A little-known provision of the energy bill that is slowly winding its way through Congress would significantly weaken federal laws that require private dam owners to install fish ladders and reform how their dams are operated.

Since the mid-1980s, private dam owners seeking new licenses from the Federal Energy Regulatory Commission have been forced to remedy centuries of impacts caused by their dams. In particular, amendments to the Federal Power Act forced dam owners to install fish ladders and other structures that help fish move past the man-made obstacles to reach critical spawning grounds.

A “fish lift” on the Conowingo Dam on the Susquehanna River was among the first structures built as a result of the new law. At the time the bill passed, the dam’s owners did not believe the small number of shad—only 167 were captured below the dam in 1984 and driven upstream in a truck—justified the fish elevator.

But hatcheries began to produce more fish, and the dam owners agreed to spend $59 million to build the Conowingo fish lift and fish passages on three other upstream dams in the late 1980s. Today, the aquatic elevator helps more than 100,000 American shad pass over the 100-foot-high dam every year, and the fish lift is hailed as a model for other dams.

Now, a provision of the energy bill would allow power companies to propose cheaper alternatives to fish ladders, fish lifts and other methods of moving fish over dams if the dam owner could show that the alternative was “no less protective of the fish resources.”

The vague provision would weaken current standards and could allow dam owners to use hatcheries to supplement wild fish, use trucks to move fish upstream, or replace native fish with non-native fish altogether, critics say.

Two years ago, Rep. John Dingell, the ranking Democrat on the House committee with jurisdiction over the energy bill, brokered a compromise that would have permitted dam owners to use structures and strategies that were “no less effective” than the fish ladders proposed by FERC engineers and biologists. But, the hydropower industry walked away from the deal when Republicans took control of the Senate.

In addition to setting a weaker standard for fish passage, the energy provision also creates a new administrative appeals process that is only available to dam owners. Environmental groups hoping to appeal license conditions must instead seek relief in federal court.

“Utilities block rivers with walls of concrete and the energy bill will allow them to block fish restoration with walls of red tape,” said Andrew Fahlund, a hydropower expert with American Rivers, a national river conservation group.

Dozens of private dams in the Bay watershed will need new licenses in the new few decades, including dams in the Susquehanna and James watersheds.

Many of those dams last received licenses decades ago and were not subject to modern environmental standards. New licenses typically last 30 to 50 years and create the opportunity to impose new conditions, including dam operations that restore spawning cues and habitat restoration as well as fish ladders.

Overall, nearly one in five of the nation’s private hydropower dams will receive new licenses in the next decade, according to American Rivers.

Lobbyists for hydropower companies say dam owners simply want the chance to help fish for less money, and contend that FERC imposes needlessly costly conditions on new licenses.

In some cases, they say, the conditions imposed on the license give dam owners no choice but to abandon the dam altogether. So far, though, only one dam has ever been removed because of the license conditions imposed by FERC—a 100-year-old dam on the White Salmon River in Washington that blocked endangered salmon and steelhead runs.

“There’s only so many ways to build a mousetrap,” said Fahlund of American Rivers. “The industry already has plenty of opportunities to offer cheaper alternatives, and good actors already work with agencies like FERC to seek creative solutions. What we need is a backstop for the bad actors.”