People have been building dams across the Susquehanna River — originally for canals and later for hydropower — for nearly two centuries. For nearly as long, they’ve been debating the best way to get migratory fish, particularly American shad, past those dams.

Early next year, it appears likely that debate will take place in front of a judge.

Exelon Corp. has taken the unusual step of requesting a “trial-type hearing” to challenge recommendations made by federal biologists who are calling for a massive upgrade to fish passage operations at its Conowingo Dam.

The request is in response to a “preliminary prescription” from the U.S. Department of Interior in August. The prescription, developed by state and federal agency biologists, spells out steps needed to get 5 million shad and 12 million river herring upstream of the 94-foot-high dam each year.

Among other changes, the steps call for the construction of a state-of-the art elevator capable of moving four times as many fish as the current 25-year-old fish lift.

Exelon contends the upgrades would cost $56 million and are unlikely to achieve the fish passage goals. It wants to instead upgrade and improve its existing lift, and revive a program to trap shad and truck them around Conowingo and the three dams upstream of it.

Hundreds of pages of documents filed by both sides show sharply different views about why the numbers of shad getting past Conowingo have plummeted in recent years, and how that trend is best reversed.

Both sides are poised to make their arguments before an administrative law judge early next year.

The recommendations that come out of the hearing would form the basis for the Interior Department’s final prescription for fish passage improvements at the dam. If Exelon can show that its alternatives would achieve the same results at lower costs, the Interior Department would be obligated to go along with them.

Those recommendations would become part of Exelon’s new operating license, which is pending before the Federal Energy Regulatory Commission.

Exactly when that license will be issued is unclear. It’s essentially been on hold until a contentious issue about how to deal with sediment stored behind the dam is resolved — something that could take several years.

While the sediment issue has dominated discussions concerning the new license, the stakes are huge for the fish passage issue. Because Exelon is seeking a 46-year license, the decisions made in coming months could determine how — and how many — shad and river herring get up the Bay’s largest tributary for decades to come.

Two centuries of controversy

The debate over the best way to get shad and herring around the dam is the latest chapter in a controversy that has gone on for nearly 200 years. American shad and river herring are anadromous species, which spawn in freshwater rivers but spend most of their lives in the ocean until they return to their native rivers to spawn again.

They once migrated up the Susquehanna River in huge numbers. Early settlers in Cooperstown, NY, — 444 miles upstream from the Bay — were once reduced to eating wild leeks after a harsh winter, until they were saved from starvation by the spring river herring run.

Catching shad and river herring during their spawning runs was a springtime ritual for communities along the Susquehanna and its tributaries. The annual migration once supported commercial fisheries as far upstream as Binghamton, NY.

Conflicts over fish passage date to the early 1800s, as canal companies began building dams along the river and its tributaries. Of particular concern was a wood-and-stone dam built in the 1830s near Columbia, PA, just 45 miles upstream from the Bay.

Complaints about its impact on shad spurred the Pennsylvania legislature to pass a law in 1866 requiring fishways at dams. But the fishways at that time proved largely ineffective. Some fish still managed to get upstream. The canal dams were relatively low, and some shad made it upstream as dams were breeched by ice flows or inundated by high springtime river flows.

In the early 1900s, annual shad landings in Pennsylvania still averaged between 200,000 and 400,000 pounds a year.

That changed with the construction of larger hydroelectric dams built to meet the rapidly growing demand for electricity as the 20th century began. The oldest and northernmost is York Haven, completed in 1904. It was then the third largest hydroelectric dam in the world, and is located 55 miles upstream from the Bay. Conowingo is the southernmost — just 10 miles upstream from the Bay — and the largest, standing 94 feet high and 4,648 feet long. It was completed in 1928.

Those dams, plus Holtwood and Safe Harbor, which stand between them, closed almost the entire 27,500-square-mile Susquehanna drainage — the largest river basin on the U.S. East Coast — to migrating fish.

Starting in the early 1990s, the utilities that owned the dams invested an estimated $100 million in fish passages, the last of which was completed at York Haven in 2000.

But getting fish past four dams has been problematic. The best performance was 2001, when 16,200 shad made it past all four. Just eight made it this year.

Fish passage at Conowingo has declined steadily after peaking at 193,574 American shad in 2001. This year, just 10,425 were hoisted over the structure — the lowest number since the fish lift went into operation in 1997.

More fish were actually getting upstream before the fish passages in some years through a temporary program funded by the utilities to truck shad captured below Conowingo upstream. That program moved as many as 56,370 fish in 1995, but was discontinued after passages were opened at all four hydro dams.

Why the decline?

Different perspectives about what is driving recent shad declines helps to shape the recommendations of both sides in the dispute.

Shad have faced population drops of more than 90 percent along the East Coast in recent decades. Scientists have cited a host of contributing factors, including degraded habitats, water pollution, loss of historic spawning areas because of dams and other migration barriers, consumption by other fish, and bycatch in coastal fisheries.

In its arguments, Exelon highlights the overall coastal decline of shad and puts more emphasis on factors that would affect the entire stock, such as bycatch — which has been a growing concern in recent years — and factors such as predation by other fish. Most factors affecting shad, it said, are “unrelated to hydropower.”

Interior, though, says that shad numbers were rising in the Susquehanna until the trap-and-transport program ended. Hatchery stocking efforts were reduced shortly thereafter. The department suggests that since then, fish passages have gotten too few returning fish to spawning grounds.

