Performance Standard:

258.54(a) Detection monitoring is required at MSWLF units at all ground-water monitoring wells defined under sec. 258.51(a)(1) and (a)(2) of this part. At a minimum, a detection monitoring program must include the monitoring for the constituents listed in appendix I of this part.

Waiver:

258.54(a)(1) The Director of an approved State may delete any of the appendix I monitoring parameters for a MSWLF unit if it can be shown that the removed constituents are not reasonably expected to be contained in or derived from the waste contained in the unit.

258.54(a)(2) The Director of an approved State may establish an alternative list of inorganic indicator parameters for a MSWLF unit, in lieu of some or all of the heavy metals (constituents 1-15 in appendix I to this part), if the alternative parameters provide a reliable indication of inorganic releases from the MSWLF unit to the ground water. In determining alternative parameters, the Director shall consider the following factors:

258.54(a)(2)(i) The types, quantities, and concentrations of constituents in waste managed at the MSWLF unit;

258.54(a)(2)(ii) The mobility, stability, and persistence of waste constituents or their reaction products in the unsaturated zone beneath the MSWLF unit;

258.54(a)(2)(iii) The detectability of indicator parameters, waste constituents, and reaction products in the ground water; and

258.54(a)(2)(iv) The concentration or values and coefficients of variation of monitoring parameters or constituents in the groundwater background.

258.54(b) The monitoring frequency for all constituents listed in appendix I to this part, or in the alternative list approved in accordance with paragraph (a)(2) of this section, shall be at least semiannual during the active life of the facility (including closure) and the post-closure period. A minimum of four independent samples from each well (background and downgradient) must be collected and analyzed for the appendix I constituents, or the alternative list approved in accordance with paragraph (a)(2) of this section, during the first semiannual sampling event. At least one sample from each well (background and downgradient) must be collected and analyzed during subsequent semiannual sampling events.

Waiver:

The Director of an approved State may specify an appropriate alternative frequency for repeated sampling and analysis for appendix I constituents, or the alternative list approved in accordance with paragraph (a)(2) of this section, during the active life (including closure) and the post-closure care period. The alternative frequency during the active life (including closure) shall be no less than annual. The alternative frequency shall be based on consideration of the following factors:

258.54(b)(1) Lithology of the aquifer and unsaturated zone;

258.54(b)(2) Hydraulic conductivity of the aquifer and unsaturated zone;

258.54(b)(3) Ground-water flow rates;

258.54(b)(4) Minimum distance between upgradient edge of the MSWLF unit and downgradient monitoring well screen (minimum distance of travel); and

258.54(b)(5) Resource value of the aquifer.

Performance Standard:

258.54(c) If the owner or operator determines, pursuant to sec. 258.53(g) of this part, that there is a statistically significant increase over background for one or more of the constituents listed in appendix I to this part, or in the alternative list approved in accordance with paragraph (a)(2) of this section, at any monitoring well at the boundary specified under sec. 258.51(a)(2), the owner or operator:

258.54(c)(1) Must, within 14 days of this finding, place a notice in the operating record indicating which constituents have shown statistically significant changes from background levels, and notify the State director that this notice was placed in the operating record; and

258.54(c)(2) Must establish an assessment monitoring program meeting the requirements of sec. 258.55 of this part within 90 days except as provided for in paragraph (c)(3) of this section.

Waiver:

258.54(c)(3) The owner/operator may demonstrate that a source other than a MSWLF unit caused the contamination or that the statistically significant increase resulted from error in sampling, analysis, statistical evaluation, or natural variation in ground-water quality. A report documenting this demonstration must be certified by a qualified ground-water scientist or approved by the Director of an approved State and be placed in the operating record. If a successful demonstration is made and documented, the owner or operator may continue detection monitoring as specified in this section. If, after 90 days, a successful demonstration is not made, the owner or operator must initiate an assessment monitoring program as required in sec. 258.55.