U.S., Mexico soon to delineate gulf 'gap'

The governments of Mexico and the U.S. are expected to soon begin negotiating a division of the previously disputed "western gap" in the central Gulf of Mexico.

The two countries formally enacted the 1978 maritime boundary treaty last month, during Mexican President Ernesto Zedillo's visit to the U.S.

Negotiations would permanently demarcate the maritime border between the two countries in the gulf, thus eliminating any doubts as to where the U.S. Minerals Management Service can offer leases for petroleum exploration and production.

Concerns have mounted in Mexico in recent months over apparent encroachment of MMS leasing in the disputed area, especially with a surge of interest by companies in the deepwater Gulf of Mexico.

Treaty background

Although the boundary treaty was first signed by the executive branches of Mexico and the U.S. almost 20 years ago, the U.S. Senate foreign relations committee did not ratify it until Oct. 26 of this year.

Ratification was delayed at first due to fears that the U.S. was unnecessarily giving away potential hydrocarbon resources in the deepwater central gulf. The issue subsequently faded in importance until, in recent years, oil companies began to lease tracts closer and closer to the then-provisional boundary. Due in part to encouragement from the U.S. petroleum industry, the U.S. State Department, and the Department of the Interior, the full Senate gave its consent to the treaty last month.

The treaty delineates the maritime boundary between the two countries in waters 200 miles or less from their respective coastlines. Two areas in the central gulf, however, fall beyond 200 miles from either country, and must be divided in negotiations according to the Law of the Sea Convention (see map, OGJ, Apr. 22, 1996, p. 31). The eastern of the two "gaps," as they are known, also involves Cuba and is thus unlikely to be addressed in the near future because of the dicey geopolitical implications involved.

Negotiation concerns

The western gap is to be divided in bilateral negotiations between the U.S. and Mexico, and according to State Department officials, this process is now about to begin.

The first step in dealing with the gap is to determine if the region meets the legal definition of continental shelf, which under international law allows the two countries to divide the gap bilaterally. This step is not expected to be controversial.

Once the region is defined as continental shelf, the most common division method is to draw an equidistant line across the gap, measuring from the coastline of each country. This was the same method used for drawing the original treaty line.

However, in bilateral negotiations other methods may be used, and special circumstances may be brought up. Article 76 of the Law of the Sea does not actually provide any formula for dividing continental shelf. It merely states: "Delimitation of continental shelf between states with opposite or adjacent coasts shall be effected by agreement on the basis of international law in order to achieve an equitable solution."

Negotiations timetable

According to Ash Roach, attorney advisor to the Office of Oceans, International Environment and Scientific Affairs, talks with Mexico are likely to begin next year, but he would not say how long it would take to finalize the gap demarcation.

"One would like to do it quickly, but we have no idea what Mexico's position is," Roach said. "For that matter, we haven't even got our own fully resolved. Often, these things take time not because there's any substantive difficulty, but you need to get good data...One of the things that has to be done is to get good current survey data. You have to have common data before you can even begin to measure what you would put forward as an equidistant line."

Leonora Rueda, Director General of Mexico-U.S. frontier issues at the Mexican Foreign Relations Secretariat, agreed that it might take some time to gather all the technical data required to divide the gap and added that an equidistant line was the most likely method to be used to close the gap.

Rueda added that the two countries may have to discuss the division of resources located underneath the gap, should the resources cross the boundary. "If there are trans-frontier resources, there already exists mechanisms between the U.S. and Mexico for the exploitation of these resources, for example, for underground water or river water," she said.

Negotiations with Mexico are to be led by Mary Beth West, Deputy Assistant Secretary for Oceans and Space.

U.S. leasing history

Although the western gap has not yet been formally divided, MMS has been offering leases in the northern portion of the gap-the part likely to end up on the U.S. side-for the last several years.

For the last lease sale covering the western gap, last Aug. 26, MMS included a clause in the lease notice stipulating that bids for tracts in the gap would remain sealed until March 3, 1998. If the gap boundaries have not been resolved by that time, the bids are to be returned unopened to the companies involved. Companies are allowed to withdraw their bids any time before this date.

According to MMS officials, bids were submitted for tracts in the western gap, but details of the bids are unknown. If the gap remains open for the next lease sale, expected for March 1998, the same stipulations are likely to apply.

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