Problems with the Great Salt Lake causeway

The last remaining culvert on the causeway is in danger of collapsing and may need to be filled.
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The one remaining culvert on the Union Pacific causeway across the Great Salt Lake is in "imminent" peril of collapse, putting vital freight traffic at risk of derailing unless the culvert is filled immediately, according to documents the company submitted to the U.S. Army Corps of Engineers last month.

The railroad is seeking emergency permission to retire the culvert, now the only spot on the causeway that allows water to move between the super-saline North Arm and the rest of the lake. After years of sinking into the soft lake bed, the culvert is beyond repair, according to Union Pacific.

Union Pacific wants to replace the culvert with a proposed 180-foot bridge that has yet to be designed.

It sounds like the causeway is a major maintenance headache, as well as being bad for the ecology of the lake. It basically cuts the lake in half, causing an imbalance in salinity between the halves(hence the need for culverts).