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' B18e8 Environmental Management Inc 3rd Qtr 2004 Groundwater Monitonng Report 002-70950-04 U-Haul#709-50 i ' 4 0 CONCLUSIONS Blaes Environmental conducted the groundwater monitoring and sampling event for the Third Quarter 2004 at U-Haul Facility 4709-50 in Stockton, California on August 30 and 31, 2004, with a confirmation ' sampling event on September 28, 2004 Average groundwater levels recorded in August 2004 were approximately eight feet lower than those recorded during the May 2003 monitoring event Groundwater was not encountered in the"A"horizon ' Based on the groundwater level measurements from the middle "B" wells and the Former Harry's Auto Mart monitoring wells, the groundwater surface map for August 2004 indicates a flat gradient across the ' northern portion of the site, and a flow direction toward the southeast across the southern portion of the site Analytical results of groundwater samples collected in May 2004 from both "B" and "C" casco well Y g s indicated the presence of hydrocarbons in groundwater beneath the U-Haul Facility Comparison of analytical results from groundwater samples between U-Haul and the Former Harry's Auto Mart is limited this quarter due to lower than usual groundwater levels and inconsistencies between the analytical results procured by Blaes Environmental and GZA Analytical results of groundwater samples collected from the "B" casing wells revealed that the main portion of the U-Haul hydrocarbon plume is located around wells MW-2B, MW-3B, and MW-4B Analytical results of groundwater samples collected from the "C" casing wells revealed higher hydrocarbon concentrations near wells MW-2C and MW-4C ' Based on the August 2004 analytical results, there appears to be limited communication between the "B" —� -and "C" horizons The-LNAPL such as TPH and BTEX, appears to be concentrated in the "B" horizon - while the heavier DNAPL such as 1,2 DCA,has penetrated more extensively into the "C"horizon ' On September 28, 2004, a Blaes Environmental representative re-sampled monitoring wells MW-5C, MW-7C, and MW-8C due to suspicion that uncharacteristically high concentrations of petroleum ' hydrocarbons in groundwater samples during the third quarter 2004 groundwater monitoring event may have been the result of cross contamination of samples rather than seasonally low groundwater levels lI