In this subchapter, the following definitions apply:

(1) "100-year flood" means a flood that has a one percent or greater chance of recurring in any given year or a flood of a magnitude equalled or exceeded once in 100 years on the average over a significantly long period.

(2) "Airport" means public-use airport open to the public without prior permission and without restrictions within the physical capacities of available facilities.

(3) "Active portion" means that part of a facility or unit that has received or is receiving wastes and that has not been closed in accordance with ARM 17.50.1403.

(4) "Aquifer" means any geologic formation, group of formations, or part of a formation capable of yielding significant quantities of ground water to wells or springs.

(5) "Areas susceptible to mass movement" means those areas of influence (i.e., areas characterized as having an active or substantial possibility of mass movement) where the movement of earth material at, beneath, or adjacent to the Class II or lined Class IV landfill unit, because of natural or artificially-caused events, results in the downslope transport of soil and rock material by means of gravitational influence. Areas of mass movement include, but are not limited to, landslides, avalanches, debris slides and flows, soil fluction, block sliding, and rock fall.

(6) "Bird hazard" means an increase in the likelihood of bird/aircraft collisions that may cause damage to the aircraft or injury to its occupants.

(7) "Class II landfill facility" has the meaning given in ARM 17.50.504.

(8) "Class III landfill facility" has the meaning given in ARM 17.50.504.

(9) "Closure" has the meaning given in ARM 17.50.502.

(10) "Department" has the meaning given in ARM 17.50.502.

(11) "Destruction or adverse modification" means a direct or indirect alteration of critical habitat that appreciably diminishes the likelihood of the survival and recovery of threatened or endangered species using that habitat.

(12) "Displacement" means the relative movement of any two sides of a fault measured in any direction.

(13) "Disposal" has the meaning given in 75-10-203, MCA.

(14) "Endangered or threatened species" means any species listed as such pursuant to section 4 of the federal Endangered Species Act of 1973.

(15) "Existing," when used in conjunction with "unit" or a type of unit, has the meaning given in ARM 17.50.502.

(16) "Facility" has the meaning given in ARM 17.50.502.

(17) "Fault" means a fracture or a zone of fractures in any material along which strata on one side have been displaced with respect to that on the other side.

(18) "Floodplain" means the lowland and relatively flat areas adjoining inland and coastal waters, including flood prone areas of offshore islands, that are inundated by the 100-year flood.

(19) "Ground water" has the meaning given in ARM 17.50.502.

(20) "Holocene" means the most recent epoch of the Quaternary period, extending from the end of the Pleistocene Epoch to the present.

(21) "Karst terranes" means areas where karst topography, with its characteristic surface and subterranean features, is developed as the result of dissolution of limestone, dolomite, or other soluble rock. Characteristic physiographic features present in karst terranes include, but are not limited to, sinkholes, sinking streams, caves, large springs, and blind valleys.

(22) "Landfill" has the meaning given in ARM 17.50.502.

(23) "Lateral expansion" has the meaning given in ARM 17.50.502.

(24) "Leachate" has the meaning given in ARM 17.50.502.

(25) "Licensee" has the meaning given in ARM 17.50.502.

(26) "Lithified earth material" means all rock, including all naturally occurring and naturally formed aggregates or masses of minerals or small particles of older rock that formed by crystallization of magma or by induration of loose sediments. This definition does not include artificial materials, such as fill, concrete, and asphalt, or unconsolidated earth materials, soil, or regolith lying at or near the earth surface.

(27) "Maximum horizontal acceleration in lithified earth material" means the maximum expected horizontal acceleration depicted on a seismic hazard map, with a 90 percent or greater probability that the acceleration will not be exceeded in 250 years, or the maximum expected horizontal acceleration based on a site-specific seismic risk assessment.

(28) "New," when used in conjunction with "unit" or a type of unit, has the meaning given in ARM 17.50.502.

(29) "Operator" has the meaning given in ARM 17.50.502.

(30) "Owner" has the meaning given in ARM 17.50.502.

(31) "Poor foundation conditions" means those areas where features exist that indicate that a natural or artificially-caused event may result in inadequate foundation support for the structural components of a Class II or lined Class IV landfill unit.

(32) "Post-closure care" has the meaning given in ARM 17.50.502.

(33) "Run-off" means any rainwater, leachate, or other liquid that drains over land from any part of a facility.

(34) "Run-on" means any rainwater, leachate, or other liquid that drains over land onto any part of a facility.

(35) "Seismic impact zone" means an area with a ten percent or greater probability that the maximum horizontal acceleration in lithified earth material, expressed as a percentage of the earth's gravitational pull (g), will exceed 0.10g in 250 years.

(36) "Solid waste management system" has the meaning given in 75-10-203, MCA.

(37) "Structural components" means liners, leachate collection systems, final covers, run-on/run-off systems, and any other component used in the construction and operation of a Class II or lined Class IV landfill unit that is necessary for protection of human health and the environment.

(38) "Taking" means harassing, harming, pursuing, hunting, wounding, killing, trapping, capturing, or collecting or attempting to engage in such conduct.

(39) "Unit" has the meaning given in ARM 17.50.502.

(40) "Unstable area" means a location that is susceptible to natural or artificially-caused events or forces capable of impairing the integrity of some or all of the landfill structural components responsible for preventing releases from a landfill. Unstable areas can include poor foundation conditions, areas susceptible to mass movements, and Karst terranes.

(41) "Washout" means the carrying away of solid waste by waters of the base flood.

(42) "Wetlands" has the meaning given in 40 CFR 232.2.