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Dirt exodus at CityCenterDC. (Lydia DePillis)

There is an impressive amount of digging going on in Washington these days: There are towering cranes and gaping holes in the ground everywhere you look, especially along 14th Street NW and in NoMa, not to mention CityCenterDC, the Marriott Marquis hotel across the street, and St. Elizabeths in Ward 8. Where does it all go?

Well, it depends what kind of dirt it is. “You basically have three types of dirt,” explains Neil Stablow, vice president at the Donohoe Companies, which is working on big digs at 2400 14th Street NW and South Capitol Street.

There’s “good dirt,” which can be used as fill for other projects that might need to create a grade or a building pad. Back when the Woodrow Wilson Bridge was under construction, for example, a lot of projects sent their dirt there. These days, the mega-development Konterra is absorbing a lot of dirt. Each subcontractor includes dirt disposal or acquisition as part of their bids; there are even “dirt brokers” who buy and sell it as needed for each project.

“If they have material that is usable, and then they have a place to take it, it’s all money,” Stablow says. “If it’s the cheapest thing,  they find a home on another project.”

The second type is “unsuitable dirt,” which can’t be used for other projects, usually because it’s got organic material that would decompose and create problems for building on top of it. That stuff has to be hauled off site and dumped in a landfill somewhere. According to Clark Construction, that’s mostly what’s happening to the 450,000 cubic yards of dirt that will come out of the CityCenterDC footprint: Trucks are taking it to a big hole on Palmer Road just off Indian Head Highway in Prince George’s County.

The third type is contaminated dirt, which has been rendered toxic by things like underground storage tanks (this will be an issue at Walter Reed Army Medical Center, for example). That has to be taken to a special facility, like SoilSafe in Columbia, Maryland.

As long as construction keeps rolling, the D.C. dirt economy will do well.