I-35/CSAH 2 Interchange and Corridor Improvements – Forest Lake, MN

Washington County partnered with SRF to lead the preliminary and final design and environmental documentation for the reconstruction of County State Aid Highway (CSAH) 2 (Broadway Avenue) in Forest Lake. This vital east-west corridor, which includes the I-35/CSAH 2 interchange, serves as the only local connection to and from I-35 in Forest Lake and supports the city’s primary commercial area.

This transformative $30 million federally-funded project addressed longstanding safety and mobility issues while incorporating streetscape elements to create a welcoming gateway into Forest Lake. The project included two new bridges, pedestrian and bicycle facilities, enhanced intersections, and a complete reconstruction of the arterial corridor.

Traffic Analysis and Design Solutions

SRF began with a subarea traffic study to understand potential pattern shifts from various network alternatives. Using Washington County’s Travel Demand Model, the project team analyzed traffic volumes, route shifts, and operational performance. Simulation tools such as Synchro/SimTraffic and PTV Vissim were used to model corridor operations under various scenarios.

Key design elements included:

• New diamond interchange at I-35/CSAH 2
• Overpass construction at County Road 83
• Raised medians and channelized turn lanes for access management
• Enhanced pedestrian crossings, sidewalks, and multiuse trails
• Evaluation of signalized and roundabout intersection control
• Five new traffic signals to improve safety and flow

Construction Administration Services

As the project transitioned to implementation, SRF provided full construction administration services including:

• Contract administration and change management
• Field construction observation
• Materials sampling, testing, and quality control
• Bridge walk plans and inspection coordination
• Public relations, traffic control planning, and stakeholder communication

Throughout the process, SRF maintained close collaboration with Washington County staff to ensure smooth delivery and consistent public engagement. The SRF team’s technical expertise and transparent reporting enabled informed decision-making at every phase.

Resource Links:
Washington County Public Works
City of Forest Lake

Internal Categories:
Traffic & Technology
Roadway Design
Project Delivery & Construction Services

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