Title 18 . Environmental Conservation

Chapter 75 . Administrative Enforcement

Section 345. Groundwater and surface water cleanup levels

18 AAC 75.345. Groundwater and surface water cleanup levels

(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.

(b) Contaminated groundwater must meet

(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;

TABLE C. GROUNDWATER CLEANUP LEVELS (Carcinogenics in Bold Type) Hazardous Substance CAS Registry Number Groundwat er Cleanup Level (mg/L) Acenaphthene 83-32-9 2.2 Acetone 67-64-1 3.65 Aldrin 309-00-2 0.00005 Anthracene 120-12-7 11.0 Antimony 7440-36-0 0.006 Arsenic 7440-38-2 0.05 Barium 7440-39-3 2.0 Benzene 71-43-2 0.005 Benzo(a)anthracene 56-55-3 0.001 Benzo(b)fluoranthene 205-99-2 0.001 Benzo(k)fluoranthene 207-08-9 0.01 Benzoic acid 65-85-0 146.0 Benzo(a)pyrene 50-32-8 0.0002 Beryllium 7440-41-17 0.004 Bis(2-chloroethyl)ether 111-44-4 0.00077 Bis(2-ethylhexyl)phthalate 117-81-7 0.006 Bromodichloromethane 75-27-4 0.1 Bromoform (Tribromomethane) 75-25-2 0.1 Butanol 71-36-3 3.65 Butyl benzyl phthalate 85-68-7 7.3 Cadmium 7440-04-39 0.005 Carbazole 86-74-8 0.04 Carbon disulfide 75-15-0 3.65 Carbon tetrachloride 56-23-5 0.005 Chlordane 57-74-9 0.002 p-Chloroaniline 106-47-8 0.15 Chlorobenzene 108-90-7 0.1 Chlorodibromomethane 124-48-1 0.06 Chloroform 67-66-3 0.1 2-Chlorophenol 95-57-8 0.2 Chromium (Total) 7440-47-3 0.1 Chromium +3 16065-83-1 55 Chromium +6 18540-29-9 0.1 Chrysene 218-01-9 0.1 Copper 7440-05-08 1.3 Cyanide 57-12-5 0.2 DDD 72-54-8 0.0036 DDE 72-55-9 0.0025 DDT 50-29-3 0.0025 Dibenzo(a,h)anthracene 53-70-3 0.0001 Di-n-butyl phthalate 84-74-2 3.65

TABLE C. GROUNDWATER CLEANUP LEVELS (Carcinogenics in Bold Type) Hazardous Substance CAS Registry Number Groundwat er Cleanup Level (mg/L) 1,2-Dichlorobenzene 95-50-1 0.6 1,4-Dichlorobenzene 106-46-7 0.075 3,3-Dichlorobenzidine 91-94-1 0.002 1,1-Dichloroethane 75-34-3 3.65 1,2-Dichloroethane 107-06-2 0.005 1,1-Dichloroethylene 75-35-4 0.007 cis-1,2-Dichloroethylene 156-59-2 0.07 trans-1,2-Dichloroethylene 156-60-5 0.1 2,4-Dichlorophenol 120-83-2 0.1 1,2-Dichloropropane 78-87-5 0.005 1,3-Dichloropropene 542-75-6 0.009 Dieldrin 60-57-1 0.00005 Diethyl phthalate 84-66-2 29.0 2,4-Dimethylphenol 105-67-9 0.7 2,4-Dinitrophenol 51-28-5 0.07 2,4-Dinitrotoluene 121-14-2 0.00125 2,6-Dinitrotoluene 606-20-2 0.00125 Di-n-octyl phthalate 117-84-0 0.7 Dioxin 174-60-16 0.00000003 Endosulfan 115-29-7 0.2 Endrin 72-20-8 0.002 Ethylbenezene 100-41-4 0.7 Fluoranthene 206-44-0 1.46 Fluorene 86-73-7 1.46 Heptachlor 76-44-8 0.0004 Heptachlor epoxide 1024-57-3 0.0002 Hexachlorobenzene 118-74-1 0.001 Hexachloro-1,3-butadiene 87-68-3 0.01 alpha-Hexachlorocyclohexane 319-84-6 0.0001 beta-Hexachlorocyclohexane 319-85-7 0.00047 gamma-Hexachlorocyclohexane (Lindane) 58-89-9 0.0002 Hexachlorocyclopentadiene 77-47-4 0.05 Hexachloroethane 67-72-1 0.06 Indeno(1,2,3-c,d)pyrene 193-39-5 0.001 Isophorone 78-59-1 0.9 Lead 7439-92-1 0.015 Mercury 7439-97-6 0.002 Methoxychlor 72-43-5 0.04 Methyl bromide 74-83-9 0.05 Methylene chloride 75-09-2 0.005 2-Methylphenol (o-cresol) 95-48-7 1.8 Naphthalene 91-20-3 0.7 Nickel 7440-02-0 0.1

