Current through Register Vol. 48, No. 38, September 20, 2024
An owner or operator subject to this Subpart M must establish
an unsaturated zone monitoring program to carry out the following
responsibilities:
a) The owner or
operator must monitor the soil and soil-pore liquid to determine whether
hazardous constituents migrate out of the treatment zone.
1) The Agency must specify the hazardous
constituents to be monitored in the facility permit. The hazardous constituents
to be monitored are those specified under Section
724.371(b).
2) The Agency may require monitoring for
principal hazardous constituents (PHCs) in lieu of the constituents specified
under Section
724.371(b).
PCHs are hazardous constituents contained in the wastes to be applied at the
unit that are the most difficult to treat, considering the combined effects of
degradation, transformation, and immobilization. The Agency must establish PHCs
if it finds, based on waste analyses, treatment demonstrations, or other data,
that effective degradation transformation or immobilization of the PHCs will
assure treatment at least equivalent levels for the other hazardous
constituents in the wastes.
b) The owner or operator must install an
unsaturated zone monitoring system that includes soil monitoring using soil
cores and soil-pore liquid monitoring using devices such as lysimeters. The
unsaturated zone monitoring system must consist of a sufficient number of
sampling points at appropriate locations and depths to yield samples that
fulfill the following:
1) Represent the
quality of background soil-pore liquid quality and the chemical make-up of soil
that has not been affected by leakage from the treatment zone; and
2) Indicate the quality of soil-pore liquid
and the chemical make-up of the soil below the treatment zone.
c) The owner or operator must
establish a background value for each hazardous constituent to be monitored
under subsection (a). The permit will specify the background values for each
constituent or specify the procedures to be used to calculate the background
values.
1) Background soil values may be
based on a one-time sampling at a background plot having characteristics
similar to those of the treatment zone.
2) Background soil-pore liquid values must be
based on at least quarterly sampling for one year at a background plot having
characteristics similar to those of the treatment zone.
3) The owner or operator must express all
background values in a form necessary for the determination of statistically
significant increases under subsection (f).
4) In taking samples used in the
determination of all background values, the owner or operator must use an
unsaturated zone monitoring system that complies with subsection
(b)(1).
d) The owner or
operator must conduct soil monitoring and soil-pore liquid monitoring
immediately below the treatment zone. The Agency must specify the frequency and
timing of soil and soil-pore liquid monitoring in the facility permit after
considering the frequency, timing, and rate of waste application and the soil
permeability. The owner or operator must express the results of soil and
soil-pore liquid monitoring in a form necessary for the determination of
statistically significant increases under subsection (f).
e) The owner or operator must use consistent
sampling and analysis procedures that are designed to ensure sampling results
that provide a reliable indication of soil-pore liquid quality and the chemical
make-up of the soil below the treatment zone. At a minimum, the owner or
operator must implement procedures and techniques for the following:
1) Sample collection;
2) Sample preservation and
shipment;
3) Analytical procedures;
and
4) Chain of custody
control.
f) The owner or
operator must determine whether there is a statistically significant change
over background values for any hazardous constituent to be monitored under
subsection (a) below the treatment zone each time it conducts soil monitoring
and soil-pore liquid monitoring under subsection (d).
1) In determining whether a statistically
significant increase has occurred, the owner or operator must compare the value
of each constituent, as determined under subsection (d), to the background
value for that constituent according to the statistical procedure specified in
the facility permit under this subsection (f).
2) The owner or operator must determine
whether there has been a statistically significant increase below the treatment
zone within a reasonable time period after completion of sampling. The Agency
must specify that time period in the facility permit after considering the
complexity of the statistical test and the availability of laboratory
facilities to perform the analysis of soil and soil-pore liquid
samples.
3) The owner or operator
must determine whether there is a statistically significant increase below the
treatment zone using a statistical procedure that provides reasonable
confidence that migration from the treatment zone will be identified. The
Agency must specify a statistical procedure in the facility permit that it
finds fulfills the following:
A) Is
appropriate for the distribution of the data used to establish background
values; and
B) Provides a
reasonable balance between the probability of falsely identifying migration
from the treatment zone and the probability of failing to identify real
migration from the treatment zone.
g) If the owner or operator determines,
pursuant to subsection (f), that there is a statistically significant increase
of hazardous constituents below the treatment zone, it must do the following:
1) Notify the Agency of this finding in
writing within seven days. The notification must indicate what constituents
have shown statistically significant increases.
2) Within 90 days, submit to the Agency an
application for a permit modification to modify the operating practices at the
facility in order to maximize the success of degradation, transformation, or
immobilization processes in the treatment zone.
h) If the owner or operator determines,
pursuant to subsection (f), that there is a statistically significant increase
of hazardous constituents below the treatment zone, it may demonstrate that a
source other than regulated units caused the increase or that the increase
resulted from an error in sampling, analysis, or evaluation. While the owner or
operator may make a demonstration under this subsection (h) in addition to, or
in lieu of, submitting a permit modification application under subsection
(g)(2), it is not relieved of the requirement to submit a permit modification
application within the time specified in subsection (g)(2), unless the
demonstration made under this subsection (h) successfully shows that a source
other than regulated units caused the increase or that the increase resulted
from an error in sampling, analysis, or evaluation. In making a demonstration
under this subsection (h), the owner or operator must do the following:
1) Notify the Agency in writing within seven
days of determining a statistically significant increase below the treatment
zone that the owner or operator intends to make a determination under this
subsection (h);
2) Within 90 days,
submit a report to the Agency demonstrating that a source other than the
regulated units caused the increase or that the increase resulted from error in
sampling, analysis, or evaluation;
3) Within 90 days, submit to the Agency an
application for a permit modification to make any appropriate changes to the
unsaturated zone monitoring program at the facility; and
4) Continue to monitor in accordance with the
unsaturated zone monitoring program established under this Section.
