This morning, Interior Secretary Bruce Babbitt would just like to say to the American shad population, on behalf of the American people: We're sorry.

It's not that no one was looking out for the shad when federal engineers constructed the Little Falls Dam on the Potomac River in 1959. The return of the shad was a popular harbinger of spring. A shad run looked to some like shiny dimes thrown into the water.

Everybody knew even then that the shad wouldn't be able to vault four feet over the dam to get upriver to lush spawning grounds. The fish couldn't fly, not even for love.

So the people paid for a "fish ladder." It was a series of pools, connected by channels, not unlike the locks of the nearby C&O Canal. The pools were installed on Snake Island, which is at the middle of the dam. The shad were supposed to swim from pool to pool, do their bit upriver for posterity, then wash back with the water that passes over the dam and return to the sea.

But it was a lousy fish ladder, and the shad refused to climb. The location was apparently poorly chosen, and the passages filled with logs, tires, silt. It was a maintenance nightmare, and the people threw up their hands. For 40 years, the only water creature that made it upstream was the intrepid American eel, which knew how to slither around the dam in wet grass.

Add pollution and overfishing, as well as a bunch of other dams on rivers and streams in the Chesapeake Bay watershed, and soon you had a local shad population in free fall. Even outlawing shad fishing in the Potomac in 1982 didn't help.

This morning, Babbitt and an ingratiating platoon of the people's federal, state and local leaders are scheduled to make amends to the shad. They will gather for a ceremonial "dam-breaking" to mark the beginning of $2 million in surgery on the dam. A new passage for the migrating fish, called a fishway, is being constructed. And this one, according to some of the best minds in fish biology and river hydraulics, should work.

"For seven years I've watched hundreds of cities restore their communities by restoring their rivers," Babbitt plans to say in remarks prepared for the event. "Now it's our turn."

The dam extends between the Maryland shore just northwest of the District and the Virginia shore just southeast of CIA headquarters. The federal government is footing 75 percent of the cost and Maryland is providing the rest. The effort, prodded along by Sen. Paul S. Sarbanes (D-Md.) since 1992, is a couple of years behind schedule, because of complications assembling the funding.

Carrying a sledgehammer for effect, Babbitt has ordered the dismantling of obsolete dams across the country to restore access to spawning grounds for salmon, shad and other species.

But he won't be taking a sledgehammer to the Little Falls Dam, because the people still need it. Deep water pools above the dam so that, when levels are too low for water to enter the District's supply system through upriver intakes, it can be pumped from the Little Falls Dam.

Instead of removing the dam, a 24-foot notch is being cut in the 1,400-foot dam near the Virginia shore. In the notch will be a succession of three "weirs," or barriers, each shaped like a W.

It's an unusual design, and the eureka moment for the shad came when hydraulic research engineer Mufeed Odeh inserted a piece of scrap wood into a model he and his team had been tinkering with for months at a U.S. Geological Survey lab in Massachusetts.

They found the right position and angle for the weirs to slow the water down from as fast as 22 feet per second to less than 13 feet per second. Yet the water will still flow over the weirs deep enough to allow the shad to swim ahead, rather than having to climb or jump.

A number of migratory species will benefit, including the rockfish and the river herring. But unlike other species, which have bounced back in response to cleaning up waterways and regulating fishing, shad remain devastated by lack of access to historic spawning grounds.

In a recent ranking of the health of species populations by the Chesapeake Bay Foundation, shad got three of 100 on the scale, while rockfish were 75 of 100. Just the 10 extra Potomac miles the shad will gain between the Little Falls Dam and Great Falls, which blocks their progress upriver, will make a huge difference, fish experts said. Meanwhile, other dams are being circumvented on the Susquehanna River and elsewhere in the watershed.

The prospect of the return of the shad has everyone from federal bureaucrats and environmentalists to recreational anglers fairly wriggling with gladness.

"This is a great story of mankind trying to heal the wounds which he has inflicted on a great river," said Mike Hayden, president of the American Sportfishing Association and a former assistant secretary at the Interior Department who helped launch the dam project eight years ago. "If we're smart enough, we can fix what we mess up."

Shad are prized for their tasty roe and for their starring role in traditional shad planking parties, where the fish are slow-cooked on oak boards over campfires. The annual political Shad Planking in Wakefield, Va., now must import shad from out of state.

"You know it's spring because you have shad roe to eat and shad plankings to attend," said Mike Hirshfield, vice president for resource protection of the Chesapeake Bay Foundation. "It's tragic that a generation of kids is growing up not even knowing what a shad is."

For those who have never seen a shad, the blue and silver fish grow to 30 inches and have the classic profile employed by untrained fish doodlers everywhere: an elongated oval, on its side, with a triangle on one end.

So now that the American people have done the right environmental thing, what happens if the shad come back to their former strength?

"I've got my fishing rod ready to meet their return," Babbitt said.