Since last year, the Utah Transit Authority has been quietly buying land along a favored route for a proposed light-rail system. But negotiations are becoming more complicated as efforts to fund the $225 million train system get under way.

The purchases are being made without publicity out of fear that speculators might drive up the price of property needed for the project once it is known that UTA does not have the power of eminent domain, the right to condemn private property for public use.At the same time, an aggressive campaign is under way to win support from local government and business leaders for the tax increases needed to pay for the electric-powered commuter trains.

UTA officials acknowledge that these competing interests have put them between a rock and a hard place and that the squeeze can only become worse as the start of the 1989 Legislature draws nearer.

Lawmakers will be asked to approve some kind of tax increase to fund the project. UTA is funded through a quarter-cent sales tax, and while doubling that tax has been frequently referred to as a likely means of raising money for the light-rail system, no decision has yet been made.

Such a tax increase first would have to be approved by the Legislature, then would go before voters for a final decision. Depending on how quickly a financing method is approved, the trains could be running as soon as 1993.

And, of course, depending on how difficult it becomes to acquire the needed property.

Six pieces of property have already been purchased by UTA for just under $880,000, most of it centered on a nearly seven-acre parking lot and station planned for light-rail riders in Midvale.

The preferred route for the trains is along the Union Pacific Railroad tracks that roughly parallel I-15, from downtown to 106th South. Should the railroad and UTA not be able to reach an agreement on the little-used tracks, an alternate route along State and Main streets to the South Towne Mall is also being studied.

Most stations for the light-rail system would be within the right of way acquired for the two sets of train tracks, although land would probably need to be purchased at or near 13th South, 27th South, 33rd South, 39th South, 45th South and 48th South.

Property would also need to be purchased for four or five "park and ride" lots and a repair yard. The approximately 10-acre repair yard would likely straddle the railroad tracks between 53rd South and Vine Street.

The lots planned for the route along the existing railroad tracks include a seven-acre lot near 64th South; a 2.5-acre lot near 72nd South; a nearly seven-acre lot in Midvale bordered by State Street, Center Street and 78th South; a 7.1-acre lot between 90th South and Center Street; and a 12-acre lot near 106th South.

Should the State Street route be selected, proposed lots include a 4.4-acre lot near 64th South; a 10-acre lot near 90th South; and a five-acre lot near the South Towne Mall at 106th South.

So far, besides portions of the proposed Midvale lot, UTA officials have purchased property for the proposed 12-acre lot near 106th South. Because it is bordered by State Street, the Midvale lot could serve either route.

The land at 106th South, which cost more than $350,000 and is the single most expensive piece of property purchased to date, could be used only for the route along the existing railroad tracks.

A couple who declined to sell a portion of the land needed for the Midvale lot that their business is located on recently focused attention on the transit authority's purchases.

Verl and Sharon Tapp, owners of Midvalley Glass at 7802 S. State, said they were approached by UTA officials about 18 months a year and a half ago with the first of several offers.

All of the offers were eventually either withdrawn or rejected, they said. But their dealings led them to question whether UTA should be buying land before the light-rail system is approved.

UTA officials are quick to point out that nothing legally prevents them from making the purchases and that the land is being paid for out of a $5 million surplus in the 1987 budget.