The proposed Iowa Hill Development would be located on Iowa Hill approximately one mile upstream of the existing Slab Creek Dam on the south bank of the Slab Creek Reservoir. The 13,335-acre-foot capacity Slab Creek Reservoir is a component of the UARP, located on the South Fork American River (SFAR), near the communities of Camino, Swansboro/Mosquito, Pollock Pines and the city of Placerville. The design of the project was developed to minimize the visual effects by incorporating existing facilities like Slab Creek Reservoir and existing UARP transmission lines, by placing a majority of the plant equipment underground and moving the switchyard near the top of the ventilation shaft to minimize large cuts and eliminate new transmission lines running up Iowa Hill or across Slab Creek Reservoir.

The principle of a pumped-storage project, like the proposed Iowa Hill Development, is to make use of electricity during lower energy demand periods or when non-dispatchable energy from wind resources is available to pump water from a lower reservoir to a higher reservoir, then to generate electricity by releasing water from the upper reservoir during high energy demand periods and during times of electrical emergencies. Generally, the low energy (off-peak) pumping periods occur at night and weekends, while the high energy (on-peak) generation periods are in the early afternoon to late evenings in summer and early morning and late evenings in winter.

The proposed Iowa Hill Development would incorporate the use of existing UARP infrastructure and the construction of new facilities. The primary features of the development include: 1) the use of the existing Slab Creek Reservoir as a lower reservoir; 2) the construction of a new 6,400-acrefoot capacity reservoir atop Iowa Hill (the upper reservoir); 3) the excavation of underground tunnels/shafts and a cavern to enclose a 400 MW powerhouse and pumping facility within Iowa Hill; 4) the construction of an underwater intake/outlet structure in Slab Creek Reservoir; 5) the upgrade and improvement of existing access roads; and 6) the construction of a new 230-kV switchyard adjacent to the upper reservoir and about 2 miles of new electrical transmission line that would tie-in to existing UARP transmission lines.

Iowa Hill Pumped-storage Development Preliminary Construction Schedule