Monthly Archives: May 2012

Proof of LID?

Washington DC, like hundreds of other cities in the U.S., has a dirty water problem. The problem goes by the name of combined sewer overflow (CSO). CSO is a fancy way of saying when it rains a lot, our shit and piss go straight into the river untreated.

This foul condition is caused by sewer systems that combine sewage flows (from toilets and drains) with stormwater flows (from lots and streets). Seven hundred and seventy-two cities in the U.S. have these antiquated systems that overflow when it rains a lot. Cities that were built after 1900-1910 solved the problem by building separate systems for sewage and stormwater.

Washington DC is under a court order to fix the problem. The original court-ordered plan is a multidecade, multibillion-dollar program of installing giant water storage tunnels. It would reduce raw sewage discharges by 98 percent and would be paid for by doubling water bills over a 20-year period.

In August 2011, the DC Water and Sewer Authority proposed a test of low-impact development (LID) in order to reduce its costs and construction requirements. LID is a set of stormwater management practices that directs runoff to places where it can soak into the ground: swales, rain gardens, trenches, porous pavement, etc. If we put stormwater into the ground instead of sewer pipes, says DC Water, the pipes will overflow less often.

But local environmental groups are wondering just how feasible the DC Water proposal is. They are objecting to it — in particular, the proposed eight-year delay in tunnel construction and potential reductions in tunnel capacity. While proven cleanup techniques are delayed, DC Water will experiment with LID techniques that may or may not provide significant reductions of stormwater runoff. Washington Post columnist Mike DeBonis describes the situation:

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