A new diesel fuel casing trench was constructed in a highly contaminated and active railroad yard. The project consisted of installing two parallel 20-inch diameter steel pipes and three access vaults. The depth of the excavation was approximately 12 feet deep.

Groundwater highly contaminated with petroleum product was encountered approximately 3 feet below the ground surface. Although remediation of the contaminated soil and groundwater was not required at the site, a typical dewatering approach would result in a significant amount of water to collect, store, treat, and discharge. In addition, there were rail lines that crossed the trench that needed to remain active for as long as possible.

Frozen soil shoring was selected to provide a stable shoring system for the excavation and cutoff contaminated groundwater inflow from outside the excavation. The system was installed adjacent to the rail lines and excavation was staged so that the disturbance to the rail system was limited during construction of the casing trench.

The excavation and construction of the casing trench was successful. Dewatering and associated collection, storage, treatment, and discharge of contaminated groundwater was significantly minimized and limited to the volume trapped within the limits of the excavation. No disturbance to the rail lines was measured during the freezing process.