Beneficial Use Options

Before deciding amongst beneficial uses it is important to first determine whether the dredged material is acceptable for beneficial use. Evaluation of the contaminant status of the dredged material is the first step. In general, contaminated sediments will not be suitable for a majority of beneficial use applications. Thus, different applications may require decontamination or treatment prior to use. Other things to take into account are technical feasibility, environmental acceptability, physical alterations, costs/benefits, and legal constraints.

The distance of the proposed site from dredging project site, accessibility, mode of transport, rehandling requirements, and timing of the beneficial use need in relation to the dredging needs are things that need to be considered when evaluating the technical feasibility of a beneficial use application.

The use of dredged material in beneficial use applications must first consider all applicable legal constraints, including, but not limited to: state, county and local land use zoning laws; ownership of disposal sites; national, state and local regulations and standards.

Potential beneficial uses must take into account any compelling environmental considerations on a site-specific basis. Consideration must also be given to likely interference with other uses at or adjacent to the site. For instance, the creation of berms must avoid interference with other uses such as fisheries, ports, harbors, outfalls and intakes. The cleanliness of the sediment must also be considered due to the different degrees of contamination that would/would not be acceptable for some of the uses.

It is important for the physical, chemical and engineering characteristics of dredged material to be identified, including an examination of contaminants, prior to application to a beneficial use. These characteristics will largely determine which beneficial uses the specific dredged material is suitable for. Ecological impacts of the discharge of dredged material must also be taken into consideration.

Logistics must also be considered such as site utilization, transport, handling, storage, and dewatering.

Categories of Beneficial Use:
1. Land Improvement/Enhancement
a. replacement fill

E.g. - fill for abandoned/closed gravel or clay mines
-fill for obsolete canals/docks
-strip mine reclamation: would require large quantities of dewatered dredged material

b. capping

Dredged material is utilized as a cover for contaminated dredged sediment disposed in open water or on upland sites as a method of isolating the contaminated material from the surrounding environment.
E.g. - Brownfield remediation

c. land improvement

Dredged material can be used to improve the quality of land where the current land is not adequate to support a planned use or where the elevation is too low to prevent flooding.

d. Topsoil

Maintenance dredging produces sediment mixtures of sand, silt, clay and organic matter that can be excellent topsoil for use on agriculture fields.

e. Agriculture, Horticulture, Forestry

i. Agriculture: Livestock pastures requiring natural grass colonization; incorporation of dredged materials into marginal soils to provide additional nutrients
Considerations - heavy metal uptake by plants; salinity; oil and grease; nutrient availability; pH; water content
ii. Horticulture: Production of crops of vegetables, fruits, nuts, commercially grown plants, sod farms
iii. Forestry: used for improving marginal soil on timber land; dredged material can have higher contaminant levels than required for food production

f. Parks and Recreation

Include such developments as riverside/coastal picnic areas, water parks, marinas, athletic fields, golf courses, campgrounds, trails, and playgrounds

2. Shore Protection
a. beach nourishment

May be necessary along eroding beaches to protect the historic profile of the beach and to moderate the wave climate along the shoreline. Must also take into account the effects of dredged material placement on beach organisms. The dredged sediment used to nourish the beach must closely match the sediment composition of the eroding beach and be low in pollutants.

Concerns to keep in mind when considering this option include:
- impacts on benthic organisms
- impacts on offshore organisms
- impacts of dredge anchors and pipelines on environmentally sensitive habitats (e.g. seagrass beds, dunes)

b. in-water disposal

In-water disposal of dredged material is a beneficial use of the material. In recent years scientists have noted that the net sediment transport of the Columbia River has decreased. As a result, the beaches along the shores are not receiving the quantities of sand that they once did and erosion is threatening them. In-water disposal keeps the sand within the littoral system and helps feed the beaches.

c. berm creation

Berms are used to improve beach stability by modifying the shoreline wave climate. The berm may be designed to alter wave direction and to modify the rate/direction of local sediment transport. Could simultaneously be used for stockpiling sand for beach nourishment purposes

3. Habitat Enhancement
Habitat enhancement is attractive as a low-cost mitigation procedure that can be used to offset any environmental impacts that were incurred during disposal. Restoration or enhancement is preferable to habitat development.

