Los Vaqueros Reservoir Expansion

The Los Vaqueros Dam was constructed by the Contra Costa Water District in 1998 to create the Los Vaqueros Reservoir. In 2012, RECo’s MSE walls helped expand the reservoir’s capacity.

In 2011 and 2012, the Los Vaqueros dam height was raised to a height of 226 feet in order to increase the storage capacity of the reservoir from 100,000 to 160,000 acre-ft. The resultant is an increase in height of 34 feet over the originally constructed dam. The expansion of the dam was carried out by the Contra Costa Water District to develop water supplies for environmental water management purposes and the improved reliability of the water supply to the San Francisco Bay area.

The walls constructed for this project, which reached up to 49’ in height, were designed to be nearly completely submerged during a 100 year probable maximum flood.

The walls constructed for this project, which reached up to 49’ in height, were designed to be nearly completely submerged during a 100 year probable maximum flood. Therefore, highly permeable gravel back fill was utilized within the MSE mass to accommodate exposure to fluctuating conditions resulting from changing water levels in the reservoir. Due to the location of the dam clay core and unknown existing bedrock elevations at the MSE wall locations, the soil reinforcements were designed with a trapezoidal distribution which required field-modification of the soil reinforcements to match the achievable excavation for the construction of the walls. In addition to the corrosive marine environment, all of the reasons above led to the selection of the GeoMega system for this project. Although the achievable limits of excavation were not known when the initial design was performed, close coordination between Barnard and the design staff at RECo allowed real-time analysis of the actual field conditions to enable the contractor to make changes during the construction process while maintaining the project schedule.