1. (1) An owner or operator of a Class II or Class IV landfill unit shall conduct assessment monitoring at that unit as required in ARM 17.50.1306 and this rule.
2. (2) Within 90 days after being required by ARM 17.50.1306 to establish an assessment monitoring program, and annually thereafter, the owner or operator shall sample and analyze the ground water for all constituents identified in Appendix II to 40 CFR Part 258 (July 1, 2008), set forth below. A minimum of one sample from each downgradient well must be collected and analyzed during each sampling event. For any constituent detected in the downgradient wells as a result of monitoring of all constituents in Appendix II to 40 CFR Part 258 (July 1, 2008), a minimum of four independent samples from each background and downgradient well must be collected and analyzed to establish background for the constituent. The owner or operator shall conduct assessment monitoring for constituents in Appendix II to 40 CFR Part 258 (July 1, 2008) for any subset of wells specified by the department. The department may exempt an owner or operator of a Class II or Class IV landfill unit from monitoring a constituent in Appendix II to 40 CFR Part 258 (July 1, 2008) if the owner or operator makes a written demonstration, approved by the department, that the exempted constituent is not reasonably expected to be in, or derived from, the waste contained in the unit.

3. (3) The department may specify, and an owner or operator shall comply with, an appropriate alternate frequency for repeated sampling and analysis of the constituents in Appendix II to 40 CFR Part 258 (July 1, 2008) required by (2), during the active life and closure and post-closure care periods of the unit, considering the following factors:

   1. (a) lithology of the aquifer and unsaturated zone;
   2. (b) hydraulic conductivity of the aquifer and unsaturated zone;
   3. (c) ground water flow rates;
   4. (d) minimum distance between upgradient edge of the Class II or Class IV landfill unit and downgradient monitoring well screen (minimum distance of travel);
   5. (e) resource value of the aquifer; and
   6. (f) nature (fate and transport) of any constituents detected by monitoring required by this rule.

4. (4) After obtaining the results from the initial or subsequent sampling events required in (2), the owner or operator shall:

   1. (a) within 14 days, place a notice in the operating record identifying the constituents in Appendix II to 40 CFR Part 258 (July 1, 2008) that have been detected and notify the department that this notice has been placed in the operating record;
   2. (b) within 90 days, and on at least a semiannual basis thereafter, resample all wells described in ARM 17.50.1304(1), conduct analyses for all constituents in Appendix I to 40 CFR Part 258 (July 1, 2008) or in the alternative list of parameters established in accordance with ARM 17.50.1306(3), and for those constituents in Appendix II to 40 CFR Part 258 (July 1, 2008) that are detected by monitoring required by (2), and record their concentrations in the facility operating record. At least one sample from each background and downgradient well must be collected and analyzed during these sampling events. If specified by the department, the owner or operator shall conduct sampling and analyses under this subsection at an alternative frequency during the active life and closure and the post-closure care periods of the unit. The alternative frequency may be no less frequent than annual during the active life of the unit, including closure. The alternative frequency must be based on consideration of the factors specified in (3);
   3. (c) establish the background concentration for each constituent or parameter detected pursuant to (2) or (4)(b); and
   4. (d) establish the ground water protection standard for each constituent or parameter detected pursuant to (2) or (4)(b). The ground water protection standard must be established in accordance with (8).
5. (5) If the owner or operator determines that concentrations of all constituents in Appendix II to 40 CFR Part 258 (July 1, 2008) are at or below background values, using the statistical procedures described in ARM 17.50.1305(8), for two consecutive sampling events, the owner or operator shall submit this determination to the department for approval and may, if approved, return to detection monitoring.
6. (6) If the owner or operator determines, using the statistical procedures in ARM 17.50.1305(8), that the concentration of a constituent in Appendix II to 40 CFR part 258 (July 1, 2008) is above background, but that all concentrations are below the ground water protection standard established under (8), the owner or operator shall submit this determination to the department for approval and shall continue assessment monitoring in accordance with this rule, unless notified otherwise by the department.

