(1) Purpose. A hazard assessment shall be performed to gather existing and available information to further characterize each station cluster of potential concern identified per WAC 173-204-510.

(2) Hazard assessment requirements. On-site dischargers, lessees, landowners, and adjacent dischargers shall submit, upon the department's request, all existing and available information or, if determined necessary by the department, shall perform sampling for a known or suspected release that would enable the department to:

(a) Determine the concentration and/or areal extent and depth of sediment contamination at the station cluster of potential concern by:

(i) Identifying the contaminants exceeding the applicable sediment cleanup objectives of WAC 173-204-562 or 173-204-563;

(ii) Identifying individual stations within the station cluster of potential concern exceeding the applicable sediment cleanup screening levels of WAC 173-204-562 or 173-204-563;

(iii) Identifying the level of toxicity to the applicable biological test organisms of WAC 173-204-562 or 173-204-563;

(iv) Determining where the applicable sediment cleanup objectives of WAC 173-204-562 or 173-204-563, for any given chemical, is met;

(v) Determining if concentrations of chemicals exist that exceed applicable cleanup screening levels of WAC 173-204-560; and

(vi) Defining the location where the cleanup screening level as defined in WAC 173-204-560 is not met.

(b) Identify and characterize the present and historic source or sources of the contamination;

(c) Identify the location of sediment impact zones authorized under WAC 173-204-415;

(d) Identify sensitive resources in the vicinity of the station cluster of potential concern;

(e) Compile other information as determined necessary by the department for evaluating sites under WAC 173-204-530; and

(f) Compile existing and available information from other federal, state, and local governments.

(3) Identification of cleanup sites. To identify cleanup sites, the department shall use all available information of acceptable quality gathered from the hazard assessment to evaluate station clusters of potential concern identified pursuant to WAC 173-204-510(2). For the purpose of identifying a cleanup site per the procedures of this subsection, three stations with the highest chemical concentration for any particular chemical or the highest degree of biological effects as identified in WAC 173-204-562 or 173-204-563, as applicable, are selected from a station cluster of potential concern. This procedure may be repeated for multiple chemicals recognizing that the three stations with the highest concentration for each particular chemical may be different and the respective areas for all chemicals may overlap. The department shall review the list of station clusters of potential concern to identify cleanup sites via the following process:

(a) Station clusters of potential concern that meet the conditions in WAC 173-204-510 (2)(a)(ii) or (b) shall be defined as cleanup sites if concentrations are above the regional background cleanup screening level in WAC 173-204-560(4), as applicable;

(b) For the purpose of identifying a cleanup site per the procedures of this subsection, stations that meet the biological standards of WAC 173-204-562(3) or 173-204-563(3), as applicable, shall not be included in the evaluation of chemical contaminant concentrations for benthic community toxicity;

(c) After completion of the hazard assessment, if the conditions of (a) or (b) of this subsection do not apply, then the station cluster is defined as a station cluster of low concern for benthic community toxicity; and

(d) If the department determines that each of three stations within the station cluster of potential concern exceed any one of the following criteria, then the station cluster of potential concern may be defined as a cleanup site or area for potential further investigation:

(i) The applicable human health and regional background cleanup screening levels in WAC 173-204-560(4);

(ii) The other toxic, radioactive, biological, or deleterious substances criteria in WAC 173-204-562 or 173-204-563, as applicable; or

(iii) The nonanthropogenically affected criteria of WAC 173-204-562 or 173-204-563, as applicable.