SITE INFORMATION AND CORRESPONDENCE

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ToXlcity ° Where natural turbidity is between 50 and 100 All waters shall be maintained free of toxic NTUs, increases shall not exceed 10 NTUs. substances in concentrations that produce detrimental physiological responses in human, plant, ° Where natural turbidity is greater than 100 animal, or aquatic life. Compliance with this NTUs, increases shall not exceed 10 percent. objective will be determined by analyses of indicator organisms, species diversity, population density, Exceptions to the above limits will be considered growth anomalies, and biotoxicity tests of When a dredging operation can cause an increase in appropriate duration or other methods as specified turbidity. In those cases, an allowable zone of by the Regional Board. The Regional Board may dilution within which turbidity in excess of the also refer to criteria for toxic substances developed limits may be tolerated will be defined for the by the State Water Resources Control Board, the U.S. operation and prescribed in a discharge permit. Food and Drug Administration, the National Academy of Sciences, the Environmental Protection For Folsom Lake(50)and American River(Folsom Agency, and other organizations to evaluate Dam to Sacramento River) (51), except for periods conformity with this objective. of storm runoff, the turbidity shall be less than or equal 10 NTUs. To the extent of any conflict with The survival of aquatic life in surface waters the general turbidity objective, the more stringent subjected to a waste discharge or other controllable applies. water quality factors shall not be less than that for the same water body in areas unaffected by the For D_tta waters, the general objectives for waste discharge, or, when necessary, for other turbidity apply subject to the following: except for control water that is consistent with the requirements periods of storm runoff, the turbidity of Delta for "experimental water" as described in Standard waters shall not exceed 50 NTUs in the waters of Methods for the Examination of Water and the Central Delta and 150 NTUs in other Delta Wastewater, latest edition. As a minimum, waters. Exceptions to the Delta specific objectives compliance with this objective as stated in the will be considered when a dredging operation can previous sentence shall be evaluated with a 96-hour cause an increase in turbidity. In this case, an e bioassay. allowable zone of dilution within which turbidity in excess of limits can be tolerated will be defined for i In addition, effluent limits based upon acute the operation and prescribed in a discharge permit. biotoxicity tests of effluents will be prescribed where appropriate; additional numerical receiving water quality objectives for specific toxicants will be established as sufficient data become available; and source control of toxic substances will be WATER QUALITY OBJECTIVES encouraged. FOR GROUND WATERS Turbidity The following objectives apply to all ground waters Waters shall be free of changes in turbidity that cause nuisance or adversely affect beneficial uses. of SA, SB, and SC. Increases in turbidity attributable to controllable water quality fauiure ,hull not exceed the following Bacteria limits: In ground waters used for domestic or municipal supply (MUN) the most probable number of Where natural turbidity is between 0 and 50 coliform organisms over any seven-day period shall Nephelometric Turbidity Units (NTUs), be less than 2.2/100 ml. increases shall not exceed 20 percent. 111-9