U.S. Geological Survey researchers applying coal-tar sealant for an experiment. Credit: Barbara Mahler, USGS Research Hydrologist
P8230044
Great Lakes Echo (http://greatlakesecho.org/2012/11/08/great-lakes-lawmakers-consider-statewide-bans-on-pavement-sealants/p8230044/)
U.S. Geological Survey researchers applying coal-tar sealant for an experiment. Credit: Barbara Mahler, USGS Research Hydrologist