17.36.324 SEWAGE SYSTEMS: FLOODPLAINS
(1) The applicant shall identify the location of any floodplain on the lot layout document. The department may require the applicant to provide additional information, such as elevations at specific locations.
(2) The applicant shall submit evidence adequate to allow the department to establish the location of the floodplain if:
(a) the federal or state government has not designated the floodplain, or if the location of the floodplain is in question with respect to a proposed subdivision; and
(b) the stream is shown as an intermittent or perennial stream on the most current USGS 7 1/2 minute (1:24,000) topographic map (unless the applicant provides adequate information that the stream is not subject to flooding) .