Institute for Transportation

Environmental concerns about preservative bleeding (or migrating) from timber bridges have increased in recent years. This preliminary study examined the creosote reten-tion levels at six timber highway bridges in Michigan’s lower peninsula during the summer of 2000. Several test core samples were removed from the bridge superstructures (four bleeders and two controls) and were evaluated for creosote content in the laboratory. Results from three of the four bleeder bridges indicated high creosote retention levels between 36 and 52 lb/ft cubed (576.7 and 833 kg/m cubed) after several years in service.