18 AAC 60.850. Detection monitoring program

(a) Except as provided in 18 AAC 60.460(c) , detection monitoring is required in all groundwater monitoring wells at facilities required to have groundwater monitoring under this chapter. At a minimum, detection monitoring requires monitoring for the applicable constituents and parameters listed in 18 AAC 60.840. For a Class I MSWLF, the department will

(1) delete any of the monitoring parameters required by this subsection if the owner or operator demonstrates that the removed constituents are not reasonably expected to be in or derived from the waste contained in the MSWLF; and

(2) establish an alternative list of inorganic indicator parameters for the MSWLF, instead of some or all of the heavy metals identified in 18 AAC 60.840, if the alternative parameters provide a reliable indication of inorganic releases from the MSWLF to the groundwater; in determining alternative parameters, the department will consider the

(A) types, amounts, and concentrations of constituents in wastes managed at the MSWLF;

(B) mobility, stability, and persistence of hazardous constituents or their reaction products in the unsaturated zone beneath the MSWLF;

(D) concentration or values and coefficients-of-variation for monitoring parameters or constituents in the groundwater background.

(b) Except as expressly provided elsewhere in this chapter, the required frequency of groundwater monitoring is as follows:

(1) for a newly installed groundwater monitoring system, the first sampling must take place immediately after installation is completed; at that first sampling, the owner or operator shall collect at least four independent samples from each well; the owner or operator shall conduct at least three more samplings during the following two years, ensuring that samples are collected at least one time during each of the four seasons; during these subsequent samplings, the owner or operator shall collect at least one sample from each well;

(2) if a facility owner or operator constructs a new landfill, samples must be collected at least once during the first six months of landfill operation and, at that sampling, the owner or operator shall collect at least four independent samples from each well that monitors the landfill waste management area;

(3) where this chapter requires monitoring to begin upon the happening of a specific event, such as closure or installation of a cap, monitoring must be conducted in the manner and at the frequency required for a new system by (1) of this subsection;

(4) after completing the initial monitoring of (1) - (3) of this subsection, as applicable, sampling must continue for the remainder of the active life of the facility and during any post-closure care period, at a frequency established by the department; the frequency will be no less than annual and will be based on consideration of the

(A) lithology of the aquifer and unsaturated zone;

(B) hydraulic conductivity of the aquifer and unsaturated zone;

(D) minimum distance between the upgradient edge of the waste management area and the downgradient monitoring well screen (minimum distance of travel);

(E) resource value of the aquifer; and

(F) evidence of groundwater or surface water contamination.

(c) If the owner or operator determines under 18 AAC 60.830(j) that there is a statistically significant increase over background for one or more of the constituents monitored, at any monitoring well at the point of compliance, the owner or operator

(1) shall, within 14 days after making the determination, place a notice in the operating record of the facility indicating which constituents have shown statistically significant changes from background levels, and submit written notification to the department that this notice was placed in the operating record;

(2) shall, within 90 days, either establish an assessment monitoring program that meets the requirements of 18 AAC 60.860, or make the demonstration allowed by (3) of this subsection; and

(3) may demonstrate that a source other than the monitored waste management area caused the pollution, or that the statistically significant increase resulted from error in sampling, analysis, statistical evaluation, or natural variation in groundwater quality; a report documenting this demonstration must be certified by a qualified groundwater scientist or otherwise approved by the department and must 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 shall initiate the assessment monitoring program required by 18 AAC 60.860.

History: Eff. 1/28/96, Register 137; am 10/29/98, Register 148

Authority: AS 44.46.020

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