For purposes of subchapters 1, 3, 6, and 8, the following definitions apply:

(1) "Accessory building" has the same meaning as defined in ARM 17.38.101(3)(a).

(2) "Approved well drilling area" is an area or areas designated on a lot layout within which a well may be drilled. The area must meet all required well location setbacks, including those for well isolation zones.

(3) "Bedrock" means material that cannot be readily excavated by hand tools, or material that does not allow water to pass through or that has insufficient quantities of fines to provide for the adequate treatment and disposal of wastewater. The term does not include gravel and other rock fragments as defined in Department Circular DEQ-4, Appendix B.

(4) "Bedroom" means any room that is or may be used for sleeping. An unfinished basement is considered an additional bedroom.

(5) "Campground" is defined in 50-52-101, MCA.

(6) "Certificate of survey" is defined in 76-3-103, MCA.

(7) "Cesspool" means a seepage pit without a septic tank to pretreat the wastewater.

(8) "Commercial unit" means the area under one roof that is occupied by a business or other nonresidential use. A building housing two businesses is considered two commercial units.

(9) "Condominium" is defined in 70-23-101, MCA.

(10) "Connection" means a line that provides water or sewer service to a single building or main building with accessory buildings. The term is synonymous with "service connection" as defined in ARM 17.38.101. For purposes of ARM 17.36.123, "connection" means a water or sewer line that connects a subdivision to a public system.

(11) "Department" means the Montana Department of Environmental Quality.

(12) "Deviation" means a department-approved departure from a requirement contained in a department circular.

(13) "Drainage way" means a course or channel along which storm water moves in draining an area.

(14) "Dry well" means a storm water detention structure that collects surface runoff and discharges the water below the natural ground surface.

(15) "Escarpment" means any slope greater than 50% that extends vertically six feet or more as measured from toe to top.

(16) "Existing system" means a water supply or wastewater disposal system that was installed prior to the submittal of a subdivision application under this subchapter.

(17) "Experimental system" means a wastewater treatment system for which specific design standards are not provided in Department Circular DEQ-4 or DEQ-2.

(18) "Facilities" means public or private facilities for the supply of water or disposal of sewage, storm water, or solid waste and any pipes, conduits, or other stationary method by which water, storm water, sewage, or solid wastes might be transported or distributed.

(19) "Fill" means artificially placed soil.

(20) "Floodplain" means the area adjoining the watercourse or drainway that would be covered by a flood that is expected to recur on the average of once every 100 years or by a flood that has a one percent chance of occurring in any given year. The floodplain consists of the floodway and the floodfringe, as defined in ARM 36.15.101.

(21) "Gray water" means wastewater that is collected separately from sewage flow and that does not contain industrial chemicals, hazardous wastes, or wastewater from toilets.

(22) "Ground water monitoring" means measuring the depth from the natural ground surface to the seasonally high ground water performed in accordance with Department Circular DEQ-4.

(23) "Holding tank" means a watertight receptacle that receives wastewater for retention and does not as part of its normal operation dispose of or treat the wastewater. The term does not include surge tanks used in a gray water irrigation system if the system meets the requirements of ARM 17.36.319 and Department Circular DEQ-4.

(24) "Impervious layer" means any layer of material in the soil profile that has a percolation rate slower than 240 minutes per inch.

(25) "Individual water system" means any water system that serves one living unit or commercial unit and that is not a public water supply system as defined in 75-6-102, MCA.

(26) "Individual wastewater system" means a wastewater system that serves one living unit or commercial unit and that is not a public sewage system as defined in 75-6-102, MCA.

(27) "Limiting layer" means bedrock, an impervious layer, or seasonally high ground water.

(28) "Living unit" means the area under one roof that can be used for one residential unit and that has facilities for sleeping, cooking, and sanitation. A duplex is considered two living units.

(29) "Local health officer" means health officer as defined in 50-1-101, MCA, or the health officer's designee.

(30) "Lot" is synonymous with "tract" or "parcel" for purposes of this chapter.

(31) "Main" is defined in ARM 17.38.101.

(32) "Mixing zone" is defined in 75-5-103, MCA.

(33) "Mobile home" means a trailer equipped with necessary service connections that is designed for use as a long-term residence.

(34) "Multiple-user wastewater system" means a wastewater system that serves, or is intended to serve, more than two living units or commercial units or a combination of both and that is not a public sewage system as defined in 75-6-102, MCA. In estimating the population that will be served by a proposed residential system, the reviewing authority shall multiply the number of living units by 2.5.

(35) "Multiple-user water supply system" means a water supply system that serves, or is intended to serve, more than two living units or commercial units or a combination of both and that is not a public water supply system as defined in 75-6-102, MCA. In estimating the population that will be served by a proposed residential system, the reviewing authority shall multiply the number of living units by 2.5.

(36) "Municipal" means pertaining to an incorporated city or town.

(37) "Natural soil" means soil that has developed through natural processes and to which no fill material has been added.

(38) "Parcel" means a part of land which is created by a division of land. The term is synonymous with "tract" and "lot" for purposes of this chapter.

(39) "Permanent space" means a space, regardless of occupancy, for recreational camping vehicles or mobile homes, with facilities for the supply of water or disposal of sewage provided by individual hookups, a service building, or centralized dump stations for sewage or fill stations for water.

(40) "Plat" is defined in 76-3-103, MCA.

(41) "Preliminary plat" is defined in 76-3-103, MCA.

(42) "Professional engineer" means an engineer licensed or otherwise authorized to practice engineering in Montana pursuant to Title 37, chapter 67, MCA.

