VANTAGE — The boat ramp stretches out into mud, mud and more mud. Nearly 100 feet of mud now stands between the launch at Wanapum Recreational Area and the water.

That’s what a 26-foot drop in this stretch of the Columbia River looks like — dead-end docks, drying and dying mussels, newly exposed sandbars and a couple stranded boats tied up below the Interstate 90 bridge. Farther upriver, the low water revealed what authorities suspect are human bones.

It has been a half-century since the water was this low. That was 1964, the year the Wanapum Dam began full hydropower operations.

Now, long-submerged shorelines are again visible because the Grant County Public Utility District has dropped water levels to relieve pressure from a recently discovered crack in one of the dam’s 12 spillways.

The 2-inch-wide, 65-foot-long crack, which runs horizontally along one of the affected spillways, was discovered last week, prompting officials to start dropping the water level over the weekend.

“By reducing the water behind the dam, we’ve seen the crack close up by about one inch. So that’s good news,” said PUD spokesman Chuck Allen, adding that the move eases fears of further damage to the dam.

But Allen said the PUD is still evaluating the crack to determine how it happened and how best to proceed with repairs.

“There isn’t a timeline yet for raising the water level,” Allen said. “Our No. 1 priority is to ensure that area of the dam with the crack is stable.”

Meanwhile, the drawdown has been attracting the curious. On Tuesday, some visitors snapped photographs of a beached sailboat at a dry Vantage marina. Others simply walked amid the rocks and sandbars that were previously hidden beneath the water.

A family from Mattawa was exploring with a metal detector, unaware it’s illegal to treasure hunt because the shoreline is a federally protected cultural site because of its tribal history.

Linda Wright of Vantage, who was strolling with her dog, said she had heard about the water drop, but was surprised how far the mud bank stretched from the dock.

“I guess this is what 20 feet looks like,” she said.

If the water level has to stay low for a few months while repairs are made, she worried about how the lack of boat access would impact the local economy come summer.

“It’s just such a tourist draw. It’s a good place to come and cool off,” Wright said.

Downriver and closer to the dam, Rick Adams of Mattawa strolled the shoreline, tossing stranded mussels back into the river. There were far more than he could save — if they were even still alive to save — but he tossed them anyway while marveling at the distance between the driftwood marking the regular water height and the current state of the river.

“I’ve never seen it this low, even in a drought year, and I’ve been here since 1979,” Adams said. “It smells fishier than usual, too.”

On Tuesday evening, the Grant County Sheriff’s Office announced someone walking along recently exposed land near Crescent Bar earlier in the day discovered what detectives believe are human bones.

How long the bones have been there is unclear, the sheriff’s office said in a news release.

“Many areas upstream (that) are typically underwater are now exposed. The discovery of the bones was in such an area,” the news release said.

It’s possible the bones are those of an early settler or a Native American, and leaders of the nearby Wanapum tribe visited the scene Tuesday afternoon, the news release said.

Investigators were expected to remain on scene overnight, while the sheriff’s office and technicians with the Washington State Patrol’s crime lab will collect the remains today for analysis, the news release said.

At Blustery’s Burgers in Vantage, the newly exposed shoreline was the subject of lunchtime conversation at several tables, but no one wanted to speak on the record. A couple men declined to give their names because they were PUD employees.

Conversation, however, centered on concern that damage to river life could be high. Countless crawdads and mussels already are dead or dying.

The water is home to the lamprey and the large California floater mussel, which are both listed as species of concern under the federal Endangered Species Act.

Lowered water levels mean that salmon may not be able to access the fish ladders during spring migration.

“It’s safe to say it’s not an optimum depth of migrating salmon,” Allen said. “That’s a huge concern for us going forward.”

He said PUD biologists already were evaluating the environmental impacts.

“It’s just too soon to tell how long the river is going to be drawn down,” Allen said. “The Columbia River is a huge resource — not just for power generation — and what happens at Wanapum Dam affects the whole system. So we are working around the clock to figure out the plan.”

In the meantime, people are going to be exploring the newly exposed terrain. They are welcome to wander, Allen said, but not to disturb the shoreline.

The shoreline above the dam is considered a culturally significant area, however, because there are tribal sites along both sides of the river.

“We know that this is of interest — this shoreline hasn’t been seen since 1964,” Allen said. “It’s fine for people to look and walk and check things out, but metal detecting and looking for artifacts is illegal. And if caught, people could be prosecuted.”

The PUD is working to stabilize the dam so river operations can return to normal as quickly as possible, Allen said. He expected to have a better sense of how long the water would remain drawn down next week.