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11 C C: 1 8 October 1986; Updated — June 1989 SUMMARY OF THE STAFF REPORT OF THE CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD, CENTRAL VALLEY REGION California is a state that is significantly limited by the availability and quality of its water resources. Improper waste management practices and contami- nated sites pose significant threats to the quality of California's usable ground and surface water re- sources. The purpose of this narrative is to outline a system for selecting numerical limits, consistent with these standards, that may be used to assess impacts from waste management activities and pollutant re- leases on the quality of waters of the state and the ben- eficial uses of these waters. This paper summarizes information contained in a staff report of the California Regional Water Quality Control Board, Central Vallzy Region entitled The Des- ignated Level Methodology for Waste Classification and Cleanup Level Determination. This report establishes a framework for classifying wastes so that water quality protective treatment, storage, and disposal practices may be selected and for determining water quality pro- tective soil cleanup levels. To determine whether a particular waste manage- ment activity or pollutant release has caused or threat- ens to cause pollution, staff of the Regional Water Quality Control Boards must apply California's water quality standards, contained in the Water Quality Con- trol Plans, to select applicable numerical water quality limits for each pollutant involved. At concentrations equal to or greater than these numerical limits, California's water quality standards have been ex- ceeded and the pollutants are considered to have ad- versely impacted the beneficial uses of waters of the state. To further assess the impact or potential impact of waste materials or contaminated soils, "soluble des- ignated levels" may be calculated from the water qual- ity numerical limits, using information specific to the waste or pollutant and to the site of waste discharge or pollutant release. If the soluble concentration of a pol- lutant in a waste or soil exceeds its calculated soluble designated level, the waste or soil is assumed to pose a site-specific threat to water quality. WASTE CLASSIFICATION In California, the classification of wastes is per- formed by two separate Cal/EPA state agencies with separate regulatory authority. The Department of Toxic Substances Control (DTSC; formerly the Toxic Substances Control Division of the Department of Health Services) classifies wastes as hazardous or non- hazardous based on their direct threat to public health. The State Water Resources Control Board, together with the nine Regional Water Quality Control Boards, classify non -hazardous wastes as "designated", "non- hazardous solid" or "inert", based on the threat that each waste poses to the beneficial uses of ground and surface waters, as required by the Porter -Cologne Wa- ter Quality Control Act and regulations, water quality control plans and policies set forth by the Water Boards. As shown in Figures 2 and 3, Water Board regula- tions divide wastes into four categories which, in turn, determine the classes of waste management units to which their discharge is permitted for treatment, stor- age or disposal. Detailed criteria are contained in Title " of the California Code of Regulations, Division 4.5, Chapter 11 for determining whether a waste falls into the hazardous category. These criteria fall under the headings of toxicity, ignitability, reactivity, corrosivity, and listing under the federal Resource Conservation and Recovery Act (RCRA). Hazardous wastes may be discharged only to Class I waste management units which provide both natural geologic and engineered containment features to isolate the wastes from the environment, unless a specific variance has been granted by DTSC from California's hazardous waste management requirements. "Noi-dlazardous solid waste" is the regulatory