As in all real estate decisions, location, location and location is key when figuring out where to dig a drug smuggling tunnel in the San Diego area.
Go too far west and the ground will be sandy and potentially soggy from the water of the Pacific Ocean. That could lead to flooding, which wouldn't be good for the drug business. Too far east and you'll hit a dead end of hard mountain rock.
But, in a strip of land that runs between roughly the Tijuana airport and the Otay Mesa neighborhood in San Diego, there's a sweet spot of sandstone and volcanic ash that isn't as damp as the oceanic earth and not as unyielding as stone.
"It's really the ideal place for a tunnel," said Pat Abbott, a geology professor at San Diego State University. "It's quite easy to dig through. You could do it with a pickax."
And because both sides of the border are heavily industrialized, earth-moving equipment including trucks carrying large loads don't necessarily stand out.
"It's not uncommon to see that kind of commercial traffic, so it's so easy to hide," said Dave Shaw, the special agent in charge for Immigration Customs Enforcement Homeland Security Investigations in San Diego.
Not surprisingly, the majority of the 27 drug passages discovered in California over the past decade were located in the Otay Mesa area, according to law enforcement officials. The latest example was a half-mile tunnel near the corner of Enrico Fermi and Marconi drives that officials raided last week.
That bust was the third tunnel authorities have discovered along Marconi Drive since 2010.
In 2015, authorities shut down a half-mile tunnel in Otay Mesa that also led to Tijuana, seizing 12 tons of marijuana and arresting 22 men. A task force arrested six suspects and seized more than 32 tons of marijuana after closing a passage in same area in 2011. And in 2010, law enforcement closed two passages in the same neighborhood.
Overall, authorities have discovered almost 190 tunnels along U.S. borders over the last decade. Most were unfinished.
The Otay Mesa tunnel most recently found ran between a Tijuana flophouse to a fenced-in lot and ran about 2,600 feet, the length of about nine football fields, according to law enforcement officials, who had been watching the business since late 2015 after receiving a tip.
On April 15, sheriff deputies stopped a truck coming from the site with more than 13,000 pounds of drugs. The six men arrested in connection to the tunnel face charges including conspiracy to import and distribute cocaine.
Shaw said drug cartels adjust to law enforcement tactics. Undoubtedly, some tunnels are being dug right now.
"If we completely caught every tunnel, they would stop doing it," he said.
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