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Global Presence HERST & ASSOCIATES, INC.® Personal Attention ;ec W- Mr.Rick Jaime I r j California Department of Corrections and Rehabilitation No Y 3 � v 7650 S.Newcastle Road/P.O.Box 213004 EIVV 200j ' Stockton,CA 95213-9004 pFR �r�EjyTh��(November 28 2007 �RV�eF r� ' Dear Mr.Jaime: Summary of Northern California Youth Center Sampling Results ' October 2007 On October 11, 2007, sampling was performed at the Northern California Youth Center (NCYC) to ' provide supplemental information regarding volatile organic compound(VOC) concentrations at Well #2, Well #4, and the indoor faucet location included in other recent sampling events. Sampling was performed by Herst&Associates,Inc. VOC analyses were performed by BC Laboratories,Inc. ' Based on the analytical results,there were no National Primary Drinking Water Standards-Maximum Contaminant Level (MCL) exceedances during the October 2007 sampling event. A summary of ' detected VOCs is provided in the attached table. Well #2 (reported to be a supplemental water supply well that operates about 20% of the year during ' peak demand periods) exhibited a tetrachloroethene concentration slightly below the MCL. The October 2007 tetrachloroethene concentration at Well#2 was reported at 4.8 ug/l compared to an MCL of 5 ug/l. Well #4 (reported to be the primary water supply well for the facility) yielded a tetrachloroethene concentration well below the MCL. The October 2007 tetrachloroethene concentration at Well#4 was reported at 1.5 ug/l. Quality assurance samples collected during the October 2007 sampling event included a field blank at Well#4,a field blank at the indoor faucet,a trip blank,and duplicate samples at Well#2 and the indoor faucet. The field blank sample at Well#4 was collected to provide an indication of VOCs present in the ambient outdoor air or the laboratory analytical process. The field blank sample at the indoor faucet location was collected to provide an indication of VOCs present in the ambient indoor air or the ' laboratory analytical process. The trip blank sample was collected to provide an indication of any VOCs associated with shipment or the laboratory analytical process. The duplicate samples were collected to provide an indication of sampling and laboratory testing reproducibility. ' The October 2007 field blank samples yielded no detectable concentrations of VOCs. All VOCs were reported as non-detect in the trip blank sample. Besides a methylene chloride (a common laboratory- induced compound) concentration (2.3 ug/L) reported in the duplicate sample collected at Well #2, ' duplicate sample results for the October sampling event were similar to the original sample results, indicating good reproducibility. 4630 South Highway 94—North Outer Road Telephone 636 939-9111 9 Y P ( ) St.Charles,Missouri 63304 Fax(636)939-9757