Portland’s ‘Big Pipe Project’ Gets Down to The Big Grind
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 citys 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 citys annual number of overflow incidents to five per year. The work is driven by a 1991 stipulation and order the city signed with the states Dept. of Water Quality.
The gravity line, driven through difficult soft-ground conditions, will divert combined stormwater and sewage overload from an interceptor on the west side of the Willamette River, under the river to a pump station on the other side. Dubbed the "Big Pipe Project," the rate-funded work is the most expensive capital construction job in Portlands history.