When the department considers a watershed analysis for approval under WAC 222-22-080 or 222-22-090, the department will perform a review under SEPA as a nonproject proposal. When making the SEPA threshold determination, the department shall only make a determination of significance if, when compared to rules or prescriptions in place at the time of the analysis or the reanalysis, the prescriptions will cause a probable significant adverse impact on elements of the environment other than those addressed in the watershed analysis process.