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Wm. kHunter & Associates ;,) 2220 Loma Vista Dr. Registered Geologists "= Sacramento, CA 95825 Petroleum &Mineral Appraisers t, r ) ' 1 Q (916) 972-7941 • $ FAX (916) 972-1683 February 9, 1998 Wendy Wiles, Engineering Geologist CRWQCB, Central Valley Region 3443 Routier Road, Suite A Sacramento, CA 95827-3098 RE: SECOND HALF 1997 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 October 11, 1997 by Del-Tech Geotechnical. There are eight (8) wells on the Independent Trucking facility, 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 on the site adjacent to the east. We are measuring and recording depth to water data from this well, but are no longer collecting and analyzing groundwater samples. 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 prior 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. Del-Tech reported that all of the wells on the property are in poor condition. The well box for MW-1 has been dislodged and the top of the casing possibly damaged. The top of MW-2 is broken off, and water depth measurement is not accurate. The top of the casing in MW-3 has had an extension glued on it after pouring a cement pad around the well. The well box of MW- 4 is in very bad shape, and the field technician has been unable to locate MW-6. We are obtaining bids for restoring the integrity of those wells. PLATE I shows the inferred potentiometric surface based upon the latest sampling. The gradient is towards the north at about .0025/ft. However, because MW-2 & MW-6 could not be used, the map may not be an accurate representation of the gradient pattern. The average depth to water in the wells sampled was -12.75' msl datum, a drop of 2.03' since the March event. PLATES n through V show the approximate limits (where applicable,) and concentrations of • benzene, toluene, ethylbenzene, xylene, TPHg, and TEPH (as diesel.) from the October event. 1