Creating a SR-18 pedestrian tunnel under Bluff Street in St. George, Utah, consisted of two phases. During Phase 1, Sunroc excavated and placed precast box culverts that were 18′ by 13′ with a total length of 188 feet to form a pedestrian tunnel under Bluff Street. Each concrete precast section weighed 56,000 pounds. This phase of the project had completion deadline of 15 days. Crews worked 24 hours a day 7 days a week, and completed the installation in 11 days, earning full incentive from UDOT. Crews excavated 6,500 cubic yards of material, placed the box culvert (along with waterproofing membrane, trench drain pipe, and conduits), backfilled 4,000 cubic yards of material, placed granular borrow, road base, concrete curb and gutter, median curb, concrete median filler, and asphalt paving.
Phase 2 of the project was the trail system connection and pedestrian tunnel structural concrete. 14,500 cubic yards of dirt were excavated, along with grading, storm drain pipe, road base placement, and asphalt paving all taking place. Additionally, 120 cubic yards of structural concrete headwalls were poured, and electrical and fencing was installed.
Traffic was detoured throughout the duration of the project in order to meet the 15-day timeline set by the city. Vehicles were redirected away from the construction zone which helped keep the installation on schedule.
Challenges on the project included the coordination between working with suppliers, subcontractors, and the owner to make sure deadlines were met. Sunroc was able to problem solve quickly to help complete the project on time. Additionally, an ATMS line stretching across the culvert had to be avoided due to it being the main trunk line that runs communications in the city. It took effort and ingenuity to make sure there was clearance and so that communications weren’t interrupted during the completion of the project.