The Portsmouth Force Main Segment 1 project will be honored at the annual Colorado School of Mines Microtunneling banquet on Thursday, Feb. 10. The recently completed project for the City of Portland serves as an example of state-of-the-art microtunneling. The microtunneling portion of the project, completed by Northwest Boring, included a 1,903-ft drive – the second-longest drive completed in the United States to date and the longest using jacked steel casing. It was completed at an average jacking force of 130 tons under 40 ft of cover and an outside diameter of 81.6 in. In addition, crews bored through difficult geology including sands, silts and gravels with a host of wooden piles, logs and fill materials that crossed the alignment. Despite the challenges, the job was completed safely, on time and on budget.
[Source: Colorado School of Mines. Image: Colorado School of Mines email]