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<br /> April 27, 2010 RECRYED
<br /> Project No. 10626.000
<br /> Hr'r� .11 Q LUft)
<br /> Mr. Howard Hold
<br /> California Regional Water Quality Control Board ENVIRONMENT HEALTH
<br /> Central Valley Region PERMIT/SERVICES
<br /> 11020 Sun Center Drive#200
<br /> Rancho Cordova, California 95670
<br /> Re: Summary of Recent Groundwater Monitoring at Lathrop Facility
<br /> MonierLifetile LLC Lathrop Facility
<br /> Lathrop, California
<br /> Dear Mr. Hold:
<br /> AMEC Geomatrix, Inc. (AMSC), is submitting this letter to the California Regional Water Quality
<br /> Control Board —Central Valley Region (RWQCB), to summarize recent groundwater monitoring
<br /> activities and laboratory results for the MonierLifetile LLC (MonierLifetile) Lathrop Facility
<br /> located at 342 Roth Road, Lathrop, California (Figure 1). As you are aware, previous site
<br /> assessment and groundwater monitoring activities at the Lathrop Facility were conducted in
<br /> accordance with RWQCB Cleanup and Abatement Order No. 5-01-722 (Order) dated October
<br /> 15, 2001 (finalized in February 2002).
<br /> Pursuant to the Order, a groundwater monitoring system was installed at the Lathrop Facility as
<br /> described in the Groundwater Monitoring Plan (GMP) and Addendum (Brown and Caldwell,
<br /> 2002).' The groundwater monitoring system was proposed to further assess groundwater
<br /> quality, flow direction, and site-specific background conditions in the area of the stockpiled
<br /> material. The GMP was approved by the RWQCB on January 31, 2002. Since March 2002,
<br /> and under the GMP, groundwater monitoring has been conducted at the Lathrop Facility.
<br /> The removal of the stockpile of broken and uncured roof tile materials was completed in October
<br /> 2007, and vadose zone soil testing was completed beneath the area of the former stockpile in
<br /> November 2007, pursuant to the soil investigation work plan (Geomatrix, 2005).2 The results of
<br /> the Lathrop Facility soil investigation were summarized in the Soil Investigation Report,
<br /> MonierLifetile LLC, Lathrop Facility (Geomatrix, 2007).3 Since the removal of the stockpile,
<br /> eight groundwater monitoring/sampling events have been conducted at the Lathrop Facility.
<br /> Brown and Caldwell,2002,Groundwater Monitoring Plan and Addendum, MonierLifetile LLC, Lathrop and French
<br /> Camp Facilities,California,January.
<br /> 2 Geomatrix Consultants, Inc.,2005, Soil Investigation Work Plan December 2005, Lathrop and French Camp,
<br /> California, December 6.
<br /> 3 Geomatrix Consultants, Inc., 2007,Soil Investigation Report, MonierLifetile LLC, Lathrop Facility, Lathrop,
<br /> California, December 31.
<br /> P:\10626.000.0\Docs\Semi-Annual Groundwater Monitoring&Sampling\Lathrop Monthly Groundwater Monitoring\Ltr_042710.doc
<br /> AMEC Geomatrix,Inc.
<br /> 510 Superior Avenue,Suite 200
<br /> Newport Beach,CA
<br /> USA 92663-3627
<br /> Tel (949)642-0245
<br /> Fax (949)642-4474 'AMEC
<br /> www.amecgeomatrixinc.com
<br />
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