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Draft Amended Report of Waste Discharge (AROWD)/ Work Plan Austin Road Landfill 1 .0 Introduction The City of Stockton's(City)Austin Road Landfill(ARL)is operating under the Central Valley Regional Water Quality Control Board's (CVRWQCB)Waste Discharge Requirements (WDRs) Order No.96-175. The Order specifies the implementation of a Corrective Action Program, developed in accordance with Title 23,Chapter 15,Article 5 requirements,to address the Volatile Organic Compound (VOC) groundwater plume downgradient of the site. The current system consists of two groundwater extraction wells,an on-site groundwater treatment facility,and a network of groundwater monitoring wells to verify system effectiveness (Figure 1). Data obtained from the 1997 first quarter groundwater monitoring at the ARL indicated that contaminants from the landfill have migrated beyond the 1,000 foot plume boundary established in the 1991 Corrective Action Plan. In correspondence dated March 7, 1997,the CVRWQCB directed the City to submit an amended report of waste discharge (AROWD) to bring the landfill into compliance with Section 2550.10(j)of the Article 5 regulations. The purpose of the AROWD is to define the tasks required to investigate the plume and modify the corrective action system to achieve compliance with Article 5. The primary element of the AROWD/Work Plan is a detailed presentation of the activities required to delineate the vertical and lateral extent of groundwater pollution at the disposal facility. Also included is a schedule to conduct the investigation,and to submit the revised engineering feasibility study. 1.1 Objectives The objectives of the plume delineation investigation are presented below: ■ Define the current nature and extent of the VOC contaminant plume at the ARL. Plume characterization includes defining the vertical and lateral plume extent,assessing the impact of the two extraction wells and local water supply wells on plume movement,and evaluating the attenuation rates of the VOC migration and contamination. ■ Installation of permanent monitoring wells outside the limits of impacted groundwater. These wells will provide data to evaluate plume movement and the effectiveness of the modified corrective action program and to verify the plume delineation data. ■ With the use of computer modeling,estimate the rate and direction of plume movement in the aquifer. Lithologic,water level,and water quality data obtained during the field investigation will be used to develop the solute transport model. F W:\REPORTS\STOCKTON\AUSTIN\WORKPLAN.DOC Page 1