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I-84 Corridor Improvements, SH-44 Interchange to Karcher Road Interchange | Canyon County, ID

Horrocks provided environmental clearance, planning, preliminary design, and PS&E services for multiple segments of the I-84 corridor between Caldwell and Nampa. This corridor serves as a critical regional and local route through one of the Treasure Valley’s fastest-growing communities, requiring long-term solutions to improve safety, capacity, and operations.

Project Overview

Horrocks provided environmental clearance, planning, preliminary design, and PS&E services for multiple segments of the I-84 corridor between Caldwell and Nampa. This corridor serves as a critical regional and local transportation route through one of the Treasure Valley’s fastest-growing communities, requiring long-term solutions to improve safety, capacity, and operations. The project addressed more than 8 miles of interstate infrastructure and supported ITD’s vision for durable, future ready corridor improvements.


Services Provided:

  • Corridor planning, traffic and safety studies, and environmental documentation

  • Alternatives development for additional general-purpose lanes, interchange improvements, and bridge reconstruction

  • In-depth traffic analysis to identify operational constraints, establish corridor limits, and guide design decisions

  • 2050 design-year traffic sensitivity analysis to ensure long-term effectiveness of proposed improvements

  • Survey and right-of-way mapping, environmental resource fieldwork, and hydraulic screening

  • Extensive public involvement and coordination with ITD and local agencies

  • Preliminary design and PS&E development across multiple project segments


Challenges

Since I-84 passes through urbanized areas of Caldwell and Nampa, intense development along the corridor constrained construction space and increased sensitivity to traffic, utility, and community impacts. Key challenges included:

  • Traffic Maintenance and Phasing: Maintaining two lanes of interstate traffic in each direction while preserving circulation on Centennial Way, 10th Avenue, and other local routes

  • Noise Impacts: Residential neighborhoods adjacent to the corridor required detailed noise analysis and mitigation

  • Stormwater and Environmental Constraints: Legacy stormwater systems discharged directly to the Boise River through a combined ITD and City of Caldwell system

  • Utilities and Irrigation: Numerous utility conflicts and historic irrigation facilities required preservation and uninterrupted operations


Horrocks addressed these challenges through ITD-compliant construction phasing and traffic control plans, incorporation of a noise wall, design of a separated stormwater system with detention, and use of advanced 3D pipe modeling to resolve utility conflicts while coordinating closely with irrigation districts.


Successes

  • Delivered three PS&E packages resulting from environmental study and preliminary design

  • Delivered one PS&E package on an accelerated schedule and $1.279 million under budget

  • Successfully separated ITD and City of Caldwell stormwater systems while improving water quality prior to discharge to the Boise River

  • Improved safety and operations through interchange reconfiguration, including removal of a loop ramp at the 10th Avenue Interchange to reduce weaving between closely spaced interchanges


Through technical expertise, innovative problem-solving, and close collaboration with ITD and local stakeholders, Horrocks delivered forward-compatible transportation solutions that support regional mobility, community needs, and environmental stewardship along one of Idaho’s most critical corridors. Horrocks is currently providing CE&I services for the Centennial Way Interchange to Franklin Road Interchange segment.

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