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Title: Aquatic disposal field investigations, Galveston, Texas, offshore disposal site : evaluative summary
Authors: Wright, Thomas D.
Mathis, David B., 1947-
Brannon, James M.
Keywords: Sedimentation and deposition
Water quality
Sediment transport
Dredged material
Dredging spoil
Galveston (Tex.)
Publisher: U.S. Army Engineer Waterways Experiment Station
Series/Report no.: Technical Report (Dredged Material Research Program (U.S.)) ; no. D-77-20
Abstract: An investigation of the physical (sedimentological), chemical, and bio-logical impacts of dredged material disposal was conducted in 1975 and 1976 at an authorized disposal site offshore from Galveston, Tex. A hopper dredge was used for dredging and disposal, and most of the dredged material consisted of clean sand and sandy silt from the Galveston Bay Channel. A small amount of contaminated material from the Texas City Turning Basin was also placed in the disposal site. Three areas within the site were employed for disposal. Two reference areas, also within the site, were chosen to provide a basis for distinguishing natural changes from those which might result from disposal. The disposal and reference areas were selected on the basis of information obtained from a predisposal pilot study. The physical (sedimentological) effort consisted of the installation of equipment to determine current direction and magnitude, overflights to assess turbidity, sediment grain-size analyses, bathymetric surveys for the rate of disposal mound erosion, and sediment tracers (labelled sediment) to describe the direction of sediment transport. The chemical studies were oriented toward the determination of changes in the water column during dredged material disposal and in the sediments after disposal. Although a number of variables were evaluated, primary emphasis was placed upon heavy metals, nutrients, and changes in dissolved oxygen. The primary thrust of the biological investigations centered upon the impact that disposal of dredged material might have upon communities of bottom-dwelling organisms (benthic macroinvertebrates). Samples were taken to determine the numbers and kinds of organisms present in disposal and reference areas before and after disposal. The results indicated that the authorized disposal site was appropriate for the disposal of material from the areas that were dredged. Sediment movement after disposal was away from the dredged areas; disposition would not occur in navigation channels. As expected, material deposited in the shallow parts of the disposal site had a rather rapid rate of erosion and dispersal, while that placed in the deeper areas tended to remain in place throughout the study period. The chemical impact of disposal on water quality and sedimentological parameters was minimal. Although some changes were observed, these could best be described as having little, if any, significance and were difficult to separate from natural variation in the reference areas. Biological impacts also appeared to be of marginal significance. Changes in the abundance and types of organisms in disposal areas could not be distinguished from changes in reference areas. There appeared to be very large seasonal (natural) changes in organism abundance, and these changes coincided with the disposal of dredged material.
Description: Technical Report
Gov't Doc #: Technical Report D-77-20
Rights: Approved for Public Release; Distribution is Unlimited
Appears in Collections:Technical Report

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