At 4 p.m. each day, when workers building the Marble Hill nuclear plant here change shifts, the rural road beside the plant looks like New York's Fifth Avenue during rush hour. The traffic is bumper to bumper.
Yet more than 3,000 workers at this half-finished plant have been laid off during the last month. And the close to 5,000 workers left are concerned that they, too, could be out of a job within weeks.
The dilemma facing Marble Hill - and many other nuclear plant construction sites these days - is chiefly financial. The same kind of crunch has already led to the cancellation of work on many other nuclear plant sites. The small ''for sale'' signs advertising private property nestled close to a Marble Hill may yet prove more prophetic than those posting them realized.
Energy demand has risen much more slowly than utilities predicted, and the cost of building nuclear plants has also far surpassed even the most liberal predictions.
The cost of building the two units at Marble Hill, for instance, originally estimated at $1.4 billion in 1973, is now pegged at close to $7 billion. It includes the cost of a two-year delay so the owners can pace the rate of construction to their current cash flow.
Like a majority of states, Indiana forbids charging ratepayers the cost of utility construction work until a plant is actually producing electricity - unless special circumstances warrant it. Utilities must either borrow or rely on profits as they build. Public Service of Indiana (PSI), owner of the Marble Hill site, proposed as an emergency compromise - to ease the shock, it said, on ratepayers later when the plant was running - that electric rates be raised 8 percent for each of the next six years. Many consumers and legislators were outraged.
''It's only a $1 billion utility in the first place, and it's pretty clear it doesn't make financial sense for the company to go on,'' says Janelle Cousino, director of the Indianapolis-based Citizens Action Coalition.
To ease concerns, Indiana Gov. Robert D. Orr (R) appointed a task force of business leaders to explore whether continued construction at Marble Hill is economically feasible and, if so, how it should be financed. The group is expected to report back to him by Jan. 1. But neither its word nor the governor's may be final.
''The task force report isn't binding, and it's still not clear who will make the final decision,'' says PSI spokesman Brad Bishop.
But Mr. Bishop is the first to admit that Marble Hill's financial troubles are far from unique.
At the Zimmer plant in nearby Moscow, Ohio, a plant that utility owners insist is 97 percent complete, safety and quality problems in construction have complicated the financial picture to the point where the owners say they will consider scrapping the project. And a major rate increase proposed by the Long Island Lighting Company to help pay for its new Shoreham plant in New York has spurred Gov. Mario M. Cuomo to appoint a panel to explore what the impact would be of halting construction.
Over the last decade some 102 nuclear plants under construction have been canceled. But the cost to ratepayers is not as steep as it might have been, according to Nuclear Regulatory Commission (NRC) spokesman Frank Ingram. ''Most of them weren't very far along,'' he says.
Few experts appear to have given much thought to the question of what should be done with nuclear plants that are scrapped for one reason or another before completion or after use.
Once-operating plants that are shut down are required by the NRC to be decommissioned so that any radioactivity hazard is eliminated. But the commission does not specify how the job should be done, or how swiftly. And it is questionable whether a once-used nuclear plant could ever be reused for another purpose.
Gov. Richard L. Thornburgh (R) of Pennsylvania, the home state of the long-shut-down Three Mile Island plant, drew a sympathetic laugh from his colleagues at the Republic Governors' Association meeting in Chicago recently when he said:''If you hear of anybody who wants to buy a used nuclear power plant, be sure to let me know.''
Owners of some plants halted in midconstruction have tried to peddle reactor parts as one way to recoup losses on their investment. The Tennessee Valley Authority, which has canceled plants in both Tennessee and Mississippi, has sold some surplus construction equipment from the plants. But spokesman Alan Carmichael says the TVA has so far found no domestic takers in its efforts to sell reactor steam-supply systems.
''Utilities in this country are all in the same situation,'' he explains, ''but we've been talking with Taiwan and Turkey.''
Many of the abandoned nuclear plants are in rural areas where there is little prospect of heavy demand from businesses looking for used facilities. ''My impression is that a lot of plants will probably lie fallow with little possibility for intense use until things begin to grow up around them,'' says Dean Schwanke of the Urban Land Institute.