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N omorand um CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD • CENTRAL VALLEY REGION 3443 Routier Road Phone : ( 916) 361 - 5600 Sacramento, CA 95827- 3098 ATSS : 8-495- 5600 TO : Antonia K . J . Vorster FROM : Gary Reents Senior Engineer Project Engineer DATE : 3 July 1987 SIGNATURE : SUBJECT: UNDERGROUND TANK CONTAMINATION WORK PLAN , CRYSTAL REAM AND BUTTER , SAN JOAQUIN COUNTY The subject work plan , dated 22 April 1987 , was submitted to the San Joaquin Local Health District by Applied Geosystems , consultants to Crystal Creamery and Butter Company ( Crystal ) . The work plan was prepared based on the results of previous work detailed in letter reports of 10 October and 17 November 1986 , and 23 January 1987 . To date , Crystal has removed the leaking underground tank , excavated contamina- ted soils , and installed one ground water monitoring well . Contaminated soils east of the excavation and south beneath a warehouse , remain in place . Samples from the monitoring well contained volatile aromatic constituents above State Action Levels . The 22 April work plan proposes to install and operate a soil venting ( vapor extraction ) system to mitigate soil contamination , conduct a soil gas study to define the plume , and pump the existing monitoring well to mitigate ground water contamination . At this time the primary objective at the site is to define the extent of soil and ground water contamination . Once the contamination extent is determined , complete mitigation measures can be implemented . The proposed soil vapor and ground water extraction measures may be appropriate as interim remedial measures , but their effectiveness as final mitigation actions cannot be determined . Mitigation measures cannot be designed or compared until the extent and degree of contamination is determined . Accordingly , the primary object of the site investigation should be to : i . Define the areal extent of soil contamination . 2 . Define the horizontal and vertical extent of ground water contamination . 3 . Design and implement measures to mitigate impacts from the site . Based on the actions proposed in the 22 April work plan , Crystal could meet these objectives by : i . Performing a soil gas survey to define the extent of soil contamination and qualitatively estimate the horizontal extent of ground water contamination .