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-3- The clay liner will be a minimum of two feet in thickness with field and lab testing to insure that this liner will prevent water movement into the waste. The clay liner will consist of selected site materials that contain sufficient clays and silts to meet the minimum requirements. The quality assurance plan has been prepared to handle field and lab testing and problems that might be encountered during construction. The vegetative/drainage layer will be one foot in thickness and will consist of native material and be placed on top of the clay liner. This layer will then be seeded with natural grasses and maintained to insure that erosion is controlled. This layer will also allow the clay liner to drain adequately during rainfall .- events. The culvert drainage system is designed to gather the run-off that originates from the vegetative layer and route the water into a holding pond. The use of corrugated steel culverts to route the water will prevent erosion caused by channelized flowing water. The groundwater monitoring system will consist of 13 groundwater monitoring wells to collect information about the nature of the flow and quality of groundwater underneath the facility. Twelve of the 13 wells presently exist at the facility and have been used to gather groundwater quality and flow information. The groundwater flow information gathered thus far indicates that one additional well is needed to detect any contamination that might be released from WMU-A. The vadose zone directly below the landfill unit will be monitored with the use of suction lysimeters. Suction lysimeters are monitoring devices that extract water from soil that is not fully water-saturated but not completely dry. These devices will be placed directly under the hazardous waste unit liners in order to detect a leak, should it occur, before the contamination can reach groundwater. Regulatory Basis The Forward, Inc. Closure Plan for the hazardous waste unit and supplementary documents would allow Forward, Inc. to permanently close the hazardous waste unit in accordance with all of the requirements set forth in: the Resource Conservation and Recovery Act (RCRA) of 1976, as amended by the Hazardous and Solid Waste Act (HSWA) of 1984 ; the California Health and Safety Code; Title 22 of the California Code of Regulations; and any other more stringent conditions required by DHS and EPA in the final Closure Plan to insure protection of public health and the environment.