The construction site is about two miles (3km) east of San Diego's Otay Mesa border crossing at the end of steel-mesh fencing that runs from the Pacific Ocean.
Construction began in Otay Mesa Tuesday on prototypes for a new border wall between the United States and Mexico, marking the start of a proposed project that served as a bitterly divisive centerpiece in President Donald Trump's ascension to the White House.
Local activists have dismissed the construction of the prototypes as "political theatre for a wall that has no funding, and has really no way to exist", NBC San Diego reports. According to CBP, they "will inform future design standard (s) which will likely continue to evolve to meet (U.S. Border Patrol) requirements".
The contractors are erecting eight prototypes in San Diego - four made of concrete and four of other materials. The companies have about 30 days to complete their prototypes. "Our multi-pronged strategy to ensure the safety and security of the American people includes barriers, infrastructure, technology and people", Ronald Vitiello, CBP's acting deputy commissioner, said in a statement Tuesday.
Four will be made of concrete, while the other four will be constructed of alternate or "other materials", CBP officials said.
The designs are between 18 and 30 feet, and will be evaluated on how well they deter climbers, how well they withstand breach attempts and what sort of awareness they allow agents who patrol the border.More news: United's Fellaini to miss CSKA trip
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Mr Trump recently said the wall should be see-through, in order to prevent people from being hit on the head with sacks of drugs.
Earlier it was reported that the total cost of the construction of a wall on the border with Mexico is estimated at $21.6 billion.
The President has since said he will find a way to make Mexico repay the U.S. for construction of the wall, but hewould require Congress to fund it first.
"The border between the USA and Mexico spans some 2,000 miles - the list of laws violated by the president's administration in order to build this campaign wall is nearly as long", Becerra told reporters then.
Funding to extend the wall beyond its distance of 1,046 kilometres is in doubt.