A federal grant does not cover all of the costs of local border-security enforcement, a memo between the Pima County Sheriff’s Department and the county administrator shows.

In response to county supervisors voting earlier this month to reject a $1.4 million Operation Stonegarden grant, County Administrator Chuck Huckelberry requested additional information from the Sheriff’s Department about costs and reporting.

The Board of Supervisors is scheduled to reconsider its decision Tuesday after Supervisor Ramón Valadez, one of three Democrats who voted to reject the grant, said he now has more information and will change his vote. The board’s earlier vote was 3-2 to reject the grant, with Republican supervisors dissenting.

The Operation Stonegarden grant pays for overtime and equipment to help local law enforcement agencies better collaborate with the U.S. Border Patrol to secure the border. Pima County had accepted the grant since 2004.

One of the board majority’s recent concerns was about the cost of accepting the grant and what it could mean for the county’s retirement obligations, because overtime pay earned by deputies increases the pensions they’re due. Huckelberry has said every dollar of overtime requires the county to pay an additional 67 cents into the state retirement fund on behalf of a deputy.

In the memo since sent to Huckelberry, Sheriff’s Department Chief Karl Woolridge explained that all employer-related expenses were covered under the grant.

But the mileage reimbursement is about half of what the county estimates is the actual cost of maintaining and repairing county vehicles used in Operation Stonegarden.

While the county gets reimbursed about 45 cents per mile under Stonegarden, officials estimate that the expense of operating a marked law enforcement vehicle is 76 cents per mile and 92 cents per mile for a four-wheel-drive vehicle.

“That’s typical of grants, to cap mileage,” Huckelberry said, “It’s costing us more to operate our vehicles than what we are being reimbursed for.”

From the last two grants, the Sheriff’s Department got $184,645 for 414,931 miles driven, the memo states. Depending on the county rate used, that could mean a loss for Pima County of at least $131,000 to nearly $200,000.

Besides mileage, supervisors and Huckelberry wanted to know how much money it was costing the county to house people arrested under Stonegarden.

While there are no current estimates, a 2014 memo reported that total estimated detention costs by the Sheriff’s Department in the fiscal year 2013 Operation Stonegarden deployments was nearly $880,000. The amount includes people booked by the Sheriff’s Department and those by its law enforcement partners, not including the Arizona Department of Public Safety, according to the department’s document.

When reached Friday afternoon, Huckelberry said he hadn’t fully reviewed the 46-page response memo, which includes a handful of attachments.

But he said earlier that part of his inquiry was to figure out total cost versus total benefits and to know that facts are being accurately reported.

Over time, the federal government has shifted more of the costs to local jurisdictions for things such as incarcerating or detaining non-citizens, he said. “You see a lot more critical review of these programs simply because of the cost implications.”

While he said he understands the benefit of the grant from the Sheriff’s Department’s perspective, “What we have to do is to have our eyes wide open. If we want to accept this one million, we need to understand we are spending money, in local taxpayers’ money, for housing and prosecuting.”

In Pima County, Sheriff Mark Napier has said most of the Stonegarden deployments are in areas that include one of the busiest trafficking corridors along the border with Mexico. Just having a bigger law enforcement presence serves as deterrence, he said.

A handful of incident reports from the ACLU of Arizona also show deputies who’ve worked Stonegarden shifts with Border Patrol agents at checkpoints have stopped drivers for cracked windshields or illegal tints, arrested people with outstanding warrants and issued citations for lack of proof of insurance.

Not accepting the grant will also impact the six other agencies in the county that in total were to receive $3.2 million for overtime and equipment, Woolridge wrote.

This includes the Marana, Oro Valley, Sahuarita, Tohono O’odham and Tucson police departments, as well as the Arizona Department of Public Safety.

Huckelberry said he expects Tuesday’s vote to include “more clarity in regards to what the board expects in future reporting, billing and in regards to the (Sheriff’s Department) policies regarding immigration enforcement and the actions of its deputies.”