Maximum contaminant levels ground water

Trace contaminants Contaminants in ground water or drinking water that are carcinogenic when present in excess of minute concentrations as set by the US government maximum contaminant levels. Mostly halogenated hydrocarbons (typically 1—100 pg/1 or ppb) and heavy metals (typicallyO.l—1.0 mg/1 orppm). 

The definition of water reference level or the level which triggers a report if found in surface or ground water, has been modified. The level depends on the levels established in section 304 of the Clean Water Act, the Maximum Contaminant Level (MCL) established by the EPA, the Health Advisory Level (HAL) or the lowest detectable limit depending on the chemical. 

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