Endangered mussels moved in advance of I-74 bridge replacement

MOLINE, ILLINOIS — What may be the world's largest mussel relocation project got underway Tuesday below the Interstate 74 bridge linking Iowa and Illinois.

'It's definitely the largest known mussel relocation for a transportation project,' said Heidi Woeber, a biologist with the U.S. Fish and Wildlife Service, which is coordinating the multiagency effort.

Before the end of October, SCUBA divers employed by Ecological Specialists Inc. are to grope the bottom of the opaque Mississippi River water to find and remove about 450,000 mussels at an estimated cost of $2.4 million.

Woeber and Iowa Department of Natural Resources fisheries biologist Scott Gritters, the state's mussel coordinator, spent much of the morning explaining to reporters why anyone would want to do that.

'To start with, it's the law,' Woeber said. 'Mussels are a 'trust resource' that the government must protect and maintain in the public interest. It is required that we avoid and minimize impact to them.'

Woeber also explained that the mussel bed beneath the bridge is one of the world's richest and most diverse.

Based on 2014 surveys, about 850,000 mussels, representing 25 different species, live in the direct impact zone of the I-74 bridge replacement project. They include three species — the sheepnose, the spectacle case and the Higgins eye pearl mussel — on the federally endangered list and two others — the butterfly and the black sandshell — on state lists.

'For sure, the river bed beneath the bridge is one of the greatest mussel strongholds on the river,' said Gritters, who has led successful efforts to reintroduce the Higgins eye into the Iowa and Wapsipinicon rivers.

Pool 15, he said, sits atop the former Rock Island rapids, which were blasted and flooded to facilitate navigation.

Though the pool is highly developed with an industrial appearance, 'it flows across a rocky, gravelly bottom that is well suited for mussels,' he said.

During the 2014 survey, samplers found about 25 mussels per square meter of bottom surface in Sylvan Slough, where most of Tuesday's activity took place, he said.

'If you want practical human benefits, consider that each mussel filters bacteria, algae and sediment out of 10 gallons of water each day. They trash-compact it, kick it out, and a fish eats it,' he said.

Gritters, who said he has never put his hands on a live spectacle case, said he knows of no other place where they can be found.

Woeber said each of the 450,000 mussels is to be individually handled more than once during the relocation process.

After the divers pick them off the bottom, in depths ranging from 5 to 15 feet, biologists on the dive platform count them. They are then transferred via boat to a shore crew that identifies and marks them before they are transported to recipient mussel bed sites out of harm's way.

'You can't see a thing down there. I had my face mask just off the bottom and I could not see the bottom,' diver Cristopher Brouillette said.

'If it feels like it could be a mussel, we throw it in the sack and let them sort it out up above,' he said.

Sam Shea, a transportation planner with the Iowa Department of Transportation, said the transportation departments of Iowa and Illinois are splitting the cost of relocating the mussels.

Shea said the I-74 bridge is actually two bridges — one built in the 1930s for two-way traffic, and the other built beside it in the 1950s.

With narrow lanes, no shoulders and poorly designed ramps, 'they no longer meet today's standards,' he said.

The new bridge, with its $1 billion estimated cost, should be complete in late 2021, according to Shea. It is to be built in stages so that the first half can accommodate two-way traffic while the second half is built, he said.