The sinkhole has been filled in. Photos courtesy of the US Army Corps of Engineers.
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The sinkhole that occurred at the Tuttle Creek stilling basin parking lot July 9, 2015 is scheduled to be filled July 16, primarily to eliminate the public hazard associated with the open hole in the parking lot. This measure will allow access to the area below the dam to be reopened to the public. The opening of the area is expected to occur by the end of the day July 17. Some parts of the stilling basin parking lot will be fenced to restrict public access.
U-S Army Corps of Engineers officials indicate the likely cause of the sinkhole was a corrosion (rust) failure of a backwall drainage pipe that equalizes pressures on both sides of the stilling basin wall, especially during high releases. Planning and design of an interim solution is currently underway. Additional short-term closures of the area will occur in the coming weeks while instrumentation to monitor this area is installed.
While the wall backfill is stable, (the Corps of Engineers believes that will remain the case), the plan is to await a previously planned October 2015 inspection of the dam and stilling basin to initiate steps of an interim repair. During this dewatering, water will be pumped from the stilling basin to allow a thorough inspection of the basin and the wall drain below the sinkhole. Following the inspection, measures will be completed to cover the system’s outlet to allow an interim repair to move forward.
A permanent solution is being designed and expected to be funded for construction in the future. It is anticipated that the permanent solution will also require closure of the area to the public for an extended period during construction.
