6.3. SR 07-09-2012 - Laserfiche WebLink

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~lir~r~esl~ta ~~I I uti+~r~ ~C~rttrl A~~n~y Coal Tar-based Sealcoat Environmental concerns wq-strm4-12 September 2009 f ~ ou decide to Sealcoat ~rour asphalt diiti~e~~ a~ this rear, these are a feR° things ~~ou should kno« . Sealcoating makes old asphalt look ne« and protects its surface, but there are serious environmental concerns with its use. Sealcoat comes iii t«~o basic vai7eties: coal tar-based and asphalt-based. The coal tar variety- is more resilient, but it contains much higher levels of a class of chemicals called PAHs (poh-c~ clic aromatic hti-drocarbons) that harm fish, and «ith prolonged eiposure, pose a risk of cancer in humans (see Figure 1). Environmental problems Coal tar is a «~aste material generated in the conversion of coal to coke. Manufacturers choose coal tar for Sealcoat because of its resistance to petroleum products like gasoline and oil, wl>ich drip from cars quid deteriorate asphalt surfaces. In time, sunlight and vehicle traffic wears do~~n Sealcoat and Sealcoat flakes are ~~-ached a~~~a~~ b~- rain or carried a« a~- b~T wind, contaminating stonm~-ater ponds. streams and lakes ~~=ith PAHs. PAHs cause tumors in some fish, disrupts the reproduction of aquatic organisms, and causes some «ater-bottom species to avoid sediment altogether. Health risks to humans related to PAHs are based on the length of exposure to vapors or sediments contaminated «ith PAHs. PAH Concentrations Coal tar contains as much as 30 percent PAHs by ~~eight. A stud~~ in Austin, Texas, compared the level of PAHs in ~~ ater coming off parking lots without Sealcoat to «~ater coining off parking lots coated «~ith asphalt- and coal-tar Sealcoat (Figure 2). Figure 1: Relative amounts of PAHs in Sealcoat products - ~ _.~`. ~li~~~t ~~~lial# bx~~ ~ r~ An Austin, Texas, study determined that Sealcoat products based on coal tar contained up to 1,000 times more PAHs than asphalt-based products. Consider asphalt- based Sealcoat if you choose to coat your driveway. Figure 2: Concentrations of PAHs in runoff Asphalt-based Sealcoat runoff (B) can contain 10 times more PAHs than an uncoated driveway (A) and runoff from acoal-tar sealcoated driveway (C) may have concentrations of PAH 65 times higher than an uncoated driveway. Minnesota Pollution Control Agency 520 Lafayette Rd. N., St. Paul, MN 55155-4194 www.pca.state.mn.us 651-296-6300 800-657-3864 TTY 651-282-5332 or 800-657-3864 Available in alternative formats '~"