D. Impact on Air and Water Quality 1. Impact on Air Quality The quality of air over the sale area could be degraded by exhaust emissions of stationary power units and service vessels, and by the accidental release of oil and gas from wild wells. The impact of exhaust emissions is unknown, but thought to be small and unimportant. According to one authority 1/ the average composition of Natural Gas as delivered to pipelines in the U.S. is: (Small amounts of sulphur and other materials could also be present in some localities.) If the wild well were not burning, obviously, the above gases would be released into the air. If the gas well was on fire, combustion would be essentially complete and the emissions would consist almost entirely of carbon dioxide (CO2) and water; the nitrogen would remain as N2 and any sulfurous gases would be oxidized to SO2. The resulting impact would not be great. 1/ Henry A. Ley, "Natural Gas", in Geology of Natural Gas, Amer. Assoc. Petrol. Geol. Tulsa, Okla. (1935) pp. 1073-1149. as cited by Levorsen (1958). If a wild oil well were releasing crude oil onto the water, the result ing impact would be substantially greater. If the oil does not burn, a significant amount of it will evaporate. During the Chevron, 1970, spill it was estimated that 15% of the roughly 30,000 bbl. spilled evaporated. At an average density of 310 lb./bbl., this incident would have introduced almost 14,000 lb. of hydrocarbons into the air. Some oil spills in the past have resulted in fires. A reasonable estimate of the range of emissions, assuming complete com bustion, that an oil well fire could produce per 1,000 bbl. burned, might be as follows 1/: (As a point of reference, during the Chevron 1970 fire and spill, the maximum spillage rate was estimated to be 1,000 bbl. per day.) Combustion of oil would in reality be incomplete, however, and emission would contain somewhat less of the above compounds, but would include, 1/ Values used in calculation are based on world averages for crude oil of 310 lb/bbl.; Percent content of weight is: carbon 82.2 to 87.1, sulfur - 0.1 to 5.5, nitrogen- 0.1 to 1.5 (Levorsen, 1958). 2/ SO2 emission would be less for Gulf of Mexico crudes, which range from 0.1 to 0.5% sulfur. in addition, such materials as volatilized petroleum, particulate carbon, carbon monoxide, nitrous oxide, sulphur monoxide, along with other altered or partially oxidized matter. There is no reliable way to predict in advance the relative volumes of each of these possible emissions because it would depend, among other things, upon moisture content of the air, wind speed, pattern of oil spray from wild wells, number of wells involved, chemical content and physical character of the oil itself, and types of equipment and materials other than oil that might also burn. Massive spills from wild wells are not the only source of spilled oil. Information presented in section III. B. 2. c. demonstrates that over 800 bbl. were spilled in the first nine months of 1972 as the result of an equal number of minor spills. The net result is that a small amount of spilled oil is floating somewhere on the waters of the northwestern Gulf almost continually. Concern has been expressed 1/ that the evapo Gulf. ration of this spilled oil may be the cause of the substantial levels of hydrocarbons which have been detected in the sea breeze coming off the Preliminary surveys 2/ indicate that the content of reactive (smog-producing) hydrocarbons in the sea breeze between Corpus Christi and Port Arthur are at a level three times higher than the national average. At the present time there is no hard evidence as to the source of these materials. 1/ Personal communication with Mr. Kenneth Ports. Texas Air Pollution Control Service. At this time, we are unable to predict the degree of deterioration in air quality that will occur because of this proposed sale. 2. Impact on Water Quality The natural condition of sea water may be altered and de graded in several ways during oil and gas operations. Debris and bilge will be released into Gulf waters from the many seismic vessels, crew boats, tugs, and service and supply boats used throughout the operation. No estimate can be made of the quantities involved. They should be similar to amounts released off all types of vessels nationwide. During drilling operations, drilling fluids and drill cuttings will be discharged into the sea. Most drill cuttings in the Gulf consist of sand and shales and therefore cause no turbidity, but settle to the bottom quite rapidly, on the order of minutes. It has been estimated that 1,700 barrels of cuttings are discharged overboard during the course of drilling an average 10,000 foot well. The production and discharge of formation waters (oil-field brines) has been discussed earlier (section III.A.3.b.). Three components or properties of formation waters contribute to water quality degradation when released into the sea. One is the small amount of entrained liquid hydrocarbon. There are some locations disposing of formation water where the treatment equipment puts out an entrained oil averaging less than 50 ppm. Louisiana. This contrasts sharply to the average sea water salinity of 35,000 mg/1. The third degrading property results from the fact that formation waters are devoid of dissolved oxygen. Unfortunately, no estimate of the amount of formation water to be discharged as a result of this sale can be made at this time. Water quality could be further degraded as the result of accidental oil spills. It was estimated in section III.B.2. that, based on the 1971-72 rate of oil spillage, 267 bbl. per year could be spilled from tracts included in this sale. In addition, a few hundred bbl. per year will likely be released through minor spillage. Part of this spilled oil would be removed by clean-up operations and some would evaporate, but the largest proportion would probably be dispersed into the waters of the Gulf. |