For years, San Diego Unified has known plumbing was aging at 78-year-old Emerson-Bandini Elementary School in Mountain View. In fact, three times in the past 13 years, Emerson’s plumbing needs were held up to voters as one of the reasons they should approve tax hikes to fund school repairs. Voters approved all three measures, pumping billions of dollars into the district. But the plumbing repairs have yet to happen. In the meantime, school officials found alarming levels of toxic chemicals in the water at Emerson.