1. (a) Except as otherwise provided in this section, cleanup of a discharge or release of a hazardous substance to groundwater or surface water must meet the requirements of this section.

2. (b) Contaminated groundwater must meet

   1. (1) the cleanup levels in Table C if the current use or the reasonably expected potential future use of the groundwater, determined under 18 AAC 75.350, is a drinking water source;
   2. (2) an approved cleanup level based on an approved site-specific risk assessment conducted under the Risk Assessment Procedures Manual, adopted by reference in 18 AAC 75.340;
   3. (3) an alternative cleanup level for a hazardous substance not listed under (1) of this subsection proposed by the responsible party and approved by the department, using the procedures set out in the department's Risk Assessment Procedures Manual, adopted by reference in 18 AAC 75.340, unless the responsible person demonstrates that an alternative cleanup level is not necessary to ensure protection of human health, safety, and welfare, and of the environment; or
   4. (4) an alternative cleanup level for a hazardous substance not listed under (1) of this subsection set by the department using the procedures set out in the department's Risk Assessment Procedures Manual, adopted by reference in 18 AAC 75.340,

   TABLE C. GROUNDWATER CLEANUP LEVELS Hazardous Substance CAS Number1 Health effect that

   drives risk:

   carcinogen (ca);

   noncarcinogen (nc);

   mutagen (m) Groundwater

   Human Health

   Cleanup Level2

   (micrograms/liter) Acenaphthene83-32-9nc530 Acenaphthylene3208-96-8nc260 Acetone67-64-1nc14000 Aldrin309-00-2ca0.0092 Anthracene120-12-7nc43 (1800)4 Antimony (metallic)7440-36-0nc7.8 Arsenic, Inorganic57440-38-2ca0.52 Barium7440-39-3nc3800 Benz[a]anthracene56-55-3m0.30 Benzaldehyde100-52-7nc190 Benzene71-43-2ca4.6 Benzo[a]pyrene50-32-8m0.25 Benzo[b]fluoranthene205-99-2m2.5 Benzo[g,h,i]perylene3191-24-2nc0.26 (600)4 Benzo[k]fluoranthene207-08-9m0.80 (25)4 Benzoic Acid65-85-0nc75000 Benzyl Alcohol100-51-6nc2000 Beryllium and compounds7440-41-7nc25 Bis(2-chloroethyl)ether111-44-4ca0.14 Bis(2-ethylhexyl)phthalate117-81-7ca56 Bromobenzene108-86-1nc62 Bromodichloromethane75-27-4ca1.3 Bromoform75-25-2ca33 Bromomethane74-83-9nc7.5 Butadiene, 1,3-106-99-0ca0.18 Butanol, N-71-36-3nc2000 Butyl Benzyl Phthalate85-68-7ca160 Butylbenzene, n-104-51-8nc1000 Butylbenzene, sec-135-98-8nc2000 Butylbenzene, tert-98-06-6nc690 Cadmium (Diet)7440-43-9nc9.2 Carbon Disulfide75-15-0nc810 Carbon Tetrachloride56-23-5ca4.6 Chlordane12789-03-6ca0.20 Chlordecone (Kepone)143-50-0ca0.035 Chloroaniline, p-106-47-8ca3.7 Chlorobenzene108-90-7nc78 Chloroform67-66-3ca2.2 Chloromethane74-87-3nc190 Chloronaphthalene, Beta-91-58-7nc750 Chlorophenol, 2-95-57-8nc91 Chromium(III), Insoluble

   Salts616065-83-1nc22000 Chromium(VI)618540-29-9m0.35 Chrysene218-01-9m2.0 (250)4 Copper7440-50-8nc800 Cresol, m-108-39-4nc930 Cresol, o-95-48-7nc930 Cresol, p-106-44-5nc1900 Cumene98-82-8nc450 Cyanide (CN-)57-12-5nc1.5 Cyclohexane110-82-7nc13000 DDD72-54-8ca0.060 DDE, p.p'-72-55-9ca0.46 DDT50-29-3ca2.3 Dibenz[a,h]anthracene53-70-3m0.25 Dibenzofuran132-64-9nc7.9 Dibromochloromethane124-48-1ca8.7 Dibromoethane, 1,2-

