US Army Corps of Engineers
Seattle District

Dredged Material Management Office (DMMO)


The Seattle District DMMO is the main point of contact for the interagency Dredged Material Management Program (DMMP). The DMMP brings together agencies with roles in management and regulation of dredged material to streamline testing and decision-making.  Together the DMMP agencies manage a network of multiuser open-water disposal sites in Washington State.



Contact the DMMO

Seattle District (CENWS)
Dredged Material Management Office
PO Box 3755
Seattle, WA 98124-3755


USACE Seattle

USACE Seattle

News and Updates


Now Available: DY18/19 Biennial Report

The Biennial Report for Dredging Years 2018 and 2019 is now available on the Reports, ESA, and History page (at the very bottom).  The Biennial Report compiles information on all DMMP projects, testing data, disposal information and monitoring results for the given reporting period. The DY18/19 report covers June 16, 2017 through June 15, 2019.


DMMP Project-Specific Issue Resolution Process

In response to the recommendations made by the 2016 Ecology and DNR Management Review of the Dredged Material Management Program, DMMP agency managers and staff developed a process for elevating individual project decisions before the management of all four DMMP agencies.  The issue resolution process may be used to address issues or disagreements with DMMP determinations before or after decision documents are signed.  This issue resolution process was presented at the 2019 SMARM and is now in effect and available for use by project proponents.  Detailed information on the project-specific issue resolution process is available on the User Manual page.


2018 DMMP User Manual

A new, updated version of the DMMP User Manual is now in effect.  For more information and a link to the document, see the DMMP User Manual page.



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The Dredged Material Management Program (DMMP) consists of four agencies that work collaboratively to make sure that material proposed for dredging in Washington State is appropriately tested and managed. The DMMP agencies are the U.S. Army Corps of Engineers, Seattle District (USACE); the U.S. Environmental Protection Agency, Region 10 (EPA); the Washington Department of Ecology (Ecology); and the Washington State Department of Natural Resources (DNR).

The federal government, ports, marinas and other entities dredge to maintain navigational waterways and berth depths when those areas are filled in by natural sediment deposition. The DMMP agencies oversee testing for contaminants to determine what material can be disposed of at open-water disposal sites. The state-owned sites are managed by DNR. The DMMP does not manage contaminated sediment cleanups--those are managed by cleanup programs within Ecology and EPA.
Dredging affects the lives of nearly every Washington State citizen and visitor.  Maintenance and navigation dredging is done frequently in harbor areas, ports and marinas. These areas naturally silt in. Dredging is performed to maintain the depths needed for boats to operate, and to develop new areas or achieve increased depths for boat access. A significant component of Washington's economy depends on navigation and commerce, which in turn depends on dredging the state's waterways; between 2000 and 2015, over 50 million cubic yards of dredged material have been dredged and disposed of at the open-water disposal sites.

An extensive analytical, public process was used 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 non-dispersive.

Dredged material placed at non-dispersive sites remains on-site and is the subject of long-term monitoring.  Non-dispersive sites are managed to allow minor adverse effects such as sub-lethal effects to some species after long-term exposure.

Dredged material placed at dispersive sites--which are located in areas with strong tidal currents--disperses quickly. 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 non-dispersive) and two dispersive estuarine sites each in Grays Harbor and Willapa Bay. 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.

The multi-agency, multi-state RSET (Regional Sediment Evaluation Team) is an umbrella organization whose role is to provide a consistent regional framework for the evaluation of dredged material.  RSET developed the Sediment Evaluation Framework (SEF 2016) as a guide to regional sediment testing.  The RSET is tasked with maintaining and updating the SEF based on customer feedback and changes in science and national policy. 

Both the DMMP User Manual and the Sediment Evaluation Framework for the Pacific Northwest are used in the Northwest for evaluating the suitability of dredged material for unconfined aquatic disposal. 

The interagency DMMP covers most projects in Washington State:  all Puget Sound and coastal Washington projects should reference the DMMP User Manual and related guidance when developing characterization plans. Projects on the Washington side of the Columbia River--EXCEPT for Washington public ports--should also use the DMMP guidance.  Questions regarding sediment evaluation for DMMP projects should be directed to the DMMO team.

The Portland Sediment Evaluation Team (PSET) is headquartered at the USACE Portland District, and functions similarly to the DMMP for Oregon projects. The PSET agencies include the Portland District, Environmental Protection Agency, Oregon Department of Environmental Quality, Washington Department of Ecology, U.S. Fish and Wildlife Service, and National Marine Fisheries Service. The PSET evaluates dredging and habitat restoration projects in the Portland District, including dredging projects proposed by the Washington public ports on the Columbia River. The SEF should be used for Portland District projects.  Questions regarding dredged material testing and evaluation procedures for Portland District projects (including Corps dredging permits) should be directed to the PSET Lead.