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Groundwater Monitoring

Groundwater investigations began in 1984 under the direction of the Regional Water Quality Control Board Regional Water Quality Control Board (RWQCB). In 1988, the program oversight transferred to DTSC.

Between 1984 and 2005, over 400 groundwater monitoring wells have been drilled at the site. These wells have been sampled routinely over the years. In addition to drilling wells and collecting and analyzing groundwater samples, the nature of the groundwater system has been investigated through a series of aquifer tests, through the detailed mapping of the geology of Simi Hills, and through the identification and sampling of seeps and springs.

In 2000, DTSC approved a detailed investigation into the fractured bedrock and deep groundwater at SSFL. Several new investigation techniques were developed and used for the first time at the site. The first phase of the investigation included the drilling and installation of coreholes to depths in excess of 900 feet. 4,500 rock samples were collected and analyzed for solvents such as TCE. In addition, sophisticated monitoring and measuring devices were installed in numerous wells in order to study, in the three dimensions, the distribution of the chemical contamination. Numerous wells across the site were also logged using sensitive devices that measure rock properties. Additional groundwater tests such as aquifer tests were conducted to evaluate groundwater flow characteristics beneath the site. Water quality data collected from the wells will be used to assess contaminants in the subsurface bedrock.

The data collected to date, especially over the past few years, has provided valuable information and insight into the movement of groundwater and contaminants at the site. This detailed level of characterization is scheduled to continue over the next few years with the goal of understanding the nature and extent of contaminants in the groundwater at the site. It is this information that will make it possible to make decisions regarding short-term and long-term remediation approaches for groundwater cleanup.