   (Ethylene Dibromide)106-93-4ca0.075 Dibromomethane

   (Methylene Bromide)74-95-3nc8.3 Dibutyl Phthalate84-74-2nc900 Dichlorobenzene, 1,2-95-50-1nc300 Dichlorobenzene, 1,3-3541-73-1nc300 Dichlorobenzene, 1,4-106-46-7ca4.8 Diehlorobenzidine, 3,3'-91-94-1ca1.3 Dichlorodifluoromethane75-71-8nc200 Dichloroethane, 1,1-75-34-3ca28 Dichloroethane, 1,2-107-06-2ca1.7 Dichloroethylene, 1,1-75-35-4nc280 Dichloroethylene, 1,2-cis-156-59-2nc36 Dichloroethylene, 1,2-

   trans-156-60-5nc360 Dichlorophenol, 2,4-120-83-2nc46 Dichlorophenoxy Acetic

   Acid, 2,4-94-75-7nc170 Dichloropropane, 1,2-78-87-5nc8.2 Dichloropropene, 1,3-542-75-6ca4.7 Dieldrin60-57-1ca0.018 Diethyl Phthalate84-66-2nc15000 Dimethylphenol, 2,4-105-67-9nc360 Dimethylphthalate3131-11-3nc16000 Dinitrobenzene, 1,2-528-29-0nc1.9 Dinitrobenzene, 1,3-99-65-0nc2.0 Dinitrobenzene, 1,4-100-25-4nc2.0 Dinitrophenol, 2,4-51-28-5nc39 Dinitrotoluene, 2,4-121-14-2ca2.4 Dinitrotoluene, 2,6-606-20-2ca0.49 Dinitrotoluene, 2-Amino-

   4,6-35572-78-2nc39 Dinitrotoluene, 4-Amino-2,6-19406-51-0nc39 Dioxane, 1,4-123-91-1ca4.6 Diphenylamine122-39-4nc1300 Endosulfan115-29-7nc100 Endrin72-20-8nc2.3 Ethyl Chloride75-00-3nc21000 Ethylbenzene100-41-4ca15 Ethylene Glycol107-21-1nc40000 Fluoranthene206-44-0nc260 (800)4 Fluorene86-73-7nc290 Formaldehyde50-00-0ca4.3 Heptachlor76-44-8ca0.014 Heptachlor Epoxide1024-57-3ca0.014 Hexachlorobenzene118-74-1ca0.098 Hexachlorobutadiene87-68-3nc1.4 Hexachlorocyclohexane,

   Alpha-319-84-6ca0.072 Hexachlorocyclohexane,

   Beta-319-85-7ca0.25 Hexachlorocyclohexane,

   Gamma- (Lindane)58-89-9ca0.42 Hexachlorocyclopentadiene77-47-4nc0.41 Hexachloroethane67-72-1ca3.3 Hexahydro-1,3,5-trintro-

   1,3,5-triazine (RDX)121-82-4ca7.0 Hexane, N-110-54-3nc1500 Hexanone, 2-591-78-6nc38 Hydrazine302-01-2ca0.011 Indeno[1,2,3-cd]pyrene193-39-5m0.19 (2.5)4 Isophorone78-59-1ca780 Isopropanol67-63-0nc410 Lead and Compounds77439-92-1nc15 Manganese7439-96-5nc430 Mercuric Chloride37487-94-7nc5.7 Mercury (elemental)7439-97-6nc0.52 Methanol67-56-1nc20000 Methoxychlor72-43-5nc37 Methyl Ethyl Ketone (2-

