In a bid to win federal approval and matching funds for a new foray into light rail, the board of the Orange County Transportation Authority on Monday pledged $56 million in local sales taxes to the OC Streetcar.

With the commitment, the agency stands to gain up to $144 million from a competitive federal grant program called New Starts to spend on the planned $289 million light-rail line. The hop-on, hop-off service would would carry commuters, tourists and shoppers to jobs, stores and the Santa Ana train station, traversing four densely populated miles from Santa Ana to Garden Grove.

Supporters say the streetcar brings much-needed mass transit to car-centric Orange County. Critics contend that ridership estimates of 6,000 passengers per day seem optimistic, and say operating costs will be steep.

With fares projected to cover 30 percent of the streetcar’s estimated $5 million annual cost of operation, OCTA director Michelle Steel, who represents District 2 on the Orange County Board of Supervisors, remarked, “We have to think about…how we’re going to cover these expenses.”

Under a deal approved in July, OCTA will pay 90 percent of the balance, with Santa Ana covering 10 percent.

Others asked about a fall-back plan if state and federal funds fall through. Santa Ana mayor Miguel Pulido, an OCTA director and champion of the project, maintained: “Without a project, we’re not going to get any money.”

Anaheim mayor Tom Tait, who voted against the pledge, questioned the cost and ridership estimates. He pointed to the Anaheim Regional Transportation Intermodal Center, where the city is shoring up a multi-million operating deficit after over-hopeful financial projections didn’t pan out.

The Federal Transit Administration is expected to rate the OCTA’s application late this year or early next, and make a final decision in 2017. The project is expected to break ground that same year. OCTA officials have said money from Measure M, a transportation sales tax, is available to pay for the entire project, but that decision would require board approval.

The streetcar is the county’s second recent attempt at light rail. The more ambitious, $1 billion CenterLine project, scuttled about a decade ago, was to run from Santa Ana to John Wayne Airport.

Contact the writer: nshine@ocregister.com or Twitter:@nicolekshine