The gates at the Seven Oaks dam, at the foot of the San Bernardino mountains, southern California, were tested successfully last week, even though a 9m by 9m section of concrete inside the dam began eroding.

David Wert, public information officer for the county of San Bernardino, is quoted on as saying that the erosion does not pose any danger.

The test, with water releases ranging from 438m3 to 767m3/sec, was to ensure the safety of the dam, which holds back the flood prone Santa Ana river. At 168m, it is one of the tallest in the US.