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C7ealogual recluucsInc Page 5 Groundwater Monitoring Report Project No 770 2 April 30, 2003 ' As required under AB2886� the laboratory data was submitted electronically to GeoTracker q 1 on January 10, 2002 - confinnation numbers 3917768657 & 8680761396 ' 20 FINDINGS AND DISCUSSION The results of the groundwater sample analysis indicate the following • Diesel range petroleum hydrocarbons were detected in six of the site's eleven monitoring wells • Well MW-5 contained 12,300 gg/l diesel and remains the most highly impacted well I • Gasoline range petroleum hydrocarbons (TPH-G) are present in MW-6 at 67 9 ug/l This is the second time that TPH-G was detected for this well for the ten monitoring events that it has been sampled Four of the wells contained TPH-G for the September i2001 event only MW-1, 4, 6, & 105 • Minor BTEX constituents are present at levels ranging from 0 4 --3 7 µg/l in wells MW- 4, MW-5, MW-6, MW-7 and MW-104 • Motor oil range petroleum hydrocaibons were not present in any of the groundwater samples at concentrations above the laboratory reporting limits • Deep well MW-104 contained 04 ug/l xylene This is the first time the well has contained detectable contaminants • Deep well MW-105 contained 84 9 ug/l TPH-D The well has intermittently contained ' TPH-D • Deep well 106 did not contain contaminant concentrations above the laboratory reporting limits for the third consecutive event • The lateral extent of the diesel groundwater plume is currently undefined due to the continuing fluctuations in groundwater direction • The vertical extent of the plume is intermittently defined by MW-104, 105, & 106 0 Oxidation-Reduction Potential (ORP) measurements show that five monitoring wells are within the reaction depleted water caused by biodegradation of the contamination ' plume These wells exhibit negative ORP values and all of the well ORP data are included in Table 5 of Appendix A The other wells have relatively low positive values suggesting that the water around these wells are on the outer fringe of the impacted halo An examination of the contaminant distribution andg roundwater 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 5- MW-5 TPH-D vs Groundwater Elevation The concentrations had previously demonstrated an increasing ' trend, but wide fluctuations are noted for the past four events The plot in Figure 5 suggests a predominant direct relationship between groundwater elevation and contaminant concentrations