August 23, 1993

Implementation Memo No. 2

TO: Interested Staff

FROM: Carol Kraege

Toxics Cleanup Program

SUBJECT: Applicability of WAC 173-340-706


If a site meets the criteria for an industrial site, is it appropriate to set Method C cleanup levels for groundwater?

WAC 173-340-706(1) lists the conditions for the selection of Method C cleanup levels. One of these conditions, under subsection (d) is:

"The site is defined as an industrial site and meets the criteria for establishing soil cleanup levels under WAC 173-340-745."

Thus, how and when does the language in WAC 173-340-706(1)(d) apply to setting cleanup levels for an industrial site for media other than soil? Does such a site need to meet at least one criterion other than 706(1)(d) for the application of Method C to media other than soil?


Section 706(1) includes a list of conditions that need to be met before a Method C cleanup can be undertaken. The four conditions are:

(a) where Method A or B cleanup levels are below area background concentrations,

(b) where attainment of Methods A or B cleanup levels could create an environmental threat,

(c) where Method A or B cleanup levels are below technically possible concentrations, or

(d) where the site meets the definition as an industrial site and meets the criteria for establishing soil cleanup levels under WAC 173-340-745.


Based on language in MTCA and the Responsiveness Summary a Method C cleanup for groundwater can only be applied at sites that meet at least one of the criteria outlined in section 706(1)(a)-(c). 706(1)(d) cannot be used as the only criterion for determining which Method to use for media other than soil.

This interpretation is based on how MTCA deals with groundwater and some explanation in the Responsiveness Summary (RS). On page 161 of the RS, the conditions under which a conditional cleanup level would be set are outlined. These are:

1. compliance cleanup levels are below area background concentrations;

2. attainment of compliance cleanup levels would result in a net adverse environmental impact;

3. attainment of compliance cleanup levels is technically infeasible; or

4. attainment of compliance cleanup levels is technically impracticable.

The condition described in 706(1)(d) is not mentioned here. Furthermore, section 745 very clearly limits the application of industrial cleanup levels to soil and to no other media. The reference to this section in 706(1)(d) should therefore only be applied when soil is the medium involved.

In addition, cleanup levels for each medium are based on a reasonable maximum exposure (RME) scenario specific to that medium. Section 708(3) describes these RMEs. Soil RMEs are based on exposure through site use, while groundwater RMEs are for drinking the water rather than for site use. Sub- section (3)(b) states:

The reasonable maximum exposure is defined as the highest exposure that is reasonably expected to occur at a site under current and potential future site use. WAC 173 340 720 through 173 340 760 define the reasonable maximum exposures for groundwater, surface water, soil, and air. These reasonable maximum exposures will apply to most sites where individuals or groups of individuals are or could be exposed to hazardous substances. For example, the reasonable maximum exposure for most groundwater is defined as exposure to hazardous substances in drinking water and other domestic uses.

Therefore, one cannot assume that because a site meets the definition of an industrial site, that Method C could be applied to the groundwater. Each affected medium should be evaluated independently to determine if Method C is appropriate.


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