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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.


Introduction 1, 2
  Study Area
  Previous Studies
  Seafloor Materials

K1-93 Survey
  Scope of Work
  Sidescan Sonar

  Sonar, 3.5kHz 1, 2, 3


  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

References 1, 2, 3

Understanding oceanic circulation patterns in Mamala Bay is an important link to understanding the ultimate fate of any associated contaminants. There is a paucity of data and current measurements in Mamala Bay, but studies currently underway by the Mamala Bay Study Commission will improve the oceanographic data base. Studies by Bathen (1974), Chave and Miller (1977a, 1977b, 1978a, 1978b), Neighbor Island Consultants (1977), and Tetra Tech (1977) during the 1977-1978 dredging cycle led investigators to conclude that the general ocean circulation in Mamala Bay is to the southwest, and in the vicinity of the South Oahu disposal site water movement is both tidally and seasonally controlled (Chave and Miller. 1977a, 1977b, 1978a, 1978b; Neighbor Island Consultants, 1977; Tetra Tech 1977; U.S. Environmental Protection Agency, 1980). Some investigators believe that subsurface currents at the Mamala Bay disposal sites may also be driven by tidally induced internal waves along the thermocline (Chave and Miller, 1977a, 1977b, 1978a).

Defining the ultimate fate of the silt and clay size particles contained in the dredged material will aid in determining the fate of associated contaminants. The dredging process loses an undetermined amount of silt- and clay-size material with excess water decanted from the dredge hopper prior to disposal, while another portion is dispersed in the water column at the time of disposal (Tetra Tech, 1977; U.S. Environmental Protection Agency, 1980). Shipboard observations indicate that while a large but unknown amount of silt and clay is lost during the dredging process, a major amount of fines are retained and disposed of at the site (Tetra Tech, 1977; U.S. Environmental Protection Agency, 1980). The 1977-1978 studies observed that an unknown amount of fines disperse from the disposal site in the form of a plume that moves to the southwest immediately following disposal. It is important to understand the local circulation patterns in order to quantify the amount of material contained in the dispersing plume, and to define its final resting site, because the finer components of the dredged material are most likely to contain the highest proportion of contaminants.


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URL: https://pubs.usgs.gov/of/1995/of95-017/04ocean.html
Maintained by: Michael Diggles
Author: Florence L. Wong
Last modified: May 27, 2005 (mfd)

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