Auto surveying method used on Savanna-Sabula Bridge reconstruction project

The Savanna-Sabula bridge, built across the Mississippi river in 1932, connected Illinois and Iowa and was reconstructed in 1985. The average traffic lane is around 12 feet, but the steel truss bridge was only 20 feet wide total, making crossing dangerous. Kraemer North America and IDOT hired Fehr Graham to complete pier staking.

To keep traffic between Savanna and Sabula open, construction crews built the bridge next to the old truss structure. Our team used GPS and robotic total stations to stake each pier. We completed construction layout for the abutments, causeways and substructure. We used a Leica system to measure points in real-time. This method of auto surveying is the second known application in the Midwest. Fehr Graham also set permanent survey points and right-of-way markers.

Once the staking was completed, teams took barges with drills across the river to drill into the riverbank. Teams needed to check the area for any marine life that would be affected. Divers were sent into the Mississippi River to make sure there were no mussels that would need to be transplanted. Teams found Little Brown and Northern Long-Eared bats in the forests nearby. The Illinois Environmental Protection Agency set a timeframe for demolition and tree removal to protect the animals.

The teams had to shift the road to line up with the new bridge before demolition crews took the 86-year-old bridge down. The bridge is open and is expected to serve the community for another 50 years.

AT A GLANCE
» Completed construction staking.
» Realigned the road.
» Prepared construction layout.
» Prepared right-of-way markers.