(43) "Public wastewater system" means a system for collection, transportation, treatment, or disposal of wastewater that serves 15 or more families or 25 or more persons daily for any 60 or more days in a calendar year. In estimating the population that will be served by a proposed residential system, the reviewing authority shall multiply the number of living units by 2.5, so that ten or more proposed residential connections will be considered a public system.

(44) "Public water supply system" means a system for the provision of water for human consumption from a community well, water hauler for cisterns, water bottling plant, water dispenser, or other water supply that has at least 15 service connections or that regularly serves at least 25 persons daily for any 60 or more days in a calendar year. In estimating the population that will be served by a proposed residential system, the reviewing authority shall multiply the number of living units by 2.5, so that ten or more proposed residential connections will be considered a public system.

(45) "Recreational camping vehicle" means a vehicular unit designed primarily as temporary living quarters for recreational, camping, travel, or seasonal use, and that either has its own power or is mounted on, or towed by, another vehicle. The basic types of RVs are camping trailer, fifth wheel trailer, motor home, park trailer, travel trailer, and truck camper.

(46) "Registered sanitarian" means a person licensed to practice the profession of sanitarian in Montana pursuant to Title 37, chapter 40, MCA.

(47) "Reviewing authority" is defined in 76-4-102, MCA.

(48) "Seepage pit" means a covered underground receptacle that receives wastewater after primary treatment and allows the wastewater to seep into the surrounding soil.

(49) "Septic tank" means a wastewater settling tank in which settled sludge is in immediate contact with the wastewater flowing through the tank while the organic solids are decomposed by anaerobic action.

(50) "Sewage" is synonymous with "wastewater" for purposes of this chapter.

(51) "Shared wastewater system" means a wastewater system that serves, or is intended to serve, two living units or commercial units or a combination of both and that is not a public sewage system as defined in 75-6-102, MCA.

(52) "Shared water system" means a water system that serves, or is intended to serve, two living units or commercial units or a combination of both and that is not a public water supply system as defined in 75-6-102, MCA.

(53) "Site evaluation" means an evaluation to determine if a site is suitable for the installation of a subsurface wastewater treatment system.

(54) "Slope" means the rate that a ground surface declines in feet per 100 feet. It is expressed as percent of grade.

(55) "Soil profile" means a description of the soil strata to a depth of eight feet using the United States Department of Agriculture (USDA) soil classification system method, which can be found in Appendix B, Department Circular DEQ-4.

(56) "Spring" means natural opening in the earth's surface from which water issues or seeps.

(57) "State waters" is defined in 75-5-103, MCA.

(58) "Subsurface wastewater treatment system" means the process of wastewater treatment in which the effluent is applied below the soil surface or into a mound by an approved distribution system.

(59) "Surface water" means any water on the earth's surface including, but not limited to, streams, lakes, ponds, reservoirs, and irrigation ditches, whether fresh or saline.

(60) "Tract" is synonymous with "lot" or "parcel" for the purposes of this chapter.

(61) "Unstable land forms" means areas showing evidence of mass down-slope movement such as hummock hill slopes, debris flows, landslides, and rock falls. Unstable land forms may be evidenced by slip surfaces roughly parallel to the hillside; landslide scars and carving debris ridges; fences, trees, or telephone poles which appear tilted; or tree trunks which bend uniformly as they enter the ground.

(62) "Waiver" means a department-approved departure from a requirement contained in department rules. Granting of waivers must be in accordance with ARM 17.36.601.

(63) "Wastewater" means water-carried wastes. For purposes of these rules, wastewater does not include storm water. The term includes, but is not limited to, the following:

(a) household, commercial, or industrial wastes;

(b) chemicals;

(d) animal and vegetable matter in suspension or solution.

(64) "Wastewater treatment system" or "wastewater disposal system" means a system that receives wastewater for purposes of treatment, storage, or disposal. The term includes, but is not limited to, all disposal methods described in Department Circulars DEQ-2 and DEQ-4.

(65) "Well" is synonymous with the term "water well" defined in 75-5-103(41), MCA.

(66) "Well isolation zone" means the area within a 100-foot radius of a water well unless a smaller, site-specific radius is approved by the department under Circular DEQ-20, Standard 1.8.

(67) "Zone of saturation" means the area beneath the ground in which all open spaces are filled with ground water.

History: 76-4-104, MCA; IMP, 76-4-104, MCA; Eff. 12/31/72; AMD, Eff. 11/4/73; AMD, Eff. 11/3/75; AMD, Eff. 5/6/76; AMD, 1977 MAR p. 746, Eff. 10/25/77; AMD, 1984 MAR p. 1027, Eff. 7/13/84; AMD, 1984 MAR p. 1568, Eff. 10/26/84; AMD, 1992 MAR p. 2145, Eff. 9/25/92; TRANS, from DHES, 1996 MAR p. 1499; AMD, 2000 MAR p. 967, Eff. 4/14/00; AMD, 2000 MAR p. 3371, Eff. 12/8/00; AMD, 2002 MAR p. 1981, Eff. 5/17/02; AMD, 2003 MAR p. 221, Eff. 2/14/03; AMD, 2009 MAR p. 1786, Eff. 10/16/09; AMD, 2014 MAR p. 2098, Eff. 9/19/14; AMD, 2016 MAR p. 722, Eff. 4/23/16; AMD, 2023 MAR p. 324, Eff. 4/15/23; AMD, 2023 MAR p. 1861, Eff. 12/23/23.