The project involved a new coal handling facility for Public Service of Colorado in Englewood, Colorado. It consists of a large structure buried about 25 feet deep into which coal from trains is dumped. The coal is then transported up into a stockpiles via a long, inclined conveyor. The excavation for the facility was T-shaped with the approximate overall plan dimension of 85 by 120 feet.

The contractor was have difficulties coming up with a shoring solution that would also cut off groundwater inflow to keep within their limited dewatering quantities allowed in the permit. Sheet piles were not feasible because of the presence of large cobbles in the soil and dense claystone below the excavation level.

A thick frozen soil wall was used to shore the excavation perimeter and to cut off groundwater flow into the excavation to an acceptable amount. Freeze pipes were installed into the claystone around the entire site perimeter using auger drilling methods that allowed the freeze to extend well into the claystone and effectively cutoff most of the groundwater flow.

The 5-foot thick frozen soil was formed in about 4 weeks. With added angled freeze pipes at selected locations, the wall effectively shored the site with negligible wall movement, even next to large cranes. Ground water was significantly cutoff limiting the flow quanities to within the permitted amount. This allowed the contractor to successfully complete the facility within the project schedule.