UCA Webinar: Lake Thistle Emergency Drainage Project

Randall Essex, P.E. Executive Vice President‐ Director of Professional Excellence and Practices Mott MacDonald presents a case history on the Lake Thistle Emergency Drainage Project.

A 25 million cubic yard mudslide formed an un‐engineered, 225‐foot high dam across a river canyon near Spanish Fork, Utah. The mass of montmorillonite, judged the sixth largest landslide in the history of North America, completely blocked the flow of the Spanish Fork River, and formed a 60,000 acre‐foot, 200‐foot deep lake. The impounded runoff completely engulfed the town of Thistle, situated ½ mile upstream of the slide, and submerged the town beneath 175 feet of water.

A team of engineers and engineering geologists was retained to design and engineer an emergency system to drain the lake as quickly as possible, and provide a permanent diversion for the river around the slide‐dam. The system included a 2,230‐foot long, 13‐foot wide drill‐and blast rock tunnel, a 16‐foot diameter, 180‐foot deep shaft, a bulkhead and twin valves at the base of the shaft to control lake water discharge, and a sequentially deepened channel
excavation between the lake and the shaft.

[MrThermoBob]

Wonderful to see such detail in what was a very real problem with risks for all. Very interesting in how this was tackled and solved. Thanks for the presentation!