To create a statewide policy for determining if monitoring of ground water at small exempt municipal solid waste landfills (MSWLFs) is necessary in order to protect ground water resources and source water supplies.

This policy applies to all small exempt MSWLFs in Idaho. Small exempt MSWLFs are those that receive less than 20 tons of municipal solid waste daily, based on an annual average, with no evidence of ground water contamination from the municipal solid waste landfill unit or expansion. The small exempt MSWLF must either serve a community that experiences an annual interruption of at least three consecutive months of surface transportation that prevents access to a regional waste management facility, or must have no practicable waste management alternative and the landfill unit must be located in an area that annually receives less than or equal to 25 inches of precipitation.

DEQ is authorized to administer and enforce certain provisions of the Idaho Solid Waste Facilities Act pursuant to Idaho Code §39-105 (3) (m). The Idaho Solid Waste Facilities Act, Section 39-7410 as amended in 1997, requires ground water monitoring to be included within the design of all MSWLFs, except:

(a) When the MSWLF unit meets the conditions for exemption in 40 CFR 258.1(f) [ the conditions for small exempt MSWLF's ]; 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.

*emphasis added

Idaho Code Section 39-7410 allows for an exemption from ground water monitoring for small exempt MSWLF's under certain conditions. However, some small exempt MSWLF's have been constructed and are accepting waste in locations that have a high probability of impacting ground water from release of contaminants in leachate. Locations such as gravel pits and other porous geologic formations and shallow depth to fractured bedrock are locations where small exempt MSWLF's will be required to monitor ground water. The policy section outlines the conditions which may require ground water monitoring.

In order to comply with Idaho Code Section 39-7410, the Division shall evaluate small exempt MSWLFs on a case-by-case basis to ensure that ground water shall be protected. Each small exempt MSWLF shall be evaluated for such characteristics as waste type, type of containment, depth to ground water, geology, proximity of domestic wells and history of MSWLF operating problems. These site specific categories will be recorded on the Small Exempt Municipal Solid Waste Landfill Ground Water Evaluation Work Sheet. Small exempt MSWLFs scoring over 700 points and unable to comply with Idaho Code Section 39-7410(1)(b), shall be required to monitor ground water through use of monitoring wells. MSWLFs scoring between 500 and 700 points and unable to comply with Idaho Code Section 39-7410(1)(b), maybe required to assess ground water by conducting ground water monitoring through use of monitoring wells or implement other monitoring method(s) approved by the Director, which will effectively determine if ground water is being impacted.