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G <br /> M & ASSOCIATES <br /> S « ENOMarch 19, 1987 <br /> eHvlRol�+l�e►vr�l. INEERINO s�xvlces <br /> 112U RICHMOND AVE. <br /> BUILDING J. SUITE 100B <br /> HOUSTON, TEXAS 77042-2617 <br /> Mr. Jim Thompson <br /> Kayo Oil Company <br /> 900 South Cherokee Lane <br /> Lodi, California 95240 <br /> Reference: Review of Recent Electric Logging <br /> Site Data at the <br /> Cherokee/Lodi Station <br /> Dear Mr. Thompson: <br /> GMS & Associates has completed their review of the electric <br /> logging data from the above referenced service station. Enclosed <br /> are two cross sections of the subsurface geology. Also enclosed <br /> are marked electric logs showing where existing well records <br /> indicate the well screens and gravel packs are. <br /> The Gamma Ray and Neutron logging of the existing wells was <br /> very successful. Please refer to the enclosed marked log of well <br /> number 11. A shift to the right on the Gamma Ray curve (higher <br /> counts per second) means increased clay content. This happens at <br /> about 29 feet in well number it and stays to about 50 feet. The <br /> change is subtle but it is there. The Neutron curve reads a <br /> combination of porosity and water content. The dramatic shift to <br /> the right probably indicates low effective porosity (clay <br /> disperesed among the sand and silt grains) and low water content. <br /> At about 50 feet the Neutron curve shifts back to the left <br /> indicating higher porosity and or higher water content. This <br /> matches a Gamma Ray shift inicating cleaner sands and silts. The <br /> 2.5 foot difference between the top of the Neutron "kick" or <br /> shift and the Gamma Ray shift is probably due to perched water <br /> puddled on top of the clay that begins at 30 feet. . <br /> Please refer to the log of monitor well number 1. The <br /> original monitor well number 1 was a vertical drain that let <br /> water perched above the low permeability barrier indicated by the <br /> Neutron curve down through the barrier and into the clean sand <br /> below that is probably the water table aquifer. This perched and <br /> formerly isolated water probably had some amount of gasoline <br /> associated with it. How original monitor well number 1 was <br /> abandoned now becomes very important. Traces of gravel pack left <br /> in the hole could still provide a vertical drain. Even the <br /> replacement well , monitor well number 1 redrill, is not <br /> satisfactory since its screen and gravel pack cut across the <br /> lower two thirds of the barrier zone. <br /> ( 713 )498 - 3302 <br />