LYNX Case Study (Environmental)

3D Modeling Benefits Military Cleanup

McClellan Air Force Base, northwest of Sacramento covers almost 3000 acres of intense activity in support of jet fighter maintenance. For decades the base has been involved in use, storage and disposal of hazardous materials. In the late 1970's groundwater contamination was discovered with studies pointing to historical waste disposal practices as the source. In some cases the prevalent VOC's were detected in the groundwater to levels of 100 feet. In 1981, McClellan was incorporated into the new Air Force IRP and in 1987, the base was placed on the NPL. In 1991 a new remediation initiative began to reduce risk and accelerate the cleanup process. Under this plan a prototype remedy for a base wide model of soil gas extraction was developed.

The subjects of the pilot became three local areas on the base representing a mix of diverse contamination problems, including multiple plumes, erratic sampling and complex soil stratigraphy. VOC plumes from varying sources formed the basis of the examination. Soils were highly variable, undergoing abrupt lateral and vertical facies changes or pinch outs over short distances.

3D Geoscience Modeling Technology
McClellan AFB used the LYNX 3D Geoscience Modeling System to assist in the study. LYNX uses a volume modeling method to create 3D representations of subsurface geology, incorporating geostatistical techniques to predict contaminant distributions.

Analytical and soil data, plus site plans were imported into GMS. Soil horizons were interpreted on cross sections and a 3D volume model of each was developed. The spatial variability of contaminant samples were analyzed to produce geostatistical models. These were then used to predict concentrations in the soil volumes by controlling the prediction of contaminant distribution within the layers. Volumetrics analysis was used to determine the soil volumes where the contaminant values exceeded threshold.

The study showed that the soil vapor extraction method would be the best remediation method. It also outlined a site selection methodology for SVE removal actions. In addition, the LYNX 3D volume modeling clearly high-lighted several other interesting benefits.