TABLE C. GROUNDWATER CLEANUP LEVELS (Carcinogenics in Bold Type) Hazardous Substance CAS Registry Number Groundwat er Cleanup Level (mg/L) Nitrobenzene 98-95-3 0.018 n-Nitrosodiphenylamine 86-30-6 0.17 n-Nitrosodi-n-propylamine 621-64-7 0.0001 Pentachlorophenol 87-86-5 0.001 Phenol 108-95-2 22.0 Polychlorinated biphenyls (PCBs) 133-63-63 0.0005 Pyrene 129-00-0 1.1 Selenium 7782-49-2 0.05 Silver 7440-22-4 0.18 Styrene 100-42-5 0.1 1,1,2,2-Tetrachloroethane 79-34-5 0.004 Tetrachloroethylene 127-18-4 0.005 Thallium 7440280 0.002 Toluene 108-88-3 1.0 Toxaphene 8001-35-2 0.003 1,2,4-Trichlorobenzene 120-82-1 0.07 1,1,1-Trichloroethane 71-55-6 0.2 1,1,2-Trichloroethane 79-00-5 0.005 Trichloroethylene 79-01-6 0.005 2,4,5-Trichlorophenol 95-95-4 3.65 2,4,6-Trichlorophenol 88-06-2 0.077 Vanadium 7440-06-22 0.26 Vinyl acetate 108-05-4 36.5 Vinyl chloride (Chloroethene) 75-01-4 0.002 Xylenes (total) 1330-20-7 10.0 Zinc 7440-66-6 11.0 Petroleum Hydrocarbons GRO - C 6 -C 10 (AK 101) 1.3* DRO - C 10 -C 25 (AK 102) 1.5 RRO - C 25 -C 36 1.1 C 6 -C 10 - Aliphatics 1.3* C 6 -C 10 - Aromatics 7.3 C 10 -C 25 - Aliphatics 0.1* C 10 -C 25 - Aromatics 1.5 C 25 -C 36 - Aliphatics N (insoluble) C 25 -C 36 - Aromatics 1.1 *Standards based on estimated solubility

(2) a concentration equal to 10 times the cleanup levels in Table C, based on a determination of groundwater use made under 18 AAC 75.350 in consultation with each site landowner, the public, and appropriate government officials if

(A) the department determines that the groundwater is not a current source of drinking water or that the reasonably expected potential future use of the groundwater is not a drinking water source; and

(B) the cleanup levels in Table C are 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; or

(3) 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.

(c) The department will require 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, and

(1) 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(a) (2);

(2) groundwater hazardous substance concentrations complying with the secondary maximum contaminant levels in 18 AAC 80.300 for actual or likely drinking water supplies; and

(3) the cleanup levels 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 residual range,

(A) a Threshold Odor Number (TON) of 1 for odor, as measured by Method 2150B, Standard Methods for the Examination of Water and Wastewater, 18th edition, American Public Health Association (1992), adopted by reference; or

(B) a Flavor Threshold Number (FTN) 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.

(d) 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.

(e) 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 saturated zone 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. To be approved under this subsection, an alternative point of compliance

(1) must be within the existing groundwater contamination plume; and

(2) may not exceed the property boundary, unless a responsible person

(A) demonstrates that attainment of the applicable groundwater cleanup levels is not practicable; and

(B) provides an alternative source of water for affected persons.

(f) 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 the following factors:

(1) groundwater travel time and distance from sources of hazardous substances to surface water;

(2) the contribution of the groundwater to the chemical and physical quantity and quality of the surface water;

(3) organisms living in or dependent upon the groundwater to surface water ecosystems;

(4) climatic, tidal, or seasonal variations;

(5) feasibility of attaining applicable water quality standards to support the designated uses of the surface water;

(6) presence of sediment contamination;

(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.

(g) 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 of 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.

(h) 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) is increasing, the department will require additional followup monitoring and assess the need for additional cleanup; or

(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.

(i) 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.

(j) Groundwater monitoring wells must be installed, developed, and decommissioned in accordance with the department's Recommended Practices for Monitoring Well Design, Installation, and Decommissioning, April 1992, adopted by reference, or another approved method that is protective of human health, safety, and welfare, and of the environment.

(k) 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) .

History: Eff. 1/22/99, Register 149; am 8/27/2000, Register 155; am 1/30/2003, Register 165

Authority: AS 46.03.020

AS 46.03.050

AS 46.03.710

AS 46.03.740

AS 46.03.745

AS 46.03.755

AS 46.04.020

AS 46.04.070

AS 46.09.010

AS 46.09.020

Editor's note: Standard Methods for the Examination of Water and Wastewater, adopted by reference in this section, may be purchased from the American Water Works Association Bookstore, 6666 West Quincy Avenue, Denver, Colorado 80235, or may be viewed at the department's Anchorage, Fairbanks, Juneau, and Soldotna offices. Recommended Practices for Monitoring Well Design, Installation, and Decommissioning, adopted by reference in this section, may be viewed at, or requested from, the department's Anchorage, Fairbanks, Juneau, and Soldotna offices.