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ATC Associates Inc (: V�JRTC 1117 Lone Palm Avenue, Suite B " Modesto, California 95351 209-579-2221 fax 209-579-2225 . A S S O C t A T E S I N C SAMPLING ACTIVITIES On March 8, 2006, ATC personnel collected groundwater samples from MW 1, and MW4 through MW8 Trp locations of the wells are shown or, Figure 2 Prior to collection of groundwater samples the depth to water, pH, electrical conductivity, and temperature were measured Turbidity was visually observed to groundwater purged from the monitoring wells and recorded Approximately three well casing volumes were purged from each monitoring well prior to sampling The wells were allowed to recover and samples were collected from each well using disposable polyethylene bailers The groundwater samples collected from each well were submitted to State-certified Argon Laboratories Inc Environmental Laboratory Accreditation Program (FLAP) Certification No 2359, in Ceres, California for chemical analyses of total petroleum hydrocarbons as gasoline (TPHg) utilizing Environmental Protection Agency (EPA) Method 8015M, benzene, toluene, ethylbenzene, and xylenes (BTEX) utilizing EPA Method 8021B, and methyl tertiary butyl ether (MTBE), ethyl tertiary butyl ether (ETBE) di-isopropyl ether (DIPE), tertiary amyl ether (TAME), tertiary butyl ether (TBA), 1,2- dichloroethane (1,2-DCA), and 1,2-dzbromoethane (EDB) utilizing EPA Method 8260B Groundwater well purge and sample logs are contained in Attachment 1 GROUNDWATER FLOW DIRECTION Water levels measured in MW 1 through MW8 on March 8, 2006, ranged from 5 07 to 7 18 feet below • the tops of the well casing elevations, representing an average increase in the shallow water table elevation of approximately 0 20 feet since December 2005 The water level data were used to develop the groundwater elevation contour map (Figure 3) Shallow groundwater flow in the uppermost aquifer beneath the site is towards the northeast The average hydraulic gradient on March 8, 2006, was calculated to be 0 0017 feet per foot,or approximately 8 97 feet per mile A summary of groundwater monitoring data is presented to Table 1 ANALYTICAL RESULTS The primary analyte of concern during the first quarter 2006 was MTBE, which was present in each _ groundwater sample collected - TPHg and ethylbenzene were detected in the groundwater sample collected from MW4 at concentrations of 150 micrograms per liter (ug/L) and 0 6 ug/L, respectively TAME was detected in MWS at a concentration of 4 1 ug/L" MTBE was detected in the groundwater samples collected from MW 1, MW4, MW5, MW6, MW7 and MW8 at concentrations of 7 0 ug/L, 32 ug/L,, 36 ug/L, 71 ug/L, 1 2 ug/L, and 410 ug/L, respectively i Analytical results of groundwater samples are summarized to Table 2 Laboratory data sheets and chain- of-custody documentation are contained In Attachment 2 An isoconcentration map depicting the MTBE concentrations in groundwater samples collected during the first quarter 2006 is shown on Figure 4 GEOTRACKER DATA UPLOAD . The facility has been assigned a Geotracker global identification number T0607700120 The depth to water and laboratory data associated with the first quarter 2006 sampling event were submitted electronically to the State Water Resources Control Board (SWRCB) Geotracker database (confirmation s\enviromental125847100371reportsll stQTR-2006 doc 3