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Regional Investigation

So far, EPA and the Los Angeles Regional Water Quality Control Board have compelled the parties who may be responsible for the MTBE pollution to drill over 400 wells, and collect and analyze over 4000 groundwater samples, and over 10,000 soil samples. This investigation has focused on areas where contamination has spread beyond the boundaries of individual source sites.

Some of this investigation began as partnership between Shell, Chevron, and Exxon.Additional regional investigation has been performed by Shell under agreements with the Agencies ("Charnock Initial Regional Response Activities" or "CIRRA1"). This initial investigation focused on soil and groundwater between the Venice and Sepulveda intersection and the wellfields (see map (PDF) 1 pp 105K). Over 50 monitoring wells have been installed in locations not associated with any single specific source site.

In addition to soil and groundwater investigation, the participating oil companies have created a numerical groundwater model to simulate water flow in the sub-basin during varying pumping conditions, and pilot tested various treatment technologies.

(Click on pictures for larger view)
Pilot Treatment Testing at the City of Santa Monica Charnock Wellfield.
Monitoring Well Drilling on a Residential Street.
Interstate 405 in the Charnock MTBE Investigation Area
SimulprobeTM: tool used to collect samples from discrete-depths during drilling.(Various innovative tools have been used to collect samples.)
This map shows the location of regional monitoring wells.(54 KB PDF)

The regional investigation has involved collection of geologic information, collection of depth-discrete data, and installation of monitoring wells.Much of the drilling has taken place on streets due to the lack of undeveloped areas. EPA and the Regional Boards investigation has been limited in certain areas, because of development, such as beneath the 405 Freeway.

In March 2000 EPA and the Regional Board proposed a workplan for the investigation, groundwater modeling, regional database development, and a study of cleanup alternatives to determine the best cleanup approach.The Agencies requested that potentially responsible parties sign an agreement to do this work.Shell and its affiliates, Shell Oil Products and Equilon Enterprises, LLC were the only parties to sign an agreement to complete the tasks specified. EPA and the Regional Board refer to this work as the Charnock Initial Regional Response Activities (CIRRA1).

The majority of the CIRRA1 work was complete by December 2001. Below is a list of the major studies prepared by Shell pursuant to the CIRRA1 agreement. Click on the document name for more information.

Numerous comments have been submitted to the Agencies by other potentially responsible parties and stakeholders on the content of these documents prepared by Shell. These comments are part of the public record. The Shell documents along with comments are considered by the Agencies during decision making. Full copies of the Shell reports and the comments received on the reports are available upon request.

You will need Adobe Reader to view some of the files on this page. See EPA's PDF page to learn more about PDF, and for a link to the free Adobe Reader.

A summary table of the April 2001 fuel constituents detections in monitoring wells (PDF) (14 pp 93 K) can be can be seen by clicking this link. More recent data is available upon request.

Shell's recommendations for a remedy to the MTBE pollution can be seen in this November 2001 presentation (PDF) (25 pp 139 K) prepared by one of Shell's consultants. A partial description of the hydraulic analysis performed by Shell's consultants in support of their recommendation can be seen in an excerpt from another November 2001 presentation (PDF). (7 pp, 896K)

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