Investigation of Some Case of Oil Contamination in Mexico

Oil contamination of soil near pipeline in Tamaulipas, Mexico was studied with electrical resistivity tomography. The problem of the fist area was fast movement of contaminant found at 1.5 km distance in ten days after leakage. Fresh contamination gives higher resistivity anomaly in comparison with clean soil but after oil biodegradation anomaly changes into low resistivity in several months. Change of high resistivity object into conductive one goes through weak resistivity contrast between contaminated and clean soil. Process of anomaly change depends on the time after leakage, distance from leakage point to the point of study and amount of contaminant flowed out. For mature contamination there is successful field technology, but fresh contamination seems more difficult object. With ERT and monitoring experiments we did not find places of high hydraulic conductivity near leakage point and supposed movement of oil in pipeline trench filled with sand and then in river alluvium. In this case filtration velocity can reach 150 m/day. At the second area situated in two km from the first one at the same pipeline we found mature contamination with clear visible way of movement. And this way was similar to proposed way at the first area.