Natural attenuation means a variety of physical, chemical or biological processes that, under favorable conditions, act without hu- man intervention to reduce the mass, toxicity, mobility, volume, or concentration of hazardous substances in the environment. These in situ processes include: Natural biodegradation; dispersion; dilution; sorption; volatilization; and, chemical or biological stabilization, transformation, or destruction of hazardous substances. See WAC 173-340-370(7) for a description of the expected role of natural at- tenuation in site cleanup. A cleanup action that includes natural at- tenuation and conforms to the expectation in WAC 173-340-370(7) can be considered an active remedial measure.
Attenuation block means a block or stack, having dimensions 20 centimeters by 20 centimeters by 3.8 centimeters, of type 1100 aluminum alloy or other materials having equivalent attenuation.
Slash means all debris created on the Work area by the precommercial thinning operation.
Hydraulic lift tank means a tank holding hydraulic fluid for a closed-loop mechanical system that uses compressed air or hydraulic fluid to operate lifts, elevators, and other similar devices.
Disinfection profile means a summary of daily Giardia lamblia inactivation through the treatment plant. The procedure for developing a disinfection profile is contained in s. NR 810.32.