The Laboratory routinely collects and analyzes samples of groundwater from dozens of groundwater-monitoring wells and drinking-water-supply wells located throughout the region as part of its environmental surveillance and stewardship activities. Five water samples taken from two monitoring wells in Mortandad Canyon since June 2005 indicated the presence of the ether. The ether has not been detected in nearly 540 other water samples collected from 2005 through early 2006 at other areas of the Laboratory.
The monitoring wells where the chemical was detected provide surveillance for two perched groundwater zones located 450 feet and 250 feet above the regional aquifer. A perched groundwater zone is a segregated pocket of water located beneath the ground’s surface but above another groundwater body.
The ether was detected in amounts ranging from 20 to 50 parts per billion. Another way of expressing 20 to 50 parts per billion is thinking about 20 to 50 seconds in a 32-year period.
Federal drinking water standards for 1,4-dioxane do not exist, although some states such as California have assigned drinking water action levels for the chemical, which is a suspected carcinogen. Under California standards, if the chemical were present in drinking water wells at a concentration of 300 parts per billion (100 times the action level), the well would be recommended for removal from service.
A Consent Order from the state Environment Department requires the Laboratory to determine cleanup levels for contaminants having no regulatory standard using Environmental Protection Agency Region VI risk calculations. The chemical is at a concentration below the EPA Region VI risk levels and has not been detected in the regional aquifer or in drinking water.
The Laboratory has not identified the source of the chemical but will investigate possible origins, perform continued monitoring and, if possible, reduce or eliminate sources of the chemical that could potentially threaten the environment.
1,4-dioxane is used as a solvent for a wide range of organic products, paints, varnishes, cleaning and detergent preparations, cements, fumigants, corrosion inhibitor, in analytical measurements including liquid scintillation counting, and as a solvent stabilizer.
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