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GeologuaLTeelaucs 1AC Page 5 ' Groundwater Mozutonng Report Project No 770 2 March 16,2006 ' 2.0 FINDINGS AND DISCUSSION The results of the groundwater monitoring event indicate the following ' • The deeper aquifer has been monitored by three wells (MW-104, MW-105 and MW-106) since June 2002 and has displayed an easterly trend to groundwater direction The reversal of groundwater direction by 180° in the deeper aquifer for the April and May 2003 sounding events is anomalous to the historical data It is noted that the gradients for these two events were higher than normal suggesting that off site production is ' influencing the aquifer A receptor well survey was completed for the site in January 2001 and two agricultural wells were identified approximately 1600 feet west of the site If these wells were operated during the months in question, it is possible that the Marci ' site was within the cone of depression created by the well pumping The shallow aquifer did not reverse during this period and this may be due to the domestic wells to the southeast of the site that may be screened shallower than the agricultural wells and exert a ' primary influence on the water table that is easterly • Diesel range petroleum hydrocarbons were detected in four of the site's eleven monitoring wells sampled this quarter M • Well MW-5 contained 30,000 µg/1 diesel and remains the most severely impacted well This well also contained 1000 ug/1 TPH-G, 7 ug/l ethylbenzene and 14 ug/l xylenes • Well MW-1 contained 150 q.g/1 diesel This well intermittently contains diesel • Well MW-4 contained 880 [tg/l diesel This well consistently contains diesel • Well MW-7 contained 1400 ug/l TPH-D This well consistently contains diesel ' • Deep wells MW-104, MW-105 and MW-106 did not contain contaminant concentrations above the laboratory reporting limits • Oxidation-Reduction Potential (ORP) measurements show moderately positive and ' negative ORP values in the monitoring wells (four wells did not recover adequately from purging to record valid data) Wells' MW-1, MW-4 and MW-105 negative values indicate that the wells are within the halo of reaction depleted water caused by ' biodegradation The ORP data are included in Table 5 of Appendix A • The vertical extent of the plume is intermittently defined by MW-104, 105, & 106 The groundwater near these wells appears not to be contaminated Well MW-5 An examination of the contaminant distribution and groundwater flow direction data reveals ' groundwater elevation is slowly declining since 2000 and that diesel concentrations were fairly stable But three spikes are present in the last two years that suggest an increasing trend in this well (see Figure 6- MW-5 TPH-D vs Groundwater Elevation) A consistent factor ' previously noted in the investigation was the fluctuation in diesel concentrations in well MW-5 The concentrations had demonstrated a slight increasing trend until June 2002 when concentrations began to fluctuate for about a year Subsequently, the concentrations were