While the Susquehanna system declined, Interior noted that shad populations are increasing on the nearby Potomac River — one of the few rivers where that is happening on the East Coast. It’s also one of the few rivers where shad have access to almost all of their historic spawning habitat.

“We infer that the Susquehanna River population trend should be similar to the Potomac River since both are major Chesapeake Bay tributaries and fish migrating between their respective riverine and marine habitats would experience similar natural mortality,” Interior wrote, “…in the Susquehanna River, access to nearly all spawning habitat is substantially blocked by mainstem dams.”

Getting fish upstream

Interior said its program is intended to reverse the decline and eventually get 2 million shad and 5 million river herring past all four dams annually — a longstanding goal based on the amount of fish that could be supported by upstream habitat.

To get that many fish upstream, it calls for 5 million shad and 12 million river herring to pass Conowingo Dam each year. It then anticipates that each of the three upstream dams will pass 75 percent of the fish that make it over the previous dam.

Only one of the upstream dams, Safe Harbor — the third dam on the river — approaches that rate. The long-term passage rate at Holtwood Dam — the next dam after Conowingo — is 32 percent. The rate is 17 percent for York Haven, according to Exelon’s documents.

But Interior says that projects are planned or under way at all upstream dams to improve performance. For instance, a multi-year effort has been under way to improve passage at Holtwood and, while not complete, the facility this year passed 63 percent of the shad that made it past Conowingo — its best-ever performance.

For those upstream efforts to pay off, though, Interior says the fish first have to make it past Conowingo.

The preliminary prescription also calls for Exelon to monitor fish at the dam, and sets a goal of passing 85 percent of the shad and river herring that reach the dam’s tailrace. To do that, it calls for the construction of a new state-of-the art fish elevator to be built on the west side of the dam, which would have two 6,500-gallon hoppers able to hoist fish over the dam in 15-minute intervals.

After the new lift is built, the existing one would close but remain in place. It could come back on line, and be expanded to include two 6,500 gallon hoppers if more fish lift capacity is needed in the future or the new lift is not moving enough fish upstream.

A ‘field of dreams’?

Exelon, in its filings, has balked at the recommendations, saying there are too few fish in the river to justify what it says would be a massive $56 million investment. It labeled the proposal a “field of dreams” based on the notion that “if you build it, they will come” and ignores other factors that have contributed to the overall decline in the shad population.

Exelon also objects to the 85 percent passage goal for Conowingo, saying it opens the door for the Interior Department to continually demand changes at the project. Failure to meet the targets, it said, “is virtually assured given that no other hydroelectric facility on the Atlantic coast has achieved these efficiencies.”

As an alternative, Exelon is proposing to make improvements at the existing fish lift, including replacing the existing 3,300 gallon hopper that transports fish above the dam with two 6,500-gallon hoppers.

It also proposes to upgrade mechanical equipment so it can lift the hoppers every 15 minutes, and make a variety of other improvements aimed at doing a better job of attracting fish to the existing lift.

It also calls for reviving the old trap and transport program, including operating up to five trucks to haul shad captured below Conowingo past all four dams — something it says gets fish to upstream spawning grounds faster. Its goal would be to get up to 100,000 spawning adult shad upstream each year. Exelon says its proposal would cost about $37 million.

Concerns — and agreement

Some of those suggestions raise concerns for agency biologists. Interior’s program recognizes the benefit of trapping and transporting fish — it would give Exelon credit toward meeting the 85 percent fish passage efficiency goal if it implemented such a program — but biologists don’t consider trucking a long-term solution for Susquehanna fish passage because it could not meet upstream restoration targets.

“Although trap and transport can hasten restoration, it alone cannot achieve restoration,” Interior said.

The department also considers the west side of the river a more optimal location to collect shad because the turbines on that side are less powerful, and therefore have less impact on fish, whose migrations can be affected by turbine operation.

Biologists have also long argued that having some type of performance efficiency is important because it allows them to require modifications to improve passage operation over time. They say that is especially important given the proposed 46-year lifespan for the license.

Biologists with state and federal agencies have long contended that Exelon and previous dam owners had little incentive under the existing license in improve fish lift performance, citing a lack of maintenance and the failure to adjust flows near the fish lift to do a better job of attracting migrating fish.

They also believe the 85 percent passage rate is achievable based on past numbers at Safe Harbor, the performance of which is expected to improve with planned upgrades.

Exelon said it is open to addressing concerns that may arise in the future, but not ones tied to the 85 percent rate.

It contends that that rate and other figures are based on flawed assumptions, which it questions in its filings. It questions whether the shad population in the lower Susquehanna ever reached 5 million or river herring 12 million — the numbers it is supposed to pass over Conowingo.

And it objects to operating the fish lift at river flows greater than 113,000 cubic feet per second, saying that it could harm fish lift equipment and that fish typically do not migrate upstream in such conditions. Interior believes the fish lift could pass fish at river flows of up to 143,000 cfs and failure to do so is reducing the number of shad moved upstream.

The two sides are not totally divided on all issues, though.

The judge will probably not have to decide issues relating to another species of concern, American eels.

Both the power company and Interior largely agree on the solutions for moving eels upstream, calling for a trap-and-transport operation to continue until 2030, when an eelway is to be constructed at the dam. But because eels are able to slither up well-designed passages, they don’t require the construction of costly mechanical lifts.

For shad and river herring, the differences are substantial. The success of whichever program ultimately goes forward — whether Exelon’s or Interior’s — will determine whether, 150 years after the Pennsylvania took the first efforts to get shad upstream, people have finally figured out a solution.