18 AAC 60.830. Groundwater sampling and analysis

(a) The owner or operator shall develop groundwater monitoring procedures, including consistent sampling and analysis procedures designed to ensure that monitoring results provide an accurate representation of groundwater quality at the background and downgradient wells. The owner or operator shall set out the procedures in a handbook or similar document and shall place the document in the operating record of the facility and provide written notification to the department when that occurs. The groundwater monitoring procedures must include procedures and techniques for

(1) sample collection;

(2) sample preservation and shipment;

(3) analytical procedures;

(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 the samples are taken; and

(8) monitoring well maintenance.

(b) The owner or operator shall ensure that the groundwater monitoring procedures include sampling and analytical methods that are appropriate for groundwater sampling and that accurately measure hazardous constituents and other monitoring parameters in groundwater samples. Groundwater samples may not be field-filtered before laboratory analysis unless the owner or operator demonstrates that hazardous constituents released from the solid waste will not be filtered out or volatilized by the filtration process.

(d) Each time groundwater is sampled, the owner or operator shall measure groundwater elevations in each well immediately before purging.

(e) Groundwater elevations in wells that monitor one facility must be measured within a period of time short enough to avoid temporal variations in groundwater flow that could preclude accurate estimation of groundwater flow rate and direction.

(f) The owner or operator shall establish background groundwater quality in one or more hydraulically upgradient or background wells for each of the monitoring parameters or constituents required in the particular groundwater monitoring program that applies to the facility as determined under 18 AAC 60.850 or 18 AAC 60.860. Background data must be collected in each of the four seasons before waste is placed in the waste management area being monitored. Background groundwater quality must be established at wells that are located hydraulically upgradient from the facility unless alternative sampling locations meet the requirements of AAC 60.825(a)(1).

(g) The number of samples collected to establish groundwater quality must be consistent with the statistical methods selected under (h) of this section. The sampling procedures must be those specified in

(1) 18 AAC 60.850(b) for detection monitoring; and

(2) 18 AAC 60.860 for assessment monitoring and corrective action.

(h) The owner or operator shall specify in the operating record one of the following statistical methods to be used in evaluating groundwater monitoring data for each hazardous constituent. The statistical method selected must be conducted separately for each hazardous constituent in each well. The 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; 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 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 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; or

(5) another approved statistical test method that meets the performance standards of (i) of this section.

(i) A statistical method selected under (h) 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 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 must be transformed, or a distribution-free theory test must be used; if the distributions for the constituents differ, more than one statistical method 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 protect 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 predictional 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 protect 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 with one or more statistical procedures that protect public health and the environment; a 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; and

(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) The owner or operator shall determine whether there is a statistically significant increase over background values for each parameter or constituent required to be analyzed by the particular groundwater monitoring program that applies to the facility, as determined under 18 AAC 60.850(a) or 18 AAC 60.860. In addition,

(1) to determine whether a statistically significant increase has occurred, the owner or operator shall compare the concentration of each parameter or constituent detected in a monitoring well to the background value of that constituent, according to the statistical methods and performance standards set out in (h) and (i) of this section; and

(2) after completing sampling and analysis, the owner or operator shall determine whether there has been a statistically significant increase over background at each monitoring well.

(k) The owner or operator shall furnish groundwater sampling data and analyses quarterly to the department in a format approved by the department and keep copies in the operating record of the facility for at least five years after the data and analyses are submitted to the department.

History: Eff. 1/28/96, Register 137; am 10/29/98, Register 148

Authority: AS 44.46.020

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