effects of surface disposal are much more adverse 

 in freshwater areas. Because of tlie lack of saline 

 waters, the large volume of brine generated in the 

 Mermentau Basin is returned to disposal wells. 

 Part 3.5.3 discusses the environmental effects of 

 brine. In addition, large amounts of drill fluids 

 containing biocides are disposed of into reserve pits 

 (inland) or discharged into the Gulf. Little is knovm 

 about the environmental effects of these fluids. 



Large volumes of freshwater are an additional 

 requirement for well leaching. As an example, the 

 freshwater demand for the LOOP storage facility in 

 the Clovelly salt dome (in Barataria Bay, east of the 

 Chenier Plain) is estimated at up to 8.8 x lO"* m^ 

 (3.1 X 10^ ft^) per day. The maximum 12-month 

 withdrawal has been estimated at 30.56 x 10^ m^ 

 (1.08 X 10^ ft^). The impact of this withdrawal rate 

 would depend on the size of the watershed area and 



Table 3.4. The 1974 production of oil and gas in the Chenier Plain (Melancon 1977). 



Kcal 



equivalent^ 



(kcalx lO'^) 



Value*" 

 $1,000 



32.6 

 60.4 

 52.4 

 19.7 

 15.5 

 4.3 

 19.8 

 43.0 

 227.9 



53,151 

 114,011 

 75,633 

 52,405 

 37,045 

 14,235 

 51,280 

 91,092 

 437,572 



^Assuming one million Btu/mcf natural gas and 5.8 million Btu/bbl crude oil. 

 Calculated at the rate of $0.307/mcf for natural gas, and $6.52/bbl for crude oil. 



Table 3.5. Louisiana brine disposal by basin, 

 in mbbi (Louisiana Department 

 of Conservation 1977). 



Two potential developments related to energy 

 production on the northern Gulf coast may increase 

 the impact of brine. Both the Department of Energy 

 (DOE) and private corporations [e.g., Louisiana 

 Offshore Oil Port, Inc. (LOOP)] are leaching salt 

 from salt domes to create chambers for crude oil 

 storage. One such site is the Hackberry salt dome in 

 the Calcasieu Basin. Other sites are east of the Chenier 

 Plain in the Weeks' Island and Choctaw dome areas. 

 In addition, development of geothennal/geopressure 

 energy sources would require disposal of enormous 

 quantities of brine. Many potential brine disposal 

 locations are within the Chenier Plain (fig. 3-3; see 

 appendix 6.2 for well description). The possibility of 

 significant environmental modification by discharge 

 of this brine into the Gulf is currently under investi- 

 gation by the Division of Geothemial Energy (DGE). 



the flow of water through it. In Barataria Bay with an 

 upstream watershed area of 3,400 km^ (1,313 mi^) 

 and a mean annual rain surplus of 42 cm (16.5 in), 

 this withdrawal rate would be 1.7 to 3.4% of the 

 freshwater input (Gosselink et al. 1976). The impacts 

 of brine disposal are discussed in part 3.5.3. 



The probability of major oil spDls from transpor- 

 tation has been evaluated by Bryant (1974) from 

 U.S. Coast Guard data. He estimated a probability of 

 6.7 tons (6.1 tonnes) of crude oil spillage per vessel- 

 year of operation in the superport region east of the 

 Chenier Plain (table 3.6). This type of spill would 

 be expected only in the navigation channels and 

 approaches of the Calcasieu and Sabine waterways. 



The probability of pipeline spillage is extremely 

 small (table 3.7). Nearly all incidents are associated 

 with structural failure, ruptures, or leaks. Bryant 

 (1974) used an estimate of 320,000 km (198,839 mi) 

 of pipeHne in existence during 1971 and 1972 to cal- 

 culate an expected spillage of 16.3 l/km/yr(6.9 gal/ 

 mi/yr) or 0.008 incidents/km/yr (0.013 /mi/yr). 

 Extrapolating for the estimated 7,549 km (4,691 mi) 

 of pipelines in the Chenier Plain, an average annual 

 spillage of about 770 bbl/yr of crude oil is predicted. 

 Although this is small, the possibility of single large 

 accidents exists. 



30 



