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' Geologaal Techm"Inc Page 2 Groundwater Monitoring Report Project No 770 2 February 7,2005 efforts confirm that groundwater direction varies from month to month at the site There are numerous agricultural, commercial and residential wells near the Marci parcel and the influences from these wells are the probable cause for the groundwater direction fluctuations A site conceptual model (SCM) report dated August 23, 2004 was submitted to San Joaquin County Public Health Services/Environmental Health Divisions (SZC PHS/EHD) for approval A work plan is in process to address the County correspondence in regards to the SCM report 1.0 GROUNDWATER MONITORING ' 1.1 Hydrogeology of Site The site exhibits a primarily silty/clayey geology with minor sand layers/lenses, pebbles, ' black organics and iron staining occasionally present The groundwater monitoring schedule was modified to include monthly depth to groundwater measurements in 2002 This was necessary to better define the gradients that have varied greatly in the past ' On August 19, 2004, the water table well groundwater elevation averaged -43 09 feet mean sea level (MSL) For the December 09, 2004, event the water table well groundwater elevation averaged -42 80 feet MSL A net increase of 0 29 feet MSL was recorded between the August and December 2004 sounding events Groundwater gradient calculations indicate that the flow in the water table wells was S63°E with a slope of 0 001 ft/ft on December 09, 2004 while the deeper aquifer gradient was SWE with a slope of 0 001 ft/ft Groundwater elevation and gradient data are summarized in Tables 1 and 2, Appendix A ' The water table and deep well gradient directions are shown in Figure 2 and Figure 3, respectively, for the December 2004 event ' The historical water table gradients are illustrated in Figure 4 & 5 Groundwater Gradient Rose Diagrams for Water Table and Deep Wells, respectively The site's shallow aquifer displays highly variable shifts in groundwater direction It is noted that groundwater ' direction has been predominantly to the southeast since additional wells were installed in May 2002 The deeper aquifer flow had been consistently to the east for the previous seven ' sounding events But on April 28 and May 23, 2003, the gradient reversed 180° from an easterly direction to a westerly direction The direction reversed again to the east for the remainder of the sounding events 1 � 1