Tolt pipeline under-crossing of the Snoqualmie River.

The crossing was part of the West Snoqualmie River project for supplying water to Seattle, Washington State, USA. Tight environmental constraints on construction on the floodplain of, and under, a salmon-bearing river, and difficult and variable ground conditions characterised the project which, as planned but later modified, included six shafts and four microtunnels. The MTBM used was a 2.28 m Soltau RVS 800 STS. The eventual success of the project despite the ground conditions and unexpected river flooding was attributed to the tunnelling contractor.
The crossing was part of the West Snoqualmie River project for supplying water to Seattle, Washington State, USA. Tight environmental constraints on construction on the floodplain of, and under, a salmon-bearing river, and difficult and variable ground conditions characterised the project which, as planned but later modified, included six shafts and four microtunnels. The MTBM used was a 2.28 m Soltau RVS 800 STS. The eventual success of the project despite the ground conditions and unexpected river flooding was attributed to the tunnelling contractor.