A postaudit study of DBCP and EDB contamination in the Pearl Harbor aquifer
Rungvetvuthivitaya, Mongkolaya, Chittaranjan Ray, Richard E. Green
A simulation of the transport of dibromochloropropane (DBCP) and ethylene dibromide (EDB) in the vadose zone and ground water was conducted in the Mililani area of Central Oahu, Hawaii to revisit the groundwater contamination predictions made by researchers at the University of Hawaii in 1988 for selected wells of the Honolulu Board of Water Supply. Examination of sampled DBCP results in these wells indicated a large discrepancy between the observed and predicted concentrations in 1988. Therefore, a post-audit study was initiated in the same area to assist in better defining projected concentrations of contaminants in well waters in the future. With the new data, different modeling approaches were undertaken for simulating flow and contaminant transport in both the vadose and saturated zones. The new simulations indicate travel times of 14 to 32 years for contaminants to reach the water table, depending on the location. The approximate recovery time of wells in the study area is expected to occur after the year 2016 for DBCP. The predicted concentration of EDB in the wells is less than the current detection limit. Variabilities in model predictions due to parameter uncertainties and model limitations are also considered. While the predicted concentrations from the present simulations match sampled data better than the concentrations from earlier modeling efforts, still a number of uncertainties remain.