Jim Creek Siphon Expansion Joint Evaluation

Denver Water’s Jim Creek Siphon facility is a 52-inch diameter steel siphon installed in 1935. The above-ground siphon is exposed to extreme mountain weather conditions resulting in significant pipe material temperature fluctuations. The siphon is equipped with six expansion joints (EJs) to accommodate the thermal expansion and contraction effect that occurs. By 2018, the exposed EJs and original pipe were showing measurable signs of degradation. Denver Water performed a condition assessment of the entire siphon facility, including the EJs, which proved to be a challenging element of the system to assess. Denver Water needed to determine if it was reasonable to assume the expected life of the EJs should be similar to that of the pipe itself and if the EJs should be rehabilitated, replaced, or despite the visual degradation that was observed, if they were functioning adequately and taking no action was a viable alternative. A decision was made to replace the existing EJs and use the replacement effort as an opportunity to better understand the particulars of EJ degradation and performance issues. The goal was to develop more definitive replacement and rehabilitation triggers that could be applied to the numerous other EJs of the same style and vintage as those at the Jim Creek Siphon facility. This paper presents the results of Denver Water’s evaluation of the EJs on the Jim Creek Siphon facility which included measuring temperature and movement fluctuations, in situ interior and exterior inspection, and detailed post-demolition shop inspection. The effects of corrosion on EJ functionality were also considered. Recommendations for maintenance and triggers for replacement of exposed EJs in harsh environments will be presented.