East Lake Dam was designed and constructed by the Columbia Valley Authority between 1938 and 1952 and extends 3,979 feet and has a maximum height of 94 feet. The East Lake Dam consists of an earthen embankment and a concrete section that controls outflow to the power plant and water level control. This dam was built to control flooding, provide hydroelectric power, enhance recreational opportunities, and provide quality potable water to area communities. It impounds the Roaring River and is approximately one mile across. It is capable of producing 140,400 kW. At maximum elevation, the dam impounds 162,000 acre-feet of water.

Fifteen years after completion, a study of muddy flows and two sinkholes at the toe of the dam revealed the Karst topography of the supporting bedrock was causing significant seepage problems in the dam’s foundation, threatening its structural integrity. Ten years after the discovery of the seepage, a concrete diaphragm wall was constructed, which runs through the earthen embankment down to the bedrock. While this solution provided temporary relief from the dam’s erosion, instrumentation embedded throughout the dam has highlighted areas where seepage was not entirely blocked and has found new paths around the diaphragm. This continued degrading of the dam’s condition convinced the United States Army Corp of Engineers (USACE) to designate the East Lake Dam as “high risk” for failure. A sudden catastrophic failure of the East Lake Dam would cause a significant loss of life and cause serious economic losses. The loss estimates for Central City, the community most at risk below East Lake Dam, are loss of life of up to 5,000 individuals and a financial impact of five billion dollars.

The inundation map shows the extent of flooding that would occur if the East Lake Dam should experience a catastrophic failure. The Turtle River, south of Central City, would also be impacted all the way to the coast. Currently, remediation approaches are plans for a larger diaphragm using newer technologies along with a grout curtain and a lowering of the lake level by a fifth of its normal height. Warning sirens have been installed to provide early warning to the populace in the event of the dam’s failure.