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

US Geological Survey Scientific Crew
Michael E. Torresan (co-chief scientist)
Monty A. Hampton (co-chief scientist)
John H. Barber Jr. (geologist)
Peter Dartnell (geologist)
John T. Gann (navigator/software design)
Lawrence D. Kooker (electrical engineer)
Michael E. Boyle (electrical engineer)
Walter Olson (marine technician)

Summary of Field Operations
Cruise Dates: 20 February­26 February, 1993
(051/2200­057/1937 GMT).

The U.S. Geological Survey, Branch of Pacific Marine Geology conducted a geophysical survey off of Honolulu Hawaii, Hawaii, for the U.S. Army Corps of Engineers and the U.S. Environmental Protection Agency (figures 3 and 4). The survey was a follow­up to reconnaissance surveys conducted during the summer of 1991 in the vicinity of offshore dredged material disposal sites used for the disposal of dredge material from both Pearl and Honolulu Harbors. The geographic coordinates of the survey (table A1) define an area of about 254 km2. The survey employed sidescan­sonar and high­ resolution geophysical profiling to characterize the seafloor and surficial sediment both in, and adjacent to the disposal sites and two sewer outfalls located in Mamala Bay (figures 2­ 6). The purpose of the survey was to determine the character and topography of the seafloor in and around the disposal sites and outfalls, and determine the extent, thickness and nature of any associated deposits.

The survey was conducted aboard the University of Hawaii R/V Kila. The R/V Kila departed from the University of Hawaii Marine Center at Snug Harbor, Pier 45, Honolulu, Hawaii, at 051/2200 (1000 hrs Saturday, 20 February, 1993). We devoted the first few hours of survey time to streaming all gear and verifying that all systems were in proper working order. Once operational we collected chirp sonar and 3.5­kHz data along a predetermined reference line to "calibrate" and fine tune each profiling system. The survey commenced on 052/0500, along a series of nearly east-west lines, starting in shallow water and progressing seaward (figures 3 and 4). Lines ranged in length from 10 to 13 nm. Trackline spacing averaged 800 m, and survey speed was about 3 to 5 knots. Water depths ranged from a minimum of 20 m to a maximum of about 600 m (figure 5 and plate 1).

The survey was conducted in two phases. Phase one collected both sidescan sonar imagery and 3.5-kHz subbottom profiles, taking three days (February 20­February 23, 1993). Phase 2 also required 3 days (February 23­26, 1993), during which chirp sonar high-resolution subbottom profiles were acquired. Bathymetric data was collected during both Phase 1 and 2. The survey concluded Friday, 26 February, 1993 (057/1937). Over 300 line km of sidescan sonar, 3.5 kHz, and chirp sonar data were collected, and over 600 line km of bathymetric data were also collected. Survey Area, and Location of Dredged Material Disposal Sites and and Waste Water Outfalls