R315-265-93. Ground-Water Monitoring -- Preparation, Evaluation, and Response

  (a) Within one year after the effective date of these regulations, the owner or operator shall prepare an outline of a ground-water quality assessment program. The outline shall describe a more comprehensive ground-water monitoring program, than that described in Sections R315-265-91 and 265-92, capable of determining:

  (1) Whether hazardous waste or hazardous waste constituents have entered the ground water;

  (2) The rate and extent of migration of hazardous waste or hazardous waste constituents in the ground water; and

  (3) The concentrations of hazardous waste or hazardous waste constituents in the ground water.

  (b) For each indicator parameter specified in Subsection R315-265-92(b)(3), the owner or operator shall calculate the arithmetic mean and variance, based on at least four replicate measurements on each sample, for each well monitored in accordance with Subsection R315-265-92(d)(2), and compare these results with its initial background arithmetic mean. The comparison shall consider individually each of the wells in the monitoring system, and shall use the Student's t-test at the 0.01 level of significance, see Appendix IV to 40 CFR 265, which is adopted and incorporated by reference, to determine statistically significant increases, and decreases, in the case of pH, over initial background.

  (c)(1) If the comparisons for the upgradient wells made under Subsection R315-265-93(b) show a significant increase, or pH decrease, the owner or operator shall submit this information in accordance with Subsection R315-265-94(a)(2)(ii).

  (2) If the comparisons for downgradient wells made under Subsection R315-265-93(b) show a significant increase, or pH decrease, the owner or operator shall then immediately obtain additional ground-water samples from those downgradient wells where a significant difference was detected, split the samples in two, and obtain analyses of all additional samples to determine whether the significant difference was a result of laboratory error.

  (d)(1) If the analyses performed under Subsection R315-265-93(c)(2) confirm the significant increase, or pH decrease, the owner or operator shall provide written notice to the Director---within seven days of the date of such confirmation---that the facility may be affecting ground-water quality.

  (2) Within 15 days after the notification under Subsection R315-265-93(d)(1), the owner or operator shall develop a specific plan, based on the outline required under Subsection R315-265-93(a) and certified by a qualified geologist or geotechnical engineer, for a ground-water quality assessment at the facility. This plan shall be placed in the facility operating record and be maintained until closure of the facility.

  (3) The plan to be submitted under Subsection R315-265-90(d)(1) or Subsection R315-265-93(d)(2)shall specify:

  (i) The number, location, and depth of wells;

  (ii) Sampling and analytical methods for those hazardous wastes or hazardous waste constituents in the facility;

  (iii) Evaluation procedures, including any use of previously-gathered ground-water quality information; and

  (iv) A schedule of implementation.

  (4) The owner or operator shall implement the ground-water quality assessment plan which satisfies the requirements of Subsection R315-265-93(d)(3), and, at a minimum, determine:

  (i) The rate and extent of migration of the hazardous waste or hazardous waste constituents in the ground water; and

  (ii) The concentrations of the hazardous waste or hazardous waste constituents in the ground water.

  (5) The owner or operator shall make his first determination under Subsection R315-265-93(d)(4), as soon as technically feasible, and prepare a report containing an assessment of ground-water quality. This report shall be placed in the facility operating record and be maintained until closure of the facility.

  (6) If the owner or operator determines, based on the results of the first determination under Subsection R315-265-93(d)(4), that no hazardous waste or hazardous waste constituents from the facility have entered the ground water, then he may reinstate the indicator evaluation program described in Section R315-265-92 and Subsection R315-265-93(b). If the owner or operator reinstates the indicator evaluation program, he shall so notify the Director in the report submitted under Subsection R315-265-93(d)(5).

  (7) If the owner or operator determines, based on the first determination under Subsection R315-265-93(d)(4), that hazardous waste or hazardous waste constituents from the facility have entered the ground water, then he:

  (i) Shall continue to make the determinations required under Subsection R315-265-93(d)(4) on a quarterly basis until final closure of the facility, if the ground-water quality assessment plan was implemented prior to final closure of the facility; or

  (ii) May cease to make the determinations required under Subsection R315-265-93(d)(4), if the ground-water quality assessment plan was implemented during the post-closure care period.

  (e) Notwithstanding any other provision of Sections R315-265-90 through R315-265-94, any ground-water quality assessment to satisfy the requirements of Subsection R315-265-93(d)(4) which is initiated prior to final closure of the facility shall be completed and reported in accordance with Subsection R315-265-93(d)(5).

  (f) Unless the ground water is monitored to satisfy the requirements of Subsection R315-265-93(d)(4), at least annually the owner or operator shall evaluate the data on ground-water surface elevations obtained under Subsection R315-265-92(e) to determine whether the requirements under Subsection R315-265-91(a) for locating the monitoring wells continues to be satisfied. If the evaluation shows that Subsection R315-265-91(a) is no longer satisfied, the owner or operator shall immediately modify the number, location, or depth of the monitoring wells to bring the ground-water monitoring system into compliance with this requirement.