(CNN)Eight prototypes bidding to become the model for President Donald Trump's proposed border wall cost between $300,000 and $500,000 each to build -- with the Department of Homeland security footing the bill.
Trump's wall hasn't been built yet, but it's already cost local taxpayers millions
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But since construction of the prototypes began in September, 2017, the taxpayers of San Diego have paid about $2.3 million to protect them.
According to the San Diego Police Department and San Diego Sheriff's Department, the two local agencies have been helping to provide security around the structures. The majority of the $2.3 million was spent during the one-month construction phase from September 26 to October 26 of 2017. During that construction phase, 298 sheriff's deputies were provided for security duties.
"We're not there to protect the walls, we're there to protect the people," said Lt . Karen Stubkjaer of the San Diego Sheriff's Department. "We are providing life and safety protection to those who might come to protest and view the prototypes."
The eight prototypes were chosen by Customs and Border Protection to be built along the border in Otay Mesa, near San Diego.
The San Diego Sheriff's Department spent $1,585,749.75 in salaries, overtime pay and supplies between September 26, 2017 and March 13, 2018, according to documents obtained via the California Freedom of Information Act.
The sheriff's department primarily assisted Customs and Border Protection during protests and Trump's visit to view the prototypes in March. The single biggest expenditure was on manpower, as deputies earned $701,061 in overtime hours.
The sheriff's department was the lead agency on one protest at the site of the prototypes on December 7, 2017, which cost the department $60,570.
"We base our staffing ... on how many people we're expecting at the protests," said Stubkjaer.
Trump and Vice President Mike Pence both visited the prototypes on separate occasions. During the President's visit, on March 13, he praised the construction and said he preferred the walls with "see-through" capabilities. That visit cost the sheriff's department $155,918.75.
The San Diego Police Department spent a total of $751,375 between September 26, 2017 and April 27, 2018.
Overtime accounted for $226,368, while salaries and benefits accounted for $450,597. Supplies and services ran to $74,410 -- used to purchase Tasers, pepper-ball launchers and projectiles to be used during protests. $10,602.60 was spent on microphones, earpieces and two-way radios.
According to the police department, there were two scheduled protests on its watch -- one in October, 2017, during the construction phase of the prototypes and one during Trump's visit in March.
"The only time we deployed officers to the area was during the October and March protests," said Lt. Brent Williams of the San Diego Police Department. "We didn't have to use ammunition for either of those two events."
Neither law enforcement agency expects to be reimbursed by the federal government for their expenses.
"Our mission during the border wall construction and the presidential visit was public safety and we will not be reimbursed for costs incurred in fulfilling that mission," said Stubkjaer.
The eight prototypes in Otay Mesa will remain as part of the border infrastructure. Eight duplicate prototypes were built at an undisclosed location so DHS could conduct testing of the walls including anti-breaching, anti-climbing, anti-digging, and safety protocols for border patrol agents.
A Customs and Border Protection spokesperson said the testing phase has concluded and the department is now evaluating which wall -- or parts of various walls -- it will use.