EPA's Region 6 Office
Serving: Arkansas, Louisiana, New Mexico, Oklahoma, Texas, and 66 Tribal Nations
Contaminated soils containing residual sources of free product are still in place at the Popile site. These soils exist beneath most of the clean backfill placed during the RA activities and in some areas outside the RA work. The residual sources include Non-Aqueous Phase Liquids (NAPLs) retained in the unsaturated and saturated zones. The thickest sections of contaminated soil occur beneath the former impoundments, sludge pit and facilities area, where NAPLs extend to the top of the carbonaceous layer. However, the bulk of the free products appear to be confined within the upper layer and sand layer.
Field investigations showed that only PCP and naphthalene (PAH) plumes are amenable for spatial interpretation because of their relatively high water solubility. The lack of mobility of other PAH COCs cause them to exhibit extreme concentration drop off and virtually no spatial distribution. Dissolved phase groundwater contamination, as indicated by the PCP and naphthalene, is limited to a 185 foot travel distance within the immediate area of the former process ponds, and has not entered the Bayou de Loutre.
Although not a COC, naphthalene is the most mobile of the PAH class
of compounds, and, as such, represents the "worst-case" travel scenario
for all other PAH COCs.