Section 18 AAC 60.825 - Groundwater monitoring systems(a) When groundwater monitoring is required under 18 AAC 60.820, the owner or operator of the facility shall install a groundwater monitoring system that complies with the standards in (a) - (f) of this section, and conduct initial sampling in accordance with (g) of this section. The groundwater monitoring system must include a sufficient number of wells at appropriate locations and depths to yield groundwater samples from the uppermost aquifer that represent the quality of (1) background groundwater that has not been affected by leachate from the facility; and(2) groundwater passing the approved monitoring well locations established under (d) of this section.(b) The number, spacing, and depths of monitoring wells must be(1) determined based upon(A) aquifer thickness, groundwater flow rate, and groundwater flow direction, including seasonal and temporal fluctuations in groundwater flow; and(B) the saturated and unsaturated geologic units and fill materials overlying the uppermost aquifer, materials comprising the uppermost aquifer, and materials comprising the confining unit that constitutes the lower boundary of the uppermost aquifer, including thicknesses, stratigraphy, lithology, hydraulic conductivities, porosities, and effective porosities; and(2) certified by a qualified groundwater scientist or otherwise approved by the department as meeting the standards set out in this section; the scientist shall certify to the best of the scientist's knowledge that the wells are designed and placed where they are most likely to detect contamination from each waste management area; not later than 14 days after the date of the certification, the owner or operator of the facility shall submit written notification to the department that the certification is complete and shall place it in the operating record of the facility.(c) The location of background and downgradient monitoring wells are subject to the following considerations: (1) the determination of background quality may be made by sampling wells that are not hydraulically upgradient of the waste management area if(A) hydrogeologic conditions do not allow the owner or operator to determine which wells are hydraulically upgradient; or(B) sampling at other wells will provide an indication of background groundwater quality that is at least as representative as that provided by the upgradient wells; and(2) downgradient monitoring wells must be installed at relevant points of compliance proposed under (d) of this section and approved by the department; if a physical obstacle precludes installation of a downgradient well at an approved relevant point of compliance, the owner or operator may, with department approval, install that downgradient monitoring well at the closest practical location that is(A) hydraulically downgradient of the relevant point of compliance;(B) capable of detecting groundwater contamination in the uppermost aquifer; and(C) unlikely to be affected by groundwater contamination from sources other than the landfill.(d) The owner or operator of the facility shall propose for department approval appropriate locations for downgradient monitoring wells. Those monitoring wells (1) may not be more than 500 feet from the waste management boundary unless a facility-wide system is approved under (e) of this section;(2) must be located on land owned by the owner of the facility;(3) must ensure detection of groundwater pollution in the uppermost aquifer underlying the landfill; and(4) must be sited based upon (A) the hydrogeologic characteristics of the facility and surrounding land;(B) the volume and physical and chemical characteristics of the leachate, if known;(C) the quantity and direction of the flow of groundwater;(D) the proximity to, and groundwater withdrawal rate of, groundwater users;(E) the availability of alternative drinking water supplies;(F) the existing quality of the groundwater, including other sources of pollution and their cumulative effects on the groundwater, and whether the groundwater is used or might reasonably be expected to be used for drinking water;(G) public health, safety, and welfare; and(H) the practicable capabilities of the owner or operator to remediate contaminant releases to groundwater.(e) If a facility has more than one waste management area, the department will approve a facility-wide groundwater monitoring system instead of separate groundwater monitoring systems for each waste management area if the facility-wide system meets the requirements of (a) - (d) of this section and will be as protective of public health and the environment as individual monitoring systems for each area, based on the (1) number, spacing, and orientation of the waste management areas;(2) hydrogeologic setting;(4) engineering design of the waste management areas; and(5) type of waste accepted at the facility.(f) Monitoring wells must be designed, installed, and decommissioned in accordance with (b) of this section, the department's Monitoring Well Guidance, September 2013, adopted by reference, and 18 AAC 80.015(d).(g) Once the groundwater monitoring system in installed, not less than two years of initial monitoring is required in order to characterize groundwater beneath the facility, to establish background conditions upgradient of the facility, and to accumulate the data necessary for the statistical analysis under 18 AAC 60.830(g). Sampling shall be conducted in accordance with the approved groundwater monitoring plan prepared under 18 AAC 60.830 and at least one sample shall be collected from each monitoring well during each sampling event. Initial monitoring from a newly installed groundwater monitoring system must proceed as follows: (1) at a new landfill, monitoring must be initiated at least one year before any waste being placed into the landfill and immediately after installation of the groundwater monitoring system is complete; initial sampling shall be conducted so that at least four independent samples are collected quarterly in the 12 months immediately preceding first placement of waste into the landfill and four independent samples are collected quarterly during the 12 months immediately following; to the extent practical, each quarterly sample must represent the groundwater conditions of the season in which the sample is collected; and(2) at an existing facility or a lateral expansion of an existing facility, groundwater monitoring must be initiated immediately after installation of the groundwater monitoring system is complete; initial sampling shall be conducted so that at least four independent samples are collected quarterly from each well during the first and second years following system installation; to the extent practical, each quarterly sample must represent the groundwater conditions of the season in which the sample is collected.(h) After completing two years of initial groundwater monitoring in accordance with (g) of this section, as applicable, the owner or operator of the facility shall use the data collected from each monitoring well that is located hydraulically upgradient of the facility or that meets the requirements of (c)(1) of this section to establish background groundwater quality for each of the monitoring constituents established under 18 AAC 60.840. The data collected from all wells constituting the groundwater monitoring system shall be used to evaluate whether groundwater quality is subject to seasonal variability.(i) After completing two years of initial groundwater monitoring in accordance with (g) of this section, as applicable, the owner or operator of the facility shall continue monitoring at a frequency established by the department. The frequency will be no less than annual and will be based on consideration of(1) the lithology of the aquifer and unsaturated zone;(2) the hydraulic conductivity of the aquifer and unsaturated zone;(3) the groundwater flow rates;(4) the minimum distance between upgradient edge of the waste management area and downgradient monitoring well screen;(5) the resource value of the aquifer;(6) evidence of groundwater or surface water contamination;(7) evidence of seasonal variability in groundwater quality; and(8) the age and design of the landfill. Eff. 1/28/96, Register 137; am 10/29/98, Register 148; am 2/25/2022, Register 241, April 2022The document adopted by reference in this section, Monitoring Well Guidance, September 2013, maybe reviewed at the department's Juneau, Anchorage, and Fairbanks offices, and may be obtained from the department's website at http://dec.alaska.gov/spar/csp/guidance-forns/.
Authority:AS 44.46.020
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