Weeks Island brine diffuser site study: baseline conditions and environmental assessment technical report

Abstract

This technical report presents the results of a study conducted at two alternative brine diffuser sites (A and B) proposed for the Weeks Island salt dome, together with an analysis of the potential physical, chemical, and biological effects of brine disposal for this area of the Gulf of Mexico. Brine would result from either the leaching of salt domes to form or enlarge oil storage caverns, or the subsequent use of these caverns for crude oil storage in the Strategic Petroleum Reserve (SPR) program. Brine leached from the Weeks Island salt dome would be transported through a pipeline which would extend from the salt dome either 27 nautical miles (32 statute miles) for Site A, or 41 nautical miles (47 statute miles) for Site B, into Gulf waters. The brine would be discharged at these sites through an offshore diffuser at a sustained peak rate of 39 ft/sup 3//sec. The disposal of large quantities of brine in the Gulf could have a significant impact on the biology and water quality of the area. Physical and chemical measurements of the marine environment at Sites A and B were taken between September 1977 and July 1978 to correlate the existing environmental conditions with the estimated physical extent of tthe brine discharge as predicted by the MIT model (US Dept. of Commerce, 1977a). Measurements of wind, tide, waves, currents, and stratification (water column structure) were also obtained since the diffusion and dispersion of the brine plume are a function of the local circulation regime. These data were used to calculate both near- and far-field concentrations of brine, and may also be used in the design criteria for diffuser port configuration and verification of the plume model. Biological samples were taken to characterize the sites and to predict potential areas of impact with regard to the discharge. This sampling focused on benthic organisms and demersal fish. (DMC)