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M <br /> MEMORANDUM <br /> Calm Pete wlson <br /> T0: Barbara Coler, Chief Gp1C1 <br /> Central Valley Statewide Cleanup Operations Division, DTSC, Region 2 <br /> Regional water 700 Heinz Avenue, Suite 200 <br /> Bo <br /> Quality control <br /> Board Berkeley, CA 94710-2737 <br /> 3443 Routler Road <br /> Suite A <br /> Sacramento CA FROM: Thomas R. Pmkos <br /> 95827-3098 Assistant Executive Officer <br /> (916)255-3000 Central Valley Regional Board <br /> FAX(916)255-3015 <br /> DATE: October 16, 1996 <br /> SUBJECT: 1,4-DIOXANE <br /> In a memorandum dated 19 July 1996 (copy attached) you specified the manner by <br /> which DTSC Cleanup Operations Branch Chiefs shall respond to releases of 1,4- <br /> dioxane. The memo directed your staff not to consider 1,4-dioxane a chemical of <br /> concern (COC) unless "there has been a release," not to sample for it if there has been <br /> no such release, and, where there has been a release, to use 20 - 200 mg/l as a <br /> benchmark to determine if dioxane is a COC. <br /> Although I respect your prerogative to establish cleanup policies for your staff, the <br /> memo regarding dioxane is somewhat troublesome for cleanup staff at this Regional <br /> Board. <br /> First, the levels of dioxane used as a "benchmark" or trigger for its concern are well in <br /> excess of the Proposition 65 regulatory standard of 15 µg/1, which is promulgated by <br /> OEHHA, and other established criteria.' Dischargers (i.e., RPs) who have caused this <br /> level to be exceeded in groundwater may have significant liability under the Prop 65 <br /> statute. Furthermore because this Board has incorporated Prop 65 values into its Basin <br /> Plan cleanup policy and water quality objective for toxicity, the memo is inconsistent <br /> with those governing documents. <br /> Secondly, the instruction in the memo not to require sampling for dioxane "unless there <br /> has been a release," begs the question of what constitutes "a release." We know that <br /> 'The Proposition 65 level for 1,4-dioxane of 15 µg11 represents a 1 x 10'5 incremental cancer risk level; <br /> California and EPA criteria provide a range of 1.6 to 2.5 µg/1 for a 1 x 10* incremental cancer risk <br /> level. <br /> Recycled paper Our musion a to preserve and enhance the quality of California's wvier resources.and <br /> ensure their proper allocation and efficient use for the bexfrr of pmrent and furure generahoru. <br />