Current through Register Vol. 56, No. 18, September 16, 2024
(a) The person
responsible for conducting the Ground Water Protection Program established pursuant
to 7:14A-7.6 shall conduct ground water
sampling in accordance with the edition of the Department's Field Sampling
Procedures Manual applicable at the time of sampling, an alternate method approved
by the Department, or as set forth in the NJPDES-DGW permit.
(b) When statistical data evaluations are
specified by the Department to implement the Ground Water Protection Program, the
statistical test chosen shall be conducted separately for each specified constituent
in each well, and one of the following statistical methods shall be used to evaluate
ground-water monitoring data for each specified constituent:
1. A parametric analysis of variance (ANOVA)
followed by multiple comparison procedures to identify statistically significant
evidence of contamination. The method shall include estimation and testing of the
contrasts between each compliance well's mean and the background water quality mean
levels for each constituent;
2. An
analysis of variance (ANOVA) based on ranks followed by multiple comparison
procedures to identify statistically significant evidence of contamination. The
method shall include estimation and testing of the contrasts between each compliance
well's median and the background water quality 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 water quality 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; or
5. Another statistical test method that meets the
performance standards of (c) below, and has been approved by the Department in
writing.
(c) Any statistical
method chosen under this section shall comply with the following performance
standards, as appropriate:
1. The statistical
method used to evaluate ground-water monitoring data shall be appropriate for the
distribution of parameters. If the distribution of the parameters is shown by the
permittee to be inappropriate for a normal theory test, then the data must be
transformed or a distribution free theory test 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 water quality constituent concentrations or a ground-water protection
standard, the test shall 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 experiment
wise error rate for each testing period shall be no less than 0.05; however, the
type I error of no less than 0.01 for individual well comparison shall be
maintained. The performance standard does not apply to tolerance intervals,
prediction intervals or control charts.
3. If a control chart approach is used to evaluate
ground-water monitoring data, the specific type of control chart and its associated
parameter values shall be protective of human health and the environment. The
parameters shall be determined after considering the number of samples in the
background water quality data base, the date 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 ground-water monitoring data, the levels of confidence
and, for tolerance intervals, the percentage of the population that the interval
shall contain shall be protective of human health and the environment. These
parameters shall be determined after considering the number of samples in the
background water quality data base, the data distribution, and the range of the
concentration values for each constituent of concern.
5. The statistical method shall 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 level
(PQL) as defined in N.J.A.C. 7:9C that is used in the statistical method shall 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 shall include procedures to control or correct for
seasonal and spatial variability as well as temporal correlation in the
data.
(d) When conducting a
leak detection monitoring program, the permittee shall determine whether or not
there is a statistically significant increase over background water quality values
for each parameter or constituent required in the permit.
1. In determining whether a statistically
significant increase has occurred, the permittee shall compare the ground water
quality of each parameter or constituent at each compliance point monitoring well
designated pursuant to the permit to the background water quality value of that
constituent, according to the statistical procedures and performance standards
specified under this section.
2. Within
the period of time specified in the NJPDES discharge to ground water permit, and
after completing sampling and analysis, the permittee shall determine whether there
has been a statistically significant increase over background water quality at each
monitoring well.
(e) When
conducting an attenuation monitoring program, the permittee shall determine whether
the discharge complies with the ground water constituent standards for the
classification area established pursuant to N.J.A.C. 7:9C.
1. In determining whether the discharge complies
with the ground water constituent standards for the classification area, the
permittee shall compare the ground water quality of each parameter or constituent at
each compliance point monitoring well designated pursuant to the permit to the
background water quality value of that constituent, according to the statistical
procedures and performance standards specified under this section.
2. Within the period of time specified in the
NJPDES discharge to ground water permit, and after completing sampling and analysis,
the permittee shall determine whether there has been a statistically significant
contravention of the ground water quality standards.
