SH55 Corridor Improvements – Pear Lane to Middleton Road Canyon County, Idaho

Planning, Environmental, and Preliminary Design Leadership

Horrocks led the development of baseline traffic data collection and analysis, corridor planning, and environmental documentation to support future improvements along SH55. Our team prepared preliminary engineering across all disciplines, including roadway and intersection design, drainage and hydraulics, structures, geotechnical investigations, rightofway, and survey and mapping. Recommendations included additional generalpurpose lanes, access management strategies, intersection modernization, bridge replacements, and shareduse pathways on both sides of the corridor.

Through close collaboration between designers and environmental specialists during alternatives analysis, Horrocks identified design refinements that significantly reduced impacts to environmental and cultural resources. These efforts allowed the project to advance under a Categorical Exclusion (CE) rather than a more complex Environmental Assessment (EA), eliminating the need for a public hearing and substantially accelerating the project schedule. ITD authorized Horrocks to proceed into preliminary and phased final design of the preferred alternative.

Innovative Traffic and Intersection Solutions

Horrocks conducted a comprehensive operational and safety analysis that resulted in an innovative corridorwide traffic concept. The preferred alternative includes a combination of ThrUturn intersections, Restricted Crossing UTurns (RCUTs), and conventional signalized intersections to accommodate high throughtraffic volumes while managing access and improving safety. The design incorporates an access management plan featuring RightIn/RightOut (RIRO) treatments at minor intersections and continuous shareduse pathways with safe crossings at signalized locations.

During preliminary design, Horrocks established lane configurations, storage and taper lengths, pedestrian ramp and crosswalk layouts, signing and pavement markings, and full traffic signal designs. Signal systems include interconnects, video detection, EMS preemption, illumination, and ADAcompliant pedestrian and bicycle facilities.

Environmental Stewardship and Green Infrastructure

Horrocks completed extensive environmental baseline studies covering 27 resource areas, including visual resources, environmental justice, cultural resources, aquatic resources, and wetlands. A complex wetland and Waters of the U.S. (WoUS) delineation was conducted across a 740acre study area containing numerous irrigation canals, laterals, ditches, and drains. Ongoing coordination with the U.S. Army Corps of Engineers supported jurisdictional determinations and future permitting actions.

Given corridor constraints and existing irrigation infrastructure, Horrocks incorporated green stormwater infrastructure (GSI) solutions, including bioretention swales along much of the corridor and supplemental vegetated dry basins where additional storage was needed. These systems provide costeffective stormwater treatment and support compliance with City of Nampa MS4 requirements.

Robust and Innovative Public Involvement

A comprehensive and flexible outreach strategy was critical to project success. Horrocks supported extensive public and agency involvement, including more than 40 online property owner and stakeholder meetings, virtual and inperson public meetings, mailers, surveys, and advertisements. Innovative online GIS tools allowed residents to view alternatives, understand property impacts, and submit comments directly into a GIS database. Horrocks also managed a public hotline, email communications, and ongoing updates to keep the community informed throughout the environmental process—even during COVID19 restrictions.

Project Successes

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

• Achieved CE approval through impactreducing design refinements, avoiding a more complex EA

• Delivered advanced traffic and access management solutions tailored to a highvolume corridor

• Supported ITD with GISbased planning tools and remote environmental data collection

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

Lasting Value

Through integrated planning, technical excellence, environmental sensitivity, and transparent public engagement, Horrocks delivered a forwardlooking framework for improving one of Canyon County’s most important transportation corridors. The SH55 corridor improvements balance regional mobility needs with community values, environmental stewardship, and longterm constructability—setting the stage for successful final design and delivery.