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Torresan, M.E., Hampton, M.A., Gowen, M.H., Barber, Jr., J.H., Zink, L.L., Chase, T.E., Wong, F.L., Gann, J.T., and Dartnell, P., 1995, Final report: acoustic mapping of dredged material disposal sites and deposits in Mamala Bay, Honolulu, Hawaii: U.S. Geological Survey Open-file Report 95-17.

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

 STUDY AREA
Mamala Bay is the embayment situated between Diamond Head on the east and Barbers Point on the west, along the south coast of the island of Oahu, Hawaii (figures 1­6 and plate 1). The disposal sites are located in the north portion of Mamala Bay, about 5 km south of Honolulu International Airport, in the north­central reaches of a broad, gently sloping trough that slopes to the southeast (figure 5 and plate 1). The trough is bounded on the west by submerged reefs and banks, and on the east by an escarpment that defines the seaward edge of the narrow and shallow (< 50 m) shelf that hugs the south Oahu coast (figures 5, 6 and plate 1). The bay is floored primarily by carbonate sand, and water depths at the sites range from 300 m to nearly 600 m, with the South Oahu disposal site having a mean water depth of about 450 m (figure 5 and plate 1).

PREVIOUS STUDIES
South Oahu disposal site designation studies were conducted during 1977 and 1978 for the COE and EPA. The primary purpose of the 1977­1978 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 studies were conducted in three phases: (Phase 1) Pre­disposal studies, (Phase 2) Disposal studies, and (Phase 3) Post­disposal studies. 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). These site designations studies led the investigators and the EPA to conclude that there was no evidence to suggest that dredged material disposal would have adverse or deleterious effects on the environment of Mamala Bay, and that the South Oahu disposal site is a suitable harbor dredged material disposal site (U.S. Environmental Protection Agency, 1980).

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