7. (7) If the owner, operator, or department determines, using the same statistical procedures as required in ARM 17.50.1305(8), that, in any sampling event required in this rule, there has been a statistically significant increase above the ground water protection standard established under (8) in the concentration of a constituent in Appendix II to 40 CFR part 258 (July 1, 2008), the owner or operator shall, within 14 days, place a notice in the operating record identifying each constituent in Appendix II to 40 CFR part 258 (July 1, 2008) that has exceeded the ground water protection standard and notify the department and all appropriate local government officials that the notice has been placed in the operating record. The owner or operator shall either:

   1. (a) comply with (7)(a)(i) through (iv), as follows:

      1. (i) characterize the nature and extent of the release by installing additional monitoring wells as necessary;
      2. (ii) install at least one additional monitoring well at the facility boundary in the direction of contaminant migration and sample this well in accordance with (4)(b);
      3. (iii) notify all persons who own the land or reside on the land that directly overlies any part of the plume of contamination, if contaminants have migrated off-site if indicated by sampling of wells in accordance with (7)(a); and
      4. (iv) initiate an assessment of corrective measures as required by ARM 17.50.1308, within 90 days; or
   2. (b) demonstrate that a source other than a Class II or Class IV landfill unit caused the contamination, or that the statistically significant increase resulted from error in sampling, analysis, statistical evaluation, or from natural variation in ground water quality. A report documenting this demonstration must be certified by a qualified ground water scientist and submitted to the department for approval and placed in the operating record. If the demonstration is approved, the owner or operator shall continue monitoring in accordance with the assessment monitoring program required by this rule, and may return to detection monitoring if the concentrations of all of the constituents in Appendix II to 40 CFR Part 258 (July 1, 2008) are at or below background levels as specified in (5). Until the department approves a demonstration, the owner or operator shall comply with (7), including initiating an assessment of corrective measures.

8. (8) The owner or operator shall establish a ground water protection standard for each constituent in Appendix II to 40 CFR Part 258 (July 1, 2008) and parameter in the alternative list in ARM 17.50.1306(3) detected in the ground water. The ground water protection standard must be:

   1. (a) for a constituent for which a maximum contaminant level (MCL) has been promulgated under Montana ground water quality standards, the MCL for that constituent;
   2. (b) for a constituent for which an MCL has not been promulgated, the background concentration for the constituent established from wells in accordance with ARM 17.50.1304(1)(a);
   3. (c) for a constituent for which the background level is higher than the MCL identified under (8)(a) or health based levels identified under (9)(a), the background concentration; or
   4. (d) for a constituent or parameter in the alternative list in ARM 17.50.1306(3) for which a ground water quality standard has been established pursuant to (9), that ground water quality standard.

9. (9) If the department believes a standard is needed for a constituent or parameter in the alternative list in ARM 17.50.1306(3) for which an MCL or ground water quality standard has not been established by Montana law or rule, the department shall propose the adoption of a ground water quality standard for that constituent or parameter. The ground water quality standard proposed must be health-based and set at an appropriate level that satisfies the following criteria:

   1. (a) the level is derived in a manner consistent with EPA guidelines for assessing the health risks of environmental pollutants (51 FR 33992, 34006, 34014, 34028, Sept. 24, 1986);
   2. (b) the level is based on scientifically valid studies conducted in accordance with the Toxic Substances Control Act Good Laboratory Practice Standards (40 CFR Part 792) or equivalent requirements;
   3. (c) for carcinogens, the level represents a concentration associated with an excess lifetime cancer risk level, due to continuous lifetime exposure, within the 1×10 -4 to 1×10 -6 range; and
   4. (d) for systemic toxicants, the level represents a concentration to which the human population, including sensitive subgroups, could be exposed to on a daily basis that is likely to be without appreciable risk of deleterious effects during a lifetime. For purposes of this subchapter, systemic toxicants include toxic chemicals that cause effects other than cancer or mutation.

10. (10) In proposing a ground water quality standard under (9), the department shall consider the following:

    1. (a) multiple contaminants in the ground water;
    2. (b) exposure threats to sensitive environmental receptors; and

    3. (c) other site-specific exposure or potential exposure to ground water.

