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' Global Presence <br /> Personal Attention <br /> HERST & ASSOCIATES, INC <br /> Mr.Rick Jaimie Sep <br /> Z <br /> ' California Department of Corrections and Rehabilitation F/Vt//,YO 8 200 J <br /> 7650 S.Newcastle Road/P.O.Box 213004 pF N/GjF� <br /> Stockton,CA 95213-9004 ITjS �4 7y <br /> ES <br /> September 14,2007 <br /> ' Dear Mr.Jaimie: <br /> Summary of Northern California Youth Center Sampling Results <br /> July and August 2007 <br /> On July 31 and August 16, 2007, sampling was performed at the Northern California Youth Center <br /> ' (NCYC) to provide supplemental information regarding volatile organic compound (VOC) <br /> concentrations at Well #2, Well #4, and the indoor faucet location included in other recent sampling <br /> events. Sampling was performed by Herst& Associates, Inc. VOC analyses were performed by BC <br /> ' Laboratories,Inc. <br /> Based on the sample results, there continued to be no MCL exceedances at the indoor faucet location <br /> ' during July and August 2007. Tetrachloroethene, which previously exceeded the MCL at the indoor <br /> faucet location, was reported at a concentration of 1.9 ug/l (ppb) and 1.4 ug/l in July and August, <br /> respectively,compared to an MCL of 5 ug/l. A summary of detected VOCs is provided in the attached <br /> tables. <br /> ' Well #2 (reported to be a supplemental water supply well that operates about 20% of the year during <br /> peak demand periods) continued to exhibit a tetrachloroethene concentration slightly above the MCL. <br /> ' The tetrachloroethene concentrations at Well #2 were 5.8 ug/1 and 6.0 ug/l in July and August, <br /> respectively. <br /> ' Well #4 (reported to be the primary water supply well for the facility) yielded tetrachloroethene <br /> concentrations well below the MCL. The July and August 2007 tetrachloroethene concentrations at <br /> Well#4 were 1.5 ug/1 and 1.3 ug/l,respectively. <br /> ' Quality assurance samples collected during the July sampling event consisted of a field blank at Well <br /> #4 and the indoor faucet location,a trip blank,and duplicate samples at Well#2 and the indoor faucet. <br /> Quality assurance samples collected during the August sampling event consisted of a field blank at <br /> Well #2 and the indoor faucet location, a trip blank, and duplicate samples at Well#4 and the indoor <br /> faucet. The field blank samples near the wells were collected to provide an indication of VOCs present <br /> in the ambient outdoor air or in the laboratory analytical process. The field blank samples at the indoor <br /> ' faucet location were collected to provide an indication of VOCs present in the ambient indoor air or in <br /> the laboratory analytical process. The trip blank sample was collected to provide an indication of any <br /> VOCs associated with shipment or in the laboratory analytical process. The duplicate samples were <br /> ' collected to provide an indication of sampling and laboratory testing reproducibility. <br /> 4630 South Highway 94—North Outer Road Telephone(636)939-9111 <br /> St.Charles,Missouri 63304 Fax(636)939-9757 <br /> 1 <br />