Section 18.75.345. 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; or  
CLICK TO VIEW  TABLE C
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. "c" means carcinogenic, and "nc" means noncarcinogenic.  
		(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.  
	(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, 21st edition, American Public Health Association (2005), 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 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) alternative point of compliance must be within the existing groundwater contamination plume; and  
		(2) the cleanup levels in Table C at (b)(1) of this section must be met at the property boundary in an area where the current use or reasonably expected potential groundwater in the neighboring property is determined to be a source of drinking water, 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).  

Authorities

46.03.020;46.03.050;46.03.710;46.03.740;46.03.745;46.03.755;46.04.020;46.04.070;46.09.010;46.09.020

Notes

Reference

18 AAC 75.315
18 AAC 75.325
18 AAC 75.340
18 AAC 75.341
18 AAC 75.350
18 AAC 78.090
18 AAC 78.210
18 AAC 78.600
18 AAC 78.615
18 AAC 78.620

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.

History

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