MMS publishes deepwater Gulf of Mexico environmental assessment

The US Minerals Management Service has published an environmental assessment of the potential effects of deepwater Gulf of Mexico exploration, development, and production operations. The document is intended to be a planning tool to help envision the level of National Environmental Policy Act review that will be required for future deepwater work. MMS says most deepwater operations are substantially the same as those in shallow water and that no environmental impact statement is needed.


The US Minerals Management Service has published an environmental assessment of the potential effects of deepwater Gulf of Mexico exploration, development, and production operations. The document is intended to be a planning tool to help envision the level of National Environmental Policy Act review that will be required for future deepwater work. MMS concludes that most deepwater operations are substantially the same as those in shallow water on the Outer Continental Shelf and that no environmental impact statement is needed.

The study, "Gulf of Mexico Deepwater Operations and Activities: Environmental Assessment," is an evaluation of current and projected deepwater activities on the OCS during the 10-year period 1998-2007.

It said new discoveries are being made in progressively deeper water, leading to questions about effects on marine life, the fishing industry, water quality, air quality, and nearby communities' socioeconomic systems. The assessment sought to determine which deepwater activities are substantially the same as those on the shelf, which are substantially different, what effects the activities might have, and what mitigation measures are possible.

Marine life
Spills of deepwater-produced oil have the potential to cause catastrophic effects on marine life. Because some of this oil contains high concentrations of asphaltenes, a spill could deposit an impenetrable and nondispersing asphaltic concrete, rendering it incapable of sustaining life, says MMS. However, the likelihood of such spills is low.

Although most deepwater operations are essentially the same as those associated with conventional operations�e.g., anchoring, most drilling operations, and decommissioning�the study said seafloor discharges from pre-riser and riserless drilling operations and the discharge of synthetic drilling fluids may cause significant local impact upon chemosynthetic communities, such as tubeworms.

MMS said it has decided to alter Notice to Lessees and Operators 98-11 to recommend that deepwater wells be located at least 1,000 ft from potential high-density chemosynthetic communities. As the NTL goes through the formal review and implementation process, this mitigation is being applied on a site-by-site basis.

The assessment said that nonchemosynthetic benthic communities would likely be somewhat affected by structure placement, anchoring, and installation of pipelines, as well as mud discharges. Mud and drill cuttings discharged at the surface are expected to have little effect on deepwater ocean-bottom dwellers, because muds would be unlikely to reach the bottom beyond a few hundred meters from the surface-discharge location, and drill cuttings will be dispersed.

The deepwater study also said that coral reefs and other potential hard bottom communities not associated with chemosynthetic communities are very rare in deep water. However, they would be particularly sensitive to OCS activities. Those activities could permanently prevent recolonization of these sensitive habitats, said the study.

The MMS concluded that deepwater activities are unlikely to have long-term adverse effects on the size and productivity of marine mammals and sea turtles in the northern Gulf of Mexico, except in the case of an oil spill. Few lethal effects are expected, although stress and possible change in distribution due to exploration and production activities may have already altered the lifestyles of marine mammals and cetaceans.

Existing mitigation measures will likely be sufficient for many routine E&P operations, says MMS.

Deepwater drilling and production operations have the potential to deleteriously affect the fishing industry and fisheries, the assessment concluded. The offshore discharge of drilling fluids and produced water is expected to cause only negligible impacts. Factors like production platform placement and removal and accidental oil spills could cause deleterious effects. But in practice, the report said, actual effects on fisheries and the fishing industry from those factors are expected to be inconsequential and likely unnoticeable.

The MMS said it has historically considered the potential effects of sound from seismic surveys, even marine surveys, to be insignificant. This position has lately become controversial because of concerns about marine animals, so the MMS has commissioned a separate environmental assessment of the issue. That study will determine whether environmental impact studies will be required for seismic surveys.

Air quality
Air pollutants from OCS facilities can affect other facilities, fishermen, mariners, cruise ship passengers, marine mammals, sea turtles, birds, and to a lesser extent the onshore environment.

Current rules govern flaring and burning operations and should be sufficient, the report said.

Preliminary work indicates that stationary OCS sources will not be major contributors to exceeding SO2 limits, but they may be substantial contributors to the concentration of ozone. A subsea blowout could generate substantial quantities of volatile organic compounds, and thus ozone.

It is unclear what types, quantities, and locations of chemicals are transported, stored, and used by deepwater facilities, making it difficult to determine what the effects of accidental release might be. But current information suggests that such impacts would be relatively small or of short duration because of the relatively small size of most reported tanks, MMS concluded.

Water quality
Deepwater activities are expected to incrementally increase support activities and the expansion or construction of support bases. Most effects resulting from this growth�e.g., waste discharge, runoff, etc.�are common to all OCS support facilities and not specific to deepwater activities. Moderate, short-term water quality degradation may occur at a few support base locations, said MMS.

Over time, existing waste disposal practices for the deepwater industry may change and affect water quality as well; onshore fluid and cutting disposal may result in localized contamination onshore.

The likelihood of deepwater-related spills is considered very low. Also, because of the distance from shore, deepwater spills are not expected to cause different effects from spills in shallow water, even though some deepwater operations have the potential to cause very large oil spills. If, however, the spills occur in the Mississippi Delta and off southern Texas, a stronger current and proximity to shore may result in consequences to the coastlines.

Shuttle tankering of oil could also conceivably result in effects on coastal waters, according to the study.

And, finally, increases in usage of certain chemical products used to enhance throughput of oil and gas is expected in deep water. Some of those chemicals, if spilled, could cause a more serious threat to marine water quality than oil spills.

Socioeconomic effects
The MMS report concluded that the socioeconomic effects of deepwater activities are largely positive.

Most of the jobs created by deepwater Gulf of Mexico activities are expected to be filled by people already in similar jobs and by the unemployed and underemployed people in the region. Some importation of skilled labor may be required.

Texas and Louisiana will probably get most of the support-oriented jobs. MMS predicts only minor social and cultural problems associated with migration.

The income created should provide positive effects for the community. Some existing onshore facilities may be expanded and some new ones created.

MMS found that NEPA documents, established project-specific and program reviews, and existing mitigation measures adequately protect the environment and human life. Those activities that are substantially different from shallow-water OCS operations can be addressed through additional mitigation measures, preparation of a more-detailed environmental assessment or environmental impact statement, or additional research and scientific studies.

Mitigation measures proposed by the environmental assessment will be studied by a team of scientists.

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