ISSN:
1745-6584
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Energy, Environment Protection, Nuclear Power Engineering
,
Geosciences
Notes:
Traditional environmental investigations at tidally influenced hazardous waste sites such as marine fuel storage terminals have generally failed to characterize ground-water flow and chemical transport because they have been based on only a cursory knowledge of plume geometry, chemicals encountered, and hydrogeologic setting and synoptic ground-water- level measurements. Single-time observations cannot be used to accurately determine flow direction and gradient in tidally fluctuating aquifers since these measurements delineate hydraulic head at only one point in time during a tidal cycle, not the net effect of the fluctuations. In this study, a more rigorous approach was used to characterize flow and chemical transport in a tidally influenced aquifer at a marine fuel storage terminal using: (1) ground-water-level monitoring over three tidal cycles (72 hours), (2) geostatistical filtering of ground-water-level data using 25-hour and 71-hour filtering methods, and (3) hydrocarbon fingerprinting analysis.The results from the study indicate that naphtha released from one of the on-site naphtha tanks has been the predominant contributor to the hydrocarbon plume both on-site and downgradient off-site and that net ground-water and hydrocarbon movement has been to the southeast away from the tank since 1989. These conclusions are supported by: (1) the elongate configuration of the hydrocarbon plume parallel to the mean ground-water flow directions determined using the 25-hour and 71-hour filtering methods; and (2) the occurrence of free-naphtha-product and elevated levels of BTXE and TPH in the naphtha range (C7 to C14) downgradient, but not upgradient, of the naphtha tank. The results also indicate that ground water containing 2.1 to 3.6 ppm TPH in the motor oil range (C22 to C32) is migrating onto the site from an upgradient source area to the north and/or northwest. Therefore, the background concentration or cleanup level of TPH for the facility is 2.1 ppm or greater. This study provides a more quantitative approach than traditional approaches for characterizing flow, assessing chemical transport and upgradient impacts, determining site-specific ground-water cleanup levels, and optimally locating ground-water monitor wells and extraction wells or trenches at tidally influenced hazardous waste sites.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1745-6584.1994.tb00633.x
Permalink