Plans to produce more renewable power at a hydroelectric dam on the Susquehanna River may also provide a boost to American shad and other migratory fish trying to swim upstream.

PPL, owner of the dam, recently asked the Federal Energy Regulatory Commission for permission to boost the electricity-generating capacity at its Holtwood hydroelectric plant to 233 megawatts.

As part of the expansion, the utility plans major modifications aimed at luring more migrating shad to a fish lift built in 1997 that has been performing poorly.

"This project would have significant environmental benefits while helping to meet Pennsylvania's need for new sources of renewable electricity generation," said William Spence, PPL executive vice president and chief operating officer.

The 55-foot dam has been a major roadblock for shad trying to reach historic spawning grounds despite the completion of a $21 million fish lift in 1997.

Shad find their way upstream by swimming against the current. Fish passages are usually designed to use flow from power generation units to attract the fish to the passage.

At Holtwood, though, whenever the river flow exceeds about 40,000 cubic feet per second-a common occurrence during spring shad runs-the river "spills" over the dam. That attracts the fish to the base of the dam where they remain, instead of to the fish lift at the powerhouse on dam's east side.

PPL has proposed adding two new generating units that would add 125 megawatts of capacity-enough to power 100,000 homes-and would also release more water near the fish lift.

"We should be able to strengthen the flow that leads them to the fish lift, hence making the fish lift more efficient," said Paul Wirth, a spokesperson for PPL. The plans recently filed with FERC also call for modifications to the channel and other changes aimed at helping shad and other migrating fish find the elevator.

The Holtwood dam, completed in 1910, is one of four large hydroelectric dams in the first 55 miles of the Susquehanna River that block the migration of shad and herring, which spend most of their lives in the ocean but return to their native rivers to spawn. Before the dams were built a century ago, the Susquehanna contained the largest spawning grounds for American shad on the East Coast.

In the 1990s, the utilities that own the dams invested tens of millions of dollars to build fish lifts and other passages to help get shad upstream. Unfortunately, that migration often reached an abrupt halt at Holtwood, the second dam encountered on their migration.

Typically, less than half of the fish that make it over the Conowingo Dam-the first dam on the river-make it past Holtwood. Often, fewer than a fifth make it past.

For those fish, the migration is a dead end: Biologists say there is no suitable spawning habitat for American shad between Conowingo and Holtwood. Biologists also believe that the failure to get fish to spawning habitat is contributing to the downward trend in shad observed on the Susquehanna in recent years.

Mike Hendricks, a fisheries biologist with the Pennsylvania Fish and Boat Commission, said the project should be a "win-win" situation for fish and the utility, but cautioned that resource agencies are still negotiating some details of the plan with PPL.

"A lot of the major issues are taken care of," he said, adding that remaining points should be worked out in the next couple of months and forwarded to FERC as part of its review process. PPL hopes to begin construction next year and complete the expansion in 2012.

"The sooner they get started, the sooner the fish passage issues will be taken care of," Hendricks said. "So we are very enthusiastic at this point but we still have some negotiation to do."

Hendricks said PPL had also agreed in principle to improve the passage for American eels at the dam, another migratory species that appears to be in decline.