DTSC has approved the Revised Feasibility Study in September 2007. This report studied the technical processes and procedures that could be used to implement the remedy, assembled these processes into potential remedial alternatives, evaluated these alternatives, and identified a proposed alternative, determined to be the most appropriate remedial alternative for the Site.
A Remedial Investigation (RI) and Feasibility Study (FS) had been conducted for the Site in 1997 and 2000, respectively. DTSC had more recently concluded that a Revised FS would be required to more fully evaluate approaches to key project activities and associated potential environmental issues that are necessary to a detailed plan and method for cleaning up the Site.. On January 28, 2004, DTSC provided the Responsible Parties (RPs) the opportunity to prepare a Revised Feasibility Study (RFS). The objective of the RFS was to collect and analyze additional data for the remedy design and to expand and confirm results of previous sampling conducted during previous RI/FS programs to more fully evaluate various approaches and the potential impacts of work at the Site. The Ascon Site Responsible Parties prepared workplans for the new fieldwork. These plans were submitted to DTSC for review, comment, and approval before the fieldwork commenced. This fieldwork was performed from May through December 2004 and included:
- Drilling of approximately 50 additional boreholes to collect samples to establish a larger base of data with which to evaluate and understand the Site's subsurface physical and chemical conditions.
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- Quantification of any potential odors and emissions within the Site and at the Site's perimeter during implementation of the remedy, and evaluation and testing of mitigation procedures for the odors and emissions.
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- Excavation of temporary test trenches to determine the vertical extent and stability of wastes..
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- Sampling and depth profiling of lagoon materials to better define volumes and types of materials to be excavated and to provide additional necessary information to assist in the design of lagoon waste handling systems.
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- Sampling and waste characterization and waste-handling studies at Pit F (the pit containing styrene constituents) to evaluate various technical approaches and to optimize planning for the remedy..
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- Collection of samples, as required, for treatability studies to evaluate any necessary waste treatment at the Site during the remedy.
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- Evaluations of waste transportation and disposal methods.
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The
data and information obtained from the above studies
will be used to update and expand the Year 2000
Feasibility Study information (FS 2000). It is expected
that a full range of alternate technologies, methods,
and remedy alternatives will be developed to fully
evaluate the Site and determine the most appropriate
preferred remedy for the Site.
During 2007, additional sampling and testing was conducted on soils from three mineral estate areas of the Site, areas with existing or former oil production or mineral leases (i.e., leases for oil production). It had been determined that soils assessment in these areas was not yet adequate. The report presenting these results was be submitted to DTSC in February 2008s.
DTSC and the RPs will continue to keep the community updated on the progress of site remedy implementation and will encourage public participation and input via scheduled and noticed public meetings.
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