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f ATC Associates Inc M%TCI 1117 Lone Palm Avenue, Suite B Modesto, California 95351 209-579-2221 ASS 0 c i ATE s INC fax 209-579-2225 GROUNDWATER ELEVATION Water level measurements were collected from wells MW 1 through MW7 on January 13, 2005 Depth to water ranged from 57 37 feet below ground surface (bsg) to 58 10 feet bgs Water elevations ranged from a high of—34 05 to a low of—34 17 representing an average increase in water table elevation of 0 22 feet since October 2004 The water level data were used to develop a groundwater elevation contour map (Figure 3} Review of the groundwater elevation contour map indicates that the hydraulic gradient beneath the site on January 13, 2005, was approximately 0 001 foot per foot or approximately 5 feet per mile and the gradient direction was generally to the west-southwest (Figure 3} A summary of groundwater monitoring data is presented in Table 1 ANALYTICAL RESULTS Chemicals of Concern (CDCs) were only detected in the groundwater samples collected from MW 1 and MM2 TPHg was detected in the groundwater sample collected from MW2 at a concentration of 120 µg/L Benzene was detected in the groundwater sample collected from MW2 at a concentration of 2 0 ug/l, MTBE was detected in the groundwater samples collected � ) from MW 1 and MW2 at concentrations of 3 4 pg/L and 10 pg/L, respectively Groundwater samples collected from MW3, MW4, MW5, MW6, and MW7 did not contain concentrations of TPHg, TPHd, BTEX constituents, or fuel oxygenates at or above the laboratory reporting limits Groundwater samples collected from wells MW 1 through MW7 did not contain concentrations of TPHd and have not since March 27, 2001 Analytical results for groundwater samples are contained in Table 2 Laboratory data sheets and chain-of-custody documentation are contained in Attachment 2 ' GEOTRACKER DATA UPLOAD The site facility global ID number is T0607700242 The depth to water data was submitted electronically to the State Water Resources Control Board (SWRCB) Geotracker database (confirmation number 8056584000) and the laboratory data was also submitted electronically to the SWRCB Geotracker database (confirmation number 5159014523) Documentation of the data submittal is contained in Attachment 3 e CONCLUSIONS The concentration of petroleum hydrocarbons in groundwater samples collected from MW 1 and MW2 are within the historical range as established by previous sampling events and have generally decreased over time Concentrations of petroleum hydrocarbons remained below laboratory reporting limits in samples collected from MW3, MW4, MW5, MW6, and MW7 TPHd has not been detected in samples collected from wells MW 1 through MW4 since at least S 1625771QR-2005 doc 3