       Appendix II to 40 CFR Part 258 (July 1, 2008)
       List of Hazardous Inorganic and Organic Constituents

       Common name1	CAS RN2	Chemical abstracts service index name3
       Acenaphthene	83-32-9	Acenaphthylene, 1,2-dihydro-
       Acenaphthylene	208-96-8	Acenaphthylene
       Acetone	67-64-1	2-Propanone
       Acetonitrile; Methyl cyanide	75-05-8	Acetonitrile
       Acetophenone	98-86-2	Ethanone, 1-phenyl-
       2-Acetylaminofluorene; 2-AAF	53-96-3	Acetamide, N-9H-fluoren-2-yl-
       Acrolein	107-02-8	2-Propenal
       Acrylonitrile	107-13-1	2-Propenenitrile
       Aldrin	309-00-2	1,4:5,8-Dimethanonaphthalene, 1,2,3,4,10,10-hexachloro-1,4,4a,5,8,8a-hexahydro-(1,4,4a,5,8,8a)-
       Allyl chloride	107-05-1	1-Propene, 3-chloro-
       4-Aminobiphenyl	92-67-1	[1,1′-Biphenyl]-4-amine
       Anthracene	120-12-7	Anthracene
       Antimony		Antimony
       Arsenic		Arsenic
       Barium		Barium
       Benzene	71-43-2	Benzene
       Benzo[a]anthracene; Benzanthracene	56-55-3	Benz[a]anthracene
       Benzo[b]fluoranthene	205-99-2	Benz[e]acephenanthrylene
       Benzo[k]fluoranthene	207-08-9	Benzo[k]fluoranthene
       Benzo[ghi]perylene	191-24-2	Benzo[ghi]perylene
       Benzo[a]pyrene	50-32-8	Benzo[a]pyrene
       Benzyl alcohol	100-51-6	Benzenemethanol
       Beryllium		Beryllium
       alpha-BHC	319-84-6	Cyclohexane, 1,2,3,4,5,6-hexachloro-,(1α,2α,3β,4α,5β,6β)-
       beta-BHC	319-85-7	Cyclohexane, 1,2,3,4,5,6-hexachloro-,(1α,2β,3α,4β,5α,6β)-
       delta-BHC	319-86-8	Cyclohexane, 1,2,3,4,5,6-hexachloro-,(1α,2α,3α,4β,5α,6β)-
       gamma-BHC; Lindane	58-89-9	Cyclohexane, 1,2,3,4,5,6- hexachloro-,(1α,2α, 3β, 4α,5α,6β)-
       Bis(2-chloroethoxy)methane	111-91-1	Ethane, 1,1′-[methylenebis (oxy)]bis [2-chloro-
       Bis(2-chloroethyl)ether; Dichloroethyl ether	111-44-4	Ethane, 1,1′-oxybis[2-chloro-
       Bis(2-chloro-1-methylethyl) ether; 2,2′-Dichlorodiisopropyl ether; DCIP, See footnote 4	108-60-1	Propane, 2,2′-oxybis[1-chloro-
       Bis(2-ethylhexyl) phthalate	117-81-7	1,2-Benzenedicarboxylic acid, bis(2-ethylhexyl)ester
       Bromochloromethane; Chlorobromethane	74-97-5	Methane, bromochloro-
       Bromodichloromethane; Dibromochloromethane	75-27-4	Methane, bromodichloro-
       Bromoform; Tribromomethane	75-25-2	Methane, tribromo-
       4-Bromophenyl phenyl ether	101-55-3	Benzene, 1-bromo-4-phenoxy-
       Butyl benzyl phthalate; Benzyl butyl phthalate	85-68-7	1,2-Benzenedicarboxylic acid, butyl phenylmethyl ester
       Cadmium		Cadmium
       Carbon disulfide	75-15-0	Carbon disulfide
       Carbon tetrachloride	56-23-5	Methane, tetrachloro-
       Chlordane	See footnote 5	4,7-Methano-1H-indene, 1,2,4,5,6,7,8,8-octachloro-2,3,3a,4,7,7a-hexahydro-
       p-Chloroaniline	106-47-8	Benzenamine, 4-chloro-
       Chlorobenzene	108-90-7	Benzene, chloro-
       Chlorobenzilate	510-15-6	Benzeneacetic acid, 4-chloro- -(4-chlorophenyl)- -hydroxy-, ethyl ester.
       p-Chloro-m-cresol; 4-Chloro-3-methylphenol	59-50-7	Phenol, 4-chloro-3-methyl-
