Three-year summary report of biological monitoring at the Southwest Ocean dredged-material disposal site and additional locations off Grays Harbor, Washington, 1990--1992

摘要

The Grays Harbor Navigation Improvement Project was initiated to improve navigation by widening and deepening the federal channel at Grays Harbor. Dredged-material disposal sites were selected after an extensive review process that included inter-agency agreements, biological surveys, other laboratory and field studies, and preparation of environmental impact statements The Southwest Site, was designated to receive materials dredged during annual maintenance dredging as well as the initial construction phase of the project. The Southwest Site was located, and the disposal operations designed, primarily to avoid impacts to Dungeness crab. The Final Environmental Impact Statement Supplement for the project incorporated a Site Monitoring Plan in which a tiered approach to disposal site monitoring was recommended. Under Tier I of the Site Monitoring Plan, Dungeness crab densities are monitored to confirm that large aggregations of newly settled Dungeness crab have not moved onto the Southwest Site. Tier 2 entails an increased sampling effort to determine whether a change in disposal operations is needed. Four epibenthic surveys using beam trawls were conducted in 1990, 1991, and 1992 at the Southwest Site and North Reference area, where high crab concentrations were found in the spring of 1985. Survey results during these three years prompted no Tier 2 activities. Epibenthic surveys were also conducted at two nearshore sites where construction of sediment berms has been proposed. This work is summarized in an appendix to this report.