Some environmental concerns related to these activities include the loss of open water habitat, loss of wetland systems, changes in the hydraulic and energy regimes and potential pollutant mobilization by plants growing on contaminated sediments.

Site selection should be based on knowledge of the ecological characteristics of the site. Including, but not limited to, foundation characteristics, salinity, tidal influences, bottom topography, benthic communities, adjacent habitat, and energy conditions.

a. Wildlife / Upland

Habitat development uses dredged material as a substrate in the establishment and management of relatively permanent and biologically productive plant and animal habitats. Creation of wildlife islands for colonial nesting waterbirds.

Potential for creation/enhancement of a variety of terrestrial communities ranging from dense forest to bare soil.

Disadvantages to this form of beneficial use include the possible need for long term management of the site, limitations on future land use at the site, costs associated with the rehandling of the sediment, management and control of resulting effluent to ensure it meets water quality standards

Factors to consider during site selection include: availability, capacity of disposal need, dredging area proximity, physical and engineering characteristics, environmental suitability, public acceptability, tidal considerations, and habitat development feasibility.

b. Island

Primarily for migratory colonial nesting waterbirds (e.g. Caspian terns, pelicans, cormorants, herons, egrets etc). Confined disposal facilities (generally designed for the permanent containment of contaminated sediments) may also be useful for such habitat

Additional sediment can be added to the island during the fall or winter when the birds are not there.

These islands tend to be attractive to nesting waterbirds because they offer isolation from ground predators and human disturbance; they have the ability to provide a wide range of habitat diversity to accommodate the nesting birds (e.g. bare ground, sparse cover, dense cover, and tall shrubs and trees); ongoing dredging operations can keep this type of successional habitat available.

c. Fisheries

Bottom mounding may improve fish habitat when combined with stabilization techniques such as planting seagrasses or capping with shell.

Creation of salt marshes for fishery organisms.

d. Wetland restoration

The are different ways in which dredged material can be used in the restoration of wetlands. Dredged sediment could be applied in thin layers to bring degraded wetlands up to an intertidal elevation. Wind and wave barriers may be created to allow the regrowth of native vegetation and to prevent erosion.

Potential problems with wetland restoration/creation are:
- project timing: coordination of biological and dredging schedules
- bioaccumulation: contaminant uptake by plants
- invasion of non-native plant species

e. Aquatic

The establishment of biological communities on dredged material at or below mean tide in coastal areas or in permanent waters in lakes and rivers. These include tidal flats, seagrass meadows, clam flats, oyster beds, fishing reefs, and freshwater aquatic plant establishment. Aquatic habitats have the potential to be highly productive biological units. In many cases, it may be feasible to include aquatic habitat establishment/enhancement as part of a wetland restoration project. A major disadvantage, to date, is the lack of knowledge concerning the techniques for the establishment of such biological communities.

4. Other
a. Construction products

Dredged material can be used in the creation of the following products: concrete aggregates, backfill, bituminous mixtures and mortar, bricks, ceramics, and insulation pellets. It may also be used as riprap/blocks for the protection of levees and slopes against erosion and for use on public roads for snow and ice.

b. aquaculture

Dredged material containment areas commonly possess structural features that enhance their suitability as aquaculture areas. These features include levees and water control devices. For instance, levees that would be constructed or that currently exist to contain dredged material could also serve to impound the water necessary for aquaculture.

Aquaculture has the potential to for production of low-cost protein, contributing to demand for seafood, increasing employment in supporting industries.

c. Industrial/Commercial Development

Port enhancement or expansion

d. Residential and Urban use

Use for fill, erosion control, foundation material

e. Airports

Runways and facilities

f. Roads

Foundation material for highway/road construction

 

Table C-1: Examples of beneficial uses in the Columbia River (& other sites)

Project/Site Name	Beneficial Use
Columbia River Shoreline	Beach Nourishment
Columbia River	Shoreline Stabilization
Columbia River levees	Flood Control
Coos Bay berms	Clam bed development
Miller Sands	Wetland/Habitat development
Skamokawa Vista Park, WA	sold for construction uses
Benson Beach, WA	Beach nourishment