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' Global Presence <br /> Personal Attention <br /> HERST & ASSOCIATES, INC <br /> ' Mr.Rick Jamie <br /> L� <br /> {� Il I�L <br /> California Department of Corrections and Rehabilitation <br /> L <br /> 7650 S.Newcastle Road/P.O.Box 213004 JUN 12 2007 <br /> ' Stockton,CA 95213-9004 <br /> ENV9R0N%+EN1 HEP,JH <br /> June 11,2007 PERMI I SERVICES <br /> ' Dear Mr.Jamie: <br /> ' Summary of Northern California Youth Center Sampling Results <br /> Week of May 14,2007 <br /> ' We have received the laboratory analytical results for the pumping well samples, storage tank samples <br /> (pre- and post-sediment removal), sediment samples taken from the storage tanks, and indoor faucet <br /> samples collected after completion of tank sediment removal activities at the Norther California Youth <br /> ' Center (NCYC) during the week of May 14, 2007. The sequence of events included collection of a <br /> water sample from each of the three(3)storage tanks prior to tank sediment removal activities,removal <br /> of accumulated sediment and collection of a sample of the sediment removed from each tank, <br /> ' collection of a water sample from each of the three tanks after completion of tank sediment removal <br /> activities,and collection of indoor faucet samples after completion of tank sediment removal activities. <br /> The goal was to determine if tank sediment removal operations affected the concentration of VOCs in <br /> ' the tanks and at the indoor faucet. In addition,a sample of each of the three operating pumping wells at <br /> the facility was colleted. Following is a brief summary of the results. <br /> Water Quality in the Storage Tanks Prior to Sediment Removal <br /> ' The concentration of tetrachloroethene in the three storage tanks prior to sediment removal was <br /> consistent from tank to tank,ranging from 5.0 ug/l to 5.6 ug/l. The concentration of tetrachloroethene <br /> ' in the northern storage tank was 5.0 ug/l in a primary sample and 5.3 ug/1 in a duplicate sample. The <br /> concentration of tetrachloroethene in the center storage tank and southern storage tank was 5.3 ug/l and <br /> 5.6 ug/l, respectively. These results indicate that the water in the storage tanks prior to sediment <br /> ' removal contained tetrachloroethene at or above the Maximum Contaminant Level(MCL)of 5 ug/l. <br /> Sediment Removal Process <br /> ' Accumulated sediment in the three storage tanks at the NCYC facility was removed utilizing a <br /> technique that vacuums and then expels non-dissolved settled sediment. Sediment removal activities <br /> ' were performed by Aqua-Tech Company, located in Carmichael, California. According to the Aqua- <br /> Tech Company Contract, the sediment removal techniques are safe and sanitary, and can therefore be <br /> performed while the tanks remain on-line. The tank cleaning process utilized is approved by the <br /> California Department of Health Services according to Aqua-Tech Company personnel. NCYC <br /> ' personnel stated that during the sediment removal operations (May 14 through May 17), water was <br /> being supplied to the tanks by Well No.4. <br /> ' 4630 South Highway 94—North Outer Road Telephone(636)939-9111 <br /> St.Charles,Missouri 63304 Fax(636)939-9757 <br />