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Dredged Material Management Office

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The Seattle District DMMO is the main point of contact for the interagency Dredged Material Management Program.

The DMMP includes all dredged material management programs in the State of Washington: Puget Sound Dredged Disposal Analysis (PSDDA); Grays Harbor/Willapa Bay; the Washington side of the lower Columbia River (with the exception of port districts); and other marine and freshwater locations.

This website is updated frequently with meeting announcements, program information and decision documents.  Please check back for updates.

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The Dredged Material Management Program (DMMP) consists of four agencies that work collaboratively to manage and regulate the disposal of dredged material from dredging projects in Washington State. These agencies include 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 DMMP manages material dredged to maintain navigational waterways and berth depths when those areas are filled in by natural sediment deposition. The DMMP agencies 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 2006, approximately 20 million cubic yards of dredged material were dredged and disposed of at the open-water disposal sites.

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.

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 2009) 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.  Regional sediment evaluation policy questions and recommended modifications to the SEF should be directed to the RSET Lead

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 Users 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.

News & Updates

Save the date: SMARM 2015 will be held on Wednesday, May 6, 2015. For past SMARM summaries and all program modifications made through this annual public meeting process, see the SMARM page.

Kenmore Federal Navigation Channel:  The suitability determination and data report have been posted on the Suitability Determination page. 

UPDATED USER MANUAL:  Updates include program changes implemented via the 2014 Sediment Management Annual Review Meeting (SMARM).  See the User Manual page to download and and to view related content.

Contact the DMMO

Mailing Address Seattle District
Dredged Material Management Office
PO Box 3755
Seattle, WA  98124-3755
Phones 206-764-6083