Deer Creek Modification Project Update

Sixty year old dam upgraded to meet current seismic standards

John Robert Carman, General Manager, Metropolitan Water District of Salt Lake and Sandy

November 18, 2003

(Salt Lake City, Utah) The Deer Creek Dam Modification Project began construction in May 2003 after many years of study and planning.  The United States Bureau of Reclamation (Reclamation) is managing this work, which is expected to be complete by April 2004. Located in Provo Canyon, Utah, the 152,000 acre-foot reservoir was built by Reclamation as part of the Provo River Project.

An evaluation of Deer Creek Dam, funded by Reclamation under the Safety Evaluation of Existing Dams program, identified potentially liquefiable soils in the original design and construction of the dam.  Liquefiable soils are soils susceptible to liquefaction in a large seismic event. Extensive drilling and testing confirmed the presence of these soils.

Constructed between 1938 and 1941, Deer Creek Dam has served the population centers in Salt Lake and Utah Counties reliably for more than 60 years.  Having identified a potential risk, Reclamation design team developed a project to reinforce the dam.  The project started with dewatering the downstream toe of the dam by drilling a series of wells and then pumping to lower the groundwater level below the river level.  When the groundwater was lowered to an acceptable level, excavation began to remove the liquefiable soils.  These soils are then replaced with a dense, highly compacted soil carefully designed to retain its strength and structural integrity in the event of a large earthquake near the dam. This compacted soil is called the "shear key".  In addition to the reinforcement work, a modern seepage monitoring and drainage control system is being installed.

Shear key excavation is now complete and the backfill and compaction phase of the project has started. This work is continuing around the clock and backfill is expected to be back above the river level by the end of 2003.   The project is expected to be completed by April 2004.

The estimated cost of the project is $ 10 million and is being funded under the Safety of Dams Act passed by the United States Congress in 1978.  This legislation requires the local project sponsor, in this case the Provo River Water Users Association (PRWUA), to fund 15% of the cost with the Federal government picking up the rest of the cost.  Since the Metropolitan Water District of Salt Lake and Sandy is the largest shareholder in the PRWUA, tax and ratepayers in Salt Lake City & Sandy City are paying about $1 million towards the project costs.