Current through Register Vol. 24-06, March 15, 2024
(1) The owner or operator must calculate and
evaluate all of the following statistics for background groundwater quality
data:
(a) The background mean;
(b) The background variance;
(c) The standard deviation of the background
data;
(d) The coefficient of
variation of the background data;
(e) The standard error of the background
data; and
(f) Other statistics
testing for homogeneity of variance and the normality of the background
data.
(2) The owner or
operator must specify in the permit application in accordance with WAC
173-351-730(1)(b)(iii)
appropriate statistical methods to be used
in evaluating groundwater monitoring data for each constituent. The statistical
test chosen must be conducted separately for each constituent in each well. The
owner or operator must demonstrate that the statistical methods meet the
following performance standards, as appropriate:
(a) The statistical method used to evaluate
groundwater monitoring data must be appropriate for the distribution of
chemical parameters or constituents. If the distribution of the chemical
parameters or constituents is shown by the owner or operator to be
inappropriate for a normal theory test, then the data must be evaluated to
determine if nonnormal conditions are due to laboratory or sampling error, poor
well construction, seasonal or spatial variability, or actual site conditions.
Transformed or a distribution-free theory test may be used, upon a
determination of why nonnormal conditions exist. If the distributions for the
constituents differ, more than one statistical method may be needed.
(b) 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 comparison procedure is used, the
Type I experiment wise 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.
(c) Parameter values must be protective of
human health and the environment. The parameters must be determined after
considering the number of samples in the background data base, the data
distribution, and the range of the concentration values for each constituent of
concern.
(d) The statistical method
must account for data below the limit of detection with one or more statistical
procedures that are protective of human health and the environment. Any
practical quantitation limit (PQL) 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.
(e) 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.
(3) The owner or operator must determine
whether or not there is a statistically significant increase over background
values for each parameter or constituent required in the particular groundwater
monitoring program that applies to the MSWLF unit after each sampling event and
as determined under this section.
(a) In
determining whether a statistically significant increase has occurred, the
owner or operator must compare the groundwater quality of each parameter or
constituent at each monitoring well designated pursuant to WAC
173-351-430 or
173-351-440 to the background
value of that constituent, according to the statistical procedures and
performance standards specified under this section.
(b) Within thirty days after receipt of the
analytical data, the owner or operator must determine whether there has been a
statistically significant increase over background at each monitoring
well.
Statutory Authority:
RCW
70.95.020(3),
70.95.060(1), and
70.95.260(1),
(6). 12-23-009 (Order 07-15), §
173-351-420, filed 11/8/12, effective 12/9/12. Statutory Authority:
Chapter
70.95 RCW and 40 CFR 258.
93-22-016, § 173-351-420, filed 10/26/93, effective
11/26/93.