Before you get too excited about the $640 million Congress just set aside for five Wasatch Front mass transit projects, consider this:

It will take the equivalent of a quarter-cent sales tax increase just to operate the buses, light-rail cars and intermodal hubs that would be funded by the new federal transportation authorization act.John Inglish, general manager of the Utah Transit Authority, said Thursday it will take a new source of local funding to cover those operating costs but stopped short of actually calling for a sales tax increase.

He said the act will provide 100 percent federal funding for capital expenditures that will:

- Finish the north-south light- rail line now under construction.

- Build a new east-west light-rail line between the University of Utah and the Salt Lake International Airport.

- Purchase millions of dollars' worth of new UTA buses.

- Construct new intermodal transportation hubs such as the ones proposed for Salt Lake City and West Valley City.

- Develop more "park and ride" lots to promote bus ridership and carpooling.

But the money to maintain and operate the new mass transit facilities and equipment will have to come from local sources, Inglish told the Salt Lake County Council of Governments.

The transit authority already spends all of its income from fare box revenues and the quarter-cent mass transit tax to maintain and operate its existing system, he said.

Without a secure source of new operating revenues, the UTA chief warned, the federal money will not be forthcoming.

"Our next step is to do something about generating local revenues," he told Salt Lake area mayors and commissioners during their monthly meeting Thursday. "Something needs to happen in the near future. . . . We are at a critical junction."

While Inglish did not suggest exactly how those operating revenues should be raised, he offered a recent Dan Jones and Associates poll that found local support for a quarter-cent sales tax increase for the UTA.

The survey, which polled 1,000 Wasatch Front residents this spring, found 23 percent "strongly favor" a sales tax increase while 38 percent "somewhat favor" one - a total of 61 percent.

One person in three is against a sales tax increase, including 21 percent who "strongly oppose" the idea and 13 percent who are "some-what" opposed. The poll had a margin of error of plus or minus 3 percent.

"We're interested in any kind of appropriation," he said. "It doesn't have to be a sales tax."

But the implication of increasing the existing sales tax levy for mass transit in six Wasatch Front counties wasn't lost on local elected officials at the meeting.

A 1992 ballot proposition to increase the sales tax levy to build light rail was defeated when Salt Lake County voters - particularly those in suburban communities - rejected the proposal.

And light rail has been a bitterly contested issue ever since, with opponents warning an eventual tax increase is inevitable.

Inglish said a recent Dan Jones poll indicates the public expects improved mass transit service at the same time the UTA is operating with "one of the lowest if not lowest transportation subsidies" in the nation.

"With the equivalent of a quarter-cent sales tax increase, we can put 400 more buses out there," he told mayor and commissioners. "We need more service . . . and we need it from Salt Lake to Provo."

UTA operates about 550 buses at its current level of funding, the Utah chief noted, and 400 more vehicles would provide the convenience and shorter waits needed to win people over to mass transit.

Salt Lake County Commissioner Randy Horiuchi said it makes more sense to build light-rail spurs to West Valley City, West Jordan and Draper than to construct the proposed east-west line.