Portland's 'Big Pipe Project' Gets Down to The Big Grind

摘要

Contractors in Portland, Ore., are using two 16-ft-dia, variable pressure tunnel boring machines to build a 4.2-mile storage tunnel to handle the city's combined sewage overflows. The $293-million project includes a 220-million-gallon-per-day pump station to send storage to a treatment plant and reduce the city's annual number of overflow incidents to five per year. The work is driven by a 1991 stipulation and order the city signed with the state's Dept. of Water Quality.