In the spring of 2009, the Red River of North Dakota flooded six feet deep and ten miles wide in Pembina County. The flood was followed by arctic temperatures that froze the floodwaters 8-inches thick and also froze around the stems of seven isolation valves. These isolation valves were for pipelines carrying crude oil and natural gas liquid (NGL). The pipeline sizes varied from 36-inch to 18-inch diameters. The ice around the valves was subjected to wind forces of 50 mph putting the valves at risk. Also, when the second spring runoff came, the river current pulled ice down through the valley. This ice flow took out trees, power poles, and damaged a couple of isolation valves. The damage was minimal, but could have been worse. No leaks occurred.
This paper will explore the unique problems associated with protecting the valves and delve into keys and principles that led to an innovative solution. Technical issues will be discussed that will help future projects solve problems on how to protect equipment from ice flows. The underlying soils were known for their excessive settlements and low shear strength. The soil was predicted to settle 6-inches after adding eleven feet of fill for protective berms. The preliminary pipe stress calculations based on the predicted settlement of 6-inches put the allowable pipe stress near the limits of acceptability. The valve site was also located miles from the nearest road. The forces from the ice loads in a river can be enormous and engineering judgment had to be used to obtain a practical solution.
