Current through Register Vol. 48, No. 38, September 20, 2024
The owner or operator must comply with the following
requirements for any groundwater monitoring program developed to satisfy
Section
724.198,
724.199,
or
724.200.
a) The groundwater monitoring system must
consist of a sufficient number of wells, installed at appropriate locations and
depths to yield groundwater samples from the uppermost aquifer that fulfill the
following requirements:
1) They represent the
quality of background groundwater that has not been affected by leakage from a
regulated unit. A determination of background groundwater quality may include
sampling of wells that are not hydraulically upgradient from the waste
management area where the following is true:
A) Hydrogeologic conditions do not allow the
owner or operator to determine what wells are upgradient; or
B) Sampling at other wells will provide an
indication of background groundwater quality that is as representative or more
representative than that provided by the upgradient wells;
2) They represent the quality of groundwater
passing the point of compliance; and
3) They allow for the detection of
contamination when hazardous waste or hazardous constituents have migrated from
the hazardous waste management area to the uppermost aquifer.
b) If a facility contains more
than one regulated unit, separate groundwater monitoring systems are not
required for each regulated unit provided that provisions for sampling the
groundwater in the uppermost aquifer will enable detection and measurement at
the compliance point of hazardous constituents from the regulated units that
have entered the groundwater in the uppermost aquifer.
c) All monitoring wells must be cased in a
manner that maintains the integrity of the monitoring well bore hole. This
casing must be screened or perforated and packed with gravel or sand, where
necessary, to enable collection of groundwater samples. The annular space
(i.e., the space between the bore hole and well casing) above the sampling
depth must be sealed to prevent contamination of samples and the
groundwater.
d) The groundwater
monitoring program must include consistent sampling and analysis procedures
that are designed to ensure monitoring results that provide a reliable
indication of groundwater quality below the waste management area. At a minimum
the program must include procedures and techniques for the following:
1) Sample collection;
2) Sample preservation and
shipment;
3) Analytical procedures;
and
4) Chain of custody
control.
e) The
groundwater monitoring program must include sampling and analytical methods
that are appropriate for groundwater sampling and that accurately measure
hazardous constituents in groundwater samples.
f) The groundwater monitoring program must
include a determination of the groundwater surface elevation each time
groundwater is sampled.
g) In
detection monitoring or where appropriate in compliance monitoring, data on
each hazardous constituent specified in the permit will be collected from
background wells and wells at the compliance points. The number and kinds of
samples collected to establish background must be appropriate for the form of
statistical test employed, following generally accepted statistical principles.
The sample size must be as large as necessary to ensure with reasonable
confidence that a contaminant release to groundwater from a facility will be
detected. The owner or operator will determine an appropriate sampling
procedure and interval for each hazardous constituent listed in the facility
permit that must be specified in the unit permit upon approval by the Agency.
This sampling procedure must fulfill the following requirements:
1) It may be a sequence of at least four
samples, taken at an interval that assures, to the greatest extent technically
feasible, that an independent sample is obtained, by reference to the uppermost
aquifer's effective porosity, hydraulic conductivity and hydraulic gradient,
and the fate and transport characteristics of the potential contaminants;
or
2) It may be an alternate
sampling procedure proposed by the owner or operator and approved by the
Agency.
h) The owner or
operator must specify one of the following statistical methods to be used in
evaluating groundwater monitoring data for each hazardous constituent that,
upon approval by the Agency, will be specified in the unit permit. The
statistical test chosen must be conducted separately for each hazardous
constituent in each well. Where practical quantification limits (pqls) are used
in any of the following statistical procedures to comply with subsection
(i)(5), the pql must be proposed by the owner or operator and approved by the
Agency. Use of any of the following statistical methods must adequately protect
human health and the environment and must comply with the performance standards
outlined in subsection (i).
1) A parametric
analysis of variance (ANOVA) followed by multiple comparisons procedures to
identify statistically significant evidence of contamination. The method must
include estimation and testing of the contrasts between each compliance well's
mean and the background mean levels for each constituent.
2) An analysis of variance (ANOVA) based on
ranks followed by multiple comparisons procedures to identify statistically
significant evidence of contamination. The method must include estimation and
testing of the contrasts between each compliance well's median and the
background median levels for each constituent.
3) A tolerance or prediction interval
procedure in which an interval for each constituent is established from the
distribution of the background data, and the level of each constituent in each
compliance well is compared to the upper tolerance or prediction
limit.
4) A control chart approach
that gives control limits for each constituent.
5) Another statistical test method submitted
by the owner or operator and approved by the Agency.
i) Any statistical method chosen pursuant to
subsection (h) for specification in the unit permit must comply with the
following performance standards, as appropriate:
1) The statistical method used to evaluate
groundwater monitoring data must be appropriate for the distribution of
chemical parameters or hazardous constituents. If the distribution of the
chemical parameters or hazardous constituents is shown by the owner or operator
to be inappropriate for a normal theory test, then the data should be
transformed or a distribution-free theory test should be used. If the
distributions for the constituents differ, more than one statistical method may
be needed.
2) If an individual well
comparison procedure is used to compare an individual compliance well
constituent concentration with background constituent concentrations or a
groundwater protection standard, the test must be done at a Type I error level
no less than 0.01 for each testing period. If a multiple comparisons procedure
is used, the Type I experimentwise error rate for each testing period must be
no less than 0.05; however, the Type I error of no less than 0.01 for
individual well comparisons must be maintained. This performance standard does
not apply to tolerance intervals, prediction intervals or control
charts.
3) If a control chart
approach is used to evaluate groundwater monitoring data, the specific type of
control chart and its associated parameter value must be proposed by the owner
or operator and approved by the Agency if the Agency finds it to adequately
protect human health and the environment.
4) If a tolerance interval or a prediction
interval is used to evaluate groundwater monitoring data, the levels of
confidence and, for tolerance intervals, the percentage of the population that
the interval must contain, must be proposed by the owner or operator and
approved by the Agency if the Agency finds these parameters to adequately
protect human health and the environment. These parameters will be determined
after considering the number of samples in the background database, the data
distribution, and the range of the concentration values for each constituent of
concern.
5) The statistical method
must account for data below the limit of detection with one or more statistical
procedures that adequately protect human health and the environment. Any
practical quantification limit (pql) approved by the Agency pursuant to
subsection (h) that is used in the statistical method must be the lowest
concentration level that can be reliably achieved within specified limits of
precision and accuracy during routine laboratory operating conditions that are
available to the facility.
6) If
necessary, the statistical method must include procedures to control or correct
for seasonal and spatial variability, as well as temporal correlation in the
data.
j) Groundwater
monitoring data collected in accordance with subsection (g), including actual
levels of constituents, must be maintained in the facility operating record.
The Agency must specify in the permit when the data must be submitted for
review.
