Contractor-led quality control and quality assurance plus design-build: Who is watching the quality?

Recent innovations by the Arizona Department of Transportation (DOT) in the use of design-build procurement for highway construction are presented. Explosive population growth in Arizona has pushed its DOT to the limits of its capacity and has challenged the department to develop innovative ways to stretch its resources to meet its constituents' needs. In 1996 the department spearheaded the passage of a pilot design-build law aimed at completing public-sector construction projects more rapidly than could be done by traditional methods. An evaluation of the material quality program used in the second design-build project in this program is described. The project reconstructed an extremely congested 7-mi segment of Interstate 17, a primary artery carrying 180,000 vehicles per day through the city of Phoenix, widening it from 6 to 10 lanes. The design-build contract was awarded after A+B bidding, which considered the bid price to do the work and the time required to complete the project, and was the largest ever awarded at the time. It was won by a design-builder who implemented a very aggressive schedule that required double-shift work for nearly 2 years. In another contracting first, the agency also assigned the design-builder responsibility for the quality control and quality assurance functions on the project, with Arizona DOT providing verification sampling and testing only. The concrete compressive strength and material density for the project are examined and are compared to statewide averages for traditional design-bid-build projects in which Arizona DOT performed the quality assurance function. Analysis of the data shows that despite a highly compressed schedule, the quality of the material on the project exceeded the project specifications and was similar to the quality of work completed for the state under traditional contracting methods with an Arizona DOT-operated quality assurance program.