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Earlier this afternoon, the mayor’s office sent out notice that a mystery announcement would take place tomorrow morning at the McMillan Sand Filtration site on North Capitol Street, at which Mayor Vince Gray and others will reveal and break ground on a “major infrastructure project.”

But Mike DeBonis beat them to it—-the revealing, that is, not the groundbreaking.

DC Water and the city government, he reports, are planning to use the site to divert stormwater that’s been flooding the Bloomingdale neighborhood this year.

The long-term plan is to construct a Metro-sized tunnel under First Street to alleviate flooding, but that won’t be ready until 2016 at the earliest. So officials want to start work immediately on converting some of the site’s defunct filtration cells into runoff storage tanks, a task that could be finished by spring 2014. Three acres at the southwest corner of the site will also be used to bore the tunnel.

But there’s a catch: These measures could delay or interfere with the city’s plans to redevelop the McMillan site into a mixed-use community of housing, retail, and a medical center. D.C. Water first began exploring the possibility of using McMillan for flooding relief in September.

DeBonis reports that “officials believe that the flood relief plan will not significantly alter the development plans.” We’ll see if that holds.

Photo by David Monack (Wikimedia Commons).