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ri yr. ` M E M O R A N D U • CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD CENTRAL VALLEY REGION 3443 Routier Road, Suite A Pte: (916)255-3000 Sacramento, California 95827.3098 CARNET: 8-494.3000 TO: Wendy Cohen FROM: Polly Lowry Senior Engineer Associate Engineering Geologist SLIC SLIC DATE: 18 September 1996 SIGNATURE: SUBJECT: 1,4-DIOXANE MONITORING AT SOUTHERN PACIFIC TRANSPORTATION COMPANY'S SACRAMENTO RAIL YARD On 23 August 1996 I met with staff from the Department of Toxic Substances Control (DTSC) and representatives of Southern Pacific Transportation Company (SPTCo) to discuss the issue of 1,4- dioxane (dioxane) monitoring at the Sacramento Rail Yazd. SPTCo conducted its fust quarter of sampling for dioxane during the fourth quarter 1995, at DTSC's request. That sampling event included sampling only seven wells and effluent from two extraction and treatment systems. Dioxane was detected in all samples and ranged from 2.9 to 140 µg/1. The detection of dioxane in all samples resulted in additional monitoring points being recommended for dioxane analyses. The second quarter sampling for dioxane included additional sampling points agreed to between SPTCo, DTSC, and the Board. Samples collected during the second quarter 1996 from 62 monitoring wells and five extraction wells were analyzed for dioxane. SPTCo presented the second quarter 1996 dioxane data at the 23 August 1996 meeting. Dioxane ranged from less than 0.41 µg/1 to 500µg/l. Of particular importance was the distribution of the dioxane and the discussion of what the regulatory agencies expected next from SPTCo. It was evident from the data presented that neither the lateral or vertical extent of dioxane contamination in ground water has been determined. SPTCo has received a copy of DTSC's 19 July 1996 memo which stated dioxane is not initially a chemical of concern (COC) unless there has been a release of dioxane and that 20 mg/1 dioxane can be used to determine if dioxane is a COC in ground water. I informed SPTCo that the Regional Board will continue to use the current Proposition 65 level fordioxane (15 µg/1) until it is officially revised by OEHHA. SPTCo stated they would do what DTSC, the lead agency, recommended. In other words, they were refusing to meet the Board's requirements. I informed them that even if the Proposition 65 level is revised to the concentration suggested in the DTSC memo that our Anti-degradation policy would require further definition of the extent of dioxane. I also told SPTCo that I wasn't sure how we would enforce our requirements for dioxane monitoring. I suggested possible enforcement through the Monitoring and Reporting Program we have on them. We ended the discussion with me informing them that our office was still reviewing the DTSC memo and that the Board had not yet decided how to handle the dioxane issue at sites where contamination occurs.