I10: St. Marys to 29th

Geotechnical investigations..

I10: St. Marys to 29th

I10: St. Marys to 29th

Location: Tucson, AZ     Client: ADOT     Status: Completed

The Arizona Department of Transportation (ADOT) is proposing to widen the existing Interstate 10 (I-10) going through Tucson from six to eight lanes to cope with the increased traffic demand of a growing Tucson. ADOT retained HDR, Inc. to perform the design for section of I-10 between St. Mary’s Road and 29 th Street in Downtown Tucson. NCSG performed the geotechnical investigations under subcontract to HDR.

Update 5/19/08: Construction began on the $200 million consolidated I-10 Widening: Prince Rd. to 29th St. project in January of 2007. To shorten an estimated 10-year construction period to 3.5-years, three design projects, including our portion from St. Marys Rd. to 29th St., were combined into one massive construction project, the largest project undertaken by ADOT to date. The project is expected to be completed by Spring/Summer of 2010.

The contractor is Kiewit/Sundt Joint Venture (KSJV). The drilled shaft contractor is Case Foundations, AMEC Earth and Environmental is performing the integrity testing of the drilled shafts under contract to KSJV, and the Reinforced Earth Company (RECo) is supplying their Retained Earth™ system for the Mechanically Stabilized Earth (MSE) retaining walls. Their system consists of 5-ft by 5-ft precast concrete panels with galvanized steel bar mat reinforcement. End of 5/19/08 Update

The complete reconstruction of mainline I-10 for this segment will include 6 new bridges, 17 retaining walls totaling nearly 14,000 linear feet of walls, drainage structures paralleling the corridor, and pavement design. The field investigation program conducted by NCSG included 122 borings for the various structures. A combination of drill rigs was required, including conventional truck mounted, track mounted for drilling on slopes, and difficult access rigs for the sides of steep embankment slopes.

The proximity of the project corridor to the Santa Cruz River had a strong influence on the soil stratigraphy, and corresponding weaker fluvial (river deposited) soils located near the surface creating significant design challenges. Additionally, perched groundwater was encountered in some of the deep bridge borings, which required careful consideration during the design of the deep foundations for the bridge structures.

Updated 5/19/08: This project is currently in the construction phase. NCSG is heavily involved during the contruction phase assisting HDR and ADOT in the review of MSE-wall shop drawings and calculations, review of drilled shaft integrity testing data, recommendations for fixes of defective drilled shafts, and troubleshooting issues related to retaining walls, drilled shaft foundations and other geotechnical aspects of the project.

Photo Credits: Some photos during the construction phase are courtesy of ADOT, in particular Antonio Conte. Several others are courtesy of Ted Buell with HDR, Inc.

Project Photos