Granite has been awarded the US$267m (£193m) construction contract for a tunnel to reduce sewer overflows in the US state of Ohio.

The Lower Olentangy Tunnel (LOT) project in the city of Columbus aims to improve water quality and reduce the risk of people’s exposure to waterborne pollutants by reducing overflows from the sewer system into creeks and rivers during flooding.

LOT will connect into the upstream end of the OSIS Augmentation Relief Sewer (OARS), which was previously constructed by Granite. LOT will provide hydraulic relief to the three existing sewers that are in close proximity of each other: Franklin Main Interceptor Sewer, Olentangy Main Interceptor Sewer and OARS.

“We have had an excellent relationship with the City of Columbus and are happy to once again work on their tunnel systems,” said Granite division vice president James Nickerson. “Since this project dovetails into a tunnel project we completed for the City of Columbus approximately five years ago, we have a clear understanding of the project and our client’s expectations.”

The construction of the LOT main tunnel will consist of approximately 5.2km of 3.65m-diameter tunnel and will be mined with a tunnel boring machine and constructed of precast concrete segments. There will be three main shafts.

A microtunnel 2.3m in diameter will also be constructed to relieve a section of OARS.

Construction is expected to begin this month and conclude in December 2026.