June 21st, 2017 
(KPBS) — By Jean Guerrero
The inside of the
Photo by Jean Guerrero
Under the corrugated steel plates that divide the U.S. and Mexico in Otay Mesa, dozens of clandestine cross-border tunnels slash through the soil.
As President Trump looks to build new barriers along the border, criminal organizations in Mexico are improving the tunnels they use to smuggle people and drugs under the border fence – making them smaller and maintaining a high level of sophistication, featuring electricity and railways.
Smuggling tunnels vary in shape and size, but generally fall under one of these three categories, according to U.S. Border Patrol:
— Rudimentary tunnels, or “gopher holes,” are cheaply made and stretch short distances, maybe 50 feet. They are used to smuggle humans or small quantities of drugs under the border.
— Interconnecting tunnels exploit existing municipal infrastructure, linking up with storm drains and sewer lines. They are used to smuggle humans and drugs under the border.
— Sophisticated tunnels can stretch for long distances (the longest ever found was equivalent to the length of eight football fields) and are often equipped with lighting, electricity, ventilation, water pumps, railways and more. They are used to move large volumes of drugs under the border.