I-95 Interchange Stream Mitigation

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Project Description

Due to the I-95 Interchange Project construction, there were some unavoidable impacts to existing streams. In order to mitigate these impacts the Turnpike Commission provided compensatory stream improvements on a section of Mill Creek in Bristol Township, located in Bucks County, Pennsylvania.

The project improved bank and floodplain conditions of approximately 2,000 feet of Mill Creek south of the footbridge between the Plumbridge and Mill Creek Falls communities. This section of Mill Creek within the project limits exhibited high velocity flood flows, unstable stream banks and adjacent exposed and undermined utility components. Improvements included implementing natural stream channel design features and techniques along with stream cross section adjustments that will stabilize stream banks, provide low flow fish/aquatic habitat, protect underground utilities, and allow better flood water attenuation and access to the available adjacent floodplain.

The following stream mitigation project goals were established in conjunction with the responsible environmental regulatory agencies:

• Provide planned improvements using natural stream channel design features for an approximately 2,000-foot stretch of Mill Creek that not only addresses stable stream bank geometry but also considers long-term ecological stability
• Consider incorporating low terrace flood benches into the natural stream channel design
• Implement a sustainable solution for stream habitat restoration that will mitigate the impacts of urban development and related hydrologic and hydraulic modifications
• Develop a restoration approach that replicates natural hydrologic and ecological cycles, enhances sustainability, riparian and in-stream aquatic habitat improvements, while being mindful of improved natural riparian aesthetics for the project area, resulting in significant cost savings over structural solutions
• Incorporate and stabilize the impaired section of Mill Creek in an effort to protect existing lower Bucks County Joint Municipal Authority and Falls Township water and sewer infrastructure

Project Schedule

The construction work was completed in four stages, which started in June 2013 and was completed in January 2014.

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November 2013

• All work has been completed with installation of plantings.

October 2013

• All work has been completed except plantings, which are scheduled for early November.

September 2013

• Stage 3 work completed
• Stage 4 work area under construction
• Contractor completed installation of new water main

August 2013

• Stage 2 work completed
• Stage 3 work began in mid-August.
• Contractor started installation of new water main.

July 2013

• Stage 1 work began with pumping in northern area.
• Stage 1 excavation and stream bank restoration is completed.
• Stage 2 work anticipated to begin in early August 2013.
• Each stage is anticipated to take approximately 1 month.

May/June 2013

• The contractor mobilized to the site in early June 2013.
• In the northern area of the project site, stage 1 work shall begin with bypass pumping to create work area access.
• Contractor will complete each of the 4 stages in succession before initiating a new stage.
• Each stage is anticipated to take approximately 1 month.