Since the controversy over increased car-tab fees began, Sound Transit's CEO and board members have repeatedly claimed they've been as transparent as possible when it comes to the Sound Transit 3 tax package.

Now, state lawmakers want them to prove it.

Sens. Steve O'Ban, R-28th District, and Dino Rossi, R-45th District, are now demanding that those in charge at Sound Transit turn over essentially every email they've ever sent or received in connection to ST3, along with a long list of other documentation.

The Republican lawmakers sent a letter and public records request on Friday, referencing their extreme concern over ST3 car-tab taxes.

As we've reported, Rossi and O'Ban want Sound Transit to update the formula used to calculate car-tab fees, so that it's based on a car's fair market value instead of MSRP. 

But Sound Transit has said doing so would cause a nearly $6 billion hit to light rail projects that were promised under ST3.

O'Ban said he questions the validity of that $6 billion figure. He says that's why it's important to demand documentation and hold Sound Transit accountable. 

"If they've been transparent, if they've been absolutely forthright with us, then the information they provide to us will substantiate everything they said.  But really, the taxpayers have a right to know if this number has any validity, if it's based on real hard numbers or if it's something they have conveniently come up with to try to fend off our efforts to come up with a fair tax," said O'Ban.

The letter from O'Ban and Rossi asks Sound Transit to provide any and all documents, "including source data, spreadsheets, or financial estimates or plans used in the development of the $6 billion estimate of the impact of pending legislation introduced during the 2017 session."

Geoff Patrick, a spokesperson for Sound Transit, said the agency stands by the $6 billion figure and the calculations behind it.

Patrick said the $6 billion projected loss is the result of $2 billion in lower car-tab tax revenues plus $4 billion in new bonds needed to pay for additional debt service costs.  He said Sound Transit is working to pull together the documents needed to fulfill Senator O'Ban's request.

"Since Sound Transit is not as accountable as they need to be, we need to make them accountable," said O'Ban.