Proceedings of Strategic Petroleum Reserve Workshop on Environmental Considerations of Brine Disposal Near Freeport, Texas

The proposed brine disposal outfall considered at this workshop will be located in the Gulf of Mexico 5 miles offshore from Freeport, Texas. Brine at a concentration of about 300 ppt will be discharged through a diffuser into fifty feet of water. The fate of the brine was studied using a numerical model which considered the waste field in three zones. The near field zone had a length scale of about 100 feet. Dilution in this zone was primarily by turbulent jet mixing and the brine concentration was reduced to 3 to 5 ppt above ambient at the end of the near field. The intermediate field or second zone was characterized by buoyant lateral spreading and had a length scale of about 1000 feet. The far field zone had a length scale of about 10,000 feet before the concentration of brine reached 0.1 ppt above ambient. Dilution in the final zone was primarily by natural diffusion and dispersion. One major concern expressed at the workshop was that perhaps the increased salinity from the brine disposal operation would interfere with the migration of shrimp and other marine organisms into the estuaries. In general, it was recommended that any outfall should be located away from the major passes so that the brine waste field would not interfere with the movement of marine organisms into the estuaries. The proposed disposal site at Freeport is in a white shrimp spawning area as well as a spawning area for a number of fishes. In addition to salinity and the concentration of individual constituents in the brine, the ratio of certain ions are important in toxicity studies, particularly the ratio of calcium to magnesium. It was pointed out that the high jet velocity (25 feet per second) from the diffuser ports could create a barrier to movement and the turbulence could have harmful effects on the shrimp larvae. A complete chemical analysis will be required of the (1) brine, (2) displacement water used during the drawdown phase of the operation, and (3) leaching water used for the enlargement of the storage caverns. The temperature of the brine from the salt dome was estimated to be about 100 degree Fahrenheit which is 10 to 50 degrees Fahrenheit above ambient depending on the season of the year. The concentrations of the hydrocarbons in the brine during the refill operation are not known and additional information should be obtained and/or additional studies should be conducted to determine the concentrations of hydrocarbons in saturated brine. It was pointed out that the French had observed 17 ppm oil and grease in saturated brine from their salt dome storage of petroleum. Shrimp larvae were recommended for bioassay work because they are considered to be more sensitive to environmental changes than the other stages. Since polychaetes are a major food supply for the shrimp, they were also recommended for bioassay tests. Because of their sensitivity and availability, it was suggested that tests be conducted on the larval and juvenile stages of red drum. It was also suggested that bioassays be conducted on the juvenile southern flounders. Physical, chemical and biological monitoring of the disposal area will apparently be required to verify projections and to insure that disposal operations will not cause unknown adverse impacts. In order to establish baseline conditions, it was recommended that some pre-construction monitoring be conducted. Because of the large natural variations, it was also suggested that control areas, subject to the same natural variations as the disposal area, be established in the monitoring program. EPA is interested in insuring that certain water quality parameters not exceed their limits at the boundary of the mixing zone and that there will not be any unreasonable degradation within the mixing zone.