On December 2, 2011, the Sacramento Superior Court invalidated the numeric limits on turbidity and pH in California's Construction General Permit (CGP) because the limits were not supported by substantial evidence. The State Water Resources Control Board (State Board) has 60 days to decide whether to appeal the decision.

The Clean Water Act prohibits the discharge of pollutants without a permit issued under the National Pollutant Discharge Elimination System (NPDES). The Environmental Protection Agency is responsible for issuing NPDES permits, but in California, it has delegated this authority to the State Board.

NPDES permits set limitations on the discharge of pollutants. One type of limitation, a "technology-based effluent limitation," requires the use of specific technologies to control and reduce discharges of pollutants. A technology-based limitation may take the form of a numeric limit, which is quantitative, or a narrative limit, which describes best management practices that a permit holder must implement to control pollutant discharges.

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