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s' -AT'; OF CALIFORNIA GEORGE DEUKMEJIAN Governor CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD SUE — CENTRAL VALLEY REGION ' 3443 ROUTIER ROADf SACRAMENTO, CA 95827-3098 i 6 August 7. 987 ENV RRM;BSER HCESSH FE Ms . Laurie Cotulla San Joaquin Local Health District P . 0 . Box 2009 Stockton , CA 95201 CRYSTAL CREAM AND BUTTER COMPANY , STOCKTON , SAN JOAQUIN COUNTY I have reviewed the 29 July 1987 revised work plan submitted by Applied Geosystems an behalf of Crystal Cream and Butter ( Crystal ) . The revised work plan is acceptable with clarification of the following two points : 1 . Final delineation of the horizontal and vertical extent of ground water contamination must be accomplished with ground water samples . Soil gas sampling is a useful qualitative technique , but is not definitive ; and 2 . Vapor or ground water extraction systems must be able to demonstrate that the area limits of contamination are removed . This means that the entire extent of contamination must be defined before a final extraction system can be installed . Additionally , it must be possible to document and monitor the boundaries of any final extraction systems . As long . as these two points are clear , we have no objections to Crystal ini - tiating work if the following minor comments are incorporated into the work plan : 1 . A sketch of the vapor probe system described should be included in the report . 2 . Has actual 'Field testing of the proposed vapor probe system been performed ? Such data , since the proposed system is innovative , should be submitted . For example , the described " purging " method for the vapor probe appears questionable , depending on soil types , head pressures , volume of purge gas , and location at which purging takes place . 3 . Reference is made to " preprogrammed standards " used in the portable GC/ PID analyzer . Quality control should consist of on -site runs of standards and blanks .