       Chloroethane; Ethyl chloride	75-00-3	Ethane, chloro-
       Chloroform; Trichloromethane	67-66-3	Methane, trichloro-
       2-Chloronaphthalene	91-58-7	Naphthalene, 2-chloro-
       2-Chlorophenol	95-57-8	Phenol, 2-chloro-
       4-Chlorophenyl phenyl ether	7005-72-3	Benzene, 1-chloro-4-phenoxy-
       Chloroprene	126-99-8	1,3-Butadiene, 2-chloro-
       Chromium		Chromium
       Chrysene	218-01-9	Chrysene
       Cobalt		Cobalt
       Copper		Copper
       m-Cresol; 3-Methylphenol	108-39-4	Phenol, 3-methyl-
       o-Cresol; 2-Methylphenol	95-48-7	Phenol, 2-methyl-
       p-Cresol; 4-Methylphenol	106-44-5	Phenol, 4-methyl-
       Cyanide	57-12-5	Cyanide
       2,4-D; 2,4-Dichlorophenoxyacetic acid	94-75-7	Acetic acid, (2,4-dichlorophenoxy)-
       4,4′-DDD	72-54-8	Benzene 1,1′-(2,2-dichloroethylidene) bis[4-chloro-
       4,4′-DDE	72-55-9	Benzene, 1,1′-(dichloroethenylidene) bis[4-chloro-
       4,4′-DDT	50-29-3	Benzene, 1,1′-(2,2,2-trichloroethylidene) bis[4-chloro-
       Diallate	2303-16-4	Carbamothioic acid, bis(1-methylethyl)-, S- (2,3-dichloro-2-propenyl) ester.
       Dibenz[a,h]anthracene	53-70-3	Dibenz[a,h]anthracene
       Dibenzofuran	132-64-9	Dibenzofuran
       Dibromochloromethane; Chlorodibromomethane	124-48-1	Methane, dibromochloro-
       1,2-Dibromo-3-chloropropane; DBCP	96-12-8	Propane, 1,2-dibromo-3-chloro-
       1,2-Dibromoethane; Ethylene dibromide; EDB	106-93-4	Ethane, 1,2-dibromo-
       Di-n-butyl phthalate	84-74-2	1,2-Benzenedicarboxylic acid, dibutyl ester
       o-Dichlorobenzene; 1,2-Dichlorobenzene	95-50-1	Benzene, 1,2-dichloro-
       m-Dichlorobenzene; 1,3-Dichlorobenzene	541-73-1	Benzene, 1,3-dichloro-
       p-Dichlorobenzene; 1,4-Dichlorobenzene	106-46-7	Benzene, 1,4-dichloro-
       3,3′-Dichlorobenzidine	91-94-1	[1,1′-Biphenyl]-4,4′-diamine, 3,3′-dichloro-
       trans-1,4-Dichloro-2-butene	110-57-6	2-Butene, 1,4-dichloro-, (E)-
       Dichlorodifluoromethane; CFC 12	75-71-8	Methane, dichlorodifluoro-
       1,1-Dichloroethane; Ethyldidene chloride	75-34-3	Ethane, 1,1-dichloro-
       1,2-Dichloroethane; Ethylene dichloride	107-06-2	Ethane, 1,2-dichloro-
       1,1-Dichloroethylene; 1,1-Dichloroethene;	75-35-4	Ethene, 1,1-dichloro-
       Vinylidene chloride cis-1,2-Dichloroethylene; cis-1,2-Dichloroethene	156-59-2	Ethene, 1,2-dichloro-(Z)-
       trans-1,2-Dichloroethylene; trans-1,2-Dichloroethene	156-60-5	Ethene, 1,2-dichloro-, (E)-
       2,4-Dichlorophenol	120-83-2	Phenol, 2,4-dichloro-
       2,6-Dichlorophenol	87-65-0	Phenol, 2,6-dichloro-
       1,2-Dichloropropane	78-87-5	Propane, 1,2-dichloro-
       1,3-Dichloropropane; Trimethylene dichloride	142-28-9	Propane, 1,3-dichloro-
       2,2-Dichloropropane; Isopropylidene chloride	594-20-7	Propane, 2,2-dichloro-
       1,1-Dichloropropene	563-58-6	1-Propene, 1,1-dichloro-
       cis-1,3-Dichloropropene	10061-01-5	1-Propene, 1,3-dichloro-, (Z)-
       trans-1,3-Dichloropropene	10061-02-6	1-Propene, 1,3-dichloro-, (E)-
