SITE INFORMATION AND CORRESPONDENCE

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v CONDOR EARTH TECHNOLOGIES INC y i 7 i 188 Frank West Circle Suite I —tail Stockton CA 95206 'PE, Phone 209.234.0518 R FAX 209.234.0538 CONDOR www.condorearth.com NOV 0 3 2003 October 30, 2003 I_NVjpuu WENT 8EALT.H ,pERMIT/SERVIGES � I Jeffrey C. F. Wong � IIENT S COPY San Joaquin County Environmental Health Department 304 E. Weber Avenue, Third Floor Stockton, California 95202 Re: Approval to Destroy Monitor Well MW-1 and Install Two Additional Monitor Wells at Boyett Petroleum, 419 S. Main Street, Manteca, CA Dear Mr. Wong: The purpose of this letter is to confirm your approval to destroy monitor well MW-1 and install two replacement wells at the above referenced site. On October 24, 2003, Lee Morse of Condor Earth Technologies, Inc. (Condor) had a telephone conversation with you in which he described the results of the groundwater investigation that was conducted between October 20 and 23, 2003, at the site. The results of the cone penetrometer testing (CPT) indicated that a clay interbed is present at a depth of approximately 25 feet, and that the clay appears to be continuous across the site. Laboratory analytical results of groundwater samples collected from direct push borings advanced at the same location indicated the clay separates two aquifers. Methyl tertiary-butyl ether (MTBE) was detected in a groundwater sample collected from immediately above the clay at a concentration of 12,000 µg/L. MTBE was detected in a groundwater sample collected from immediately below the clay at a concentration of 5.3 µg/L. This large difference in concentrations indicates the clay acts as barrier to vertical movement between the two aquifers. Monitor well MW-1, installed in August 1999 by WHF, Inc., is screened across the clay interbed and appears to have acted as a vertical conduit for contaminants between the two aquifers. Mr. Nuel Henderson of your office had previously voiced his concern about the potential for this well to act as a vertical conduit. In your letter dated May 29, 2003, to Mr. Dale Boyett, you requested that the design of MW-1 be reviewed in the context of a site conceptual model and if the well potentially creates a vertical conduit between different sand layers. In your letter dated August 25, 2003, to Mr. Boyett, you recommended that submission of a work plan to replace MW-1 be delayed until the lateral and vertical groundwater investigation had been completed. On October 24, 2003, Lee Morse requested your approval to destroy MW-1 and install one four-inch diameter monitor well screened in the upper aquifer and one four-inch diameter monitor well screened in the upper portion of the aquifer immediately below the clay. The destruction of monitor wells MW-4 and MW-5 and the installation of an extraction well and a monitor well to replace MW-4 were scheduled for October 29 and 30, 2003. Scheduling this work at the same time as the previously scheduled well destructions and installations would eliminate the vertical conduit created by MW-1 as soon as possible