SITE INFORMATION AND CORRESPONDENCE

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` Water Qualitv Site Assessment -3- IDR A FT 5 November 1992 Determination of Water Quality Limits To determine whether past waste management activities have degraded or have the po- tential to degrade water quality, applicable water quality limits need to be determined for the contaminants involved. Water quality limits are numerical contaminant concen- trations, above which contaminants are considered to have adversely impacted beneficial uses (to have limited certain uses) of waters of the state. Water quality limits are used to implement the numerical and narrative water quality objectives contained in the state and regional Water Quality Control Plans. To select water quality limits, determine the following: ❑ beneficial uses of the water body being investigated; ❑ applicable water quality objectives to protect those beneficial uses; ❑ numerical water quality limits that will implement all applicable water quality ob- jectives (i.e. drinking water standards, water quality criteria for agriculture,health advisories, Proposition 65 No-Significant-Risk Levels, etc.); and finally, ❑ choose the most limiting value to be the water quality limit for each particular con- stituent,because it is protective of all beneficial uses. During the site assessment phase of a site investigation, detected constituent concentra- tions are compared to numerical water quality limits to determine if beneficial uses have been impacted. During the cleanup level determination phase, the background concen- tration is selected as the initial cleanup level, based on State Board Resolution Nos. 92-49 (Policies and Procedures for Investigation and Cleanup and Abatement of Discharges under Water Code Section 13304) and 68-16 (Antidegradation Policy). If the discharger demon- strates that it is technologically and/or economically infeasible to achieve background concentrations, then some achievable cleanup level between background and the water quality limit can be negotiated. However, any cleanup level greater than background based on feasibility must still comply with all applicable statutes and regulations, and must not cause risk to human health and the environment, including beneficial uses of water. Site-wide Background Assessment of Soils 1. Select a minimum of four soil sampling sites that,based on available information, appear to be out of the influence of past waste management activities. Off-site sam- pling may be necessary if unimpacted areas cannot be found on-site. 2. Collect a soil sample at each location from each lithology type present above the water table. Each soil sample must be large enough to perform the Waste Extraction Test (WET) procedure with deionized water,' and to analyze the extract for all of the following: The standard citrate buffer should be used if the soils are significantly acidic or could become acidic.