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i - I . 3.0 FIELD SERVICES AND LABORATORY ANALYSIS Geocon performed groundwater monitoring and sampling on July 2, 2004, and October 13, 2004,to determine water table elevation and the distribution of dissolved hydrocarbons in groundwater monitoring wells. Three offsite domestic wells were sampled to determine if potable water supplied to .adjacent residents are impacted with petroleum hydrocarbons. Groundwater elevation data and contaminant concentrations in groundwater are reported in Table 1. Operation and maintenance (O&M) services were performed for the SVE and ozone sparge systems for the reporting period of April 8, 2004 to December 2, 2004. 3.1 Water Table Elevations And Gradient On July 2, 2004 (Third Quarter 2004) and October 13, 2004 (Fourth Quarter 2004), Geocon personnel measured the depth to water in each of the eleven Site-related groundwater monitoring wells. A water level indicator was used to gauge the wells to the nearest 0.01 foot. The elevation data indicates that groundwater gradient for each quarter was generally toward the south-southeast at 0.002 ft/ft as depicted in the Elevation Contour Map, Figures 4a and 4b. Groundwater monitoring data are presented in Table 1. rw-1 3.2 Quarterly Groundwater Sampling . b_j Groundwater monitoring wells were purged using a submersible pump or a disposable bailer until pH, temperature, and conductivity readings had stabilized, Temperature, conductivity, and pH Lreadings were recorded for each well for each casing volume removed using a field instrument. Water purged from the wells is stored in a 500-gallon above ground storage tank within the treatment system compound. Adequate recovery was observed in the purged groundwater monitoring wells prior to sampling. A disposable bailer was used to collect the.groundwater samples. All samples were decanted from the bailer into the appropriate containers, preserved with ice; and transported under chain-of-custody protocol to Advanced Technology Laboratory (ATL) in Signal Hill, California -for the organic chemical analysis. The water samples were analyzed for TPHg following EPA Method.8015 and for BTEX and FOCs following EPA Method 8260. Domestic wells DW-2R, DW-3, and DW-4 were purged by opening a spigot at the well head works, draining the well's holding tank, and allowing the tank to re-fill with fresh water pumped from the aquifer.Once the tank had been recharged, water samples.were collected directly from a spigot at the holding tank. Domestic wells DW-2R, DW-3, and DW-4 are on a quarterly sampling schedule. .L: Project No.S8643-06-01 -5- December 30,2004