Summary

Introduction 1, 2
  Study Area
  Previous Studies
  Oceanography
  Seafloor Materials

K1-93 Survey
  Methods
  Scope of Work
  Navigation
  Sidescan Sonar
  Bathymetry
  Profiling

Results
  Bathymetry
  Sonar, 3.5kHz 1, 2, 3

Conclusions

Figures
  1   2   3   4   5
  6   7   8   9 10
11 12 13 14 15
16 17 18 19 20

Plate 1

Apx 1: Statistics 1
Apx 1: Statistics 2
Apx 2: Equipment 1
Apx 2: Equipment 2
Acknowledgments

References 1, 2, 3

Figure 2 shows the location of three major disposal sites in Mamala Bay (the former Pearl Harbor site, the former Honolulu Harbor site, the active South Oahu site), two U.S. Army Corps of Engineers study sites used as part of the process for designating the South Oahu site in 1980 (U.S. Environmental Protection Agency, 1980) and a 1972 disposal site. The South Oahu disposal site receives the most dredged material and currently serves Pearl, Honolulu, and Barbers Point Harbors (figure 2). From 1959 through 1978 disposal sites in Mamala Bay received about 5.3 million m³ of dredged materials from both Pearl and Honolulu Harbors (U.S. Environmental Protection Agency, 1980, table 3-4). Of that total, Pearl Harbor accounts for about 87% (4.7 million m³) while Honolulu Harbor generated the remaining 13% (0.6 million m³) of the dredged material (Goeggel, 1978; EPA, 1980, table 3-14). In comparison to all Hawaiian Island disposal sites, the South Oahu site receives the overwhelming majority of dredged material, approaching 90%. For example, in the 1977-1978 dredging cycle each Hawaiian harbor was dredged, and all five Hawaiian disposal sites were used. Of the total amount of dredged material disposed of in 1977-1978 (about 2.1 million m³), 71% (1.47 million m³) originated from Pearl Harbor, and 17% (0.35 million m³) was dredged from Honolulu Harbor, totaling 88% (Tetra Tech, 1977; Goeggel, 1978; U.S. Environmental Protection Agency, 1980). The remaining 12% (0.26 million m³) of dredged material was disposed of at the four other sites combined (Goeggel. 1978; U.S. Environmental Protection Agency, 1980, table 3-14 and figure 3-5).

In February 1993, the U.S. Geological Survey (USGS) conducted an acoustical survey in Mamala Bay for the U.S. Army Corps of Engineers (COE) and the U.S. Environmental Protection Agency (EPA), to determine the character of the seafloor and near-surface substrate, and to delimit the extent and potential transport pathways of dredged material and any associated contaminants (Torresan and others, 1994a). Trackline coverage for the survey is shown in figures 3 and 4. Tables located in Appendix 1 list the locations of each disposal site, the waste water outfalls, and the start and end coordinates for each trackline run for the 1993 survey. Data collected from the survey was used to plan strategies for a sediment sampling cruise (conducted May 9-23, 1994; Torresan and others, 1994b), with the goal of assessing both geological and environmental impacts to Mamala Bay resulting from dredged material disposal.