LAWRENCE LIVERMORE NATIONAL LABORATORY:
LIVERMORE SITE CHARACTERISTICS

Site Conditions

The Livermore Site is located in the Livermore Valley, which is bounded by branches of the San Andreas Fault system. The site slopes gently to the northwest, ranging in elevation from approximately 675 to 550 ft above sea level. The subsurface is composed of gravel, sand, silt, and clay. The depth to ground water varies from about 120 ft below ground surface in southeast corner to about 40 ft below ground surface in the northwest corner. Ground water flow is predominantly from northeast to southwest, but is locally modified due to ground water extraction. A regional confining layer separates the Upper Livermore Formation from the Lower Livermore Formation (below Unit 5 in figure below). Ground water contaminant plumes from the Livermore Site do not occur beneath the regional confining layer. The regional aquifer in the Lower Livermore Formation varies in depth from about 200 ft to over 400 ft in the northwest corner of the site.

HSU analysis

The Livermore Site subsurface is well characterized and made up of Hydrostratigraphic Units (HSUs) that contain the VOC plumes. The HSUs were defined using a methodology that relies on multiple independent data sets, including: ground water data (monthly ground water elevations and hydraulic responses to pumping tests and treatment facility operations), ground-water chemistry, and geologic and geophysical data. The HSU framework allows delineation of a complex network of contaminant ground water plumes that can be traced back to their respective source areas, allowing strategic placement of wells and treatment facilities. HSU methodology also provides the basis for building and calibrating computer models for ground water flow and contaminant migration.

Engineered Plume Collapse

The success of the HSU analysis provided the foundation for our Engineered Plume Collapse (EPC) strategy that has been so critical to the acceleration of site cleanup at the Livermore Site. EPC consists of a four-phased systematic and aggressive cleanup strategy. We have nearly completed Phases I and II in all areas and are beginning some limited cleanup of sources areas (Phase III).

We have learned that we can hydraulically contain and isolate source areas to stop resupplying contaminants to the distal plumes, and rapidly cleanup the distal plume to reduce time to cleanup. The success of EPC is apparent in the increase of mass removed at the Livermore Site since EPC was initially deployed in 1997.









The success of EPC is also apparent in the ability to cleanup the ground water plumes at the Livermore Site through isolation of the source and distal plume cleanup.







Next: Remediation Strategy