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r go30 FIELD SERVICES AND LABORATORY ANALYSIS Geocon performed groundwater monitoring and sampling on April 6, 2005, 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 rimpacted with petroleum hydrocarbons Groundwater elevation data and contaminant concentrations in groundwater are reported in Table 1 rOperation and maintenance (O&M) services were performed for the SVE and ozone sparge systems for the reporting period of February 2, 2005 to April 25, 2005 ' 31 Water Table Elevation and Gradient ' On April 6, 2005, 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 the groundwater gradient for each quarter was generally towards the south at 0 002 ft/ft as depicted in the Elevation Contour Map, Figure 4 Groundwater monitoring data are presented in Table 1 ' 32 Quarterly Groundwater Sampling 9 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 r readings were recorded for each well for each casing volume removed Water purged from the wells is stored temporarily in a 500-gallon above ground storage tank within the treatment system ' compound This tank is periodically purged and the contents transported off site for proper disposal 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 r 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 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 1 • 1 Project No 58643-06-01 -5- May 5 2005 r