A Colorado lawmaker says he will ask for an audit of the Regional Transportation District’s FasTracks program today, citing faulty planning for the Northwest Rail project.

Rep. Spencer Swalm, R-Centennial, said he will request that the Legislative Audit Committee ask State Auditor Dianne Ray to look into the RTD proposal, which critics say led to the squandering of taxpayer money.

“We need to get get to the bottom of this,” said Swalm. “RTD has received billions in taxpayer funds, and we need to find out where that money has gone.”

The FasTracks plan led to metro-area voters approving a 0.4-percent sales tax increase in 2004 to fund several commuter-rail lines to be finished by 2020.

However, cost estimates for the 41-mile stretch of planned commuter- train lines skyrocketed from $894 million to $1.7 billion. Much of the increase was placed on having to share rail lines with the Burlington Northern Santa Fe railroad, which owns the right of way RTD must use.

RTD then turned to a “hybrid” option, which calls for revenues from an additional 0.4-percent sales-tax increase RTD could ask voters to approve in November, to fund a rail line from Denver to Church Ranch Road in Westminster by 2022.

Meanwhile, the money from the 2004 vote will pay for developing a high-speed bus rapid-transit system with dedicated lanes and other service upgrades to Longmont by 2020.

The rail line to connect Denver to Longmont would be completed incrementally.

Swalm, in his letter to the audit committee, raised several questions about FasTracks, including that RTD’s financial plan assumed that sales-tax revenues would grow by about 6 percent per year from 2004 through 2017.

“Considering the history of Colorado sales taxes, have sales tax revenues ever grown by 6 percent per year every year for 13 or more consecutive years?” he wrote.

The full RTD board is scheduled to vote on the hybrid plan today.

Monte Whaley: 720-929-0907 or mwhaley@denverpost.com