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HYD <br /> `r ENVINTJ V <br /> TECH ,INC. <br /> Article 3-11, Section 66-699. Low concentrations of various metals are typically <br /> present in the sediments of the Central Valley. <br /> 4 Results of lab analysis of soil samples collected during drilling relate only to soil <br /> quality in the immediate vicinity of the individual borings. Results of ground water <br /> `' sample analysis should be primarily used to evaluate the quality of a limited area, <br /> but can also detect the presence of a contaminant that has been released from a point <br /> source(s) some distance away, if that point source is located "upstream" of the <br /> monitoring well, and if sufficient quantities of contaminant have been released so <br /> as to enable migration to the well where the sample was collected. The <br /> determination of the pattern/direction of ground water movement would be <br /> utilized to predict areas of potential chemical concentration and form the basis for <br /> the recommendation of installation of additional sampling points, if necessary. <br /> Soil sampling and well installation is considered a fundamental component of <br /> subsurface site investigation. The evaluation of the direction of ground water <br /> �- movement is of particular importance, as it allows the site investigator to predict <br /> where chemical concentrations would most likely be found, and also enables longer <br /> term site monitoring. Well installation/soil and ground water sampling cannot, <br /> however, be considered a tool capable of complete subsurface characterization. This <br /> approach is useful in efforts associated with the detection of contaminants that have <br /> bm <br /> already migrated to the areas where the wells have been installed, but in the absence <br /> of a clearly defined potential source, cannot be used to accurately predict that the <br /> areas where samples are collected will not eventually be impacted by contaminants. <br /> These limitations considered, it is apparent that this phase of site assessment has <br /> resulted in a good deal of useful environmental information. The monitoring <br /> �. wells are strategically placed within or downgradient from potential areas of <br /> concern. While it is clear that there are discrete areas of the site that have not been <br /> V individually sampled or addressed, it is also apparent that, under the scope of this <br /> project, additional investigation is not warranted. <br /> V <br /> V <br /> 8 <br /> V <br />