Manhattan Beach : Boundaries of Dangerous Vapor Pool at Beach Found

Chevron USA Inc. officials told Manhattan Beach officials this week that they have determined the borders of a gasoline-based hydrocarbon vapor plume found to be migrating along The Strand in recent weeks.

The plume, according to Chevron spokesman Norman R. LeRoy, extends from 45th Street to 39th Street along The Strand. Between 41st and 43rd Streets, he said, the plume bulges out to about Ocean Drive.

Pending clearances from state and local regulatory agencies, he said, Chevron will begin drilling the first of 14 observation wells in that area to monitor ground water for possible hydrocarbon contamination. The wells, LeRoy said, also will help Chevron determine whether there is a unknown pool of liquid hydrocarbons that is the source of the vapors.

Vapor readings in Manhattan Beach have hit extremely high levels since the vapors were first detected several weeks ago. Along 45th Street, readings have climbed as high as 95,000 parts per million, forcing Chevron to blacktop a 200-foot stretch of beach along The Strand. Gasoline-based hydrocarbons become explosive at 14,000 ppm.

Meanwhile, testing continues in El Segundo, where the initial discovery of hydrocarbon vapors was made in January. Chevron officials have already traced those vapors to a large liquid hydrocarbon pool that seeped off the refinery into El Segundo’s manufacturing district. Those vapors however, have reached only very low levels. That pool is not believed to be the source of the Manhattan Beach problem.