SH-55 Corridor Improvements, Pear Lane to Middleton Road | Canyon County, ID

Project Overview

Horrocks provides comprehensive transportation planning, environmental clearance, preliminary engineering, and public involvement services for approximately 10 miles of SH-55 between Pear Lane and Middleton Road in Canyon County. Identified by ITD as a high-priority corridor, SH-55 serves as a critical freight and commuter route supporting growing communities, agricultural operations, and regional travel demands. Horrocks’ work positioned the corridor for long-term safety, mobility, and economic growth while advancing ITD’s implementation strategy.

Services Provided:

• Baseline traffic data collection, operational and safety analysis, and corridor planning

• National Environmental Policy Act (NEPA) environmental documentation and agency coordination

• Preliminary engineering across all disciplines, including roadway and intersection design, drainage and hydraulics design, structures design, right-of-way, and survey and mapping services

• Development of corridor-wide improvement concepts, including additional general-purpose lanes, access management strategies, intersection modernization, bridge replacements, and shared-use pathways on both sides of the corridor

• Establishment of lane configurations, storage and taper lengths, pedestrian ramps and crosswalks, signing and pavement markings, and full traffic signal designs

• Design of signal systems incorporating interconnects, video detection, emergency medical services (EMS) preemption, illumination, and Americans with Disabilities Aact (ADA) compliant pedestrian and bicycle facilities

• Extensive public involvement and stakeholder coordination throughout planning and environmental phases

Challenges

SH-55 presented a complex mix of high traffic volumes, access demands, environmental constraints, and community sensitivity. Key challenges included balancing freight and commuter mobility with safety, managing access along a heavily developed corridor, navigating extensive irrigation infrastructure, and minimizing environmental impacts.

Horrocks addressed these challenges through an innovative, corridor-wide traffic concept that combines ThrU-Turn intersections, Restricted Crossing U-Turns, and conventional signalized intersections to improve safety and operations while controlling access. A comprehensive access management plan incorporated Right-In/Right-Out treatments at minor intersections and continuous shared-use pathways with safe, signalized crossings.

Environmental challenges included complex wetland and Waters of the U.S. (WoUS) conditions across a 740-acre study area containing numerous canals, laterals, ditches, and drains. Horrocks completed environmental baseline studies across 27 resource areas and coordinated closely with the U.S. Army Corps of Engineers to support jurisdictional determinations and future permitting. Through early collaboration between design and environmental teams, Horrocks identified refinements that significantly reduced environmental and cultural impacts, allowing the project to advance under a Categorical Exclusion rather than a more complex Environmental Assessment.

Stormwater management was further addressed through incorporation of green stormwater infrastructure, including bioretention swales and vegetated dry basins designed to meet corridor constraints, protect irrigation facilities, and support City of Nampa MS4 compliance.

Successes

• Completed NEPA documentation and preliminary design three months ahead of schedule and under budget

• Achieved Categorical Exclusion approval through impact-reducing design refinements, avoiding the need for a full Environmental Assessment and public hearing.

• Delivered innovative, corridor-wide traffic and access management solutions tailored to high-volume freight and commuter demands

• Deployed GIS-based planning tools and remote environmental data collection to support ITD decision-making

• Advanced the project into phased final design, including bridges, intersections, sound walls, and roadway improvements

Through integrated planning, technical excellence, environmental sensitivity, and transparent public engagement, Horrocks delivered a forward-looking framework for improving one of Canyon County’s most important transportation corridors, balancing regional mobility, community values, and long-term constructability.