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CLEA'R* WATER C. R o L P 11 C • Environmental Srrvires evaluated upon completion of four quarterly groundwater monitoring events following remediation system shut-down The results presented herein represent the fourth of those monitoring events Groundwater Monitoring Methods On July 24, 2000, all on-site wells (MW-1 through MW-7, and SW-1 and SW-2) were monitored Additionally, a water sample �,,aas collected from the on-site domestic well (DW) An electronic water level indicator was used to gauge depth to water accurate to within ±0 01-feet All wells were checked for the presence of SPH prior to purging No rneasurable thicknesses of SPH were observed it any of the wells The wells were purged until sampling parameters (e g temperature, pH and conductivity) stabilized, which occurred by approximately three wet casing volumes Groundwater monitoring and well purging information was recorded on Gauge Data/Purge Calculations and Purge Data sheets (attached) Following recovery of water levels to at least 80% of their static levels, groundwater samples were collected from the monitoring wells using dedicated polyethylene bailers Samples were transferred to laboratory supplied containers, labeled, documented on a chain-of-custody form, and placed on ice in a cooler for transport to the project laboratory • Purging devices were decontaminated between wells in an Alconox(g) wash followed by double rinse in clean tap water to prevent cross-contamination Purge water ana rinseate was stored on-site in labeled 55-gallons drums pending future removal and disposal All groundwater sainples were analyzed by Entech, a DHS-certified laboratory located in Sunnyvale, California Groundwater samples were analyzed for concentrations of TPHg and BTEX bF EPA Methods 8015 (modified)/8020 and for Five Fuel Oxygenates (MTBE, TBA, ETBE, DIPE, TAME) and Lead Scavengers (1,2-DCA, EDB)by EPA Method 8260B Groundwater Monitoring Results On July 24, 2000, static groundwater in the wells was present beneath the lite at depths ranging from approximately 14 5 to 16 5 feet bgs Gauging data, combined with well elevation data, were used to calculate groundwater elevations in these wells, and to generate a groundwater elevation contour map The groundwater flow direction was calculated to be toward the southwest at a gradient of 0 002 ft/ft (Figure 3) This groundwater flow direction is similar to that in the previous quarters event, but is not the most common direction observed The flow direction has been observed to change direction from the northeast to the southwest depending on the time of year This fluctuation of flow direction is most likely due to local agricultural irrigation activities in the area of the site Dissolved-phase contaminant concentrations were only present at low levels this monitoring event Low levels of contaminants were observed in both MW-1 and MW-2 Maximum contaminant levels found in these two wells were TPHg 220 lig/L (..MW-1), benzene 0 55 dig/L (MW-1), and MTBE 150 Pg/L ZB107C GWMR 3Q00 3 Aug.agt 3 2u00