Operation of the Tolt Dam failure warning system

The Tolt Dam and Reservoir provides storage of over 57,500 acre-feet for one-third of the water supply for 1.4 million residents in the Seattle metropolitan area and generates 16 megawatts of electrical power. The dam is located about 40 road miles from downtown Seattle and about 16 river miles upstream from the City of Carnation with a population of over a thousand residents. A dam failure warning system was initially installed in 1979 at the insistence of the downstream community. The system was replaced with a second-generation state-of-the-art warning and automated data acquisition system in 1993 to overcome false alarms and reduce maintenance requirements. This paper highlights, from an owner’s perspective, problems with operating and maintaining the second generation Tolt dam failure warning system, and how they were overcome. It also discusses the present major upgrade to the system as well proposed improvements to the system. In addition, it provides brief information on the dam failure modes being monitored. 13 pp., 6 references.