Paving Paradise with PAH Parking Lots


Instead of plodding through D.C.’s slushy streets one weekend back in December, I was happily swimming in Austin’s Barton Springs during a trip with my sister, Rachel. Swimming outside in December is a rarity, but as a spring fed pool the water there stays at about 70 degrees year round, good enough even for me, someone who is not a fan of the cold.

But another reason I had dragged Rachel to the pool was a pilgrimage of sorts. Austin and Barton Springs are the sites of important research on the effect of polycyclic aromatic hydrocarbons (PAHs) on water quality. In plain words, PAHs are a class of chemicals that are suspected human carcinogens and are known to be toxic to stream life. When elevated levels of these chemicals were found in and around the popular springs the City of Austin was worried.

Research led by the U.S. Geological Survey in partnership with the City found that the coal-tar based sealcoat that is used to coat parking lots and driveways is a major and previously unrecognized source of these pollutants as they are washed into local waterways once wear and tear loosens the sealcoat particles. Fortunately, there are more environmentally friendly alternatives including asphalt-based sealers. Acting on the problem, the City of Austin banned the sale of coal tar sealants as a way to protect their beloved Barton Springs and other waters.

Wow – if only problems could be solved so efficiently here in D.C.! Until then, I’ll just have to reminisce about my early-winter swim and let the tale of the spring be an inspiration until it warms up around here.