39-7410. GROUND WATER MONITORING DESIGN. (1) Applicability. These requirements apply to MSWLF units except:

(a) When the MSWLF unit meets the conditions for exemption in 40 CFR 258.1(f); provided however, that the director may, at his discretion, require monitoring of a MSWLF unit which meets the conditions for exemption in 40 CFR 258.1(f), if necessary to protect ground water resources. If the director does require ground water monitoring of such MSWLF unit, a method other than the ground water monitoring wells required in this section and in 40 CFR 258.51 through 258.55 may be used to detect a release of contamination from the unit; or

(b) When suspended upon demonstration in accordance with 40 CFR 258.50 that there is no potential for migration of hazardous constituents from the MSWLF unit to the uppermost aquifer during the active life of the unit and the post-closure care periods when certified by a qualified professional and approved by the director.

(2) Ground water monitoring program. All monitoring programs shall be conducted in a manner consistent with the guidance of relevant portions of appendix F per the "Federal Register" of October 9, 1991. The schedule for compliance as provided by 40 CFR 258.50 shall apply unless an alternative schedule is approved by the director.

(a) A ground water monitoring system must be installed that consists of a sufficient number of wells, installed at appropriate locations and depths, to conform with the requirements of 40 CFR 258.51(a) and (d).

(b) A multiunit ground water monitoring system may be constructed instead of separate ground water monitoring systems for each MSWLF unit as provided in 40 CFR 258.51(b).

(c) Monitoring wells must be cased in a manner that maintains the integrity of the monitoring well bore hole as provided in 40 CFR 258.51(c). Wells must be constructed in such a manner as to prevent contamination of the samples, the sampled strata, and between aquifers and water bearing strata, and in accordance with Idaho department of water resources, well construction standards and the monitoring well standards of the national ground water association.

(3) Point of compliance. For each MSWLF unit, the relevant point of compliance shall be set as a function of site and monitoring program design subject to the approval of the director. The relevant point of compliance for purposes of MSWLF unit design, well location and corrective action shall be:

(a) Located within the flow pathway(s) predicted from the results of the hydrogeologic investigation;

(b) No more than one hundred fifty (150) meters downgradient from the waste management unit boundary;

(c) On contiguous property owned, or otherwise subject to possessory rights by the MSWLF owner;

(d) Shall be identified by the qualified professional on all reports and documents pertaining to analysis of ground water protection measures; and

(e) Determined in consideration of factors provided in 40 CFR 258.40(d).

(4) Ground water characterization, sampling and analysis requirements.

(a) The ground water monitoring system must include sampling and analysis procedures consistent with 40 CFR 258.53.

(b) Monitoring wells shall be tested for the constituents listed in 40 CFR 258, appendix I, plus temperature, unless otherwise authorized by the director as provided in 40 CFR 258.54.

(c) Background values will be based on an independent sample from each well sampled at three (3) month intervals in a one (1) year period.

(5) Detection monitoring program.

(a) Detection monitoring is required throughout the active life and post-closure care period at MSWLF units as provided in 40 CFR 258.54 at all ground water monitoring wells as defined in 40 CFR 258.51(a)(1) and (a)(2) for constituents listed in 40 CFR 258, appendix I.

(b) Each well shall be monitored on a semiannual basis after background characterization. Alternative constituents and sampling frequency may be approved by the director based upon considerations as defined in 40 CFR 258.54 (a)(2) and (b). Requests for alternative constituents or frequency shall be based on a report certified by a qualified professional.

(c) Each ground water sample event must include a determination of the ground water surface elevation, flow direction and rate.

History:

[(39-7410) 1992, ch. 331, sec. 1, p. 986; am. and redesig. 1993, ch. 139, sec. 11, p. 356; am. 1994, ch. 75, sec. 6, p. 167; am. 1997, ch. 11, sec. 1, p. 11.]