Background

Increased traffic and congestion led to the reconstruction of the I-15 interchange at Exit 16, one of St. George's busiest interchanges. Ramps were redesigned to improve speed, increase capacity, and better facilitate flow and operation.

Project Details

Designs widened approximately 3 miles of mainline I-15 and added two lanes on SR-9 under I-15 to increase capacity and ease congestion for commuters entering the interstate. The project's design replaced existing interstate bridges over SR-9, added a southbound auxiliary lane, and extended a northbound climbing lane between Exit 13 and Exit 16.

Phased construction was used to replace interchange structures, retaining walls, sign structures, and a 30-foot concrete hydraulic drop structure in the median of I-15. Horrocks used in-house, mobile Light Detection and Ranging (LiDAR) survey equipment for topography and survey base mapping, helping to ensure accuracy and overal quality of the project.

Outcomes

Horrocks created an implemented a comprehensive design package for these interchange improvements, resulting in a greatly enhanced and significantly safer interchange experience. Located in southern Utah and immediately adjacent to the Red Cliffs Desert Tortoise Reserve, this project required considerable coordination and design innovation, which Horrocks was able to navigate while also accommodating the unique needs of the users and residents in the area.

Awards:

American Council of Engineering Companies (ACEC) Utah, Engineering Excellence Honor Award, 2021 

American Society of Civil Engineers (ASCE) Southern Utah, Engineering Innovation Award, 2020