Deepwater Gulf of Mexico - America's Expanding Frontier
SOURCE: U.S. Department of the Interior, Minerals Management Service, Gulf of Mexico OCS Region


Figure 12. Environmental and deepwater administrative features. (Click image to enlarge)
Figure 12. Environmental and deepwater administrative features.. (Click image to enlarge)

The extensive activity in the deepwater GOM requires thorough scientific knowledge and careful environmental considerations.

The Environmental Studies Program (ESP), initiated in 1973, gathers and synthesizes environmental, social, and economic information concerning offshore oil and gas activities.

The ESP expanded its focus to address particular issues as industry moved into deepwater. For example, studies were begun to evaluate the sensitivity of chemosynthetic ecosystems. Refer to Appendix D for a listing of selected deepwater environmental studies.

A biologically based grid system was developed as part of a comprehensive strategy to address deepwater issues. The grid system divided the Gulf into 18 areas or "grids" of biological similarity (figure 13).

Figure 13. Grid EA status. (Click image to enlarge)
Figure 13. Grid EA status. (Click image to enlarge)

Under this strategy, the MMS will prepare a programmatic environmental assessment (PEA) to address a proposed development project within each of the grids.

These grid PEA’s are comprehensive in terms of the impact-producing factors and in terms of the environmental and socioeconomic resources described and analyzed for the entire grid.

Other information on publicly announced projects within the grid is discussed, as well as any potential effects expected from their future developmental activities.

Projects selected for the grid PEA’s are representative of the types of development expected for the grid. For example, a good candidate for a grid PEA would be a proposed development of a new surface structure that might serve as a "hub" for future development within the grid.

Once a grid PEA has been completed, it will serve as a reference document to implement the "tiering" concept detailed in the National Environmental Policy Act’s (NEPA's) implementing regulations.

Future environmental evaluations may reference appropriate sections from the PEA to reduce duplication of issues and effects addressed in the grid NEPA document. This will allow the subsequent environmental analyses to focus on specific issues and effects related to the proposals.

Table 2 below shows the status of the grid PEA’s.

Table 2
Completed Grid PEA’s Within the Central and Western Planning Areas
of the Gulf of Mexico
Figure 7. Location of known gas hydrates in the Gulf of Mexico.

To continue implementation of its deepwater strategy, MMS issued Notice to Lessees and Operators (NTL) No. 2003-G03, “Remotely Operated Vehicle Surveys in Deepwater,” with an effective date of January 23, 2003.

The NTL requirements apply to activities in water depths greater than 400 m (1,312 ft) in the Central and Western Planning Areas of the GOM.
Operators submit a remotely operated vehicle (ROV) survey plan as an integral part of an Exploration Plan (EP) or a Development Operations Coordination Document (DOCD) that has a surface structure in one of the 18 grid areas.

The MMS will notify an operator in the EP or DOCD approval letter if the operator needs to conduct the ROV survey. The decision to require the survey is based on whether or not the grid area that contains the proposed activities has already received adequate ROV-survey coverage.

Figure 14 shows the location of existing ROV surveys.

Figure 14. ROV surveys including known chemosynthetic communities. (Click image to enlarge)
Figure 14. ROV surveys including known chemosynthetic communities. (Click image to enlarge)

Exploration and development activities in deepwater may have localized impact on benthic communities.

A description of these potential impacts is available in Gulf of Mexico Deepwater Operations and Activities: Environmental Assessment (USDOI, MMS, 2000).

The MMS believes that sensitive benthic communities such as chemosynthetic communities are protected by the existing review process, relying on NTL’s and mitigative measures that require avoidance of sensitive communities.

The ROV-monitoring surveys are intended to verify the effectiveness of mitigative measures and to ensure that previously unknown, high-value benthic communities do not exist in the vicinity of proposed activities. New information could lead to changes in the review process and in the mitigative measures required.

The deepwater GOM has an amazing diversity of about 20 species of whales and dolphins (cetaceans), including the endangered sperm whale. Sperm whales are the deepest diving cetacean, routinely engaging in 45-to-60-minute dives while chasing prey (predominately large squid) in 2,300-3,300 ft (701-1,006 m) of water.

Approximately 1,000 sperm whales can be found in the northern GOM. They are rarely seen in less than 2,300 ft (701 m) of water, and most likely are found at about 3,300-ft (1,006-m) water depths.
Although the whales move throughout the deeper Gulf, one preferred area is off the Mississippi River delta – an area with considerable oil and gas activity.

Sperm whales, like the majority of cetaceans, depend more on hearing than on vision to navigate, communicate, and find food.

They have complex sound-producing organs and equally complex soundreception and sound-processing capabilities. Since airguns create intense sound waves, there is concern that seismic surveys could damage whales’ hearing or interfere with their communications and biological sonar.

To date, there are no definitive data demonstrating the effect that airguns have on sperm whales and other cetaceans.

However, preliminary findings from ongoing studies suggest that sperm whales do not react to moderate levels of airgun exposure.

To mitigate potential impacts, MMS has engaged in a precautionary approach to regulating seismic operations. New rules require seismic vessels to

  • start airgun operations during daylight hours only,
  • ramp up airguns slowly when operations begin,
  • visually monitor for sperm whales within a 1,640-ft (500-m) radius, and
  • halt airgun operations if sperm whales are seen within a 1,640-ft (500-m) radius.

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