What kinds of materials are produced and discharged overboard during OCS offshore oil and gas activities?

During drilling, water-based drilling muds and cuttings are discharged overboard, whereas during production, the major discharge is produced water. In addition, treated sanitary and domestic wastewaters, deck drainage, and miscellaneous wastes, such as ballast waters, may be discharged at some point in the operation. Oily muds, produced sands, and trash and debris are produced but cannot be discharged overboard.

Aren't waste materials routinely dumped overboard with few restrictions?

No. In fact, many materials cannot be discharged overboard at all. Those that are must first be treated and tested prior to discharge to meet various limitations and requirements set by the Environmental Protection Agency (EPA). Simple dumping does not occur; the rate that a discharge occurs is controlled and restricted. After studying environmental impact data collected over the last 20 years and reviewing new technological advances, the EPA recently published new discharge limitations and more restrictive general permits for the offshore oil and gas industry. In 1993, the EPA published limitation guidelines on oil and gas discharges; these guidelines are based on "Best Available Technology." This means that if a technology exists that can limit the discharge and/or its contaminants, even if no environmental effect has been shown to occur, the oil or gas operator must use this technology or a compatible one. For example, new limits based on improved operating performance of a new gas flotation technology were set on the amount of oil and grease in produced waters. In addition to these restrictions, before any discharge can take place, the EPA must also issue an NPDES permit. Considering possible effects occurring in a particular location, new permits include further restrictions and monitoring requirements on discharges.

Who regulates these discharges?

As noted, the EPA has a major role in regulating offshore discharges. However, the Minerals Management Service (MMS) also shares in this role. MMS may require lessees and operators to regulate effluent discharges further by imposing "mitigating measures" on certain operations. Through these measures, the MMS could require operators to (1) conduct a bottom survey to locate sensitive features or areas, (2) relocate operations to avoid sensitive areas, (3) shunt drilling fluids and cuttings to the ocean bottom, thus decreasing the time these materials are suspended in the water column, (4) monitor activities to assess the adequacy of mitigating measures, and (5) regulate discharge rates. Before a company begins drilling or production activities, the MMS evaluates and approves each operation. In addition, the MMS routinely inspects drilling sites to make sure that all such waste materials are properly disposed of.

What are drilling muds?

Drilling fluids or "muds" are used during drilling operations to remove rock cuttings, lubricate and cool the drill bit and string, control the formation pressure, and seal the well. About 95 percent of all drilling mud comprises water, clay, and barite. The rest are additives, such as starch, lime, soda ash, or sodium bicarbonate. Oil-based muds require special permits and are used for high temperature wells, deep holes, or when hole stabilization poses a problem. As noted, drilling muds are regulated by the EPA and are discharged overboard only if they meet EPA's requirements.

What is produced water?

Produced water is mainly salty water trapped in the reservoir rock and brought up along with oil or gas during production. It can contain very minor amounts of chemicals added downhole during production. These waters exist under high pressures and temperatures, and usually contain oil and metals. Because of this, they must be treated prior to being discharged overboard. As with drilling muds, following treatment, they must be tested for toxicity and cannot exceed set discharge rates. In the Gulf of Mexico area west of the Mississippi River, where elevated levels of naturally occurring radioactive material (NORM) have been detected, radium must be measured and bioaccumulation monitored if the produced water is to be discharged overboard.

Don't produced water and drilling muds contain toxic chemicals?

The major components of most drilling muds and produced wastes have not been found to be toxic. However, to prevent toxic effects from additives or unknown contaminants, all drilling muds and produced waters are tested for toxicity before being discharged overboard. If they fail the toxicity tests, the materials cannot be discharged.

Won't these discharges cause long-term and widespread effects on the marine environment?

More than 30,000 wells have been drilled in the Central and Western Gulf, and no one has documented long-term or widespread effects from this drilling. More than 400 exploratory wells are safely drilled in the Gulf of Mexico each year. In particular, a study of the impacts of drilling six wells offshore Florida showed no long-term toxic effects MMS Study 93-0021.

Don't these discharges kill fish and harm the marine environment?

A number of environmental studies have examined the effects of oil and gas discharges around platforms. Many of the early studies were conducted in shallow-water areas and examined discharges with characteristics not allowed today. Some 23 drilling mud discharge field studies and 7 produced water studies were reviewed by EPA as part of the development of their new regulations. None of these studies detected harmful effects to fishes, observed toxic effects, or documented any regional scale impacts. Drilling muds and cuttings were found to settle very rapidly to the bottom, and the produced water plume rapidly dispersed. Sublethal effects to small organisms, such as worms that live in bottom sediments, and some elevated compounds were detected in the sediments adjacent to some platforms. At present, the Department of Energy, the EPA, and MMS are all conducting studies to understand more about these sublethal effects and to determine if any bioaccumulation may be occurring.