IV. ENVIRONMENTAL IMPACT OF THE PROPOSED SALE A. Impact on the Living Component of the Environment: An The possibility of impact from oil spillage is considered to be extremely low. This consideration is based on a prediction that a maximum spillage rate of 267 bbl. per year will result from the development of tracts included in this leasing proposal. The reason for such a low estimate of spillage rate is due to the fact that all tracts proposed for offering are gas prone (cf. the recent proposal to lease in oil prone areas off Mississippi, Alabama, and Florida, where the maximum predicted spillage rate was 91,510 bbl. per year). Nevertheless, we are sure that some oil will be spilled from time to time and that the potential impacts should be considered. OIL SPILLS It is important at the start, however, to point out that predictions of effects of oil at the community, even population, level have no firm basis in the existing literature. No studies aimed at determining the effects of spilled crude oil at the community level have as yet been accomplished in the Gulf of Mexico. Studies which encompass effects at the community level are unfortunately far removed geographically and not closely related to conditions in the Gulf. These latter studies include the commendable efforts of the scientists at Woods Hole in their study of the spill at West Falmouth, but the material spilled there was No. 2 fuel oil, generally conceded to be far more toxic than most crude oils. Also included are the studies at Santa Barbara and at Milford Haven and Cornwall England, which addressed various aspects of high energy beaches, natural beach erosion, rocky intertidal zones, large tidal ranges, natural oil seeps, pesticides and large quantities of emulsifiers. conditions of these studies are exactly duplicated in the Gulf of Mexico. Few of the The larger proportion of studies on oil pollution has been devoted to effects on small biotic groups or individual species, involving either accidental spills, controlled oilings, or laboratory aquarium studies, and the results are applicable at the cellular or organismic level. Thus, predictions of impact must be based on diverse and mostly unrelated studies, few of which are devoted to the Gulf of Mexico; conclusions, where made, must be regarded as tentative. In preparation of the Georges Bank Petroleum Study, MIT's Offshore Oil Task Group (1973) identified several pathways by which crude oils can exert a damaging effect on plants and animals. a) any disruption at or below cellular level is considered b) to be cellular effect any disruption above the cellular level dealing with effect c) any disruption of instinctive and/or voluntary control is considered to be a behavioral effect. They then defined five responses which are elicited by these three types of effects: 1) lethal toxicity, 2) sublethal disruption of physiological or behavioral 3) 4) 5) activities, the effects of a direct coating by oil, incorporation of hydrocarbons in organisms which cause tainting and/or accumulation of hydrocarbons in food changes in biological habitats. We have taken these responses and applied them to three broad categories of spills and the ecosystems they affect in Table 39. PIPELINE BURIAL, DRILLING MUD AND CUTTINGS DISCHARGE No attempt has ever been made to determine the effects of these operations on the marine and coastal ecosystems in the Gulf of Mexico, or, to our knowledge, anywhere in the world. This dearth of information will hopefully be remedied by future studies and the results of several promising current studies. It can be assumed that the effects of pipeline burial in offshore areas and wetlands will be qualitatively similar to those ascribed to channel dredging, but not as severe because: a) the physical dimensions of the excavation are much smaller Massive Oil Spill: Several hundreds to thousands of barrels Chronic Discharges and Minor Spills: Amounts small but very frequent or Lethal Toxicity: Sublethal Effects: continuous Interrupts physiological processes at cellular or organ Adverse effects on physiology of growth and reproduc- Coating with Weathered Oil: Large patches of tarry material which has Changes in Habitat: Lasting for several years, longer than the spill/ Shoreline: clean-up period. Intertidal to exposed beach; not including estuaries, bordering wetlands. b) the digging of a pipeline canal, or burial of a pipeline is a one-time event, whereas channel dredging is more or less continuous. It is tentatively assumed that the effects of drilling muds and cuttings discharges are also related to those of dredging, specifically, turbidity and smothering. Of further note is the presence of chromium in many marine drilling muds as the organic complex, (ferro) chrome lignosulfonate. Overboard loss or discharge of drilling fluids would introduce some of this chromium into the marine environment. On a weight basis, this element is present in unweighted commercial lignosulfonate drilling mud components at a concentration of about 12 ppt. Required sea water additions to the mud concentrate reduce this value to less than 4 ppt. the approximate concentration - of chromium in discharged drilling mud. In addition, dilution/ disperson effects associated with overboard discharge into Gulf waters would be considerable. Although data relating to toxicities of organic compounds containing chromium are scarce, recent work suggests that chrome lignosulfonate, in moderate to strong dilution, is relatively harmless. While readily soluble in sea water, the compound apparently dissociates very little. If inorganic chromate is also present in the drilling mud, however, oxidation of the chrome lignosulfonate occurs, evolving a new organic |