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Ott � groundwater gradient and direction of groundwater flow (southeast) were also generally consistent with previous data Groundwater elevation increased approximately 4 63 feet from the previous sampling event (November 1997) The oxygenates, tertiary butanol, MTBE, di-isopropyl ether, ethyl tertiary butyl ether, and tertiary amyl methyl ether were analyzed for wells MW-1, MW-3, MW-4, MW-6, MW-7, and MW-10 using USEPA Method 8260 No oxygenates were detected in the samples from wells MW-1, MW-3, MW-4, MW-6, MW-7, and MW-10 (see Table 2) Due to non-detect analytical results for oxygenates using USEPA 8260 for all wells, Pinnacle, on behalf of ARCO, requests no further analysis for oxgenates with the exception of MTBE using only USEPA Method 8020 Pinnacle shut down the SVE system on November 24, 1997, due to low sod vapor concentrations and is currently pulsing the system on a periodic basis The SVE system remained shut down during the first quarter 1998 A cumulative amount of 25,184 pounds of TPHG have been removed since commencing SVE activities (see Table 5) Figures 4 and 5 present the rate of TPHG concentration over time and extraction rate and cumulative mass of TPHG removed over time, respectively The air sparge system was shut down on November 24, 1997, along with the SVE system to evaluate feasible remediation alternatives Based on data and remediation techniques evaluation, the air sparge system was restarted on January 20, 1998, and operated at a low flow rate for bubbling and oxygen addition to the groundwater The addition of oxygen into the groundwater will help to promote biodegradation of petroleum hydrocarbons in impacted groundwater at the site As a result of air bubbling in air sparge wells AS-1, AS-2, and AS-3, since January 1998, dissolved oxygen levels in monitoring wells MS-1(s), MS-2(s), MS-3(s), and MW-2 have increased significantly as shown in Table 6 Pinnacle will continue to monitor the effects of SVE system pulsing and air bubbling during the second quarter 1998 ATTACHMENTS Table 1 Groundwater Monitoring Data • Table 2 Groundwater Analytical Results for Oxygenates • Table 3 Operational Uptime Information of the Sod Vapor Extraction System + Table 4 Flow Rates and Results of Air Sample Analyses • Table 5 Extraction and Emission Rates • Table 6 Air Sparge/Air Bubbling Flow Rates and Dissolved Oxygen Levels • Figure 1 Site Location Map • Figure 2 Generalized Site Plan • Figure 3 Groundwater Contours(March 4, 1998) • Figure 4 TPHG Concentration Vs Time • Figure 5 Extraction Rate and Cumulative Mass of TPHG Removed Vs Time • Appendix A Sampling and Analysis Procedures • Appendix B Chain-of-Custody Records and Laboratory Analysis Records • Appendix C Operation and Maintenance and Groundwater Monitoring Field Data Sheets cc Elizabeth Thayer, California Regional Water Quality Control Board Bruce Tuter, San Joaquin Valley Unified Air Pollution Control District SAC�N\PJM80"8051140 9AS-981pzusmer 1