(1) Data analysis. The department shall analyze sediment sampling data to identify station clusters of potential concern and station clusters of low concern. Station clusters of potential concern shall be further evaluated using the hazard assessment standards of WAC 173-204-520. Station clusters of low concern shall remain on the inventory and no further cleanup action determinations shall be made by the department until the stations are reexamined per subsection (5) of this section.

(2) Station clusters. A station cluster is defined as any number of stations that are determined by the department to be spatially and chemically similar. For the purpose of identifying a station cluster of potential concern, 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. 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 identify station clusters of potential concern using the process specified in this subsection.

(a) Identify, if available, the three stations within a station cluster with the highest concentration of each chemical identified in WAC 173-204-562 or 173-204-563, as applicable.

(i) For each chemical identified in (a) of this subsection, determine the average concentration for the chemical at the three stations identified.

(ii) If the average chemical concentration for any three stations identified in (a) of this subsection exceeds the applicable cleanup screening level in WAC 173-204-562 or 173-204-563, then the station cluster shall be defined as a station cluster of potential concern.

(b) Identify, if available, three stations within the station cluster with the highest level of biological effects for the biological tests identified in WAC 173-204-562 or 173-204-563, as applicable. If the level of biological effects at each of the three stations from this subsection exceeds the applicable cleanup screening level in WAC 173-204-562 or 173-204-563, then the station cluster shall be defined as a station cluster of potential concern.

(c) If the department determines that each of three stations within a station cluster exceed the following criteria, then the station cluster shall be defined as a station cluster of potential concern:

(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.

(d) If none of the conditions of (a) through (c) of this subsection apply, then the station cluster shall be defined as a station cluster of low concern.

(3) Notification. When a station cluster of potential concern has been identified, the department shall issue notification, as appropriate, to the landowners, lessees, onsite dischargers, adjacent dischargers, and other persons determined appropriate by the department if the hazard assessment as defined in WAC 173-204-530(3) results in identification of a cleanup site.

(4) No further cleanup action. No further cleanup action determinations shall be taken with station clusters of low concern until new information is available and the stations reexamined per subsection (5) of this section. Station clusters of low concern shall receive no further consideration for active cleanup, unless new information indicates an increase of chemical contamination at the stations in question. Station clusters of low concern shall be evaluated by the department for improved source control and/or monitoring requirements of this part.

(5) Reevaluation. The department may at any time reexamine a station or group of stations to reevaluate and identify station clusters of potential concern following the procedures of subsection (2) of this section when new information demonstrates to the department's satisfaction that reexamination actions are necessary to fulfill the purposes of WAC 173-204-500 through 173-204-590.