Great Salt Lake Causeway

Supporting the loads of heavy rail transportation, the Great Salt Lake Causeway of the Union Pacific Railroad is 20 miles long (32 km) and up to 50 feet high (15.25 m) as it crosses the lake. The original earth and rock causeway was constructed on sediments of Utah’s Great Salt Lake, which are very soft and mixed with a dense salt layer. Causeway long-term settlement and foundation support are major challenges for this key piece of rail infrastructure. 

When a 1,000-foot-long (305 m) section suddenly lost its foundation support and sank 10 feet (3 m) into the lake overnight, quick analysis and rapid repair were crucial to restoring rail service. Jacobs Associates Principal Frank Pita spearheaded the emergency engineering response. His completely field-based design approach used soft ground soil mechanics techniques to bridge a hole in the dense salt layer. After a portion of the early repair was completed, the site was stabilized and the causeway reopened to traffic under a “slow order” just five days after the failure. Since then, our staff has continued to monitor settlement of the entire embankment as a means of predicting additional failures that might affect this complex subsurface condition.

A unique feature of this project is that the water is at salt saturation. Its density is therefore much greater than that of fresh water, so wind-induced waves have more energy to cause damage to the causeway. Therefore, the common coastal wave erosion design parameters for this environment must be increased. This causeway is one of the longest breakwaters in the country.