Geohydrologic Summary for Herbicide Orange Sites at Eglin AFB, Florida and the the Naval Construction Battalion Center, Gulfport, Mississippi

摘要

The geohydrologic conditions at Eglin Air Force Base (EAFB), Florida, and the Naval Construction Battalion Center (NCBC) at Gulfport, Mississippi, have been evaluated to assess the potential impacts on the groundwater resulting from the contamination of surficial soils by storage and handling of military herbicides. The results from this evaluation are used to determine the likelihood of herbicide residues being transported in the shallow groundwater. A trace contaminant of one of the herbicides, 2,3,7,8-tetrachlorodibenzo-p-dioxin, is the constituent of greatest concern. A monitoring program is proposed for each of the military sites. Both sites are situated in the Gulf of Mexico Coastal Plain. The subsurface sediments are composed of quartz sand, clay, gravel, and silt. The permeable sands from aquifers, and the impermeable clays form aquicludes or confining beds. Horizontal permeabilities are much higher than vertical permeabilities. The water in the shallow aquifer at each site is soft and relatively unmineralized because of relatively insoluble quartz sand and high recharge from rainfall. Low pH and high iron concentrations are caused by the low buffering capacity of the aquifer materials. The monitoring systems proposed at each site will have one well upgradient and several wells downgradient. A monitoring plan for nearby surface waters is also recommended. The wells will sample the shallow groundwater flow system. The possibility of dioxin contaminants migrating to deeper zones is extremely remote at either site.