SH-16 Corridor

SH-16 is a new north-south highway, providing a regional connection between I-84 and Emmett and improving mobility throughout Treasure Valley in southwestern Idaho. The new highway was carefully sited to minimize impacts to the Boise River and associated floodplains, successfully balancing transportation infrastructure needs with land use goals and preservation of open space, environmental resources, and farmland. SH-16 is being developed in three phases.

Phase I: Parametrix was the prime consultant and engineer for Phase I, which constructed 2.5 miles of a new four-lane state highway from SH-44 south to US 20/26. Several new bridges were built including an 11-span, 1,730-foot-long bridge over the Boise River and a complicated crossing of the 50-foot vertical drop to the Boise River floodplain. Structures at Joplin Road and the Phyllis Canal were creatively designed and sited to avoid placing piers and piles in the canal bank and bench slope areas. The work also involved signalized intersections at US 20/26 and SH-44 and local road improvements.

Phase 2: This phase extended the highway another 4.5 miles, providing a connection between US 20/26 and I-84. This phase featured signalized intersections at Franklin and Ustick roads, as well as a reconstruction of the existing intersection at US 20/26. The team designed multiple bridges over roadways, irrigation canals, and the railroad in addition to improvements to local roadways. The Idaho Transportation Department (ITD) completed this phase with 2 consultant contracts – Parametrix was the prime consultant and engineer on Phase 2 South.

Phase 3: Parametrix is the prime consultant and engineer for Phase 3, which will develop five interchanges along the corridor. The interchanges include a System to System Interchange at I-84, Single Point Urban Interchange (SPUI) at Franklin Road, Tight Diamond Interchange (TDI) at Ustick Road, and Partial Cloverleaf Interchanges at both US 20/26 and SH 44. It will also add a northbound auxiliary lane between the Franklin Road and Ustick interchanges. Community members have participated in the design throughout the entire process. For the final phase, the community was invited to view final design plans in May 2023 at a public meeting. Over 1,200 people visited the meeting either in person or online. When complete, SH-16 will be the Treasure Valley’s first limited access, north-south highway.

SH-16 Design
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