Weber and Davis Aqueduct Condition Assessment

Weber Basin Water Conservancy District, 
Utah

Weber and Davis Aqueduct Condition Assessment

Service Type: 
Project Highlights: 
  • Utilized multiple internal and external inspection technologies, detailed flow monitoring, and hydraulic modeling in the assessment
  • Developed risk and remaining useful life models that will be continually updated as new inspection and maintenance data is obtained
  • Implemented a cost-effective plan for inspection and rehabilitation technologies in the future
GPR Inventory Grid on 60-inch RCP.
GPR Inventory Grid on 60-inch RCP.

In December 2009 Carollo Engineers was retained by the Weber Basin Water Conservancy District (WBWCD) to assess the condition of the Weber and Davis Aqueduct Pipelines. The two raw water aqueducts consist of 26 miles of 84” to 21” reinforced concrete pipe, mortar coated steel pipe, and concrete cylinder pipe constructed in 1955. The aqueducts are a lifeline to surrounding communities totaling 500,000 people and supply up to 435 mgd. Neither aqueduct has a redundant delivery alternative, so uninterrupted operation is critical. In the past the pipelines have experienced one catastrophic failure, several joint leaks, and reduced hydraulic capacity. As a result, Carollo worked with the WBWCD to implement a cost-effective assessment plan involving internal and external pipe inspection technologies, detailed flow monitoring, and hydraulic modeling.

Since conducting detailed field investigations of 26 miles of pipeline was cost prohibitive, the project team divided the pipeline into segments to facilitate prioritization. Each segment was evaluated in terms of risk (criticality and vulnerability) and the highest risk segments were scheduled for inspection.

The project team evaluated several inspection technologies and matched applicable technologies to specific pipe segments. Internal inspection technologies utilized on this project included: non-tethered leak detection, Weber Basin risk graphichigh-speed digital 3D video scanning, sonar, CCTV, in-pipe ground penetrating radar, and personnel-entry pipe inspection. External inspection technologies included pH testing, alkalinity testing, chloride testing, sulfate testing, hammer sounding, electrical continuity testing, and ultrasonic thickness testing. Pressure and flow testing was also conducted to calibrate two existing Venturi flow meters and to validate and calibrate the hydraulic model.

Overall the pipelines were in better condition than expected. The vast majority of the pipe segments were in good to very good condition. However, the field investigations did identify several segments in need of rehabilitation or repair.