By Julie Etra

In the form of crude petroleum, oil floats, at least for a while, depending on a number of variables and their interaction. Microbes can biodegrade up to 90% of some light crude oil, but the largest and most complex molecules––like the ones that make up road asphalt––are not significantly biodegradable. When refined petroleum products are spilled, their fate depends on their composition. Gasoline, kerosene, and diesel fuel are so volatile and easily biodegradable that they rarely persist in marine environments, although they can remain longer if buried in sediment, soils, groundwater, or marshes where oxygen levels are very low. Heavy fuel oils contain a large proportion of heavy components that biodegrade very slowly.

PEMEX (Petroleos Mexicanos), which is operated by the Mexican government, has six oil refineries in Mexico, listed below.

• Tula Refinery, Hidalgo
• Salina Cruz Refinery, Oaxaca
• Cadereyta Refinery, Nuevo León
• Salamanca Refinery, Guanajuato
• Minatitlán Refinery, Veracruz
• Ciudad Madero Refinery, Tamaulipas

The refineries of Veracruz and Tamaulipas are located on the Gulf of Mexico, while Salina Cruz, is located on the Pacific, specifically the Isthmus of Tehuantepec.

On September 7, 2017, the 8.2 earthquake centered on the Isthmus caused a tanker spill at Monoboya # 3 in Salina Cruz, where oil tankers load the crude which is eventually delivered to various refineries along the Pacific coast. Oily black crude petroleum contaminated the beaches of Salinas del Marqués, Zaachila, Garrapatero and Rincon Bamba, according to the the leader of the Union of the Fishing Industry, Ansélmo López Villalobos, and according to statements by the fishermen and other locals. The spill was detected at dawn after the quake. Pemex, the nationalized supplier of petroleum products, reported that the valve damaged by the earthquake had been sealed and the spill controlled. However, by noon following the quake the fishermen discovered that the leak had continued and actually increased. Pemex divers found that the damaged valves were responsible and were eventually sealed. The spill never reached Huatulco, the main concern of officials. The short- and long-term impacts of this leak on fisheries and coastal communities were not readily available.

And what is a monoboya, or monobouy? It is a floating structure that takes crude from the tankers, which is eventually delivered to the refineries. Unloading from the tankers is a complicated process.

Crude discharge begins with the mooring of the tanker for pumping to this floating device. The Port Captain directs the operation, which also involves auxiliary boats and over a dozen professionals. Once the ship has been moored to the monobouy, two unloading lines are connected through a connector or manifold. The discharge lines comprise two 20-inch floating hose lines, with a total discharge capacity of 40 inches. In addition, the mooring arm has the ability to articulate to facilitate the entire process of connection and disconnection. This allows the ship to move with the currents and winds around the monobouy throughout the unloading process. The floating hoses include a double casing as a safety measure, as well as a leak-detection system that is checked periodically. Once the crude reaches the monobouy, it descends 60 meters through two lines of 20-inch hoses to the seabed, where through pipes, valves, and 42-inch manifolds it is drilled into a reinforced concrete pipeline that transports it directly to the refinery’s tanks. Throughout the processes of connection and disconnection, a team of divers constantly monitors the operation.

Given the State of Oaxaca’s frequent seismic activity, it appears that Salina Cruz will continue to be vulnerable to leaks and spills.

Another spill occurred October 11-12 in the Gulf of Mexico, resulting in 7,000 barrels being released. This, however occurred south of Louisiana, under U.S. jurisdiction. From what I have read, most of the spills and leaks in the Gulf of Mexico are the result of transnational operations in U.S. waters.

However, on January 7, 2018, a second spill occurred in Mexico in Agua Dulce (ironically meaning fresh water), Veracruz (Gulf of Mexico). This was a particularly nasty spill as the pipelines, which deliver oil to the municipality of Las Choapas, are located along streams. This spill plus the previous spill may have had a major impact on the fisheries and the 1,000 to 2,000 fisherman of the Río Tonalá near the site of the spill. Not surprisingly, neither the city council, headed by Sergio L. Guzmán Ricardez, nor PEMEX officials offered a statement and declined to report on the regional environmental impacts of the oil spill, either short- on long-term.