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Creclogleal Tecluucs lnc. Page 6 Groundwater Monitoring Report Project No 770 2 November 8,2004 tAn examination of the contaminant distribution and groundwater flow direction data doesn't reveal any obvious trends A consistent factor previously noted in the investigation was the ' increase in diesel concentrations in well MW-5, see Figure 6- MW-5 TPH-D vs Groundwater Elevation The concentrations had previously demonstrated an increasing trend until June 2002 when wide fluctuations began The sudden increase since the June 2004 ' event is obvious, however the cause is unclear, possibly due to low water level in the well and associated poor recharge to the well during purging and sampling Purging and sampling logs suggest that sample quality may be compronused due to low water level in the well The ' plot in Figure 6 suggests that a previously direct relationship between groundwater elevation and contaminant concentrations has reversed since June 2002 ' Well MW-4 lies adjacent to the former UST field Figure 7-MW-4 TPH-D vs Groundwater Elevation suggests that a predominantly inverse relationship exists between groundwater elevation and contaminant concentrations In this figure the sudden increase since the last event is also obvious ' Well MW-5 continues to contain the highest concentrations of detected contaminants (see Figure 8) It has not been down gradient of the former UST location for the monitoring events completed by GTI to date The reason for this anomaly is not known, but could be related to geologic units that slope to the west TPH-D was detected in MW-105 at 170 ug/l It indicates that the contamination is moving vertically downward in an oblique angle to the northwest from the source In Figure 9— MW-5 & MW-105 TPH-D versus Groundwater Elevation, well MW-5 contaminant concentrations have previously correlated with changes in the water table Since ' September 2001 the relationship has been reverse Well MW-105, screened below the water table, exhibits a typically inverse relationship between contaminant concentrations and groundwater elevation ' Figure 10 illustrates the distribution of diesel in the deeper wells The data is skewed toward the single detection point in well MW-105 ' GTI makes the following recommendations m Maintain the quarterly monitoring schedule ' a Analyses for 1,2 DCA and EDB by EPA Method 8260 have been completed for two consecutive events and have been found to be non-detect These analyses should be discontinued to achieve laboratory cost savings Upon receipt of comments from SJCEHD on the site conceptual model, we recommend that additional site characterization work plan and interim remedial action plan be ' implementation ASAP