accelerate the cleaning process. Exxon Corporation has supported an active oil spill response research program for nearly 30 years - the largest commitment in the oil industry. Exxon was able to call on its own experts to provide innovative methods for accelerating the cleanup rate. One technique to achieve this was a workhorse piece of equipment called the maxi-barge. These custom-built barges had a crew of 50, some 10,000 ft of boom, several oil skimmers, fuel and storage tanks, generators, and water heaters. Many were also provided with unique equipment to treat those shorelines not accessible by foot. Called an "omni boom," this is an adaptation of a system normally used for pumping concrete on construction projects. These were ideal for the rugged rocky shorelines commonly found in the Prince William Sound and helped to clean hard-to-reach areas safely.
A second innovative application was bioremediation, pursued in partnership with the U.S. Environmental Protection Agency. The concept, covered separately at this Symposium by Dr. A. Mearns of NOAA, involves stimulation of indigenous oil-degrading microbes through the addition of fertilizers to accelerate the rate of natural degradation of the oil. Exxon spent over 10 million US$ on applications of bioremedation during 1989 through 1991. A highlight of the Exxon program was development of a unique analytical approach to map the degradation rate by tracking the concentration of a non-degradable marker called hopane. In this way, the studies confirmed that addition of nutrient accelerated the removal of hydrocarbon by 3-5 times as compared to reference beaches which were not bioremediated (1). Over 120 km of shoreline were remediated in 1989 with dramatic results. Bioremedation was only used after bulk oil had been removed.
Another advance from the VALDEZ cleanup project was an improved understanding of how natural cleanup proceeds following oiling of shorelines. Natural processes have long been recognized as effective in removing spilled oil from the marine environment. Data collected at 16 monitoring sites in Prince William Sound showed significant continued reductions in shoreline oil content during the winter of 1989-90 after cleaning operations had ceased. On high and moderate nergy beaches, this natural cleaning appeared to be a result of wave action associated with winter storms. However, observations from low-energy areas showed similar removal without benefit of the wave action and this generated high interest in better understanding how oil is released from rock surfaces.
Exxon scientists, working with specialists who had previously studied beach cleaning phenomena, confirmed a mechanism for beach cleaning not previously reported in the literature. Interactions between fine mineral particles, such as clay, and polar components in the oil residue were found to play an important role by facilitating the mobilization and removal of both surface and subsurface oil (9). These interactions formed flocculated aggregates of a solids-stabilized emulsion in which small oil droplets are coated with micro-sized mineral fines and surrounded by sea-water. In this form, the oil no longer sticks to the sediment surfaces so that it can be removed even under low energy conditions. The large specific surface area of the flocculated oil promotes its eventual biodegradation by indigenous microorganisms.
This was a major advance. Subsequent to the VALDEZ cleanup, this mechanism has been confirmed for other spills where oil removal has occurred over time under low energy conditions. At the second International Oil Spill Research and Development Forum in London in 1995, oil spill experts from around the world collectively expressed high interest in this phenomenon and rated the continued improved understanding of the role of oil/fines interactions in shoreline cleaning as a top research priority. Several internationally-funded studies are now underway aimed at better clarifying how the learnings from VALDEZ and other spills can be turned into a pro-active technique for accelerating natural cleaning through addition of fine minerals such as clay.
The final shoreline cleaning advance to come out of the VALDEZ spill was a new chemical cleaner. Realizing that the Alaska North Slope crude on the shorelines was weathering rapidly with time, making removal by water wash more difficult, Exxon's scientific task force undertook the task of developing a low toxicity chemical product which could loosen the viscous oil and render it easier to remove without having to resort to very hot water. The preference was to identify an existing product that would suit this purpose. However, after screening more than 100 different formulas, none was found that met all the criteria established by the authorities: effective, Iow toxicity, non-dispersing. Therefore, Exxon scientists developed a brand new agent in a period of only a few months- the product now marketed as COREXIT 9580. After testing at several shorelines in Alaska, and considerable toxicity evaluation in New Jersey, Exxon was certain that COREXIT 9580 was an
