Worried that an earthquake could collapse a big dam south of San Francisco, officials have ordered its reservoir to be completely drained by October to reduce the risk of floodwaters spilling into Silicon Valley. The 240-foot (73-meter) high earthen Anderson Dam, built in 1950 between San Jose and the community of Morgan Hill, poses too great a risk of collapse and must be fully drained by Oct. 1, according to the Federal Energy Regulatory Commission, which regulates dams, the Mercury News reported. Since 2009, the dam’s water level has been kept at a maximum of 74 percent of capacity because...