A draft California Public Health Goal could lead to a requirement for California water agencies to reduce hexavent chromium to the ultra-low level of 0.02 parts per billion. The naturally occurring suspected carcinogen is present in as much as a third of the state’s groundwater supply. The federal government currently only regulates total chromium levels at 100 parts per billion. The draft goal, released in December 2010, was reduced from a previously suggested 0.06 parts per billion “to account for increased sensitivity associated with early-in-life exposures,” according to a state study. The California Dept. of Public Health could set drinking-water
Arch dams, classically curved monoliths situated in narrow valleys, are not as common as other types of dams, such as embankment dams and gravity dams. ENR takes a look at some of the biggest arch dams in the world, both completed and under construction.