Washington Administrative Code › Title 173 - Ecology, Department of (See also Titles 197, 317, 372, and 508) › Chapter 173-340 - Model Toxics Control Act-Cleanup › Part 3 - SITE REPORTS AND CLEANUP DECISIONS › Section 173-340-370 - Cleanup action expectations

Current through Register Vol. 24-14, July 15, 2024
Ecology has the following expectations for cleanup actions.
				  The expectations represent the likely results of the cleanup action selection
				  process described in WAC
				  173-340-350 through
				  173-340-390. Ecology recognizes
				  that conformance with the expectations may not be appropriate at some sites.
				  Selecting a cleanup action conforming to the expectations is not a substitute
				  for conducting a feasibility study. The expectations must be considered when
				  evaluating cleanup action alternatives in the feasibility study. Any
				  nonconformance of the preferred cleanup action alternative to the expectations
				  must be documented and explained in the feasibility study report.
(1) Ecology expects that treatment
				technologies will be emphasized at sites containing liquid wastes, areas
				contaminated with high concentrations of hazardous substances, highly mobile
				materials, and/or discrete areas of hazardous substances that lend themselves
				to treatment.
(2) To minimize the
				need for long-term management of contaminated materials, ecology expects that
				all hazardous substances will be destroyed, detoxified, and/or removed to
				concentrations below cleanup levels throughout sites containing small volumes
				of hazardous substances.
(3)
				Ecology recognizes the need to use engineering controls, such as containment,
				for sites or portions of sites that contain large volumes of materials with
				relatively low levels of hazardous substances where treatment is
				impracticable.
(4) To minimize the
				potential for migration of hazardous substances, ecology expects that active
				measures will be taken to prevent precipitation and subsequent runoff from
				coming into contact with contaminated soils and waste materials. When such
				measures are impracticable, such as during active cleanup, ecology expects that
				site runoff will be contained and treated prior to release from the
				site.
(5) Ecology expects that when
				hazardous substances remain on-site at concentrations exceeding cleanup levels,
				those hazardous substances will be consolidated to the maximum extent
				practicable where needed to minimize the potential for direct contact and
				migration of hazardous substances.
(6) Ecology expects that active measures will
				be taken to prevent/minimize releases to surface water or sediment via surface
				runoff and groundwater discharges in excess of cleanup levels. Ecology expects
				that dilution will not be the sole method for demonstrating compliance with
				cleanup standards in these instances.
(7) Ecology expects that natural attenuation
				of hazardous substances may be appropriate at sites where:
(a) Source control (including removal and/or
				treatment of hazardous substances) has been conducted to the maximum extent
				practicable;
(b) Leaving
				contaminants on-site during the restoration time frame does not pose an
				unacceptable threat to human health or the environment;
(c) There is evidence that natural
				biodegradation or chemical degradation is occurring and will continue to occur
				at a reasonable rate at the site; and
(d) Appropriate monitoring requirements are
				conducted to ensure that the natural attenuation process is taking place and
				that human health and the environment are protected.