Route 252 Springton Reservoir Dam Spillway Bridge Improvements

Located in Marple and Upper Providence Townships, Delaware County, Pennsylvania, the Route 252 (Palmers Mill Road) Bridge carries motor traffic over the Springton Dam spillway.

Built in 1931, the bridge had become structurally deficient and required replacement to efficiently and safely handle existing and expected traffic and comply with the Pennsylvania Department of Environmental Protection’s (PADEP) 100-year flood plan. The project also was driven by the need to facilitate modifications to the Crum Creek dam below the bridge.

GFT provided project management, historic and environmental documentation services, survey services, and preliminary right-of-way services for the bridge replacement project, a joint endeavor between Aqua Pennsylvania (Aqua), owner of the Route 252 Springton Reservoir dam and spillway, and the Pennsylvania Department of Transportation (PennDOT), owner of the bridge.

Work included replacement of a 42-foot, single-span, concrete T-beam with a 145-foot, single-span, prestressed-concrete PA bulb tee beam and constructing a new, permanent, 360-foot-long retaining wall using staged construction to maintain one lane in each direction via a temporary vehicular bridge during the initial construction stage.

Services provided include:

• Conceptual, preliminary, and final structural and highway design.
• Maintenance and protection of traffic.
• Geotechnical.
• National Environmental Policy Act documentation.
• Categorical exclusion.
• Permitting.
• Mitigation of project’s effect on historic resources.

The replacement bridge is structurally separated from the spillway retaining walls and wider to allow for future re-decking while maintaining one lane in each direction without the need for a temporary bridge.

The related dam spillway project will take place several years after the bridge construction through a separate, supplemental project in coordination with PennDOT, local municipalities, emergency service providers, PADEP, U.S. Army Corps of Engineers, and Aqua.

Due to the proximity of the bridge and spillway, design of the replacement spillway bridge required careful consideration of the proposed bridge substructures in relation to both the existing and the enlarged spillway. For example, the design of the replacement bridge foundations needed to consider a temporary reduction in lateral support during construction of the future spillway and needed to minimize any load influence on the future spillway walls.

The project features context-sensitive designs, including a sculpted faced soil nail approach wall, stone-cladded crash worthy barriers with crenellated tops, and other aesthetic treatments to meet historic requirements.