• Frozen soil shoring was used in the construction of a 390-linear-foot section of a 60-inch-diameter water pipeline where it passed under Bear Creek, a salmon-bearing stream.
• Soils consisted of wet, loose silty sand over dense silty sand, gravel and cobbles.
• Concern about the footings of a nearby transmission tower prohibited dewatering.
• 230KV power lines limited headroom to 25 feet.
• The shoring was designed to a thickness of 4 feet and a depth of 53 feet to resist 30 feet of hydrostatic pressure for a 35-foot excavation.
• The shoring provided a dry hole for the two months the shaft was open.
• Grouting between the casing and the frozen soil completely cut off the minor groundwater in-flow after the microtunneling machine drilled through the frozen soil shoring.

Receiving cylinder (left) embedded in the frozen soil.