Multiple assessments of this very large railroad facility have been and are being conducted to determine the impact on soil and groundwater at the site and determine the potential for off site migration of grounwater contamination (primarily as petroleum). A widely effected area of dissolved phase petroleum has been identified and in the main yard area well as a more locaized area of free (product) phase petroleum. Suspected source(s) include petroleum storage distribution lines and incidential spillage over the 100+ years of the rail yard operation. The majority of the RR yard is underlain by a plume of dissolved and free product diesel fuel. Plume has migrated off site onto Waterloo high school property. Remedial action (Bioslurping) will follow assessment of extent of contamination