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PHILIPSBURG BYPASS
Challenge
The Borough of Philipsburg wanted to construct a bypass in order to reduce congestion. This bypass would require the construction of more than two miles of new arterial roadway through wetlands, floodplains, and archaeological sites (all of which were underlain by abandoned deep mines and extremely insufficient drainage systems).
Solution
PENNDOT utilized HRG's full service resources to design the needed highway, bridge, environmental, and traffic improvements. This included:
- the construction of two bridges (one new and one superstructure replacement),
- the construction of four interconnected traffic signals,
- the construction of four acres of replacement wetlands in an unprecedented collaboration with Trout Unlimited's Acid Mine Drainage mitigation projects,
- sophisticated hydraulic modeling of two convergent water bodies (Moshannon Creek and Cold Stream),
- a Phase III archaeological recovery of the Philipsburg Tannery, and
- construction of a 20 foot by 20 foot reinforced concrete cap of a vertical mine shaft that is more than 100 feet deep and was discovered in the middle of the proposed roadway.
Innovative solution to floodplain impact issues …
This project was located within the confines of a detailed FEMA flood insurance study area. Therefore, HRG produced extensive hydraulic and hydrologic modeling and coordinated extensively with both the Pennsylvania Department of Environmental Protection (DEP) and the U.S. Army Corps of Engineers. In one area of the project, we discovered that the addition of any floodplain fill (even negligible amounts) would increase the 100-year floodplain elevation and negatively impact several houses and commercial buildings nearby. However, we were able to devise an innovative solution to this problem when we exposed an abandoned and long forgotten railroad embankment obscured by vegetation. Through detailed HEC-RAS modeling, we were able to demonstrate that the removal of this embankment compensated for the roadway embankment and resulted in no net increase in the floodplain.
Context-sensitive design in tune with the community's needs …
Creative thinking was also required to address extensive right-of-way impacts for this project. In order to avoid large, old mature trees surrounding the community borough building and minimize impacts to businesses in the area, HRG made thorough refinements in both the vertical and horizontal alignment of the roadway. In order to address the concerns of area businesses about the impact a bypass would have on access to their businesses, we also recommended and PENNDOT concurred with the addition of a “slip” ramp to provide efficient and easy access to the community's business district.
This allowed PENNDOT to deliver on its promise of improved traffic flow in the area while being sensitive to the needs of community residents and businesses. |
