DESIGN-BUILD: ELEVATING PARTNERING TO A HIGHER LEVEL

摘要

The Upper Diamond Fork Project, as part of the Central Utah Project Completion Act, conveys water six miles from the existing Sixth Water Aqueduct to the Diamond Fork Pipeline. During design, a Value Engineering team proposed a single-tunnel alignment that would be less destructive on the environment and might have a lower life cycle cost than the proposed design of two tunnels connected by two pipelines on steep hillsides. A decision was made to include this option in the bid process as a design-build alternative. The bid for this option was the lowest and a contract was awarded. During the TBM excavation a segment of tunnel wall caved in containing large quantities of water saturated with extremely high levels of hydrogen sulfide (H_2S) gas (measured at 380 to 520 ppm in the air). The Central Utah Water Conservancy District (District) in consultation with Obayashi/Clyde (Contractor) quickly developed a new plan to finish the system by incorporating parts of the original tunnel/pipeline concept and re-bid the remainder of the project as a Phase 2 Design-Build contract.