In-Situ Measurements of Physical Forces, Geotechnical & Biological Parameters in Coastal & Estuarine Systems, Galveston District
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abstract
A new series of dredged material placement areas are proposed to be sited in the vicinity of Atkinson Island and the Mid Bay Placement on the east side of the Houston Ship Channel. There are believed to be historical oyster mining areas throughout Galveston Bay. Shell mining in Galveston Bay has resulted in a great deal of spatial heterogeneity in geotechnical properties and ignoring these features can result in the structural failure of the installation of dredge spoil placement facilities. Because these pits have filled with soft, unconsolidated mud, there tends to be either very subtle or no surficial expression of them. The purpose of this project is to conduct a geophysical and geological survey to delineate any oyster pits or other geological hazards that may exist within the proposed placement area. Included in this project will be the collection and analyses of four cores, two collected within oyster pits and two from outside of the oyster pits to assess the differences in geotechnical properties of the seabed. The geophysical assessment will include: 1) a side scan sonar mosaic collected at 150% coverage, using a frequency of 250 kHz or higher, to identify and delineate any surficial features or anomalies, including oyster reefs or changes in the substrate; 2) a single beam echosounder survey, collected along the side scan transect lines to map the bathymetry across the site; 3) a high-resolution seismic survey using a CHIRP subbottom profiler or equivalent ultra-high resolution seismic system for subsurface identification and delineation of oyster pits and other subsurface features; 4) a magnetometer survey to identify pipelines and any identifiable metal debris.