       Dieldrin	60-57-1	2,7:3,6-Dimethanonaphth [2,3-b]oxirene, 3,4,5,6,9,9-hexachloro-1a,2,2a,3,6,6a,7,7a-octahydro-, (1aα,2β,2aα,3β,6β,6aα,7β,7aα)-
       Diethyl phthalate	84-66-2	1,2-Benzenedicarboxylic acid, diethyl ester
       O,O-Diethyl O-2-pyrazinyl phosphorothioate; Thionazin	297-97-2	Phosphorothioic acid, O,O-diethyl O-pyrazinyl ester.
       Dimethoate	60-51-5	Phosphorodithioic acid, O,O-dimethyl S-[2-(methylamino)-2-oxoethyl] ester
       p-(Dimethylamino)azobenzene	60-11-7	Benzenamine, N,N-dimethyl-4-(phenylazo)-
       7,12-Dimethylbenz[a]anthracene	57-97-6	Benz[a]anthracene, 7,12-dimethyl-
       3,3′-Dimethylbenzidine	119-93-7	[1,1′-Biphenyl]-4,4′-diamine, 3,3′-dimethyl-
       alpha, alpha-Dimethylphenethylamine	122-09-8	Benzeneethanamine, α,α-dimethyl-
       2,4-Dimethylphenol; m-Xylenol	105-67-9	Phenol, 2,4-dimethyl-
       Dimethyl phthalate	131-11-3	1,2-Benzenedicarboxylic acid, dimethyl ester
       m-Dinitrobenzene	99-65-0	Benzene, 1,3-dinitro-
       4,6-Dinitro-o-cresol; 4,6-Dinitro-2-methylphenol	534-52-1	Phenol, 2-methyl-4,6-dinitro-
       2,4-Dinitrophenol	51-28-5	Phenol, 2,4-dinitro-
       2,4-Dinitrotoluene	121-14-2	Benzene, 1-methyl-2,4-dinitro-
       2,6-Dinitrotoluene	606-20-2	Benzene, 2-methyl-1,3-dinitro-
       Dinoseb; DNBP; 2-sec-Butyl-4,6-dinitrophenol	88-85-7	Phenol, 2-(1-methylpropyl)-4,6-dinitro-
       Di-n-octyl phthalate	117-84-0	1,2-Benzenedicarboxylic acid, dioctyl ester
       Diphenylamine	122-39-4	Benzenamine, N-phenyl-
       Disulfoton	298-04-4	Phosphorodithioic acid, O,O-diethyl S-[2- (ethylthio)ethyl] ester
       Endosulfan I	959-98-8	6,9-Methano-2,4,3-benzodiox-athiepin, 6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-, 3-oxide,
       Endosulfan II	33213-65-9	6,9-Methano-2,4,3-benzodioxathiepin, 6,7,8,9,10,10-hexachloro- 1,5,5a,6,9,9a-hexahydro-, 3-oxide, (3α,5aα,6β,9β, 9aα)-
       Endosulfan sulfate	1031-07-8	6,9-Methano-2,4,3-benzodioxathiepin, 6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-, 3,3-dioxide
       Endrin	72-20-8	2,7:3,6-Dimethanonaphth[2,3-b]oxirene, 3,4,5,6,9,9-hexachloro-1a,2,2a,3,6,6a,7,7a-octahydro-, (1aα, 2β,2aβ, 3α,6α,6aβ,7β,7aα)-
       Endrin aldehyde	7421-93-4	1,2,4-Methenocyclo-penta[cd]pentalene-5-carboxaldehyde,2,2a,3,3,4,7-hexachlorodecahydro- (1α,2β,2aβ,4β,4aβ,5β,6aβ,6bβ,7R*)-
       Ethylbenzene	100-41-4	Benzene, ethyl-
       Ethyl methacrylate	97-63-2	2-Propenoic acid, 2-methyl-, ethyl ester
       Ethyl methanesulfonate	62-50-0	Methanesulfonic acid, ethyl ester
       Famphur	52-85-7	Phosphorothioic acid, O-[4-[(dimethylamino)sulfonyl]phenyl]-O,O-dimethyl ester
       Fluoranthene	206-44-0	Fluoranthene
       Fluorene	86-73-7	9H-Fluorene
       Heptachlor	76-44-8	4,7-Methano-1H-indene,1,4,5,6,7,8,8-heptachloro-3a,4,7,7a-tetrahydro-
       Heptachlor epoxide	1024-57-3	2,5-Methano-2H-indeno[1,2-b]oxirene, 2,3,4,5,6,7,7-heptachloro-1a,1b,5,5a,6,6a,-hexahydro-,(1aα,1bβ,2α,5α,5aβ,6β,6aα)
