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Wm. J. Hunter & Associates2220 Loma Vista Dr Registered Geologists Sacramento, CA 95825 Petroleum & Mineral Appraisers 24 FAX 972-7941 FAX (916) 972-1683 t January 16, 1997 Joel Weiss, Engineering Geologist CRWQCB, Central Valley Region 3443 Routier Road, Suite A Sacramento, CA 95827-3098 Ref FOURTH QUARTER 1996 GROUNDWATER MONITORING REPORT FOR 1145 W. CHARTER WAY, STOCKTON - INDEPENDENT TRUCKING FACILITY We have enclosed a copy of the field report, water analysis results, a groundwater gradient map, and maps showing approximate lines of equal concentrations of benzene, toluene, ethylbenzene, xylene, TPHg, and TEPH (as diesel) for the above property The field work was performed on November 15, 1996 by Del-Tech Geotechnical Support Services as instructed by our office The work included the eight (8) wells located on the Independent Trucking facility, plus the latest well (MW-9,) recently placed on the JM Equipment site at 1245 W Charter Way PLATE I is a map showing the potentiomentric surface based on the 11/15/1996 monitoring event The gradient is to the northeast, the slope vanes from 0025'/ft in the As vicinity of MW-1 to 0014'/ft towards the north/northeast This pattern is very similar to that measured during the July, 1996 sampling The average depth to water based on all 9 wells was 21 00' bgl, (-14 66' msl datum ) This is a rise of 26' since September The three prior gradient directions are also indicated, which shows that the direction of groundwater flow has been within the northeast quadrant PLATES H through V show the approximate limits & concentrations of benzene, toluene, ethylbenzene & xylene based upon the latest work The maps confirm that there are two separate plumes beneath the site, one from the Nomellini site to the east and another one from the JM Equipment site to the west It is possible that the plumes are commingled, although the data in inconclusive PLATE VI shows the approximate lines of equal concentration of TPHg MW-3, located between the two sources, has not detected any gasoline compounds since it was installed, suggesting that the two areas of contamination have not reached each other, at least not in the gasoline phase PLATE VII shows the estimated limits of TPHd MW-4 is located very close to the site of the removed diesel UST's, and is the only well which has measured TPH as diesel 1