18 AAC 60.825. Groundwater monitoring systems

(a) Except as provided in 18 AAC 60.820, the owner or operator of a solid waste disposal facility subject to this chapter shall ensure that a groundwater monitoring system is installed with a sufficient number of wells, at locations and depths, that 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; determination of background quality may include sampling of 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) groundwater passing the relevant point of compliance as established under (c) of this section; the downgradient monitoring wells must be installed at the relevant point of compliance; if a physical obstacle precludes installation of the wells at the relevant point of compliance, the owner or operator may, with department approval, install the downgradient monitoring wells at the closest practical distance hydraulically downgradient from the relevant point of compliance, if the wells are capable of detecting pollution in the uppermost aquifer.

(b) 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 management area if the facility-wide system meets the requirements of (a) 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 area;

(2) hydrogeologic setting;

(3) facility's history;

(4) engineering design of the waste management areas; and

(5) type of waste accepted at the facility.

(c) A relevant point of compliance must be proposed by the owner or operator of a facility required to have a groundwater monitoring system under this chapter. It is subject to approval by the department and

(1) may be no more than 500 feet from the waste management boundary unless a facility-wide system is approved under (b) 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; and

(4) must be based upon

(A) the hydrogeologic characteristics of the facility and surrounding land;

(B) the volume and physical and chemical characteristics of the leachate;

(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) practicable capabilities of the owner or operator.

(d) Monitoring wells must be designed, installed, and decommissioned in accordance with (e) of this section and with the department's Recommended Practices for Monitoring Well Design, Installation, and Decommissioning, April 1992, adopted by reference, and with 18 AAC 80.015(d) .

(e) The number, spacing, and depths of monitoring wells must be

(1) determined based upon site-specific, technical, thorough characterization of

(A) aquifer thickness, groundwater flow rate, and groundwater flow direction, including seasonal and temporal fluctuations in groundwater flow; and

(B) 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; within 14 days after certification, the owner or operator shall submit written notification to the department that the certification is complete and shall place it in the operating record of the facility.

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

Authority: AS 44.46.020

Editor's note: The document adopted by reference in this section, Recommended Practices for Monitoring Well Design, Installation, and Decommissioning, April 1992, may be reviewed at the department's Juneau, Anchorage, and Fairbanks offices, is available for review at the Office of the Lieutenant Governor, or may be obtained from the department.

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