High quality water: parameter-by-parameter approach

Many water quality advocates believe strongly that the parameter-by-parameter approach is the only approach that meets the intent of the federal statute and regulations. According to EPA, “high quality waters are those whose quality exceeds that necessary to protect the [primary] goals of the Act (protection and propagation of fish, shellfish and wildlife and recreation in and on the water), regardless of use designation.

All parameters do not need to be better quality than the State’s ambient criteria for the water to be deemed a ‘high-quality water’ and protected as such. EPA believes that it is best to apply antidegradation on a parameter-by- parameter basis.

However, EPA evaluates each state’s interpretation of antidegradation for conformance with the statutory and regulatory intent of the antidegradation policy. EPA has accepted approaches that do not use a strict pollutant-by-pollutant basis.

(WQS Handbook, 4.5)

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