   Butanone)78-93-3nc5600 Methyl Isobutyl Ketone (4-

   methyl-2-pentanone)108-10-1nc6300 Methyl Mercury22967-92-6nc2.0 Methyl tert-Butyl Ether (MTBE)1634-04-4ca140 Methylene Chloride75-09-2nc110 Methylnaphthalene, 1-90-12-0ca11 Methylnaphthalene, 2-91-57-6nc36 Naphthalene91-20-3ca1.7 Nickel Soluble Salts7440-02-0nc390 Nitrobenzene98-95-3ca1.4 Nitroglycerin55-63-0nc2.0 Nitroguanidine556-88-7nc2000 Nitrosodimethylamine, N-62-75-9m0.0011 Nitroso-di-N-propylamine,

   N-621-64-7ca0.11 Nitrosodiphenylamine, N-86-30-6ca120 Nitrotoluene, m-99-08-1nc1.7 Nitrololuene, o-88-72-2ca3.1 Nitrololuene, p-99-99-0nc43 Octahydro-1,3,5,7-

   tetranitro-1,3,5,7-

   tetrazocine (HMX)2691-41-0nc1000 Octyl Phthalate, di-N-117-84-0nc22 (200)4 Pentachlorophenol87-86-5ca0.41 Pentaerythritol

   tetranitrate (PETN)78-11-5nc39 Perchlorate and

   Perchlorate Salts14797-73-0nc14 Perfluorooctanesulfonic

   Acid (PFOS)31763-23-1nc0.40 Perfluorooctanoic Acid (PFOA)3335-67-1nc0.40 Phenanthrene385-01-8nc170 Phenol108-95-2nc5800 Phosphorus, White7723-14-0nc0.40 Polychlorinated

   Biphenyls (PCBs)1336-36-3ca0.44 Propyl benzene103-65-1nc660 Pyrene129-00-0nc120 Selenium7782-49-2nc100 Silver7440-22-4nc94 Styrene100-42-5nc1200 Strontium7440-24-6nc12000 TCDD, 2,3,7,8-81746-01-6ca1.2 x 106 Tetrachloroethane,

   1,1,1,2-630-20-6ca5.7 Tetrachloroethane,

   1,1,2,2-79-34-5ca0.76 Tetrachloroethylene127-18-4nc41 Tetryl (Trinitrophenyl-

   methylnitramine)479-45-8nc39 Thallium (Soluble Salts)7440-28-0nc0.20 Toluene108-88-3nc1100 Toxaphene8001-35-2ca0.71 Trichloro-1,2,2-

   trifluoroethane, 1,1,2-76-13-1nc10000 Trichlorobenzene, 1,2,3-87-61-6nc7.0 Trichlorobenzene, 1,2,4-120-82-1nc4.0 Trichloroethane, 1,1,1-71-55-6nc8000 Trichloroethane, 1,1,2-79-00-5nc0.41 Trichloroethylene79-01-6nc2.8 Trichlorofluoromethane75-69-4nc5200 Trichlorophenol, 2,4,5-95-95-4nc1200 Trichlorophenol, 2,4,6-88-06-2nc12 Trichlorophenoxyacetic

   Acid, 2,4,5-93-76-5nc160 Trichlorophenoxypropionic

   Acid, -2,4,593-72-1nc110 Triehloropropane, 1,2,3-96-18-4m0.0075 Trimelhylbenzene, 1,2,4-95-63-6nc56 Trimethylbenzene, 1,3,5-108-67-8nc60 Tri-n-butyltin688-73-3nc3.7 Trinitrobellzene, 1,3,5-99-35-4nc590 Trinitrotoluene, 2,4,6-118-96-7nc9.8 Vanadium and Compounds7440-62-2nc86 Vinyl Acetate108-05-4nc410 Vinyl Chloride75-01-4ca0.19 Xylenes1330-20-7nc190 Zinc and Compounds7440-66-6nc6000 PETROLEUM HYDROCARBONS C6-C10 GROnc2200 C10-C25 DROnc1500 C25-C36 RROnc1100

   Notes to Table C:

   1. "CAS Number" means the Chemical Abstract Service (CAS) registry number uniquely assigned to chemicals by the American Chemical Society and recorded in the CAS Registry System.

