Section 366.203  A2 Factor (Water Quality)

A2 is a factor that evaluates the water quality of the receiving waterbody or proposed receiving waterbody.  These water quality evaluations are based on current waterbody specific information.  A combination of biotic integrity information and abiotic data from three categories are used in A2 calculations when available.  These categories include the Index of Biotic Integrity (IBI), the Predicted Index of Biotic Integrity (PIBI), and the Degree of Use Support (DUS).  As a result, those stream reaches resulting in the highest priority are those with the highest quality and potential for improvement (see Appendix A).  A2 calculations for stream reaches (as defined by USEPA REACH file) are derived by: