Section 18 AAC 60.830 - Groundwater sampling and analysis(a) When groundwater monitoring is required at a facility under 18 AAC 60.820, the owner or operator shall prepare a groundwater monitoring plan that includes a quality assurance project plan and that includes consistent sampling and analytical procedures that will ensure that groundwater monitoring in each monitoring event will accurately document groundwater quality in all wells constituting the groundwater monitoring system installed under 18 AAC 60.825.(b) The groundwater monitoring plan must conform to the requirements of (c) - (j) of this section and any site-specific requirements that the department determines are necessary, and must receive the department's approval. The approved groundwater monitoring plan shall be placed in the operating record of the facility and the owner or operator of the facility shall revise the groundwater monitoring plan as required by the department at the time of permit renewal, and also as needed in response to a change in(1) the groundwater monitoring system; or(2) the groundwater monitoring program that is(A) necessitated by a change in groundwater quality in the uppermost aquifer beneath the facility; or(B) required by the department.(c) The owner or operator shall ensure that the groundwater monitoring plan includes sample collection procedures and analytical methods that are appropriate for groundwater sampling and that yield accurate measurements of monitoring parameters and analyte concentrations at an acceptable level of sensitivity. The groundwater monitoring plan must include the procedures and techniques for(1) sample collection, including groundwater elevation measurements;(2) sample preservation and shipment;(3) analytical procedures and sensitivity requirements;(4) chain of custody control;(5) quality assurance and quality control;(6) compliance with (g) of this section;(7) evaluating the condition of the well at the time that samples are taken;(8) monitoring well maintenance; and(9) data processing and management.(d) Groundwater samples may not be field-filtered during collection. They must be analyzed for total constituent concentrations.(e) During each monitoring event, measurements to establish groundwater elevations shall be taken in all wells constituting the groundwater monitoring system, before purging the wells and within a period of time short enough to avoid temporal variations in groundwater elevation that could preclude accurate estimation of groundwater flow rate and direction.(f) The number of samples collected to establish groundwater quality must be consistent with the statistical methods selected under (g) of this section.(g) The owner or operator shall specify in the groundwater monitoring plan one of the following statistical methods to be selected from and used in evaluating groundwater monitoring data for each constituent retained for statistical analysis. The statistical method selected must be conducted separately for each constituent in each well and the statistical analyses under each method must be developed in consideration of the Statistical Analysis of Groundwater Monitoring Data at RCRA Facilities - Unified Guidance (EPA 530-F-09-007, March 2009), adopted by reference, unless an alternative approach is approved by the department. The statistical methods to be selected from and used are (1) a parametric analysis of variance, followed by multiple-comparisons procedures to identify statistically significant evidence of contamination; this method must include estimation and testing of the contrasts between the mean concentration in each compliance well and the background mean concentration for each constituent;(2) an analysis of variance based on ranks, followed by multiple-comparisons procedures to identify statistically significant evidence of contamination; this method must include estimation and testing of the contrasts between the median concentration in each compliance well and the background median concentration 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; or(5) another approved statistical test method that meets the performance standards of (h) of this section.(h) A statistical method selected under (g) of this section 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 the constituent concentration data; if the distribution of the constituent concentration data is shown by the owner or operator to be inappropriate for a normal theory test, then the data must be transformed, or a distribution-free theory test must be used; if the distributions for the constituents differ, more than one statistical method identified under (g) of this section might be needed;(2) if an individual well comparison procedure is used to compare an individual well's 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 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;(3) if a control chart approach is used to evaluate groundwater monitoring data, the specific type of control chart and its associated parameter values must be protective of public 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 being analyzed;(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 protective of public health and the environment; these 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 being analyzed;(5) the statistical method must account for data below the limit of detection, as that is defined in the approved groundwater monitoring plan or quality assurance project plan, in a manner that is protective of public health and the environment;(6) the 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; and(7) 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.(i) The owner or operator of the facility shall determine whether there is a statistically significant increase over background values for each constituent required to be analyzed in each well by the particular groundwater monitoring program that applies to the facility, as determined under 18 AAC 60.840. To determine whether a statistically significant increase has occurred, the owner or operator of the facility shall compare the concentration of each constituent detected in a monitoring well to the background value of that constituent, according to the statistical methods and performance standards set out in (g) and (h) of this section.(j) The owner or operator of the facility shall furnish groundwater sampling data and analyses to the department in the format approved by the department not later than 90 days after completing each sampling event or on an alternate date or schedule approved by the department, and shall maintain in the operating record of the facility a complete record of all groundwater monitoring conducted under this section.Eff. 1/28/96, Register 137; am 10/29/98, Register 148; am 2/25/2022, Register 241, April 2022Authority:AS 44.46.020
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