Ironwood Drive Improvements
Kimley-Horn provided preliminary and final design services for 16 miles of Ironwood Drive in Pinal County, AZ, widening its current two-lane section into a four-lane roadway with sections of raised median, curb and gutter, and sidewalk, with some locations widened to six lanes where funded by developers.
The project area is developing rapidly, with adjacent commercial and residential developments being planned and constructed. This corridor provides a significant transportation improvement for the quickly developing portions of Pinal County and Apache Junction. This project involved coordination with developers and numerous agencies, including the Arizona State Land Department, the Flood Control District of Maricopa County, City of Apache Junction, Union Pacific Railroad, property owners, and utility companies.
For this project, Kimley-Horn designed a new three-span AASHTO precast girder bridge to span the Central Arizona Project (CAP). In designing the expanded crossing of the CAP canal, Kimley-Horn proposed an alternative to a widened at-grade crossing because County-required access control was not being met. The canal crosses the existing alignment at a heavy skew and a grade-separated parallel crossing would have required a two-span bridge. The proposed alternative maintained the CAP-required access parallel to the canal. Kimley-Horn’s proposed new alignment for the bridge reduced the skew and allowed for a lower profile bridge, saving more than $1 million over all other alternatives.
Innovative Drainage Design
Kimley-Horn worked closely with the Arizona State Land Department (AZSLD), private land owners, and developers to design innovative drainage alternatives that improved flood protection for the roadway, reduced costs for the project, and appealed to stakeholders. AZSLD requires all road improvements that need state land right-of-way to meet the 100-year storm water design criteria, while the County wanted to meet the 25-year design criteria. The difference in cost was significant and included a higher profile, additional right-of-way, and potential liability associated with inconsistent design criteria being used throughout the County. Kimley-Horn was able to justify the use of the 50-year design criteria, which maintained the original road profile while reducing the amount of additional right-of-way.
In working with developers in an area where the alignment had to be shifted off the Section Line and required the developer on the west side of the road to dedicate more right-of-way than the developers on the east side of the road, Kimley-Horn designed a storm drain system that reduced the pavement drainage runoff that the west side developer had to retain and transferred the additional retention requirement to the east side developer who benefited from the reduced right-of-way dedication. Better yet, the developers were so pleased with the solution that they paid for the storm drain costs, which provided a ‘no cost’ solution for the County while maintaining positive relationships with the stakeholders.
Overcoming Challenges for Award-Winning Solutions
This project provided many challenges in a fairly rural yet quickly developing portion of Pinal County; however, it is the solutions to these challenges that helped the project become award winning. Creative avoidance of utility conflicts with high voltage Western Area Power Administration (WAPA) transmission lines, successful coordination of irrigation pipeline relocations with adjacent developers, coordination and design of cohesive street improvements for adjacent developers, cost saving alternatives for crossing the Central Arizona Project (CAP) canal, cost saving drainage alternatives which allowed for the reduction of material import and right-of-way acquisition, thorough understanding of the Union Pacific Railroad (UPRR) design process, positive public involvement, and responsive communication with the County are among the many successes on this project.