Method for evaluating dense nonaqueous phase liquid (DNAPL) presence from VOC concentrations in soil gas

Conference · · Ground Water; (United States)

OSTI ID:5898281

Cudzilo, T F; Rainger, L E ^[1]

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1. Radian Corp., Sacramento, CA (United States)

Because DNAPLs pose significant problems in remedial alternative selection, a method for identifying DNAPLs in soils with VOC concentrations in soil gas was developed for an NPL site with a 100-foot-thick, VOC-contaminated vadose zone. Calculations based on VOC concentrations in soil and soil liquids indicated that DNAPL presence could not be determined consistently, and the path of DNAPL migration could not be determined consistently, and the path of DNAPL migration could not be tracked without additional sampling. Concentrations of 1,000 to 6,900 parts per million by volume (ppmv) of two halogenated VOCs suggested that the DNAPL mass was greater than indicated by soil analyses. The remedial investigation of a 5.5 acre area within the NPL site consisted of soil, ground water, and discrete-interval soil gas sampling and analysis. The area includes a number of potential discharge points, the most important of which is a degreaser waste collection sump for a metal plating shop. During the investigation, analyses of soil gas samples collected from four to five depth intervals between 20 and 100 feet below surface, in 81 soil borings, indicated that TCE and PCE were most highly concentrated, most frequently detected, and mixed throughout the vadose zone. Neither soil nor ground-water concentrations were great enough to indicate DNAPLs, assuming equilibrium conditions. To identify volumes of soil or ground water where DNAPLs would affect remedial actions, a method was derived for using the available soil gas sample data instead of additional, costly drilling and sampling to identify DNAPLs in the soil volume.

• OSTI ID: 5898281
• Report Number(s): CONF-9310166--
• Conference Information: Journal Name: Ground Water; (United States) Journal Volume: 31:5
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540220* -- Environment
Terrestrial-- Chemicals Monitoring & Transport-- (1990-)
CHLORINATED ALIPHATIC HYDROCARBONS
CONTAMINATION
ECOLOGICAL CONCENTRATION
GROUND WATER
HALOGENATED ALIPHATIC HYDROCARBONS
HYDROGEN COMPOUNDS
INDUSTRY
METAL INDUSTRY
MONITORING
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
OXYGEN COMPOUNDS
REMEDIAL ACTION
SOILS
WATER