Administrative Rules of Montana
Department 17 - ENVIRONMENTAL QUALITY
Chapter 17.50 - SOLID WASTE MANAGEMENT
Subchapter 17.50.13 - Ground Water Monitoring and Corrective Action
Rule 17.50.1306 - DETECTION MONITORING PROGRAM

(1) The owner or operator of a Class II or Class IV landfill unit shall conduct detection monitoring for the unit at all ground water monitoring wells defined under ARM 17.50.1304(1)(a) and (b). At a minimum, that detection monitoring must include monitoring for each constituent in Appendix I to 40 CFR Part 258 (July 1, 2008), set forth below, unless exempted in (2), and each parameter in any alternative list established under (3) for which the department has mailed notification to the owner or operator.

(2) The department may exempt an owner or operator of a Class II or Class IV landfill unit from monitoring a constituent in Appendix I to 40 CFR Part 258 (July 1, 2008) if the owner or operator makes a written demonstration, approved by the department, that the exempted constituent is not reasonably expected to be in, or derived from, the waste contained in the unit.

(3) The department may establish an alternative list of inorganic indicator parameters for a Class II or Class IV landfill unit, in lieu of some or all of the heavy metals that comprise constituents 1 through 15 in Appendix I to 40 CFR Part 258 (July 1, 2008), if the department determines that the parameters in the alternative list provide a reliable indication of inorganic releases from the Class II or Class IV landfill unit to the ground water. In determining parameters in the alternative list, the department shall consider the following factors:

(4) An owner or operator of a Class II or Class IV landfill unit required to conduct ground water monitoring under this subchapter shall monitor for all constituents and parameters required in this rule at least semiannually during the active life of the facility, including closure and the post-closure period. During the first semiannual sampling event, a minimum of four independent samples from each background and downgradient well must be collected and analyzed for all constituents and parameters for which monitoring is required in this rule. At least one sample from each background and downgradient well must be collected and analyzed during subsequent semiannual sampling events. The department may specify an appropriate alternative frequency for repeated sampling and analysis for constituents and parameters for which monitoring is required in this rule during the active life of the unit, including closure and the post-closure care period. An alternative frequency during the active life of the unit, including closure, may be no less frequent than annual. An alternative frequency must be based on consideration of the following factors:

(5) If the owner or operator of a Class II or Class IV landfill unit, or the department, determines, pursuant to ARM 17.50.1305(8), that there is a statistically significant increase over the background level for a constituent or parameter other than pH required to be monitored in this rule, at any monitoring well at the boundary specified under ARM 17.50.1304(1)(b), the owner or operator shall:

(6) If pH is a parameter of an alternative list established under (3), and if the department determines that there has been a statistically significant decrease from background in pH, at a monitoring well at the boundary specified under ARM 17.50.1304(1)(b), and that assessment monitoring is necessary to protect human health or the environment, the department shall notify the owner or operator of the Class II or Class IV landfill unit of the determination, and the owner or operator shall give notice and establish assessment monitoring as required in (5).

(7) An owner or operator required to establish an assessment monitoring program under (5) or (6) may submit for department approval a demonstration that a source other than a Class II or Class IV landfill unit caused the statistically significant change described in (5) or (6) or that it resulted from error in sampling, analysis, or statistical evaluation, or from natural variation in ground water quality. A report documenting this demonstration must be certified by a qualified ground water scientist and placed in the operating record. If the department approves the demonstration, the owner or operator is not required to commence assessment monitoring, but shall continue detection monitoring as specified in this rule. If the department has not approved a demonstration, within 90 days after the determination described in (5) or (6) has been made, the owner or operator shall establish an assessment monitoring program as required in ARM 17.50.1307.

Appendix I to 40 CFR Part 258 (July 1, 2008)

Constituents for Detection Monitoring

Organic Constituents:

1Common names are those widely used in government regulations, scientific publications, and commerce; synonyms exist for many chemicals

2Chemical Abstract Service registry number