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Excerpts on Ground Waters and Site Cleanup Page 10 <br /> from the Water Quality Control Plan <br /> by background concentrations and applicable water quality objectives. The extent of <br /> information necessary will depend on the specific conditions of the discharge. For example, <br /> use of best professional judgment and limited available information may be sufficient to <br /> do-termine that ground or surface water will not be degraded. In addition, the discharger must <br /> icentify treatment or control measures to be taken to minimize or prevent water quality <br /> &-gradation. <br /> 8. Policy for Application of Water Quality Objectives <br /> Water quality objectives are defined in the Water Code as "the limits or levels of water quality <br /> constituents or characteristics which are established for the reasonable protection of beneficial <br /> uses of water or the prevention of nuisance within a specific area". (see Chapter III). Water <br /> quality objectives may be stated in either numerical or narrative form. Water quality <br /> objectives apply to all waters within a surface water or ground water resource for which <br /> b--neficial uses have been designated, rather than at an intake, wellhead or other point of <br /> c 3nsumption. <br /> Ili conjunction with the issuance of NPDES and storm water permits, the Regional Water <br /> Board may designate mixing zones within which water quality objectives will not apply <br /> provided the discharger has demonstrated to the satisfaction of the Regional Water Board that <br /> the mixing zone will not adversely impact beneficial uses. If allowed, different mixing zones <br /> niay be designated for different types of objectives, including, but not limited to, acute <br /> aquatic life objectives, chronic aquatic life objectives, human health objectives, and acute and <br /> chronic whole effluent toxicity objectives,depending in part on the averaging period over <br /> which the objectives apply. In determining the size of such mixing zones, the Regional <br /> Vater Board will consider the applicable procedures and guidelines in EPA's Water Quality <br /> 'l-tandards Handbook and the Technical Support Document for Water Quality-based Toxics <br /> Control. Pursuant to EPA guidelines, mixing zones designated for acute aquatic life <br /> Objectives will generally be limited to a small zone of initial dilution in the immediate vicinity <br /> of the discharge. <br /> State Water Board Resolution No. 68-16 requires the maintenance of the existing high quality <br /> Of water(i.e., "background") unless a change in water quality "will be consistent with <br /> maximum benefit to the people of the State....". This policy explains how the Regional <br /> Water Board applies numerical and narrative water quality objectives to ensure the reasonable <br /> protection of beneficial uses of water and how the Regional Water Board applies Resolution <br /> No. 68-16 to promote the maintenance of existing high quality waters. <br /> The numerical and narrative water quality objectives define the least stringent standards that <br /> the Regional Water board will apply to regional waters in order to protect beneficial uses. <br /> Numerical receiving water limitations will be established in Board orders for constituents and <br /> ,parameters which will, at a minimum, meet all applicable water quality objectives. However, <br /> -he water quality objectives do not require improvement over naturally occurring background <br /> ,:oncentrations. In cases where the natural background concentration of a particular <br /> :onstituent exceeds an applicable water quality objective,the natural background <br />