       Hexachlorobenzene	118-74-1	Benzene, hexachloro-
       Hexachlorobutadiene	87-68-3	1,3-Butadiene, 1,1,2,3,4,4-hexachloro-
       Hexachlorocyclopentadiene	77-47-4	1,3-Cyclopentadiene, 1,2,3,4,5,5-hexachloro-
       Hexachloroethane	67-72-1	Ethane, hexachloro-
       Hexachloropropene	1888-71-7	1-Propene, 1,1,2,3,3,3-hexachloro-
       2-Hexanone; Methyl butyl ketone	591-78-6	2-Hexanone
       Indeno(1,2,3-cd)pyrene	193-39-5	Indeno[1,2,3-cd]pyrene
       Isobutyl alcohol	78-83-1	1-Propanol, 2-methyl-
       Isodrin	465-73-6	1,4,5,8-Dimethanonaphthalene,1,2,3,4,1 0,10-hexachloro-1,4,4a,5,8,8a hexahydro-(1α, 4α, 4aβ,5β,8β,8aβ)-
       Isophorone	78-59-1	2-Cyclohexen-1-one, 3,5,5-trimethyl-
       Isosafrole	120-58-1	1,3-Benzodioxole, 5-(1-propenyl)-
       Kepone	143-50-0	1,3,4-Metheno-2H-cyclobuta-[cd]pentalen-2-one, 1,1a,3,3a,4,5,5,5a,5b,6-decachlorooctahydro-
       Lead		Lead
       Mercury		Mercury
       Methacrylonitrile	126-98-7	2-Propenenitrile, 2-methyl-
       Methapyrilene	91-80-5	1,2,Ethanediamine, N,N-dimethyl-N′-2-pyridinyl-N′-(2-thienylmethyl)-
       Methoxychlor	72-43-5	Benzene, 1,1′-(2,2,2,trichloroethylidene)bis [4-methoxy-
       Methyl bromide; Bromomethane	74-83-9	Methane, bromo-
       Methyl chloride; Chloromethane	74-87-3	Methane, chloro-
       3-Methylcholanthrene	56-49-5	Benz[j]aceanthrylene, 1,2-dihydro-3-methyl-
       Methyl ethyl ketone; MEK; 2-Butanone	78-93-3	2-Butanone
       Methyl iodide; Iodomethane	74-88-4	Methane, iodo-
       Methyl methacrylate	80-62-6	2-Propenoic acid, 2-methyl-, methyl ester
       Methyl methanesulfonate	66-27-3	Methanesulfonic acid, methyl ester
       2-Methylnaphthalene	91-57-6	Naphthalene, 2-methyl-
       Methyl parathion; Parathion methyl	298-00-0	Phosphorothioic acid, O,O-dimethyl
       4-Methyl-2-pentanone; Methyl isobutyl ketone	108-10-1	2-Pentanone, 4-methyl-
       Methylene bromide; Dibromomethane	74-95-3	Methane, dibromo-
       Methylene chloride; Dichloromethane	75-09-2	Methane, dichloro-
       Naphthalene	91-20-3	Naphthalene
       1,4-Naphthoquinone	130-15-4	1,4-Naphthalenedione
       1-Naphthylamine	134-32-7	1-Naphthalenamine
       2-Naphthylamine	91-59-8	2-Naphthalenamine
       Nickel		Nickel
       o-Nitroaniline; 2-Nitroaniline	88-74-4	Benzenamine, 2-nitro-
       m-Nitroaniline; 3-Nitroaniline	99-09-2	Benzenamine, 3-nitro-
       p-Nitroaniline; 4-Nitroaniline	100-01-6	Benzenamine, 4-nitro-
       Nitrobenzene	98-95-3	Benzene, nitro-
       o-Nitrophenol; 2-Nitrophenol	88-75-5	Phenol, 2-nitro-
       p-Nitrophenol; 4-Nitrophenol	100-02-7	Phenol, 4-nitro-
       N-Nitrosodi-n-butylamine	924-16-3	1-Butanamine, N-butyl-N-nitroso-
       N-Nitrosodiethylamine	55-18-5	Ethanamine, N-ethyl-N-nitroso-
       N-Nitrosodimethylamine	62-75-9	Methanamine, N-methyl-N-nitroso-
       N-Nitrosodiphenylamine	86-30-6	Benzenamine, N-nitroso-N-phenyl-
       N-Nitrosodipropylamine; N-Nitroso-N-dipropylamine; Di-n-propylnitrosamine	621-64-7	1-Propanamine, N-nitroso-N-propyl-
