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Figure 5 shows the distribution of TPH-G, BTEX, and MTBE in groundwater and the lateral limits <br /> • of the TPH-G in groundwater as determined from groundwater samples collected on December 5, <br /> 1997 The decrease in groundwater elevations since the previous quarterly monitoring round in <br /> May 1997 has been accompanied by an increase in TPH-G and BTEX concentrations at MWI, <br /> while the remaining wells show no analytes above laboratory detection limits <br /> RECOMMENDATIONS <br /> 1) Continue quarterly groundwater monitoring to determine rate of contaminant decline <br /> 2) Analyze samples from MW 1 only for oxygenant concentrations by EPA method 8260 during <br /> next quarterly sampling round <br /> 3) Implement the existing workplan for delineating the vertical and lateral extent of soil and <br /> groundwater contamination to historical groundwater elevations at the site <br /> LIMITATIONS <br /> The discussion presented in this report is based on the following <br /> 1 The observations and data collected by field personnel <br /> 2 The results of laboratory analyses performed by a state certified analytical laboratory <br /> 3 Our understanding of the regulations of San Joaquin County and the State of California <br /> Changes in groundwater conditions can occur due to variations in rainfall, temperature, local and <br /> regional water use, and local construction practices In addition, variations in the soil and <br /> groundwater conditions could exist beyond the points explored in this investigation <br /> State Certified Laboratory analytical results are included in this report This laboratory follows <br /> EPA and State of California approved procedures, however, WEGE is not responsible for errors in <br /> these laboratory results <br /> The services performed by Western Geo-Engineers, a corporation under California Registered <br /> Geologist #3037 and/or Contractors License#513857, have been conducted in a manner consistent <br /> with the level of care and skill ordinarily exercised by members of our profession currently <br /> practicing under similar conditions in the State of California and San Joaquin County Our work <br /> and/or supervision of remediation and/or abatement operations, active or preliminary at this site is <br /> no way meant to imply that we are owners or operators of this site Please note that the known <br /> contamination of soil and/or groundwater must be reported to the appropriate agencies in a timely <br /> manner No other warranty expressed or implied is made If you have any questions concerning <br /> this report or if we can be of further assistance, please do not hesitate to contact us at (530) 668- <br /> 5300 <br /> ,JACK"_ l <br /> NAPPER <br /> Z-2 <br /> s�tiF r��F°�`�P <br /> Jack E Napper 0F cDavid Threlfall <br /> R G 43037 Project Geologist <br /> 3 Sanchez QM 12-97 <br />