A new study estimates that it will cost from $6.2 million to $46 million to expand the Corona del Mar Freeway and its junction with the San Diego Freeway to handle traffic from a planned tollway.
Without modifications, the report concludes, traffic will move at speeds below 30 m.p.h. for three hours or more during peak periods of congestion once the San Joaquin Hills tollway connects to the Corona del Mar Freeway near Birch Street in Newport Beach. The tollway is expected to be completed by 1994.
The cost estimates were prepared for the Orange County Transportation Commission by two Newport Beach consulting firms, LSA, and Robert Bein, William Frost and Associates. The study envisions three ways of increasing freeway capacity. They are:
* Adding two general purpose lanes in each direction and widening the existing northbound Corona del Mar Freeway connector ramp to the northbound San Diego Freeway near Fairview Road in Costa Mesa. Cost: $6.2 million, with congestion still approaching "breakdown conditions" or so-called system failure.
* Installing one general purpose lane and one car-pool lane in each direction, widening the existing connector, and adding special, direct car-pool ramp connections between the two freeways. Cost: $45 million, with speeds of 40 to 50 m.p.h. during rush hours.
* Adding two general purpose lanes and one car-pool lane in each direction, widening the existing connector to the San Diego Freeway, and constructing direct car-pool ramp connections. Cost: $46 million, with speeds of 50 to 55 m.p.h. during rush hours.
The issue of who will pay for the improvements to the Corona del Mar Freeway--and also to other freeways affected by confluences with planned tollways--is still unresolved, state and county transportation officials said Thursday.
County officials expect the tollway agencies to finance the improvements, since it is tollway-generated traffic that is producing the need for modifications to existing freeways.
Although tollway agency officials have acknowledged the problem, they are still studying the design and funding issues involved, said Donna Stubbs, spokeswoman for the Orange County Transportation Corridor Agencies. The agencies are to plan and build three tollways, including the San Joaquin Hills route, which will be a 15-mile extension of the Corona del Mar Freeway from Newport Beach to Interstate 5 near San Juan Capistrano.