"All right, here come some live ones."

With that shout, at shortly before 11 a.m. Tuesday, a boat carrying a bucket full of mussels arrived at the Mississippi River shoreline just downriver of the Interstate 74 bridge in Moline.

Immediately, more than a dozen people set to work on the hard-shelled creatures. Using drill-like tools to mark them, the workers identified the mussels by species and sorted them into buckets.

Within hours, they would be moved back to the river, to new locations.

Over the next couple of months, this will happen countless times. By October, federal and state officials say, nearly a half million mussels will be pulled from the Mississippi River upstream of the I-74 bridge, one of the largest relocations of mussels in U.S history.

The mass collection stems from the planned construction of a new I-74 bridge. The path of the new bridge, slightly upstream of the existing structure, will have an impact on the habitat for a variety of freshwater mussels, including three that are protected by federal law — the Higgins eye, Sheepnose and Spectaclecase.

As a result, Iowa and Illinois will spend $2.4 million to remove 450,000 of the mussels. Only a fraction, 5,000 to 7,000, are protected, either by federal law or by the states of Iowa or Illinois, according to the U.S. Fish and Wildlife Service. But officials say that it only makes sense to gather them all up.

The Fish and Wildlife Service says mussels are valuable because they monitor and purify aquatic systems, feeding on algae, plankton and silts. Of the three mussels on the federal endangered list, the Higgins eye listing dates to 1976.

On Tuesday, federal and state officials hosted area media outlets to observe the process. The collection actually began on a small scale on Monday.

Emily Robbins, a malacologist, or mussel specialist, said she expected that 3,000 to 4,000 mussels would be collected Tuesday, but eventually, the goal is to work up to 10,000 per day.

"Common species, we'll sort them out by species and just get a rough count of how many of them there are," said Robbins, who works for Ecological Specialists Inc., a contractor on the project. "Then, any of the listed species, we'll actually be measuring how long they are and figuring how old they are, which you can do by counting the growth rings on the outside of the shell."

A 2014 survey identified 25 different species in the area.

Robbins, a 2009 Augustana College graduate who was in charge of the site, added the federally listed mussels also would be assigned a number. Officials say they intend to track the mussels into the future.

Heidi Woeber, a fish and wildlife biologist with the U.S. Fish and Wildlife Service, said the agencies hope to measure the impact the move has on the mussels and take the lessons learned with this collection and apply them to other bridge projects that require the same thing.

The mussels are being gathered by divers who go into the water just upstream of the existing I-74 bridge. They work within square grids marked on the river bed.

The divers have hardly any visibility as they go about six feet below the surface. So instead of working by sight, they follow a line down to the grid and collect mussels by feel.

"It's very tactile," Woeber said.

Officials say the 2014 survey estimated there are 850,000 mussels in the construction area of the I-74 project. Most of the mussels are on the Illinois side, but some are along the Iowa shoreline. Those will be collected in a few weeks.

The collection won't be without harm to the mussels. Woeber said they estimate that between 3,000 and 5,000 will die in the process.

Still, there are extensive efforts being made to minimize impact, not just over the next two months but in the future, too.

When it comes time to demolish the existing I-74 bridge, which is now scheduled for late 2020 and early 2021, there will be a separate collection and relocation of mussels.

In fact, destruction of the existing bridge has been altered because of the mussel presence. Demolition of the existing structure won't be allowed on the Illinois side of the river, nor will materials be dropped into the river there, according to federal documents.

In addition, a single pier in Sylvan Slough, called Pier K, will be left standing because it provides habitat for the mussels. Officials say the pier will stick out of the water about 30 feet.

The overall cost of the I-74 corridor project has been estimated at $1.2 billion. Construction on the new span is expected to begin next spring, with the building of support piers in the river.