Market Street Bridge



Williamsport, Lycoming County, PA

AEG performed hydrologic and hydraulic analyses, levee impacts hydraulic design, permit coordination, and geotechnical analysis and design to analyze the proposed stream encroachment and possible floodplain impacts of a proposed S.R. 0015, Market Street Bridge replacement over the West Branch of the Susquehanna River, within the City of Williamsport and the Borough of South Williamsport within Lycoming County, Pennsylvania. AEG evaluated three bridge replacement alternatives. AEG also performed geotechnical investigations and hydrologic and hydraulic analyses for the river bridge replacement impact on the levee system and prepared permit applications for the encroachment.

This project involves several points of interest. The bridge is located within a reach of the West Branch Susquehanna River bounded on both banks by earthen levees designed by the Corps of Engineers (COE) and certified to contain the 100-year flood event by FEMA under 44 CFR, Part 65.10. The hydraulic analysis confirmed a proposed bridge and temporary causeway design would not adversely impact the 100-year flood elevation and therefore keeps the levee certified. Because of the existing and proposed bridge location within the levee system, access restrictions and construction scheduling will require access roadways over the levees to the causeways. AEG coordinated with the COE to develop designs to minimize structural impacts to the levees. The causeway will be in place for at least three construction seasons and will be designed as to not impact the 100-year flood event, nor hinder the migration of fish within the river.

Additionally, an existing pier is located within the north bank levee protecting the City of Williamsport. The proposed bridge will require impacting this existing pier. The design also proposed that structures supplement to the main bridge span be constructed on and within the existing levee. Therefore geotechnical investigations and detailed coordination with the COE were completed to ensure integrity of both the structures and the levee. If required, AEG was scoped to submit the results of the proposed project to FEMA as a Conditional Letter of Map Revision (CLOMR).

Coordination was required with the City of Williamsport, the Borough of South Williamsport, the Williamsport Flood Control District, the Pennsylvania Department of Environmental Protection, The Pennsylvania Fish and Boat Commission, The U.S. Army Corps of Engineers and FEMA.