       N-Nitrosomethylethalamine	10595-95-6	Ethanamine, N-methyl-N-nitroso-
       N-Nitrosopiperidine	100-75-4	Piperidine, 1-nitroso-
       N-Nitrosopyrrolidine	930-55-2	Pyrrolidine, 1-nitroso-
       5-Nitro-o-toluidine	99-55-8	Benzenamine, 2-methyl-5-nitro-
       Parathion	56-38-2	Phosphorothioic acid, O,O-diethyl-O-(4-nitrophenyl) ester
       Pentachlorobenzene	608-93-5	Benzene, pentachloro-
       Pentachloronitrobenzene	82-68-8	Benzene, pentachloronitro-
       Pentachlorophenol	87-86-5	Phenol, pentachloro-
       Phenacetin	62-44-2	Acetamide, N-(4-ethoxyphenyl)
       Phenanthrene	85-01-8	Phenanthrene
       Phenol	108-95-2	Phenol
       p-Phenylenediamine	106-50-3	1,4-Benzenediamine
       Phorate	298-02-2	Phosphorodithioic acid, O,O-diethyl S- [(ethylthio)methyl] ester
       Polychlorinated biphenyls; PCBs	See footnote 6	1,1′-Biphenyl, chloro derivatives
       Pronamide	23950-58-5	Benzamide, 3,5-dichloro-N-(1,1-dimethyl-2-propynyl)-
       Propionitrile; Ethyl cyanide	107-12-0	Propanenitrile
       Pyrene	129-00-0	Pyrene
       Safrole	94-59-7	1,3-Benzodioxole, 5-(2- propenyl)-
       Selenium		Selenium
       Silver		Silver
       Silvex; 2,4,5-TP	93-72-1	Propanoic acid, 2-(2,4,5- trichlorophenoxy)-
       Styrene	100-42-5	Benzene, ethenyl-
       Sulfide	18496-25-8	Sulfide
       2,4,5-T; 2,4,5-Trichlorophenoxyacetic acid	93-76-5	Acetic acid, (2,4,5- trichlorophenoxy)-
       2,3,7,8-TCDD; 2,3,7,8-Tetrachlorodibenzo- p-dioxin	1746-01-6	Dibenzo[b,e][1,4]dioxin, 2,3,7,8-tetrachloro-
       1,2,4,5-Tetrachlorobenzene	95-94-3	Benzene, 1,2,4,5-tetrachloro-
       1,1,1,2-Tetrachloroethane	630-20-6	Ethane, 1,1,1,2-tetrachloro-
       1,1,2,2-Tetrachloroethane	79-34-5	Ethane, 1,1,2,2-tetrachloro-
       Tetrachloroethylene; Tetrachloroethene; Perchloroethylene	127-18-4	Ethene, tetrachloro-
       2,3,4,6-Tetrachlorophenol	58-90-2	Phenol, 2,3,4,6-tetrachloro-
       Thallium		Thallium
       Tin		Tin
       Toluene	108-88-3	Benzene, methyl-
       o-Toluidine	95-53-4	Benzenamine, 2-methyl-
       Toxaphene	See footnote 7	Toxaphene
       1,2,4-Trichlorobenzene	120-82-1	Benzene, 1,2,4-trichloro-
       1,1,1-Trichloroethane; Methylchloroform	71-55-6	Ethane, 1,1,1-trichloro-
       1,1,2-Trichloroethane	79-00-5	Ethane, 1,1,2-trichloro-
       Trichloroethylene; Trichloroethene	79-01-6	Ethene, trichloro-
       Trichlorofluoromethane; CFC-11	75-69-4	Methane, trichlorofluoro-
       2,4,5-Trichlorophenol	95-95-4	Phenol, 2,4,5-trichloro-
       2,4,6-Trichlorophenol	88-06-2	Phenol, 2,4,6-trichloro-
       1,2,3-Trichloropropane	96-18-4	Propane, 1,2,3-trichloro-
       O,O,O-Triethyl phosphorothioate	126-68-1	Phosphorothioic acid, O,O,O-triethyl ester
       sym-Trinitrobenzene	99-35-4	Benzene, 1,3,5-trinitro-
       Vanadium		Vanadium
       Vinyl acetate	108-05-4	Acetic acid, ethenyl ester
       Vinyl chloride; Chloroethene	75-01-4	Ethene, chloro-
       Xylene (total)	See footnote 8	Benzene, dimethyl-
       Zinc		Zinc

