Fish and macroinvertebrates were collected at unimpacted reference locations and downstream of NPDES discharges in Upper Three Runs and its tributaries, Fourmile Branch, Pen Branch/Indian Grave Branch, and Steel Creek/Meyers Branch to determine if the receiving streams have been impacted by the NPDES discharges. The results of the macroinvertebrate and fish surveys conducted during this study were generaly in close ageement. Both indicated that most SRS streams were characterized by high biotic integrity and unaffected by SRS NPDES discharges. Possible exceptions included Crouch Branch, McQueen Branch, and Tims Branch, all of which are tributaries of Upper Three Runs. The fish data indicated that these three streams did not differ significantly from the control, while the macroinvertebrate data indicated possible impairment. Of the three, only Crouch Branch was identified as degraded in the earlier (1997-1998) survey. Subsequent investigations in Crouch Branch identified elevated concentrations of copper from the H-O2 outfall as the primary cause of the degradation, although habitat degradation resulting from stormwater runoff also is a factor in the midreaches of the stream.