WILLOWSTICK CASE STUDY: CONTAMINANT PLUME

Mountainous terrain in Lawrence Livermore National Lab
where AquaTrack survey was completed.

Lawrence Livermore National Laboratory had an area contaminated with solvents, including trichloroethene (TCE). They wanted to map the location and extent of a shallow perched groundwater zone and a deeper water zone located beneath the perched groundwater to help determine potential flow paths for the contaminant. Some drill holes had already been drilled to monitor the groundwater levels and to obtain their approximate location and depth.

Saving Time and Money

More drill holes were needed to define the extent of these water zones. This was going to require roads to be built and drilling pads to be excavated on steep mountainous terrain, at a tremendous cost to the lab. Even with this effort and expense, the exact perimeter of these water zones would only be approximate between drill holes.

Mapping Water Flow paths

LLNL chose to use Willowstick and its AquaTrack™ technology to delineate the area of influence of the two water-bearing zones.

AquaTrack is a patented non-intrusive geophysical technology capable of mapping groundwater at significant depths (thousands of feet), over significant areas (square miles), and within a short timeframe (weeks). The water body to be mapped is energized and the electrical current flows preferentially through saturated subsurface materials, creating an induced magnetic field that is measured at multiple points on the ground surface, typically in a grid pattern.

The two water zones were energized from existing drill holes placed for monitoring the water zones. Return electrodes were placed into adjacent deeper boreholes. In this survey two separate perched zones were energized. Survey lines were run along the hills and across the gully surrounding the water zones. Two magnetic reading sets were taken and recorded at each survey station, one for the upper perched water zone and one for the deeper water zone.

The measured magnetic field data were processed, contoured, and correlated to other hydrogeologic data, resulting in enhanced definition of the extent and preferential flow paths of the groundwater bodies.

This map represents one of many contour maps prepared for LLNL.
Colored dots represent wells where levels of TCE concentration
were measured. Blue zone represents perched water zone. This
map shows two distinct perched zones with no measurable
contaminants moving between the zones. The lower perched
water zone is up gradient from the area of contamination.

As a result of our study, impact to the natural surrounding ground in this area was minimized because the drilling of several exploratory drill holes was avoided. The avoidance of drilling these exploratory drill holes saved the significant expense of drilling and pre-drilling costs. Moreover, drill hole locations for further monitoring can now be optimized.

More importantly, a comprehensive understanding of the perched water zones and the preferential flow paths was developed. This information was then used to more effectively track the flow of contaminants and to evaluate potential remediation efforts.

To learn more about Willowstick and our contaminant mapping capabilities, please contact us.