Workers begin to fill tunnels at Mexican border

SAN DIEGO —  Workers poured concrete into the largest tunnel under the U.S.-Mexico border Tuesday as federal authorities began an effort to fill subterranean passages that were created to funnel drugs north.

Five tunnels in California and two in Arizona will be filled during the next two months to permanently close off pipelines that smugglers in some cases had managed to reuse after border authorities discovered them. The project comes three months after The Times reported that the tunnels had not been filled in, largely because of jurisdictional issues and lack of funding.

The U.S. Department of Homeland Security provided $2.7 million after Sen. Dianne Feinstein (D-Calif.) demanded the tunnels be closed, calling them a national security risk.

Workers began drilling holes Tuesday into the so-called El Grande tunnel, which runs for nearly half a mile between warehouses in Tijuana and San Diego.

The tunnel, which features reinforced walls and ventilation and lighting systems, presented unique challenges that required weeks of preparation, authorities said.

Drugs and bodies have been found in tunnels in the past. So workers sent a robot into the tunnel’s depths to look for obstructions. The robot sent back images of digging tools, but found no major blockages.

The tunnel featured a water-pumping system, but groundwater had flooded much of the passage since it was abandoned more than a year ago. Workers pumped thousands of gallons of water out of the tunnel, which is an average of 80 feet below the surface. They then drilled holes every 40 feet along its length before beginning to pour in the concrete. It is expected to take three days and more than 100 truckloads of concrete to fill the passage, authorities said.

The number of border tunnels has grown sharply in response to a massive increase in above-ground enforcement. More than 50 have been discovered in the last few years, but most are small, crudely built passages that are easily destroyed.

U.S. authorities have typically left the bigger tunnels largely intact, capping them only at the border and exit points. Smugglers have reused at least two large tunnels after digging around those caps.

The project will fill tunnels on the U.S. side, but the state of passages on the Mexican side is unknown. U.S. authorities say they don’t know how much progress authorities have made there.

Mexican authorities want to close off their side, too, but they lack the resources and technology to do so, said Frank Marwood, head of the San Diego-based U.S. Tunnel Task Force. It includes agents from Immigration and Customs Enforcement, the U.S. Drug Enforcement Administration and U.S. Customs and Border Protection.

The Tijuana-based Arellano-Felix drug cartel is suspected to be behind the construction of El Grande, which authorities stumbled upon in January 2006 when they found an opening in an Otay Mesa warehouse. More than two tons of marijuana was found near the tunnel, and a Los Angeles-area man arrested at the warehouse later pleaded guilty to drug-related charges. No other suspects have been arrested.

Later this month, authorities are expected to start filling in the so-called Taj Mahal of tunnels, another passage running from Tijuana to San Diego that features concrete flooring and lighting. It was discovered 13 years ago. Three tunnels in Calexico and two in Nogales, Ariz., will also be filled, authorities said.

richard.marosi@latimes.com