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Bank of Stockton - Cutter Lumber Site Page 4 Quarterly Groundwater Monitoring Report ' Project No 102 2 April 23,2003 ' the analytical laboratory) All samples were checked for head space bubbles, labeled, inserted into foam holders and placed in an ice chest cooled to 4°C for transport to the laboratory ' Gasoline contaminated purge & rinseate water generated during the activities described above was stored in poly drums located on the site American Valley ' Environmental will remove this material prior to the next scheduled depth to water measuring event 2.2 Groundwater Sample Analyses Groundwater samples were analyzed as follows ' • Total Petroleum Hydrocarbons as Gasoline (TPH-G) by EPA method 503018015(m) • Benzene Toluene, Ethylbenzene and total Xylene (BTEX) and MTBE by EPA ' method 602 The detection limits are included in the summary analytical data table (Table 2) ' Detectable levels of gasoline range petroleum hydrocarbons and/or BTEX compounds were found in 4 of the 8 water samples that were collected In addition, a trace of MTBE (3 8 ppb) was reported in the sample from MW-1 Insofar as MTBE has not been detected previously at the site, and given that several other hydrocarbon compounds can yield false positive results in the method 602 screening test, it is believed unlikely that there is actually any ' MTBE in the sample ' 2.3 Field Data The field data for this groundwater monitoring event are summarized in Appendix B and Table 1 The level of groundwater has risen dust over one foot ' since the groundwater monitoring event completed on September 12 of 2002 The bearing of the groundwater flow has remained generally consistent Groundwater gradient calculations for MW-6, 10 & 11 yield the following gradients and directions Table: Groundwater Gradient, 2001, 2002 & 2003 ' Date Gradient, Direction/Slope March 12, 2001 N490E, 0 0016 ft/ft June 7, 2001 N39-E, 0 0035 ft/ft September 18, 2001 N48-E, 0 0042 ft/ft ' December 5, 2001 N68-E, 0 0015 ft/ft March 20, 2002 N66-E, 0 0028 ft/ft June 17, 2002 N49-E, 0 0033 ft/ft September 12, 2002 N62-E, 0 0041 ft/ft December 20, 2002 N42-E, 0 0030 ft/ft March 24, 2003 N48-E, 0 0040 ft/ft ' 2937 Veneman Ave ,#B 240 Geo-Phase Environmental Inc Phone (209) 569-0293 Modesto, CA 95356 Fax (209) 569-0293 1