R 299.4908 Landfill groundwater monitoring; statistical procedures.

Rule 908. (1) The owner and operator of a landfill shall evaluate groundwater-monitoring data for each hazardous constituent, except pH and conductivity, using 1 of the following statistical tests: (a) A parametric analysis of variance (ANOVA) followed by multiple comparisons 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 mean levels for each constituent. (b) An analysis of variance (ANOVA) based on ranks followed by multiple comparisons 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 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 is in compliance with the performance standards of subrule (2) of this rule. The owner or operator shall place a justification for this alternative in the operating record and notify the director of the use of this alternative test. The justification shall demonstrate that the alternative method is in compliance with the performance standards of subrule (2) of this rule. (2) Any statistical method chosen under subrule (1) of this rule shall be in compliance with all of the following performance standards: (a) The statistical method used to evaluate groundwater-monitoring data shall 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 shall be transformed or a distribution-free theory test shall be used. If the distributions for the constituents differ, more than 1 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 shall be done at a type I error level of not 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 not less than 0.05; however, the type I error of not less than 0.01 for individual well comparisons shall be maintained. This performance standard does not apply to tolerance intervals, prediction intervals, or control charts. (c) If a control chart approach is used to evaluate groundwater-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 database, the data distribution, and the range of the concentration values for each constituent of concern. (d) If a tolerance interval or a predictional interval is used to evaluate groundwater monitoring data, then the levels of confidence and, for tolerance intervals, the percentage of the population that the interval must contain shall be protective of human health and the environment. These parameters shall 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. (e) The statistical method shall account for data below the limit of detection with 1 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 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. (f) 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. (3) The statistical test chosen shall be specified in the operating record and shall be conducted separately for each hazardous constituent at each well. (4) The owner or operator shall 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 unit. (5) In determining whether a statistically significant increase has occurred, the owner or operator shall compare the groundwater quality of each parameter or constituent at each monitoring well that is designated under R 299.4906 to the background value of that constituent, according to the statistical procedures and performance standards specified in this rule. (6) The owner or operator shall complete the statistical analysis at each monitoring well and submit the results within 30 days of the end of the calendar quarter in which sampling and analysis was conducted. (7) Nothing in this rule prohibits the department from evaluating monitoring data using statistical procedures it deems appropriate at a given location. (8) Verification sampling for any exceedance of the statistical limit must be completed within 90 days of the original sampling date.