Print this pageAn important aspect of site characterization at any site with negatively impacted groundwater, soil or rock is understanding regional geology. More specifically, understanding structural position, facies changes, sequence stratigraphic framework, petrophysical variation and source rock characterization of hydrocarbons in the vicinity of a petroleum contaminated site is a requisite. Many large sites (several hundred acres), as are typical of military installations, have petroleum contaminated groundwater and earth materials. Furthermore, some of these sites are located within or immediately adjacent to oil-producing basins possessing relatively shallow producing horizons. Differentiating between anthropogenic and natural sources for benzene, toluene, ethyl benzene and xylene at such sites may be difficult if thorough site characterization is not conducted. The Lexington-Bluegrass Army Depot, located near the crest of the Cincinnati Arch in Kentucky, is a good example of inherent difficulties associated with identification of contaminant sources. At this site, the Ordovician Lexington Limestone contains aquifers that are punctuated by multiple marine flooding surfaces and a sequence boundary. The Lexington penetrated by drilling at the site can be divided into the Millersburg, Tanglewood (Upper and Lower Tongues), and Grier members. The Grier is further separated by flooding surfaces which, are mainly shale-rich beds. Primary aquifers at the site can be mapped as physically separated and chemically partitioned into high salinity and low salinity hydrostratigraphic units with quite different contaminant constituents.
AAPG Search and Discovery Article #90926©1999 AAPG Eastern Section Meeting, Indianapolis, Indiana