SMUD proposed developing the Iowa Hill Pumped Storage Project. If constructed, Iowa Hill would be a 400-megawatt variable speed pumped storage hydroelectric facility, roughly 50 miles (80 km) east of Sacramento. The project would utilize an existing reservoir on the American River, from which water would be pumped up to a new 6,400-acre-foot (7.9 million cubic meters) capacity upper reservoir, where the water would be stored. During peak electrical demand periods, water would flow from the upper reservoir to the lower reservoir via a 1,400-foot-deep (427 m) shaft and 3,560 feet (1,085 m) of water tunnels.
SMUD retained the Delve Underground team to provide owner’s engineer services for preliminary design, geotechnical investigation, and construction services on the proposed Iowa Hill project.
The geotechnical investigation’s drilling program continued with the mining of a geotechnical exploratory drift (tunnel) from the surface to the proposed underground powerhouse cavern vicinity. The results of the drilling program helped SMUD determine whether the Iowa Hill project site is viable for the construction of the tunnels and underground cavern that would house the variable speed generator/motors.