(CN) - An unflattering Homeland Security audit released Tuesday shows that U.S. Customs and Border Protection has little to show for its massive investment in drones.
The Office of Inspector General's announcement on the report, titled "U.S. Customs and Border Protection's Unmanned Aircraft System Program Does Not Achieve Intended Results or Recognize All Costs of Operations," calls drones "dubious achievers."
It found that drone surveillance assisted law enforcement with less than 2 percent of illegal border crossing arrests in 2013.
The program accounted for 1 percent of marijuana seizures by Border Patrol in Arizona, and 4 percent in Texas.
And while Customs and Border Patrol (CBP) claims that drones allow it to monitor the entire U.S.-Mexican border, the majority of drones operated within a 100-mile zone in Arizona, and 70-mile stretch in Texas, according to the report.
"We believe it is misleading for CBP to report that its unmanned aircraft operate over every stretch of the southwest border," when its flights over California and New Mexico appeared to be part of a different mission, the OIG said.
CBP also "drastically" understates the costs of the program, according to the report.
Because the drones were often grounded by weather, they were airborne for only 22 percent of the goal of 16 hours per day, 365 days per year, the audit also found
That puts the program's actual price tag, including salaries for operators, equipment and overhead, at $12,255 per flying hour - five times CBP's estimate of $2,468 per hour, according to the report.
In 2013, the agency spent at least $62.5 million to operate the program.
"Notwithstanding the significant investment, we see no evidence that the drones contribute to a more secure border, and there is no reason to invest additional taxpayer funds at this time," Inspector General John Roth said in a statement. "Securing our borders is a crucial mission for CBP and DHS. CBP's drone program has so far fallen far short of being an asset to that effort."
The audit recommends that CBP abandon its plans to invest $443 million more on additional drones, "and put those funds to better use."
CBP has said that insufficient funds means that it has no plans to expand its fleet at the moment, but the OIG's response implied that this reasoning side-stepped the audit's most important finding - that the program has been largely ineffective despite spending millions of dollars on it.
The OIG also recommended that the CBP develop some measurable goals for the program, and ensure that it report all costs associated with the program in the future.
CBP concurred "in principle" with these recommendations, the 37-page report notes, but disputed the use of cost per-flight hour as a measure of the program's efficiency. It indicated that it would continue to use its old methodology for calculating costs, according to the report.
The OIG says "CBP's current methodology includes about 20 percent of the full cost to own and operate unmanned aircraft."
CBP told the OIG it would not adopt a reduction of border surveillance costs as a performance measure.
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