For the first time since California’s dam-building boom ended nearly a half century ago, state officials on Tuesday approved a windfall of cash for new water storage projects, setting the stage for at least a mini-resurgence of reservoir construction. The historic $2.7 billion of voter-approved bond money will go to elevating two Bay Area dams, at Los Vaqueros Reservoir near Livermore and Pacheco Reservoir east of Gilroy, as well as to the development of two much larger dams in the Central Valley. Funds also will go to four less traditional endeavors that store water underground.