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Barbara Coler - 2 - 23 January 1997 this new information and further guidance on acceptable levels in water is forthcoming. 2 . Samples should be analyzed by running a standard EPA Method 8270 with a detection limit of 10 µg/1; this detection limit has been routinely achieved by the Aerojet laboratory. Alternatively, 1, 4-dioxane may be analyzed using EPA Methods 8240 or 8260 with detection limits of 50 µg/1. In either case, the laboratory must be specifically requested to analyze for 1, 4-dioxane while running these methods . 3 . Once its presence has been confirmed, the nature and extent of the dioxane contamination should be established. 4. When a plume has been defined, cleanup alternatives should be evaluated in the same manner as is done for other constituents which pose a comparable impact or threat to beneficial uses . 5 . Aquifer cleanup levels and discharge levels to surface water should be developed consistent with relevant numerical criteria which are available at this time, e.g. , drinking water standards, the 1 in 106 cancer risk level, Proposition 65 levels (1 in 105 cancer risk level in a drinking water source) , and ally-other appropriate levels to protect beneficial uses, consistent with the Basin Plan. If new or revised information on the risk posed by 1, 4-dioxane becomes available, such levels should be modified accordingly. Relevant information developed during the feasibility study should also be included in the development of cleanup levels, consistent with State Water Board Resolution No. 92-49 . Please let me know if these revisions do not agree with our discussion. I can be reached at (916-255-3039; CALNET 494- 3039) . CC: Regional Board Assistant Executive Officers Dr. Jeff Wong, DISC Dr. David Siegel, OEHHA Recycled Paper Our mission it to preserve and enhance the quality of California's water resources for the bencfii of present and future generations.