The First Vadose Zone Partitioning Interwell Tracer Test for Nonaqueous Phase Liquid and Water Residual

Abstract

In 1995, a partitioning interwell tracer test was conducted in the vadose zone beneath two buried organic liquid disposal trenches at Sandia National Laboratories in New Mexico. The purpose was to estimate the amount and distribution of trichloroethylene (TCE) trapped by capillary forces as residual dense nonaqueous phase liquid (DNAPL). Screened injection and extraction wells, placed 16.8 m apart, and two monitor wells with multilevel sampling capability allowed vertical testing from 3.0 to 24.4 m below ground surface. Seven tracers were injected, but the most useful tracers in the final analysis were sulfur hexafluoride (nonpartitioning), perfluoro-1,3,5-trimethylcyclohexane (TCE-partitioning), and difluoromethane (water-partitioning). Both a TCE-partitioning tracer and a water-partitioning tracer were needed to determine average TCE DNAPL saturation. Average saturations of DNAPL and water were measured to be 0.11 ± 0.02% and 23 ± 2.0%, respectively, in the shallow zone between 3.0 and 10.7 m. Monitor well data showed no evidence of DNAPL below a depth of 9 m. These results had important implications for remedial actions at the site.

Review of Techniques to Characterize the Distribution of Chromate Contamination in the Vadose Zone of the 100 Areas at the Hanford Site

“…• PITTs were completed in the vadose zone of a NAPL contaminated site at Kirtland Air Force Base in Albuquerque, New Mexico and at Sandia National Laboratory (Deeds et al 1999;Mariner et al 1999). …”

Summary and Status of DNAPL Characterization and Remediation Activities in the A/M-Area, Savannah River Site

“…Partitioning Tracer Tests -PITT (see Mariner et al, 1999) Test injects multiple tracers in a well and extracts in a second well. Estimates the presence and quantity of DNAPL between the wells by examining the difference in behavior of the various tracers.…”

Partitioning Tracers for In-Situ Measurement of Nonaqueous Phase Liquids in the Subsurface - Final Report - 09/15/1996 - 09/14/2000

“…In related work, Deeds et al (36) used column experiments to measure the Henry's coefficient for a water partitioning tracer (difluoromethane), with the assumption that the tracer measured all of the water. Water-partitioning tracer tests have also been conducted at the field scale, in association with gas-phase partitioning tracer tests designed to characterize immiscible-liquid contamination in vadose-zone systems (30)(31)(32). However, the soil-water contents obtained in these tests were not compared to independently measured values.…”