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Wm. J..Hunter & Associates 2220 Loma Vista Dr. Registered Geologists Sacramento, CA 95825 Petroleum & Mineral Appraisers n (916) 972-7941 FAX (916) 972-1683 September 14, 1998 CRWQCB, Central Valley Region 3443 Routier Road, Suite A Sacramento, CA 95827-3098 RE: SECOND HALF 1998 GROUNDWATER MONITORING REPORT FOR 1145 W. CHARTER WAY, STOCKTON, CA - INDEPENDENT TRUCKING FACILITY We have enclosed a copy of the field report, results of water analyses, a groundwater gradient map, and maps showing inferred lines of equal concentrations of benzene, toluene, ethylbenzene, xylene, TPHg, and TEPH for the above property. The field work was performed on August 10, 1998 by Del-Tech Geotechnical. There are eight (8) wells on the Independent Trucking site, and one on the adjacent property to the west, JM Equipment. Seven wells were placed by the owner of the property, W.W. Miles; and one, MW-5, was placed by Nomellini Construction Co. to monitor existing soil & groundwater contamination which is present beneath that site. We are no longer collecting data from that well. MW-9 was placed on JM Equipment property immediately to the west in an attempt to identify the source or sources of gasoline compounds detected in monitoring wells at the west side of the subject property. Field observations and laboratory analyses of soil & water samples revealed extremely high levels of gasoline compounds - refer to the our quarterly report dated April 9, 1997, for more information., Further monitoring is the responsibility of the owners of that site, and we are no longer sampling it. PLATE I shows the inferred potentiometric surface based upon the latest sampling. The gradient is indeterminate; there is a low area "saddle," centered beneath MW-8 which trends northwest/southeast. The general gradient is to the northeast at about .0027ft. The average depth to water during this sampling was 14.06' bgl, or -7.78' ms] datum, a drop of 0.42' since March. The top of the well screen is at 20' below grade in MW-4; at 18' in MW-1, 2, & 3; and at 15' in MW-6, 7, 8, & 9. Although the water table is now slightly above the tops of the screens, the results of the sampling are considered valid. PLATES H through V show the approximate limits (where applicable,) and concentrations \ of benzene, toluene, ethylbenzene, xylene, TPHg, and TEPH (as diesel.) from the March event. Changes in concentrations since the last sampling are summarized below: MW-1 - Benzene, ethylbenzene, oxygenates, TPHg & TEPH are below detection levels. However, toluene measured 0.4 ug/L, and xylene measured 0.6 ug/L; both were ND in March. The results of all samplling events are summarized on TABLE A. MW-2 - All compounds remain below detection levels. The results of all sampling events are summarized on TABLE A. 1