An Old Site for a New Dam - The Challenges of Replacing Anderson Dam

The Santa Clara Valley Water District (Valley Water) is addressing seismic vulnerabilities of its 240-foot-high Leroy Anderson Dam by replacing the existing dam at the same location with a new dam that meets modern seismic safety standards. The project includes conversion of the Anderson Dam Tunnel Project diversion system currently being constructed to a higher capacity diversion system to bypass reservoir inflows each winter season. Earthwork to replace the dam is planned to occur over a five-year period, with a series of four lowered interim dams each protected with temporary articulated concrete block lined spillways to convey more extreme inflow events. This paper provides a project overview including key design criteria, construction sequencing considerations, geotechnical analyses of the dam sections, and evaluation of construction schedule risks and considerations. This paper also briefly discusses risk mitigation strategies, surveillance monitoring, Emergency Action Planning, and dam safety regulatory agency coordination.