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Gilmore, Mari <br /> From: Dean Hubbard [dhubbard@waterboards.ca.gov] <br /> Sent: Wednesday, April 01, 2009 2:06 PM <br /> To: Gilmore, Mari <br /> Subject: Re: 990 Beechnut Workplan modification and extension request <br /> Mari - <br /> OK, go ahead with the hand augering and lab tests, etc later this year; proceed with <br /> excavation early 2010 as weather/ground conditions allow; and 1 April 2010 for a final <br /> report is acceptable. <br /> Keep me posted as your schedule proceeds. . . <br /> Dean Hubbard <br /> >>> "Gilmore, Mari" <Mari.Gilmore@amec.com> 3/27/2009 3:58 PM >>> <br /> Hello Dean, <br /> As we've discussed, I'm writing to provide supplemental information pertaining to our work <br /> plan for the 990 Beechnut excavation and to request an extension for submittal of the <br /> excavation completion report for the site. <br /> The upcoming excavation work, to be performed on behalf of Chevron, was described in the <br /> AMEC Geomatrix workplan dated August 14, 2008. This workplan proposed an excavation based <br /> on existing site data. After an internal meeting with the Chevron Excavation Review Team, <br /> the team concluded that the excavation limits could be better defined by conducting <br /> additional pre-excavation characterization and pre-determining the excavation limits based <br /> on this additional data. <br /> As a supplement to the approved workplan, we are proposing to conduct additional pre- <br /> excavation delineation. The work will consist of a series of hand-augered borings on <br /> approximately 15-foot centers outlining the currently proposed excavation limits <br /> (approximately 15 borings) . <br /> Borings will be advanced to approximately 6 feet, or to the total depth of the observed <br /> impacted soil. If impacted soil is observed in a boring, a step-out boring will be <br /> advanced 10 feet laterally from the impacted boring. If soil in a step-out boring appears <br /> unimpacted, a soil sample will be collected at the depth of the observed impacts in the <br /> nearby borings to define the "clean" boundary. Soil samples will be <br /> analyzed for PAHs only, as they are the risk drivers for the site. If <br /> no impacted soil is observed in an original boring, a "step-in" boring will be advanced 10 <br /> feet laterally into the proposed excavation limits and step-in borings will be advanced as <br /> above until the "clean" boundary is identified based on visual indications. We propose <br /> that the results of this additional investigation be used to define the boundary of the <br /> excavation in lieu of excavation confirmation samples. After this proposed pre- <br /> characterization work, anticipated to take place during the second quarter of 2009, we <br /> will send you an amended excavation workplan showing the new excavation limits and the <br /> results of the excavation confirmation sample analyses. <br /> In your workplan review letter dated September 8, 2008, you requested that the report <br /> documenting completion of the excavation be submitted by April 1, 2009. Because the <br /> excavation will be delayed until after the pre-characterization work is completed, AMEC <br /> Geomatrix, on behalf of Chevron, would like to request an extension on the excavation <br /> completion <br /> report due date to June 2010. <br /> 1 <br />