Project Info:

Location: Norwalk, Connecticut

Role: Prime

Owner: Connecticut Department of Transportation

Client: Connecticut Department of Transportation

Construction Cost: $43,500,000

Services:

  • Interstate Design
  • Interchange Design
  • Highway/Roadway Design
  • Intersection Analysis/Design
  • Stormwater/Watershed Planning
  • Hydraulic Analysis/Design
  • Geotechnical Engineering
  • Structural Design
  • ADA Facility Evaluation/Design
  • Final Plans, Specifications, and Estimates (PS&E)
  • Construction Phasing Plan Development
  • Maintenance-of-Traffic (MOT) Plan Development

Recognitions:

2014 Connecticut Society of Civil Engineers Geotechnical Achievement in Civil Engineering (ACE) Award

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The 2,000-foot section of I-95 between Exits 14 and 15 connects I-95 with US 1 and US 7 at two major interchanges. This stretch of interstate carries 153,000 vehicles on a typical weekday, and at project inception these high traffic volumes were serviced by six I-95 travel lanes. The area was a well-known bottleneck prone to flooding. Lochner served as lead designer on this Connecticut Department of Transportation (ConnDOT) project to improve safety and traffic operations on I-95, US 1, and at both interchanges, in addition to rectifying the drainage issues with a sustainable solution.

Lochner’s design plans widened I-95 along the project length to add a continuous auxiliary lane in each direction of travel, and reconfigured the I-95 southbound exit onto US 1 to provide a two-lane exit ramp, transitioning to one right-turn and two left-turn lanes. On US 1, Lochner designed additional left-turn lanes at three intersections and approximately 2,500 feet of sidewalks on both sides of the road.

To accommodate the additional lanes on I-95, Lochner’s design lengthened three cross bridges. The vertical clearance of these bridges was also increased to meet current design standards, and Lochner worked with challenging grading issues to safely incorporate the change in bridge elevation within the cross streets’ existing geometry and to match US 1 intersection grades. Staged construction plans were developed to maintain traffic and utility service across the bridges during construction.

Drainage design was a major component of the project. The existing stormwater outlet to the Norwalk River was undersized and unable to handle runoff during storm events, resulting in frequent flooding on I-95 and US 1. Adding a second outlet created environmental impacts and required extensive permitting. Lochner’s design solution maintained the existing outlet and constructed a stormwater management pond by the new I-95 exit ramp to treat the water and hold it during peak runoff periods. The water is released in a regulated flow, within the capacity of the existing outlet. This solution reduced design and construction costs and was more environmentally sound than adding a second outlet.

The project’s highly urbanized location created a number of design challenges. Properties in close proximity to the roadways placed constrictive horizontal and vertical geometric controls on the design. The high volumes of traffic and the confined work area required Lochner to prepare complex construction staging and maintenance-of-traffic plans to minimize impacts to operations on these heavily traveled corridors. The innovative use of pipe jacking to install large reinforced concrete pipes—in one case using a unique technique of drilling directly into an existing manhole in the center of I-95—greatly decreased excavation and shoring work, which reduced the project’s construction costs and minimized lane closures.