K1-95-HW: Cruise Report 1995 - Preliminary results.

Phase III: Sediment Chemistry and Biological Sampling Survey

M.E. Torresan, M.A. Hampton, J.H. Barber, Jr., and F.L. Wong

U.S. Geological Survey Open-file Report 95-839

1995

This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards. Any use of trade names is for descriptive purposes only and does not imply endorsement by the USGS.

Summary
Introduction
Study Area
Previous Studies
  Designation
  Monitoring 1, 2
Methods
  Vessel
  Navigation
  Sampling
  Subsampling 1, 2
Results
Acknowledgments References 1, 2

Figures
1 Location
2 Box corer

Tables
1 Stations
2 Samples
3 Analyses
4 Bioassay

Appendices
1 Box Cores
2 Custody: Quanterra
3 Custody: Batelle

PREVIOUS STUDIES

Site Designation Studies
The South Oahu disposal site designation studies were conducted during 1977 and 1978 for the COE and EPA. The primary purpose of the 1977-1978 studies was to collect field and laboratory data to define the baseline environmental conditions, with the aim of documenting the environmental impact of the ocean disposal of harbor dredged material in Mamala Bay (Chave and Miller 1977a, 1977b, 1978a, 1978b, Neighbor Island Consultants, 1977; Tetra Tech, 1977; Goeggel, 1978). The three topics examined were the biological effects to the benthic and demersal communities, the geological effects on the existing bottom sediment regimes, and the effect on water quality. The results are summarized in a 1980 Environmental Impact Statement (EIS) prepared by the EPA (U.S. Environmental Protection Agency, 1980). The site designation studies led the EPA and COE to conclude that dredged material disposal would not have adverse effects on the environment of Mamala Bay, and that the South Oahu disposal site is a suiTable disposal site (U.S. Environmental Protection Agency, 1980).

Cooperative Disposal Site Monitoring Studies (1)
The surveys conducted by the USGS in conjunction with the COE and EPA in 1993 and 1994 "inventoried" the seafloor with acoustic techniques and bottom sampling to determine the character of the seafloor and near-surface substrate, to delimit the extent and potential transport pathways of dredged material and any associated contaminants, and to determine the values for specific contaminants of concern in near-surface seafloor sediment in and around disposal sites. The first seafloor monitoring study commenced in February 1993, and culminated with the production of a sidescan sonar mosaic of the seafloor and a detailed bathymetric map (Torresan 1993a, 1993b, 1994, and 1995). The 1994 survey focused on "ground truthing" the 1993 sonar and seismic-reflection data. Employing reflection profiling, seafloor video and still photography, and bottom sampling, the focus of the 1994 work was on ascertaining what the composition of the seafloor at specific sites was, thus verifying the nature of the acoustic signatures visible on the sidescan sonar mosaic. Results are summarized below.

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