   2. The "Human Health" exposure pathway is the cumulative exposure pathway through dermal contact, ingestion, and inhalation of volatile compounds from hazardous substances in the water.

   3. Where one or more toxicological values were unavailable, toxicity values from surrogate compounds or other sources were used as presented in Table 6 from the Procedures for Calculating Cleanup Levels, adopted by reference in 18 AAC 75.340.

   4. This level is set at the compound's solubility concentration using the equations set out in the Procedures for Calculating Cleanup Levels, adopted by reference in 18 AAC 75.340. The solubility value is listed first, followed by the human health risk-based cleanup level in parentheses. The human health risk-based cleanup level assumptions do not take free product into consideration. In accordance with 18 AAC 75.325(f), free product must be recovered to the maximum extent practicable. Contaminant concentrations above the solubility value trigger the need to assess the practicability of product recovery; if the department determines product recovery is impracticable, the risk-based cleanup level may be applied as long as the cumulative risk standards are met.

   5. Due to the prevalence of naturally occurring arsenic throughout the state, arsenic at a site will be considered background arsenic unless anthropogenic contribution from a source, activity, or mobilization by means of another introduced contaminant is known or suspected.

   6. Due to the prevalence of naturally occurring chromium III throughout the state, sample results reported for total chromium detected at a site will be considered background chromium III unless anthropogenic contribution of chromium III or VI from a source, activity, or mobilization by means of another introduced contaminant is known or suspected.

   7. The lead cleanup level is taken from EPA's action level for lead in water.

   8. This cleanup level is for 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) only; all cleanup levels for polychlorinated dibenzo-p-dioxin (PCDD) and polychlorinated dibenzofuran (PCDF) congeners must be determined on a site-specific basis using the TCDD toxicity equivalent (TEQ) approach described in the Procedures for Calculating Cumulative Risk, adopted by reference in 18 AAC 75.325.

3. (c) The department will set a more stringent cleanup level than the applicable level under (b) of this section, if the department determines that a more stringent cleanup level is necessary to ensure protection of human health, safety, or welfare, or of the environment, and based on actual onsite and actual or likely offsite uses of the groundwater that are likely to be affected by the hazardous substance. In making a determination under this subsection, the department may consider

   1. (1) the risks to current or potential future users of the groundwater as a drinking water source, as determined under 18 AAC 75.350;
   2. (2) the presence of sensitive subpopulations who respond biologically to lower levels of exposure to a hazardous substance;
   3. (3) the groundwater use classifications other than for drinking water, as set out under 18 AAC 70.020(a)(1)(A) and 18 AAC 70.050(2);
   4. (4) the primary or secondary maximum contaminant levels in 18 AAC 80.300 for actual or likely drinking water supplies;
   5. (5) a health advisory value developed by EPA's Office of Water; and

   6. (6) the cleanup level in this section for groundwater contaminated with petroleum; the contamination may not exceed, for each petroleum hydrocarbon range applicable, including the gasoline range, the diesel range, and the reidual range,

      1. (A) a threshold odor number (TON) of 1 for odor, as measured by Method 2150B, Standard Methods for the Examination of Water and Wastewater, 22nd edition, American Public Health Association (2012), adopted by reference; or
      2. (B) a flavor threshold number (FT) of 1 for flavor, as measured by Method 2160B, Standard Methods for the Examination of Water and Wastewater, adopted by reference in (A) of this paragraph.
4. (d) Where the department determines that toxicity information is insufficient to establish a cleanup level for a hazardous substance or a pollutant that ensures protection of human health, safety, and welfare, and of the environment, the department may require a responsible person to provide an alternative source of drinking water for the affected parties or implement other institutional controls under 18 AAC 75.375 until a cleanup level is established under (b)(2), (3), or (4) of this section.
5. (e) Toxic substances in sediment may not cause, and may not be reasonably expected to cause, a toxic or other deleterious effect on aquatic life, except as authorized under 18 AAC 70. For purposes of this subsection, "toxic substances" has the meaning given in 18 AAC 70.990.

