SITE INFORMATION AND CORRESPONDENCE

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• Excerpts on Ground Waters andSite Cleanup Page 10 from the Water Quality Control Plan by background concentrations and applicable water quality objectives. The extent of information necessary will depend on the specific conditions of the discharge. For example, use of best professional judgment and limited available information may be sufficient to determine that ground or surface water will not be degraded. In addition,the discharger must identify treatment or control measures to be taken to minimize or prevent water quality degradation. 8. Policy for Application of Water Quality Objectives Water quality objectives are defined in the Water Code as "the limits or levels of water quality constituents or characteristics which are established for the reasonable protection of beneficial uses of water or the prevention of nuisance within a specific area". (see Chapter III). Water quality objectives may be stated in either numerical or narrative form Water quality objectives apply to all waters within a surface water or ground water resource for which beneficial uses have been designated,rather than at an intake, wellhead or other point of consumption. In conjunction with the issuance of NPDES and storm water permits,the Regional Water Board may designate mixing zones within which water quality objectives will not apply provided the discharger has demonstrated to the satisfaction of the Regional Water Board that the mixing zone will not adversely impact beneficial uses. If allowed, different mixing zones may be designated for different types of objectives,including,but not limited to,acute aquatic life objectives,chronic aquatic life objectives,human health objectives, and acute and chronic whole effluent toxicity objectives,depending in part on the averaging period over which the objectives apply. In determining the size of such mixing zones,the Regional Water Board will consider the applicable procedures and guidelines in EPA's Water Quality Standards Handbook and the Technical Support Document for Water Quality-based Toxics Control. Pursuant to EPA guidelines, mixing zones designated for acute aquatic life objectives will generally be limited to a small zone of initial dilution in the immediate vicinity of the discharge. State Water Board Resolution No. 68-16 requires the maintenance of the existing high quality of water(i.e., "background") unless a change in water quality "will be consistent with maximum benefit to the people of the State....". This policy explains how the Regional Water Board applies numerical and narrative water quality objectives to ensure the reasonable protection of beneficial uses of water and how the Regional Water Board applies Resolution No. 68-16 to promote the maintenance of existing high quality waters. The numerical and narrative water quality objectives define the least stringent standards that the Regional Water board will apply to regional waters in order to protect beneficial uses. Numerical receiving water limitations will be established in Board orders for constituents and parameters which will, at a minimum,meet all applicable water quality objectives. However, the water quality objectives do not require improvement over naturally occurring background concentrations. In cases where the natural background concentration of a particular constituent exceeds an applicable water quality objective, the natural background