Augmenting “Tunnel” Vision for Blue Horizon

Between 1870s and 1920s, major trunk sewers in Washington, D.C., were built with cobble stones, red brick, or concrete masonry. These systems convey a large flow along existing open channels. Man fill was brought to create land above for development. This has been the pillar of the urbanization in D.C. More than a century later, these trunk sewers carry even more flow than before. The forthcoming $3.5 billion CSO tunnel system in D.C. will supplement the trunk sewer system to relieve local flooding, reduce overflow thus improve water quality. The century old trunk sewers present a daunting task for DC Water to optimize its resources to manage the linear asset, a significant part of the goals in the Blue Horizon 2020 Strategic Plan. DC Water engineers synergize our engineering efforts to assess, improve, and protect our mission critical infrastructure. This presentation showcases our engineer’s holistic effort, from tooling mindset, sharpening skillsets, to managing our collection system in Washington, D.C. Updating DC Water infrastructure design guidelines to summarize tried and true lessons learned from the past decades, promoting the best proactive practices in design, and impact assessments to improve risk management. Categorize recent sewer failures in Washington, D.C., to define the outside factors and inside factors, identify common cause(s): thinking outside the tunnel so as to gauge the sensitivity and vulnerability of the system and thus identify a threshold for open-cut and trenchless methodologies. Besides CCTV inspection, deploying sophisticated entry inspections in mission critical sewer tunnels, with non-destructive scanning and testing tools to perform at-contact inspections from inside the pipe, and to calibrate scanning and testing from outside the pipe as needed. Implementing in-house finite element model analysis of common sizes and shapes of sewer tunnels to reveal the loading conditions and in-situ capabilities so as to gauge the general as-is condition. Strategizing rehabilitation technologies to balance the effectiveness, longevity and cost: promoting a sensible discretionary composite rehabilitation design instead of a new pipe-in-pipe. Such composites appear more sustainable hydraulically and financially. Taking technical stewardship in managing spincast rehabilitation technology when lacking a consistent indirect engineering criteria among vendors, i.e., DC Water engineers do more to establish consistent design approach so that the public work contract can be assessed on equal ground.