Great Falls Water Main Crossings

The City of Great Falls relies on 4 river crossings to maintain pressure and flow in the distribution system west and north of the Missouri River. Although these crossings provide sufficient capacity and pressure, they offer little redundancy. In the event a crossing or connecting water main requires repair, the feed may be out of service for several weeks.

To address water supply redundancy limitations, the City of Great Falls contracted with TD&H to complete a River Crossing Route Evaluation that investigated and recommended horizontal alignments for 3 proposed water main crossings in the City of Great Falls; one under the Sun River and two under the Missouri River.

TD&H’s geotechnical investigation included 100’+ bore holes within two Missouri River channels, the Sun River channel, Park Island and several ground locations, was completed following permitting approval. Pre-selecting bore hole locations was critical to collect representative soil conditions for technical analysis.  However, maintaining separation from the drill path was necessary to prevent a conduit for drilling fluid frac-out. Soils collected during the field investigation were tested in the accredited TD&H Materials Lab to identify various engineering properties necessary to analyze river scour geometry, evaluate frac-out potential and provide site specific data for HDD materials and methods design.

This project won the ACEC Honor Award in Water Resources in 2019.