Report Backs Traffic Use of L.A. River Bed : Roadways: Consultants support Assemblyman Katz’s contention that car pools and trucks could utilize the concrete channel in dry times.

The bed of the Los Angeles River could be used in dry weather as a roadway for car pools between North Hollywood and downtown and by trucks from there to the Los Angeles Harbor, according to a preliminary report prepared for the Los Angeles County Transportation Commission.

The report by independent consultants, to be delivered to the commission on Tuesday, concludes that the proposal would cost about $700 million and could be in operation by 1995.

Assemblyman Richard Katz (D-Sylmar), who proposed the plan, said Thursday that the study shows “it would lessen congestion and improve the air, and could be done quickly.”

The long-awaited preliminary report--a summary of which was obtained by The Times--seems certain to reignite the debate over the future of the river, a freeway-like concrete-lined channel along three-fourths of its 44 miles, which is dry most of the time.

Katz and others contend it should be used to solve some of Los Angeles’ traffic problems. Mayor Tom Bradley leads those who contend the river should be converted to a park.

The report suggests that the commission could largely bypass the contentious issue of whether to pave the riverbed between Riverside Drive in Burbank and the Pasadena Freeway near Dodger Stadium--an eight-mile segment that has an earth or cobblestone bottom where heavy vegetation grows.

The consultants said that along the paved sections, vehicles would travel along the river bottom, where the low-flow channel now is. The channel would be relocated to the sides. However, on unpaved sections, cars could be moved out of the river bottom and onto the bank, the consultants said.

Friends of the Los Angeles River, an environmental group, is heading efforts to convert the unpaved section of the river into a greenbelt.

The report said it would cost $346 million to convert the river to car-pool use from the North Hollywood-Studio City border to the Hollywood Freeway at the northeast corner of downtown--a distance of 15 miles.

Consultants said that with two lanes--both open southbound in the morning and both open northbound in the evening--the river could carry 14,000 vehicles a day, each required to carry at least two occupants.

For the 18 miles of paved riverbed between downtown and the harbor, the consultants suggest construction of one lane in each direction for trucks, which would pay a toll of about 25 cents per mile.

The truck toll road would cost $365 million. It would draw 14,000 trucks a day, the report estimates, bringing in $15 million a year in tolls.

Between 220 and 275 days a year, the river is dry except for a slight runoff in the center channel, the report said.

However, during recent drought years, the number of dry days has reached 325 a year, consultants said.

The report was prepared by Wilbur Smith & Associates and Howard, Needles, Tammen & Bergendoff.