Interstate 10 – Twin Peaks Interchange

Interstate 10 – Twin Peaks Interchange, completed 2010

Client Program / Project Description. The Twin Peaks Interchange provides an important regional connection for the northern Pima County communities of Marana, Dove Mountain and Continental Ranch to Interstate 10 and Tucson.  This project is one of the Regional Transportation Authority’s (RTA) major accomplishments in the first phase of its 20 year plan.

Improvements include three new bridge structures (over the Santa Cruz River, I-10 and the Union Pacific Railroad) and access to local businesses.

WSA-designed Architectural Treatments on the bridges and other structures are all inspired by the river.  In the summer of 2006, WSA met with Ora Horne, former mayor of the Town of Marana, and presented four themes: Santa Cruz River, Cotton/Cattle, Multicultural, and What Brought People to Marana.  And at the end of the meeting, the Mayor stated, “It all comes down to the river. Marana would not exist if it wasn’t for the Santa Cruz River.” Subsequently, the Marana Aesthetic Committee selected the Santa Cruz River Concept as the design theme for the project.  Cattails and Cottonwoods, commonly occurring along the River, appear in metal work on the I-10 bridge and pier formliners, and are represented in the barrier sidewalk along Twin Peaks Road, respectively.  A design feature in the Road’s median also reflects elements of the River: monoliths constructed of layers of colored concrete depict layers of riverbed sediment, and the metalwork wrapping the concrete echoes cottonwood leaves.

WSA Scope and Role.  WSA’s work included native plant inventory, salvage and planting plans for Pima County and ADOT, in compliance with the mitigation requirements of the County Native Plant Ordinance, Arizona’s Native Plant Law and the 404 permit.  Additional, native, low-water and low-maintenance plants were incorporated within the project limits. Architectural treatment plans included formliner design for the MSE walls, bridge barriers, bridge piers and sidewalk barriers; decorative sidewalk design; median feature and decorative metal work for the pedestrian fencing on the I-10 and railroad bridges.  Erosion control, irrigation and hardscape plans were also prepared.

Project Team.

• Owner: The Town of Marana and the Arizona Department of Transportation
• Client: URS Corp.
• Design Team:
  • URS Corp.: lead
  • WSA: landscape design, aesthetic treatments, native plant inventory and salvage plans for Pima County and ADOT, erosion control plans, Aesthetic Guidelines for Town of Marana
  • Carl Kominsky, Landscape Architect: irrigation design