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' 1 � 1 Historical Background ' AGE-NC ProjectNo 00-0764 Page 3 of 3 ' GROUND WATER MONITORING WELL INSTALLATION On 13 and 14 August 2002, five ground water monitoring wells were Installed near the UST area ' (MW-1 though MW-5)to quantify the hydrocarbon concentration in ground water and determine the direction of ground water flow Field work was performed as described in the AGE-prepared Monitoring Well Installation Work Plan, dated 08 July 2002, as amended and approved by the San ' Joaquin Country Environmental Health Department(EHD) by letter dated 18 July 2002 ' MW-1 through MW-5 were completed as ground water monitoring wells with slotted screens Installed from approximately 15 to 35 feet bsg in borings MW-1 through MW-4 and from approximately 69 to 74 feet bsg in boring MW-5 Locations of the monitoring wells are illustrated on Figure 2 of this report Results of the well installation and subsequent sampling delineated the dissolved hydrocarbons and indicated direction of ground water flow to be generally toward the northeast Ground water monitoring enabled delineation of the dissolved hydrocarbon plume The dissolved hydrocarbon plume has been vertically delineated Analytical data is presented in the attached tables lie STRATIGRAPHY AND DEPTH TO GROUND WATER Silt with a tanbrown or gray color (color apparently depending on hydrocarbon Impact) was generally encountered from a depth of approximately 5 feet to 35 feet bsg in the shallow well ' borings, the coarsest material was silty sand, collected at a depth of 25 feet bsg in boring MW-2 Silty sand was generally encountered to a depth approximately of 40 feet to 45 feet bsg Generally, poorly graded sand and silty sand was encountered between 60 and 75 feet bsg in boring MW-5 ' Ground water was encountered at a depth of 30 feet bsg during drilling r r r r • r Advanced GeoEnvlronmentai,Inc � r