US contractor Frank Coluccio Construction has successfully broken through on the 1.9km long, 4.5m i.d. Mercer Street sewer tunnel in Seattle, Washington.
Using a refurbished 5m diameter Lovat EPBM the contractor smashed through the reception shaft on March 6, after some 10 months of boring through the very dense, hard Glacial Tills.
The tunnel features a primary lining of 1.3m long x 2m wide concrete segments installed by the Lovat’s ring type segment erector. To negotiate the curved drive and gravity flow gradient, the contractor installed a fully automated Tacs guidance system to the TBM.
The contractor was awarded the US$29.5M project at the end of 1999 by the client, the City of Seattle and the wastewater Treatment Division of King County Department of Natural Resources. The tunnel runs from Mercer Street to Dexter Avenue North and is an integral part of the city’s Denny Way/Lake Union combined sewer overflow. It has been designed to eliminate an outfall into Lake Union by increasing the capacity of the city’s existing combined sewers.
