New Install Honorable Mention: Portsmouth Force Main Segment 1
October 27, 2011
A United States record for the longest steel casing microtunnel at 1,903 lf and a world record for performing the entire 1,903 lf-run while only averaging 130 tons of jacking force (without engaging any of the five intermediate jacking stations in the tunnel) were awarded to Northwest Boring Co. for its completion of the City of Portland’s (Ore.) Portsmouth Segment 1 Force Main. The project was one of the final within Portland’s 20-year combined sewer overflow program, consisting of three miles of pressurized pipeline that will carry combined stormwater and sewage from Swan Island Pump Station to the existing Portsmouth Tunnel. Northwest Boring Co. completed the run in just 40 shifts and tunneled through difficult mining conditions, including soft ground with obstructions and more than 60 wood logs and piles, as well as attempting to avoid business, traffic and railroad disruptions. Microtunneling was accomplished by the complete removal of the excavated soil by the soil’s separation plant without having to pump, tanker and dispose of the slurry.
Owner: City of Portland
Engineer: Brown & Caldwell, Jacob Associates Inc., Garry Struthers Associates
Contractor: Northwest Boring Co. Inc.