ARCHIVED REPORTS_SEMI-ANNUAL GROUNDWATER MONITORING REPORT AUGUST 2010

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amec'9 (WQG) for TPH-diesel at 100 micrograms per liter (Ng/L) and the California Department of Public Health (CDPH) Maximum Contaminant Level (MCL) for Cr at 50 pg/L. At the French Camp facility, the removal of the stockpile of broken and uncured roof tile materials was completed in late 2005. Pursuant to the Soil Investigation Work Plan (Geomatrix, 2005a), vadose zone soil testing was completed beneath the area of the former stockpile in January 2006. The results of the French Camp soil investigation were summarized in a Soil Investigation Report, MonierLifetile LLC, French Camp Facility (Geomatrix, 2006a). At the Lathrop facility, the removal of the stockpile of broken and uncured roof tile materials was completed in October 2007, and vadose zone soil testing was completed beneath the area of the former stockpile in November 2007. The results of the Lathrop soil investigation were summarized in the Soil Investigation Report, MonierLifetile LLC, Lathrop Facility (Geomatrix, 2007a). Since the removal of the stockpiles, semi-annual groundwater monitoring has continued at the Facilities to assess the stability of the groundwater conditions. In a meeting with the RWQCB on October 22, 2009, Mr. Howard Hold of RWQCB indicated that at least eight consecutive groundwater monitoring events after the removal of the stockpiles at each Facility must be completed prior to MonierLifetile submitting a request to rescind the Order. At the conclusion of the November 2009 semi-annual groundwater monitoring event, the requisite number of groundwater monitoring events were completed at the French Camp facility. To facilitate meeting the monitoring frequency requirement at the Lathrop facility, Mr. Hold indicated that the remaining monitoring events could be performed monthly rather than continuing on the semi-annual schedule currently in place. Therefore, AMEC Geomatrix, on behalf of MonierLifetile, completed three additional groundwater monitoring events at the Lathrop facility in December 2009, January 2010, and February 2010 (AMEC Geomatrix, 2010a). At the conclusion of the three groundwater monitoring events at the Lathrop facility, AMEC Geomatrix submitted a site closure request letter to the RWQCB to start the process to rescind the Order (AMEC Geomatrix, 2010b). Currently, the RWQCB's approval to rescind the Order is pending. Therefore, semi-annual groundwater monitoring was conducted at the Facilities in August 2010 in compliance with the Order. 1.2 SCOPE OF WORK Initially, groundwater monitoring was conducted at the Facilities on a quarterly schedule between March and December 2002 (URS, 2004a). The frequency of the groundwater monitoring activities was changed to semi-annual monitoring in January 2003. The first semi- annual groundwater monitoring event for 2010 was conducted at the Facilities on August 25 and 26, 2010. The second semi-annual groundwater monitoring event for 2010 is scheduled in November 2010. AMEC Geomatrix, Inc. PA10626.000.0\Docs\Semi-Annual Groundwater Monitoring&Sampling\Semi-Annual 1-10 2