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Aquatic Invertebrate Biological Assessments Streams Tributary to the Pools of Dams #2, #3, and #4 on the Allegheny

Michael Koryak, M.S.| Linda Stafford, B.S.

Aquatic macroinvertebrate communities are sensitive indices of stream water quality and ecological health. In the second phase of a three year effort to conduct invertebrate-based bioassessments of urban/suburban streams within Allegheny County, PA, chemical and invertebrate samples were collected during the spring of 2002 at twenty-two stream stations. All of these stations were located near the mouths of streams tributary to the navigation pools of Allegheny River Dams 2, 3, and 4.

More than 8,213 invertebrate organisms from sixty-seven different taxa were collected, identified, and enumerated at the twenty-two stations. All but one of the stream stations examined were impaired to various degrees; 19.0% severely impaired, 47.6% moderately impaired, and 28.6% slightly impaired. While it is disappointing that there was only one small stream without measurable degradation (Riddle Run), it is still encouraging that 28.6% of the streams examined were only slightly impaired and that 47.6 % were only moderately impaired. The diversity of aquatic life found in these streams exceeds what might have been expected from historical memories and impressions of these urban waterways as industrial waste conduits and/or open sewers. The streams sampled during the Phase 2 effort also tended to be in better condition than streams tributary to the Pittsburgh (Emsworth Locks and Dam) Pool and the pools of Monongahela River Dams 2 and 3, which were previously sampled in 2001 during Phase 1 of the study. The average condition score of the Phase 1 streams was 45.1, and 42.8% were severely degraded, compared to an average Phase 2 score of 52.9 with only 19.0% severely degraded. The ten Phase 2 streams with the highest condition scores were Riddle Run (95.6), Buffalo Creek (75.3), Tawney Run (75.2), Blacks Run (71.0), Chartiers Run (64.1), Bull Creek (63.7), Pucketa Creek (61.8), Little Bull Creek (59.0), Bailey Run (56.3), and Plum Creek (53.5).