NWFSC 1993 Publications/Coastal Zone and Estuarine Studies Division
Benthic and epibenthic invertebrates, fishes, and sediments at and adjacent
to a proposed new site for Area D, an in-water dredged-material disposal
site in the Lower Columbia River, 1991.
G. T. McCabe, Jr., S. A. Hinton, & R. L. Emmett
Final Report to U.S. Army Corps of Engineers, Contracts E96910017
and E96910040, 42 p.
The U.S. Army Corps of Engineers (COE), Portland District, is responsible
for maintaining navigation channels in the Columbia River estuary. This
responsibility requires annual dredging and disposal of millions of cubic
yards of bottom sediments. One in-water disposal site in the lower estuary,
commonly referred to as Area D, no longer provides safe operating depths
for large dredges, so the COE has proposed relocating the disposal site
immediately downstream from the present Area D (Fig. 1).
In February 1991, the COE contracted the National Marine Fisheries Service
(NMFS) to conduct two biological surveys: one in March and one in June 1991.
These surveys were conducted at the proposed site for Area D and two adjacent
areas to provide baseline information concerning species composition and
abundance of benthic invertebrates, Dungeness crabs (Cancer magister),
shrimps, and fishes. Subsequently, the COE funded two additional surveys,
which were completed in September and December 1991.
Study areas adjacent to the proposed Area D included a reference area of
similar depth (Stations 8-11) and a deeper-water area (Stations 12-14) (Fig.
1). Sampling stations in the reference area were established to serve as
reference sites for stations in the proposed Area D (Stations 1-6). The
deeper-water area is downstream and northwest of the proposed Area D. This
deeper-water area may be less biologically productive than the proposed
Area D, and therefore could be a possible alternative disposal site.
Preliminary results from the March, June, and September 1991 surveys were
presented in previous progress reports. This report presents final results
for all four surveys.
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