In Washington, D.C., the neighborhoods of Bloomingdale and LeDroit Park feature beautiful Victorian-era row homes along narrow, tree-lined streets. A less desirable characteristic is the regular flooding due to the low-lying geography. DC Water’s First Street Tunnel Project will alleviate that flooding by constructing a 20-foot diameter, 2,700-foot tunnel. When this tunnel enters service — scheduled for April 2016 — it will store up to nine million gallons of rainwater that would otherwise fill streets and soak basements. The water will be pumped into D.C’s sewer system.
But how are we constructing this tunnel system beneath dense city streets while striving for minimal disturbance to residents? Key to our solution is ground freezing, which converts water within soil pores to ice. With this, we create ice walls up to nearly 10 feet thick that enable us to safely excavate while keeping groundwater out. But more important to nearby residents is that ground freezing involves far less noise and vibration and requires a smaller work area than conventional methods. Our latest infographic describes the process: