The DMMP agencies went through an extensive public process to define open-water sites for dredged material disposal, and to define the guidelines for dredged material that can be disposed at these sites. There are two types of sites, dispersive and nondispersive. Dispersive sites are located in areas with strong tidal currents; dredged material placed at these sites disperses quickly.
Dredged material placed at nondispersive sites remains on-site and is the subject of long-term monitoring; nondispersive sites are managed to allow minor adverse effects, such as sub-lethal effects to some species after long-term exposure. No adverse effects are allowed at dispersive sites, so dredged material must meet more stringent evaluation guidelines to be eligible for disposal at these sites.
There are eight dredged material disposal sites around Puget Sound (three dispersive and five nondispersive) and two dispersive estuarine sites each in Grays Harbor and Willapa Bay. Additionally, Grays Harbor has one 3.9-mile Ocean disposal site. The DMMP agencies collectively evaluate the suitability of dredged material for disposal at these sites. As owner of the state's aquatic lands, DNR manages the disposal sites and is responsible for environmental monitoring of all nondispersive disposal sites.