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i Current Phase of Project: Monitoring/ Interim Remediation Frequency of Groundwater Sampling: All Monitoring Wells= Quarterly Frequency of Groundwater Monitoring: Quarterly Sampling Date: May 19, 2003 Is Free Product(FP) Present on Site: No FP Recovered This Quarter: NIA Cumulative FP Recovered to Date: NIA Approximate Depth to Groundwater: 41.50 to 42.20 feet below oround surface(b9s) Groundwater Flow Direction: Radial flow into MW-5 Groundwater Gradient: 0.003 ft/ft DISCUSSION: Groundwater elevations have increased approximately 0.40 to 1.10 feet since the previous sampling event (February 26, 2003). The groundwater flow direction on May 19, 2003, was calculated to be radial toward well MW-5 at a gradient of approximately 0.003 ft/ft. Groundwater flow directions have predominantly been toward the northeast and east during previous monitoring events. Depth-to-water measurements were corrected to mean sea level (MSL) and used to construct a groundwater elevation cnntnur man (Fioure 31 In addition to quarterly groundwater sampling, additional groundwater samples were collected during the second auarter 2003 sampling event to evaluate and optimize the performance of ozone iniection system. Tabulated results of groundwater elevation and analytical summary of groundwater samples collected under ozone injection monitoring plan and quarterly monitoring program are presented in Tables 1 and 2. A discussion on the results of petroleum hydrocarbon concentrations is presented later in remediation system status section of this report. REMEDIATION SYSTEM STATUS System Descriptiora The C-SpargeTM system, manufactured by KVe, consists of a control panel (ozone generator, air compressor, and tubing manifold), and strategically located injection points (IW-1 through IW-5, see Figure 2) used to inject low concentrations of ozone into groundwater. In addition, the control panel also has a programmable timer that limits the amount of ozone injected into each injection point. The system injects a timed pulse of ozone at low flows and low pressures (10-30 psi) to each of the five injection points in a sequence. The ozone dissolved in groundwater is anticipated to oxidize petroleum hydrocarbons into carbon dioxide and water, and any un-reacted ozone will degrade to dissolved oxygen, which is likely to enhance natural biodegradation of residual petroleum hydrocarbons. System Operation Details The C-SpargeTM system was started on December 26, 2002. The C-SpargeTM control panel was programmed and scheduled to inject ozone cyclically in each injection point for 14 minutes. Based on this programming, each injection point will have ozone injection in 18 cycles for 4.2 hours every day. PA3p-.Arco for URS640 Quanerly�2003kAreo_54G9_2Q03.doe 3TKA j`Lrj