Questar Pipeline Co., subsidiary of Questar Corp. and principal supplier of Mountain Fuel Supply Co., plans to build a 77-mile pipeline in eastern Utah to connect its northern and southern natural gas transmission systems.

The $19 million project must undergo a lengthy hearing process before construction begins in 1989, company spokesman Curtis Burnett said.Questar's northern leg begins in the northwestern Colorado and southeastern Wyoming gas fields, runs through Wyoming and into Utah, serving customers on the Wasatch Front. The southern leg begins in central Colorado, runs through Utah's Uintah Basin ending at Payson, where it provides natural gas for Mountain Fuel's central and southwestern Utah customers.

Burnett said the proposed underground line would run north and south, allowing Questar to transport surplus gas from its southern system to its northern system to balance the entire network of more than 2,000 miles of pipeline.

The line branching from the southern system would link with the northern line at Clay Basin in northeastern Utah the southern tip of a spur from the northern system, Burnett said.

Because 55 miles of the line would traverse federal land, the Bureau of Land Management is accepting public comment on the project to help put together an environmental assessment or impact study on the line, a BLM spokesman said. Public hearings on the proposed project will be held April 27 at 7 p.m. in the Vernal BLM office and April 28 at 7 p.m. in the Flaming Gorge Dam visitors center.

Burnett said Questar must also obtain approval from the Federal Energy Regulatory Commission before construction begins.