Devil's Lake, ND: Soil Bentonite Slurry Wall Installation, Devil's Lake City Embankments
Devil's Lake is the largest natural body of water and the second largest body of water in North Dakota. The city of Devil's Lake takes its name from the lake and is located on its northeastern shores. Over the past two decades, the water level of the lake has been steadily increasing at an alarming rate. The water must reach a certain elevation before it has a natural run-off into the Tolna Coulee. The city of Devil's Lake is located below this target elevation. The Army Corps of Engineers designed a levee to help protect the city of Devil's Lake from the rising lake elevation. Part of the levee design included the use of a soil-bentonite slurry wall to aid in flood prevention.
Geo-Solutions Inc. worked with the Subcontractor, Strata Corporation, to install a 7,463 LF soil-bentonite slurry wall. The wall included two tie-ins to an existing slurry wall. For the construction effort, Geo-Solutions provided all the materials, equipment and personnel to complete the slurry wall. The specialty equipment included GSI custom long boom/stick excavator attachment to fit a Komatsu PC 750, custom boom cylinders to reach maximum depths, trenching buckets with rock rippers, slurry mixing plant and piping.
Initially the personnel included a supervisor, an engineer, four operators, and one laborer. Later, a change of conditions prompted the mobilization of a second crew and equipment. Two more operators and one more laborer came to the site. A PC 800, equipped with a GSI extended stick and boom, was used for excavation. Once mobilization was complete, the two digging excavators were placed at opposite ends of the project, where they began to excavate towards each other. Both machines continued excavation until they were within a hundred feet of one another. Then one machine was pulled out and moved to another portion of the job. Meanwhile, the other machine continued excavation until it tied-into the first machine's trench. In the end, GSI constructed four separate slurry trenches all tied-into each other or an existing slurry wall.
The frequent occurrence of boulders caused a change of conditions. Large boulders were removed from the trench on a daily basis. Not only did these boulders cause production delays to remove but they caused a substantial amount of down time for equipment repairs.
Due to the many delays and downtime the project was not finished on schedule but was completed before the frigid winter months. Overall, the contractor was pleased with the final product and was impressed with Geo-Solutions' resilience.