USA. California. 2006. San Diego-Tijuana border. New concrete barrier under construction with steel doors and numerical punch codes for Border Patrol entrance and exit. This wall is currently being built approximately one hundred yards north of the original steel wall, the construction of which began in 1994 under President Clinton's Operation Gate Keeper. The original wall was built from recycled steel once used in the Gulf War for helicopter landing pads. The Border Patrol is able to survey from various vantage points. A road runs along both walls for patrol access. In the most densely populated areas the wall is equipped with sensors and spot lights. This surveillance has driven migrants to cross in mountain and desert regions where many die of exposure and dehydration or may be attacked by vigilante groups on the US side.