Current through Register Vol. 48, No. 38, September 20, 2024
a) The groundwater monitoring program must
include consistent sampling and analysis procedures that are designed to ensure
monitoring results that provide an accurate representation of groundwater
quality at the background and downgradient wells required by Section 845.630.
The owner or operator of the CCR surface impoundment must develop a sampling
and analysis program that includes procedures and techniques for:
1) Sample collection;
2) Sample preservation and
shipment;
3) Analytical
procedures;
4) Chain of custody
control; and
5) Quality assurance
and quality control.
b)
The groundwater monitoring program must include sampling and analytical methods
that are appropriate for groundwater sampling and that accurately measure
constituents and other monitoring parameters in groundwater samples. For
purposes of this Subpart, the term "constituent" refers to both constituents
and other monitoring parameters listed in Section 845.600.
c) The owner or operator must perform the
following each time ground water is sampled:
1) Measure groundwater elevations in each
well before purging;
2) Determine
the rate and direction of groundwater flow; and
3) Measure groundwater elevations in wells
that monitor the same CCR management area within a time period short enough to
avoid temporal variations in groundwater flow that could preclude accurate
determination of groundwater flow rate and direction.
d) The owner or operator of the CCR surface
impoundment must establish background groundwater quality in a hydraulically
upgradient or background well for each of the constituents listed in Section
845.600. Background groundwater quality may be established at wells that are
not located hydraulically upgradient from the CCR surface impoundment if it
meets the requirements of Section 845.630(a)(1).
e) The number of samples collected when
conducting monitoring (for both downgradient and background wells) must be
consistent with the statistical procedures chosen under subsection (f) and the
performance standards under subsection (g). The sampling procedures must be
those specified by Section 845.650(a) through (c).
f) Statistical Methods
1) The owner or operator of the CCR surface
impoundment must select one of the statistical methods specified in subsection
(f)(1) to be used in evaluating groundwater monitoring data for each specified
constituent. The statistical test chosen must be conducted separately for each
constituent in each monitoring well.
A) A
parametric analysis of variance followed by multiple comparison 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.
B) An analysis of variance based on ranks
followed by multiple comparison 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.
C) 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.
D) A control chart approach
that gives control limits for each constituent.
E) Another statistical test method that meets
the performance standards of subsection (g).
2) The owner or operator of the CCR surface
impoundment must obtain a certification from a qualified professional engineer
stating that the selected statistical method is appropriate for evaluating the
groundwater monitoring data for the CCR surface impoundment. The certification
must include a narrative description of the statistical method selected to
evaluate the groundwater monitoring data. The certification must be submitted
to the Agency with the appropriate permit application.
3) The owner or operator of the CCR surface
impoundment must submit the following to the Agency in an operating permit
application:
A) Documentation of the
statistical method chosen; and
B)
The qualified professional engineer certification required by subsection
(f)(2).
g)
Any statistical method chosen under subsection (f) must comply with the
following performance standards, as appropriate, based on the statistical test
method used:
1) The statistical method used
to evaluate groundwater monitoring data must be appropriate for the
distribution of constituents. Normal distributions of data values must use
parametric methods. Non-normal distributions must use non-parametric methods.
If the distribution of the constituents is shown by the owner or operator of
the CCR surface impoundment to be inappropriate for a normal theory test, then
the data must be transformed or a distribution-free (non-parametric) theory
test must 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 of at least 0.01 for each testing
period. If a multiple comparison procedure is used, the Type I experiment wise
error rate for each testing period must be at least 0.05; however, the Type I
error of at least 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 constituent values must be
such that this approach is at least as effective as any other approach in this
Section for evaluating groundwater data. The constituent values must 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.
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 such that
this approach is at least as effective as any other approach in this Section
for evaluating groundwater data. These constituents must 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 at least as effective as any other approach in this Section for
evaluating groundwater data. Any practical quantitation limit 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. For
the constituents identified in Section 845.600(a)(1), the practical
quantitation limit must be less than the groundwater protection
standards.
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.
h) The owner or operator of the
CCR surface impoundment must determine whether there is a statistically
significant increase over background values for each constituent in Section
845.600.
1) In determining whether a
statistically significant increase has occurred, the owner or operator must
compare the groundwater quality of each constituent at each monitoring well
designated under Section 845.630(a)(2) or (d)(1) to the background value of
that constituent, according to the statistical procedures and performance
standards specified by subsections (f) and (g).
2) Within 60 days after completing sampling
and analysis, the owner or operator must determine whether there has been a
statistically significant increase over background for any constituent at each
monitoring well.
i) The
owner or operator must measure total recoverable metals concentrations in
measuring groundwater quality. Measurement of total recoverable metals captures
both the particulate fraction and dissolved fraction of metals in natural
waters. Groundwater samples must not be field filtered before
analysis.
j) All groundwater
samples taken under this Subpart must be analyzed by a certified laboratory
using Test Methods for Evaluating Solid Waste, Physical/Chemical Methods,
SW-846, incorporated by reference in Section
845.150.
