The Analysis of the Natural Attenuation of Chlorinated Solvents in Groundwater at the Former Westinghouse Site in Bloomfield, New Jersey

Data for a contaminated site in Bloomfield, New Jersey were gathered from the New Jersey Department of Environmental Protection (NJDEP), in order to evaluate the hydrogeological conditions at the site. In particular, the data were analyzed to determine whether: 1) the site is still significantly contaminated, 2) natural attenuation is occurring at the site, and 3) natural attenuation will completely remediate the site in a reasonable period of time. The occurrence and distribution of Trichloroethene (TCE) and its daughter products, Dichloroethene (cis 1,2 DCE) and Vinyl Chloride (VC) show that the site is still contaminated. It was observed that the concentration of Trichloroethene (TCE) decreased over time, showing that natural attenuation is occurring at the site. However, in some wells TCE concentration increases with time, and therefore this site can still be considered contaminated. This increase in concentration of TCE does not support natural attenuation. Dissolved oxygen levels in groundwater wells are above 1 milligram/Liter (mg/L), which indicates aerobic conditions. It is known that anaerobic conditions are the desired and optimal conditions for the natural attenuation of TCE and of the daughter products for TCE (cis 1,2 DCE and Vinyl Chloride) that were found at the site. The observation of daughter products at the site supports the occurrence of natural attenuation even though conditions are not optimal. Due to the inconclusive results from the analysis of the field data, numerical modeling was used to determine the nature and length of time required for natural attenuation to remediate the site. The MODFLOW code was used to generate regional and local groundwater flow patterns. The RT3D code was then used to analyze the natural attenuation of the TCE and the length of time it would take to remediate the site. The simulations show that if natural attenuation was the only remediation process occurring at this site, the TCE would be removed in a period of eight years. The continuous presence of TCE, beyond eight years as predicted by the models, indicates that natural attenuation may not be the optimal remediation technique at this site. This study shows that a combination of field and theoretical techniques may be used in our understanding of natural attenuation of contaminants at a contaminated site