       1 Common names are those widely used in government regulations, scientific publications, and commerce; synonyms exist for many chemicals.

       2 Chemical Abstracts Service registry number.

       3 CAS index names are those used in the 9th Cumulative Index.

       4 This substance is often called bis(2-chloroisopropyl) ether, the name Chemical Abstracts Service applies to its noncommercial isomer, propane, 2,2"-oxybis[2-chloro-(CAS RN 39638-32-9).

       5 Chlordane: This entry includes alpha-chlordane (CAS RN 5103-71-9), beta-chlordane (CAS RN 5103-74-2), gamma-chlordane (CAS RN 5566-34-7), and constituents of chlordane (CAS RN 57-74-9 and CAS RN 12789-03-6).

       6 Polychlorinated biphenyls (CAS RN 1336-36-3); this category contains congener chemicals, including constituents of Aroclor-1016 (CAS RN 12674-11-2), Aroclor-1221 (CAS RN 11104-28-2), Aroclor-1232 (CAS RN 11141-16-5), Aroclor-1242 (CAS RN 53469-21-9), Aroclor-1248 (CAS RN 12672-29-6), Aroclor-1254 (CAS RN 11097-69-1), and Aroclor-1260 (CAS RN 11096-82-5).

       7 Toxaphene: This entry includes congener chemicals contained in technical toxaphene (CAS RN 8001-35-2), i.e., chlorinated camphene.

       8 Xylene (total): This entry includes o-xylene (CAS RN 96-47-6), m-xylene (CAS RN 108-38-3), p-xylene (CAS RN 106-42-3), and unspecified xylenes (dimethylbenzenes) (CAS RN 1330-20-7).

Authorizing statute(s): 75-10-204, MCA

Implementing statute(s): 75-10-204, 75-10-207, MCA

History: NEW, 2010 MAR p. 317, Eff. 2/12/10; AMD, 2024 MAR p. 253, Eff. 2/10/24.