Image caption: From left, side scan sonar, macrofauna sediment sample processing and preparation, and sediment grab sampling.
Near many major U.S. coastal navigable ports, the U.S. Environmental Protection Agency (EPA) has permitted designated Offshore Dredge Material Disposal Sites (ODMDS) to control the deposition of dredged material generated during dredging operations.
ODMDSs are located near these frequently dredged areas to minimize impacts to benthic communities and not interfere with navigational channels. As part of the EPA’s planned expansion of these ODMDS to accommodate more dredge material, CSA Ocean Sciences Inc. (CSA) conducted high-resolution geophysical surveys off Port Aransas and South Padre Island and sediment sampling offshore Matagorda, Corpus Christi, and South Padre Island, Texas. The surveys and sampling provided on-going monitoring information within existing ODMDS boundaries and also baseline information for the potential expansion areas.
In July and August 2019, under a subcontract with Tetra Tech, CSA conducted high-resolution geophysical surveys aboard the CSA Surveyor vessel in the Aransas Pass and Brazos Island Harbor ODMDS areas to map and document water depths, bottom surface profiles, and identify the presence of any potential historical or archaeological sites of significance. The surveys provide bathymetric depth maps, sediment surface mosaics, and marine magnetic data.
In February 2020, EPA and CSA staff worked together to conduct sediment sampling in and around three EPA’s Region 6 ODMDSs offshore Texas. EPA and CSA staff conducted sampling operations aboard the Louisiana Universities Marine Consortium’s vessel, the Point Sur, offshore Matagorda, Corpus Christi, and South Padre Island’s Brazos Island Harbor. Sediment grab samples were collected from 90 sample locations in and around the three ODMDSs for analysis of sediment chemistry (industrial contaminants, metals, hydrocarbons, etc.), physical properties (sediment type and particle size), and the number and type of biological specimens collected in the sediment.