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Water: Water Quality Standards Academy

Deriving the CMC: Step 2—Rank the Genus Mean Acute Values

Aquatic Life Criteria

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Basic Course: Supplemental Topics

Steps in the
FAV Calculation
  • Calculate the GMAVs.
  • Rank the GMAVs.
  • Calculate the FAV.

The GMAVs from the minimum eight families of aquatic organisms are then ranked based on sensitivity, from high (most resistant to the chemical) to low (most sensitive to the chemical). From this ranking, the lowest four GMAVs are used in deriving the CMC, as described in the next step.

A sample ranking of the lowest four GMAVs is presented below.

µg/L Species µg/L
4 100 Rainbow Trout, Oncorhynchus mykiss 100
3 36 Cladoceran, Daphnia ambigua 42
Cladoceran, Daphnia pulex 38
Cladoceran, Daphnia magna 29
2 25 Amphipod, Gammarus pseudolimnaeus 25
1 19 Amphipod, Hyalella azteca 19

For informational purposes only–Not official statements of EPA policy.

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