6. (f) The point of compliance where groundwater cleanup levels must be attained is throughout the site from each point extending vertically from the uppermost level of the zone of saturation to the lowest possible depth that could potentially be affected by the discharge or release of a hazardous substance, unless the department approves an alternative point of compliance as part of the cleanup action under 18 AAC 75.360. For the department to approve an alternative point of compliance under this subsection, the

   1. (1) alternative point of compliance must be within the existing groundwater contamination plume; and

   2. (2) cleanup levels established in (b) and (c) of this section must be met at the property boundary in an area where the current use or reasonably expected potential future use of groundwater in the neighboring property is determined to be a source of drinking water, unless a responsible person

      1. (A) demonstrates that attainment of the applicable groundwater cleanup levels is not practicable; and
      2. (B) provides an alternative source of water for affected persons.

7. (g) Groundwater that is closely connected hydrologically to nearby surface water may not cause a violation of the water quality standards in 18 AAC 70 for surface water or sediment. The department will, in consultation with local, state, and federal officials and the public, establish points of compliance with this subsection, taking into account

   1. (1) groundwater travel time and distance from sources of hazardous substances to surface water;
   2. (2) the contribution of the groundwater to the chemical and physical quantity and quality of the surface water;
   3. (3) organisms living in or dependent upon the groundwater to surface water ecosystems;
   4. (4) climatic, tidal, or seasonal variations;
   5. (5) feasibility of attaining applicable water quality standards to support the designated uses of the surface water;
   6. (6) presence of sediment contamination; and
   7. (7) if conducted for the site, the conclusions of a site-specific risk assessment conducted under the Risk Assessment Procedures Manual, adopted by reference in 18 AAC 75.340.
8. (h) If the groundwater point of compliance is established at or near a property boundary or if groundwater is closely connected hydrologically to a surface waterbody, the department will, if the department determines that sentinel monitoring is necessary to ensure protection of human health, safety, or welfare, or the environment, require a responsible person to develop sentinel monitoring wells that monitor for any hazardous substances likely to migrate to the applicable point of compliance at concentrations that exceed the cleanup levels.

9. (i) The department will require long-term monitoring if the department determines that monitoring is necessary to ensure protection of human health, safety, or welfare, or of the environment, and if groundwater, surface water, soil, or sediment contains residual concentrations of a hazardous substance that exceed the applicable cleanup levels. If long-term monitoring is required under this subsection, a responsible person shall submit a plan and schedule for monitoring as part of the requirements for cleanup operations under 18 AAC 75.360. Unless otherwise approved by the department, a responsible person shall conduct monitoring quarterly for at least one year to establish the concentration trend. The department will evaluate the monitoring program yearly. If the monitoring indicates that the concentration trend

   1. (1) is increasing, the department will require additional follow-up monitoring and assess the need for additional cleanup; or
   2. (2) is stable or decreasing, and that hazardous substance migration is not occurring, the department will decrease or discontinue the monitoring frequency and locations, if the responsible person demonstrates that continued monitoring is not necessary to ensure protection of human health, safety, and welfare, and of the environment.
10. (j) The department will require groundwater, surface water, soil, or sediment monitoring to estimate contaminant flux rates and to address potential bioaccumulation of each hazardous substance at the site, if the department determines that monitoring is necessary to ensure protection of human health, safety, or welfare, or of the environment. If monitoring is required under this subsection, a responsible person shall submit a plan and schedule for monitoring as part of the cleanup operation requirements under 18 AAC 75.360.
11. (k) Groundwater monitoring wells must be installed, developed, and decommissioned in accordance with an approved method that is protective of human health, safety, and welfare, and of the environment.
12. (l) For a cleanup conducted under (b)(1) of this section, a chemical that is detected at one-tenth or more of the Table C value must be included when calculating cumulative risk under 18 AAC 75.325(g).

(Eff. 1/22/99, Register 149; am 8/27/2000, Register 155; am 1/30/2003, Register 165; am 10/9/2008, Register 188; am 6/17/2015, Register 214; am 11/6/2016, Register 220; am 9/29/2018, Register 227)