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Open Access Publications from the University of California

Environmental considerations for construction of bridges and protected freshwater mussel species, a case study

  • Author(s): Reutter, David S.
  • Patrick, Frank
  • Charters, David A., Jr.
  • et al.

The Kennerdell Bridge is located within the Allegheny River National Wild and Scenic River Corridor, approximately 50 miles north of Pittsburgh. The former bridge was identified as being in fair-to-poor condition, with the original main truss spans exhibiting the most serious deterioration. Several bridge replacement options were developed during informal consultation with the United States Fish and Wildlife Service (USFWS) due to the known occurrence of two federally endangered freshwater mussel (Unionidae) species, the clubshell (Pleurobema clava) and the northern riffleshell (Epioblasma torulosa rangiana). The selected option involved the replacement of the former bridge, with the reuse of the existing river piers.

Field surveys of the proposed project area identified a diverse mussel population, including the listed species, around the bridge. The results of the field survey triggered formal Endangered Species Act (ESA) Section (7) consultation with the USFWS, and the development of a biological assessment. The required assessment included a construction/demolition options evaluation, hydraulic and hydrologic analyses, and development and implementation of a mussel relocation program as one mitigation measure to ameliorate impacts to the species.

Overall, 15,737 mussels representing 17 species were recovered and relocated. A total of 529 federally endangered northern riffleshell (Epioblasma torulosa rangiana) and 41 clubshell (Pleurobema clava) mussels were relocated from the primary impact area of the Kennerdell Bridge construction site. A follow-up one-month monitoring of one relocation site indicated good health of the relocated mussels and mortality rates consistent with undisturbed mussel populations. The success of the relocated mussels will be monitored and evaluated by the Biological Resource Division (BRD) of the United States Geological Survey (USGS) for five years.

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