Because of their location, the groundwater is more protected than the surface water, although some contaminants degrade its quality and diminish its usefulness. In the process of contamination below the earth's surface, in a contaminating plume, for example, it may take years to discover the source and the contaminating agent. This slow process, the fact that groundwater and pollutants are not easily detected, make it hard to identify and control pollutant sources. The quality of these waters is very susceptible to contamination by socioeconomic activities, land use and occupations, causing the contamination of these aquifers, which is becoming more and more common. The most common form of storage of fuels (gasoline, diesel oil and alcohol) at gas stations is the use of underground tanks. These products, represent an important source of contamination of the environment, which usually occurs through leaks in storage tanks due to corrosion, spills caused by accidents in the transportation of these products, or by improper installation and improper handling of tanks. In São Miguel do Guamá, northeastern state of Pará, the only operational station in the city was built in the 1970s, which creates a problem, since underground storage tanks have an average life span of 20 to 25 years. The geophysical methods can greatly help in the detection of contamination plume, allowing both its rapid delimitation as well as the continuous lateral and in depth distribution of the plume of contamination. Considering that the GPR equipment has been shown to be an excellent geophysical tool for indirect subsurface investigation, this method was adopted in thIS study aiming the contamination of the subsurface by the hydrocarbons from the occurrence of underground tank leaks from the resale points of fuels in the city of São Miguel do Guamá (PA). The results obtained with the electromagnetic signature of the GPR profiles will be compared with the analyzes of water samples to verify the content or not of BTEX using the analytical technique of Gas Chromatography (GC). The results of the water analysis suggest the existence of low concentrations of BTEX, however existent, in the sampling stations of the Tabocas station gas, in enterprises and public agencies close to the station gas (P1), however the samplings are within the potability standards defined by Ministry of Health.
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