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STATE OF CALIFORNIA-Environmental Protectency • PETE WILSON, Governor <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD <br /> CENTRAL VALLEY REGION _ <br /> 3443 Rcutier Road, Suite A <br /> Sacramento, CA 95827-3098 MAY 2 1993 <br /> PHONE: (916)255.3000 <br /> DOD FAX (916) 255.3052 ENVIRUNMENTAL HEALTH <br /> PERMIT/SERVICES <br /> Mr. Abel Haines 17 May 1993 <br /> Environmental Protection Office <br /> Bldg. S-108, Sharpe Site <br /> Defense Distribution Region West <br /> P. 0. Box 960001 <br /> Stockton, CA 95296-0710 <br /> 1992 ANNUAL PROGRESS REPORT, GROUNDWATER MONITORING PROGRAM, DEFENSE <br /> DISTRIBUTION REGION WEST (DORW), SHARPE, SAN JOAQUIN COUNTY <br /> We have reviewed the 1992 Annual Progress Report, submitted as part of DDRW, <br /> Sharpe's ground water monitoring program. Overall , the report was well <br /> prepared. Our major concerns are summarized below and are discussed in more <br /> detail in the enclosed memorandum. <br /> 1 . Some of the extraction wells in the South or North Balloon Areas have been <br /> operated in the past for more than two quarters when the contaminant <br /> concentrations are below the aquifer cleanup level . It appears that NA-7 <br /> continues to be operated although contamination has been below all aquifer <br /> cleanup levels since installation. Use of this well should be <br /> discontinued. The criteria for determining when an extraction well should <br /> be discontinued or returned to service should be discussed with the <br /> Project Managers. <br /> 2. We do not concur with annual and semi-annual monitoring for benzene, <br /> toluene, xylene and ethylbenzene (BTXE) , polychlorinated biphenyls (PCBs) <br /> and heavy metals in specific monitor wells because the site-wide <br /> investigation of all solid waste management units (SWMUs) and underground <br /> storage tanks (USTs) is incomplete. We recommend that wells with <br /> confirmed historical detections of these contaminants be monitored on a <br /> quarterly basis, in addition to the wells designated for quarterly <br /> monitoring for the volatile organic constituent (VOC) plumes. Semi-annual <br /> monitoring should be conducted for wells that have had sporadic detections <br /> of contaminants and are down gradient of potential source areas and annual <br /> monitoring should be conducted at all other wells. <br /> 'Iff you have yany questions",) please call me at (916)255-3065. <br /> JAMES TAYLOR <br /> Associate Engineering Geologist <br /> JDT:jt <br /> Enclosure <br />