18 AAC 75.340. Soil cleanup levels; general requirements

(a) This section provides the requirements for cleanup levels for hazardous substances in soil. For each site, except as provided in (b) of this section, a responsible person shall propose soil cleanup levels for approval, shall base those cleanup levels upon an estimate of the reasonable maximum exposure expected to occur under current and future site conditions, and shall develop those cleanup levels using one or more of the following methods:

(1) method one for petroleum hydrocarbon-contaminated soil in

(A) a non-Arctic zone as set out in Table A1 of 18 AAC 75.341(a) ; or

(B) an Arctic zone as set out in Table A2 of 18 AAC 75.341(b) ;

(2) method two for soil contaminated with

(A) chemicals other than petroleum hydrocarbons as set out in Table B1 of 18 AAC 75.341(c) ; or

(B) petroleum hydrocarbons as set out in Table B2 of 18 AAC 75.341(d) ;

(3) method three, as described in (e) of this section, for developing site-specific alternative cleanup levels;

(4) method four, as described in (f) of this section, for developing site-specific alternative cleanup levels.

(b) Alternative soil cleanup levels developed under method three or method four may not be used at another site without prior approval. If alternative cleanup levels are developed for one site within a facility with multiple similarly contaminated sites, and if the department determines that the use of those cleanup levels at another site within that facility will be protective of human health, safety, and welfare, and of the environment, the department will approve the use of those cleanup levels at the other site.

(c) For methods two, three, and four, a responsible person shall demonstrate that the Arctic zone soil cleanup level, if applicable, is protective of migration to surface water.

(d) The soil cleanup levels provided under method one and method two apply at a contaminated site unless the department approves an alternative cleanup level that the responsible person has proposed under method three or method four. To obtain approval for an alternative cleanup level, a responsible person must demonstrate that an alternative cleanup level proposed under method three or method four is protective of human health, safety, and welfare, and of the environment, and must demonstrate compliance with the applicable institutional control requirements under 18 AAC 75.375.

(e) Under method three, a responsible person may propose a site-specific alternative cleanup level that modifies

(1) the migration to groundwater or inhalation levels in Table B1 of 18 AAC 75.341(c) or Table B2 of 18 AAC 75.341(d) , based on the use of approved site-specific soil data and the equations set out in the department's Cleanup Levels Guidance, dated November 7, 2002, adopted by reference; the alternative cleanup level that then applies at the site for a hazardous substance is the most stringent of the Table B1 or Table B2 ingestion-based level and the site-specific calculated levels for inhalation or migration to groundwater;

(2) the migration to groundwater levels in Table B1 or Table B2 based on approved site-specific soil data and an approved fate and transport model that demonstrates that alternative soil cleanup levels are protective of the applicable groundwater cleanup levels under 18 AAC 75.345 if the alternative migration to groundwater cleanup level does not exceed

(A) the ingestion-based level in Table B1 or Table B2;

(B) the inhalation level in Table B1 or Table B2; or

(C) a site-specific inhalation level calculated under (1) of this subsection; the level that applies at the site is the most stringent level; or

(3) the ingestion level or the inhalation level in Table B1 or Table B2 based on use of commercial or industrial exposure parameters listed in Appendix B of the Cleanup Levels Guidance, adopted by reference in (1) of this subsection, if the department determines that the site serves a commercial or industrial land use, and if the alternative ingestion level or inhalation level does not exceed the migration to groundwater cleanup level in Table B1 or Table B2 or a site-specific migration to groundwater level calculated under (2) of this subsection; the department will base a land use determination under this paragraph upon

(A) consultation with the public, including the local zoning authority, in any;

(B) a determination that the site does not serve a residential land use;

(C) a determination that the site will not serve a future residential land use based on consideration of the factors in EPA's Land Use in the CERCLA Remedy Selection Process, OSWER Dir. No. 9355.7-04, dated May 25, 1995, adopted by reference; land in an undeveloped area for which it would be difficult to determine a future use pattern is capable of being a residential area, unless demonstrated otherwise; and

(D) consent of each landowner who is affected by the contamination at the site that a cleanup level less stringent than a cleanup level appropriate to residential land use is appropriate for the site.

(f) Under method four, the department will approve a site-specific alternative cleanup level if a responsible person

(1) performs a site-specific risk assessment and submits a risk assessment report to the department for approval, and if the department determines that the alternative cleanup level is protective of human health, safety, and welfare, and of the environment, based on the site-specific risk assessment; in performing the risk assessment, a responsible person shall follow the department's Risk Assessment Procedures Manual, dated June 8, 2000, adopted by reference; and

(2) obtains the consent of each landowner who is affected by the contamination at the site that a cleanup level less stringent than a cleanup level appropriate to residential land use is appropriate for the site.

(g) The department will require a responsible person to develop a site-specific cleanup level for a hazardous substance not listed under 18 AAC 75.341(c) using methods provided under (e) or (f) of this section, unless that person demonstrates that a site-specific cleanup level is not necessary to ensure protection of human health, safety, and welfare, and of the environment.

(h) The department will approve less stringent soil cleanup levels, subject to any institutional controls required under 18 AAC 75.375, if a responsible person demonstrates that

(1) background concentrations of a hazardous substance in the site area exceed the applicable cleanup level set out in 18 AAC 75.341 for the hazardous substance; or

(2) the practical quantitation limit for the hazardous substance exceeds the applicable cleanup level set out in 18 AAC 75.341 for that substance.

(i) The department will require a responsible person to modify a cleanup level under this section or to perform a site-specific analysis of additional site risks if the department determines that

(1) as a result of site conditions or new data, a modification is necessary to protect human health, safety, or welfare, or the environment; or

(2) a site-specific analysis is necessary due to

(A) exposure pathways such as

(i) accumulation of vapors in buildings or other structures at levels that threaten human health; and

(ii) human inhalation of fugitive dust if the proposed remedy includes leaving a hazardous substance in place within the upper one foot of the surface soil at the site;

(B) sediment contamination;

(D) other site uses such as recreational, agricultural, or subsistence use.

(j) Soil cleanup levels based on

(1) migration of a hazardous substance to groundwater must be attained in the surface soil and the subsurface soil;

(2) human exposure from ingestion or inhalation of a volatile hazardous substance must be attained in the surface soil and the subsurface soil to a depth of at least 15 feet, unless an institutional control or site conditions prevent human exposure to the subsurface soil; and

(3) the maximum allowable concentrations for petroleum hydrocarbons described in Table B2 of 18 AAC 75.341(d) must be attained in the surface soil and the subsurface soil.

(k) For a cleanup conducted under methods two and three, a chemical that is detected at one-tenth or more of the Table B1 ingestion and inhalation cleanup levels set out in 18 AAC 75.341(c) 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

Editor's note: The documents adopted by reference in 18 AAC 75.340 may be reviewed at, or requested from, the department's offices in Anchorage, Fairbanks, Juneau, and Soldotna.

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