The Contra Costa Water District's board of directors has awarded a $35 million construction contract to enlarge its dam at Los Vaqueros Reservoir.
Construction is set to begin in the spring and be done by the end of 2011. The dam enlargement, part of a $120 million reservoir expansion, will be done by Barnard Construction Company.
It will increase the reservoir's capacity from 100,000 acre-feet to 160,000 acre-feet.
The bigger reservoir will better protect the Concord-based district's 550,000 customers from drought, the district says.