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yr :; 12 PURPOSE In order to begin soil and groundwater remediation at Station 434, BC has developed this comprehensive work plan for the County's and Regional Board's review and approval. The work plan consists of three parts: soil characterization work, installation of a groundwater extraction well and aquifer testing, and installation of additional off-site monitoring wells. The purpose of the soil characterization wor is to better characterize hydrocarbon occurrence in the vadose zone, particularly between the leak site and monitoring wells W-2 and W-3. The available data indicate that hydrocarbons in the vadose zone in ;this area continue to migrate downwards and enter the groundwater. Following the soil characterization work, the original soil remediatio plan can be modified, as necessary, prior to implementation. The soil characterization part of this work plan is intended to supersede the similar November 1988 soil characte zation work plan. The immediate purpose of the groundwater a traction well is to provide a means of conducting an aquifer test to determine aquifei characteristics (relevant to the final groundwater remediation system design) and to induce a cone - of depression in the groundwater beneath Station 434 to prevent further off-site migration of hy4rocarbon constituents. The extraction well will be used in t e final remediation system design. The extraction well portion of this work plan supersedes the March 1988 extraction well work plan. The question of the discharge of the treated groundwater from the extraction well has yet to be resolved. Under certain conditions, the City will allow short-term :discharge (from the extraction well pump test) of treated ater into its sewer system. The City, however, has refused to allow any long-term discharge of the treated water into ;its sewer system. Therefore, ARCO will request a National Pollutant Discharge Elimination System permit be granted at this site for the disposal of mated effluent water. The purpose of the additional off-site monitoring wells is to better define a "zero line" of hydrocarbons in the groundwater around Station 434. This information will be useful in documenting the remediation of the groundwater. Completion of this work will be dependent on obtaining off-site permission for installation of the additional off-site monitoring wells. The three parts of this work plan are sufficiently independent of one another that implementation of one part need not be tied to another. In the interest of timeliness, the County and Regional Board should approve all three pans of this work plan simultaneously. FIELD METHODS This section describes the field methods for the on-site soil characterization, on-site groundwater extraction well installation, and off-site groundwater monitoring wells installation. The locations of public undergrOLItid utility lines in the Kettleman Lane,