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04/11/2000 15:02 925-463-2559 ATC PLEASANTON '! PAGE 03 Guidelines for Investigation and Cleanup of MTBE and Other Ether-Based Oxygenates Overview This document is being promulgated in response to Executive Order D-5-99 and Senate',Bill 989 (Sher--Chapter 812,Statutes of 1999). It is intended to assist managers and staff at state and local regulatory agencies with the task of overseeing the investigation and cleanup of sites where there have been or may have been releases of MTBE-ladea petroleum. i The essence of this document is the understanding that the standard approach for dealing with petroleum releases employed over the past decade will not suffice for MTBE,because finlike i traditional petroleum constituents such as benzene,MTBE shoves quickly to pollute water and is i{( slow to degrade in the subsurface environment. Response time is critical for MTBE. A quick response to a release greatly increases the ability to check the spread of the MTBE and to clean up the mass of the release.Because time is critical,regulators will need to prioritize their cases and give first attention to those that pose the greatest risk to groundwater. It is also expected that j there will be more need for vertical definition of MTBE plumes and more reliance on active li cleanup technologies, such soil vapor extraction and groundwater pump and treat systems,than there has been for non-MTBE petroleum. This document provides criteria for identifying groundwater areas most vulnerable to contamination by MTBE and a priority classification plan for sites located in those areas. Target timeframes are provided for the completion of investigations and initiation of clear mp&. A decision-making framework is presented that focuses on the creation and use of a site conceptual model(SCM)as the principal case decision making and communication tool. Technical references are included. This document does not address the question of when to cease corrective action at an MTBE site. -< - A follow-up document will address case closure criteria specifically. Introduction - Executive and Legislative Mandates J Governor Davis issued Executive Order D-5-99 on March 25, 1999,and signed Senate,,,Bill 989 on October 8, 1999. These documerds recognize that if not managed properly,MTBE°can cause f significant adverse impacts to current and future beneficial uses of ground and surface water. The Executive Order contains eleven items that include tasks for various state departments and boards. Among these,item 8 directs the State Board to proceed to identify areas with vulnerable groundwater,prioritize resources,and to provide guidelines for the cleanup of MTBE in groundwater. a 'r STAFF DRAFT STAFF DRAFT Page 1 of 18