The Oregon Estuary Plan Book - p10

Dredged Material Disposal

Historically, dumping of material dredged from navigation channels and harbors has been a major source of damage to estuarine resources. Estuary plans will avoid or minimize further losses by identifying appropriate locations and techniques for disposing of dredge material.

Plans for each estuary where dredging is proposed include a dredged material disposal (DMD) plan. The DMD plan includes several components:

1. An estimate of the amount and location of dredging likely to occur over the next 20 years. This estimate is based on the development designations approved in the plan and needs for channel maintenance or deepening in approved navigation channels.
2. An analysis of potential sites and techniques for disposal of dredged material. The particular types of sites and methods for dredged material disposal vary, depending upon the physical setting of the estuary, the availability and cost of upland disposal sites, and the amount of material that needs to be dredged and disposed of.
3. Designation and protection of sufficient appropriate sites for future use for dredged material disposal.

Estuary plans contain a variety of approaches to protect designated dredged material disposal (DMD) sites. Despite differences, most protection measures preclude land uses on the site that would prevent its use for dredged material disposal. Temporary uses and other uses which do not involve extensive improvements, such as parking, storage, or farming, are allowed. Uses which would involve more extensive capital improvements or the extension of utilities are restricted or prohibited. Protective zones typically contain provisions which remove protective zoning once the site has been fully used for disposal. Some plans and ordinances allow protective zoning to be removed if the site is replaced by an equally suitable site.

Some jurisdictions have inventoried DMD sites that do not merit the same protection as priority sites. Called "Reserve" or Inventory" sites, they are generally not restricted as to permitted uses. Protection for these secondary DMD sites usually only involves special notice and review requirements for proposed land uses. Such provisions delay approval for up to 60 to 90 days to allow interested parties or agencies to negotiate for use of the site for dredge spoils before the land use is officially approved.

Types of dredged material disposal sites

Uplands - These are shoreland sites that are either vacant or have only minimal development. Often marginal agricultural lands are designated for dredged material disposal. In non-agricultural areas, dredged material disposal can serve to make a site more developable. In EFU-zoned areas, DMD plans typically require that the area be restored to agricultural use once disposal is complete.

Flow-lane disposal - Flow-lane disposal involves the dumping of dredged material back into the estuary to allow river currents and tidal action to push the added material out of the estuary. Designation of flow-lane sites requires careful study of estuarine hydraulics to assure that dumped material is adequately flushed out of the estuary and does not pile up and smother productive subtidal or intertidal areas.

Development sites - Dredged material is often used as a source of fill material for approved projects in development management units. It is difficult to estimate the capacity of such sites because the amount of fill allowed will usually be determined in the permit process, when the details of the particular project are known.

Ocean disposal - Ocean disposal of dredged material is regulated by the Environmental Protection Agency (EPA). EPA-approved sites are designated outside a number of the state's important ports, including the Columbia River, Tillamook Bay, Depoe Bay, Yaquina Bay, and Coos Bay. Ocean disposal involves transporting material offshore on a barge or in a hopper dredge to be dumped in open ocean waters.

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