Soil Contamination by Oil and Gas Drilling and Production Operations in Padre Island National Seashore, Texas, U.S.A.

Soil samples from 18 oil and gas drilling and production sites located in Padre Island National Seashore were analyzed for contaminating substances associated with drilling fluids and petroleum products. The results of the investigation indicate that soil contamination from these sources is widespread and persistent but generally localized in the immediate vicinity of drilling and production activity. Sixteen sites were found to have elevated levels of four heavy metals (barium, chromium, lead, and zinc), sodium, salinity, pH, and/or petroleum hydrocarbons. There was no discernible pattern of contamination between well sites, indicating the variability of methods and materials used in the drilling of individual wells and the occurrence of isolated spills and materials misuse. The levels of contaminating agents found do not represent immediate environmental threats, but the long-term cumulative effects of soil alteration and toxicants on organisms and habitats in the barrier island ecosystem is largely unknown.