AN INTERWELL SOLUBILIZATION TEST FOR CHARACTERIZATION OF NONAQUEOUS-PHASE LIQUID ZONES

It is essential that the location and chemical composition of nonaqueous phase liquids (NAPLs) be characterized for their timely and cost-effective remediation. Approaches using ground-water sampling and core evaluations do not provide adequate characterization capabilities. The use of surfactant solutions in single- and interwell NAPL solubilization tests (NSTs) provides a means to locate and characterize NAPLs in the subsurface. By injection and recovery of micellar surfactant or cosolvent solutions, significant volumes of an aquifer can be tested for the presence of a NAPL. Positive indications of NAPL can be determined based on the recovery of dissolved NAPL components at concentrations above their aqueous solubilities or based on significant increases in dissolved component recoveries associated with the test. Owing to a surfactant's capability to significantly increase the recovery of low solubility hydrophobic components of the NAPL, the complete chemical composition of the NAPL can be determined with the NAPL solubilization test, in contrast to routine ground-water monitoring surveys where only the more soluble components are identified. Two-dimensional, cross-sectional numerical simulations show that interwell NSTs can be used to positively identify the presence of a NAPL. The simulations show that a surfactant solution sweep in the presence of a NAPL causes a significant increase in NAPL recovery (including recoveries greater than the aqueous solubility of the NAPL) relative to conventional ground-water extraction. The increase in NAPL recovery is evident, even with the effects of dilution due to the extraction of uncontaminated waters.