Officials: roadside filters don’t work

Filters on Ohio roadsides used to reduce pollution from the rainwater runoff don’t work and won’t be used anymore, transportation officials said.
Associated Press
Dec 3, 2013

The state has used exfiltration trenches since 2005 as a pollution-control feature in new and expanded highways.

They were supposed to replace the concrete rain channels that separate curbs from asphalt. Instead of flowing straight to a storm drain, rainwater is supposed to soak through layers of porous concrete and gravel to filter pollutants.

Now they’ve been scratched after researchers at Ohio University determined they are prone to clogs, The Columbus Dispatch reported Monday.

“A lot of debris settles on top and around it and it decreases its effectiveness” transportation spokeswoman Melissa Ayers said.

Researchers found debris that collected on top of the trenches increasingly kept water from soaking into the porous concrete. Sand and other debris diverted as much as 80 percent of rainwater from soaking into the filters even after they were cleaned.