:
- Soils. Porous soils, such as sands and sandy loams are the soils that
may potentially yield the highest readings for LFG. If the soil appears to
collapse in the hole as the punch is removed, then the monitoring point should
be constructed by slipping a piece of PVC pipe over the rod and pounding the
pipe into the ground.
- Geomorphology. Review available plans and geological and hydrogeological
records that may indicate the most probable pathways for LFG to migrate.
Consult with appropriate Board technical staff for sites where no landfill gas
monitoring plan has been reviewed, or there is some reason to believe some
special condition may exist at the site.
- Proximity of waste and receptors to permitted boundary. Bar hole monitoring is site specific should
be done at or near the boundary, at points, which are closest to the waste or
nearby receptors. See Figure 1 below.
Diagram 2
Wells in Diagram 2 above P1, P4, P5, P6 and P7
should definitely be screened. Either one of wells 2 and 3 are optional,
unless they have had a recent history of readings above 5% methane, or they
have not been monitored in the past.
If the result of monitoring the bar hole probe
indicates that LFG is migrating at a level of 0.5-5%, the operator should be
encouraged to conduct further monitoring to determine if LFG is migrating at
levels deeper then 3 feet pursuant to 27 CCR Section 20919.
At arid, rural landfills (ARLs), with no
receptors nearby, only one bar hole location may be needed, because these sites
typically have little LFG migration. ARLs are those that usually receive less
than 10 inches of precipitation per year, and take less than 20 tons of refuse
per day. Moreover, the amount of moisture that returns to the atmosphere
through evaporation will exceed the amount of moisture that penetrates into the
ground. The result is a net loss of moisture at small dry landfills on an
annual basis.
- Proximity
to receptors. Bar hole probes should be used as close as possible to receptors
while still being at or near the boundary of the site.
Disclaimer: The above guidelines for placement and
monitoring of probes are used for screening monitoring and are not intended to
be used by operators as absolute indicators of compliance with Subtitle D or
other monitoring requirements.
Note: If bar hole monitoring results are
inconclusive, Board staff may conduct additional monitoring using the SGVIP
unit, in order to assess the risk posed by the site to the public and the
environment.
3. If monitoring system is inadequate:
A monitoring system is inadequate if it is significantly different
from an approved monitoring plan or if it has not been approved by the LEA
and/or the Board. The operator should
be required to submit a work plan to correct the inadequacies. A violation or area of concern can be given
if a monitoring system is inadequate and differs from what was specified by the
LEA, local fire control authority or the Board.
An inspector can still use the guidance in 1 and 2 above to
conduct Screening Monitoring. If a
violation or area of concern for an inadequate monitoring system is given, the
inspector should note all inconsistencies or system problems that led to the
finding.
Table of Contents | Next
page>>>
|
