SITE INFORMATION AND CORRESPONDENCE_PRE 2019

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Stantec April 30, 2010 Page 1 of 2 Reference: First Quarter 2010 Site Status, Groundwater Monitoring and Remedial Summary Report- Stockton Terminals Technical Committee Facilities Appendix K-Ozone Injection Well Monitoring Program and Revised Contingency Plan OZONE INJECTION MONITORING PROGRAM Some of the following information is included in the Revised Contingency Plan that follows this description of the ozone injection monitoring program. In accordance with Stantec's ozone- injection monitoring program, petroleum hydrocarbon trends are evaluated on a quarterly basis in select "A" zone and "B" zone compliance wells, listed in the table below. Groundwater Remedial Observation Wells Mid-Point Trigger Wells Zone Observation Wells A PS/MW-18, PS/WC-1 S, AR/MW-21A PS/MW-20A OW-2A, OW-4A B AR/MW-18B, AR/MW-21 B, PS/WC-1 M PS/MW-20B OW-21B, OW-41B * PS/MW-20 has been replaced with PS/MW-20A and PS/MW-20B as described below. Wells located immediately downgradient of the East System are designated as remedial observation wells. The remedial observation wells are used for concentration trend analysis to determine the effectiveness of the ozone system downgradient of the ozone array in the "A" and "B" zones. Wells located immediately downgradient of the remedial observation wells are designated as mid-point observation wells. In September 2008 well PS/MW-20 was replaced by PS/MW-20A as a mid-point observation well to determine the effectiveness of the "A" zone ozone remediation system downgradient between the remedial observation wells and the trigger wells. In September 2008, well PS/MW-20B was installed as a mid-point observation well for the "B" zone. The mid-point observation wells will be monitored and sampled quarterly to monitor concentrations for an early warning that the downgradient trigger wells may be impacted in the future. Wells located downgradient of the mid-point observation wells, at the downgradient boundary of the well network, are designated as trigger wells. The analytical results from the remedial observation wells and trigger wells are compared with the RWQCB-approved compliance limits shown in the tables in the following section, to evaluate the effectiveness of the ozone system downgradient of the ozone array in the "A" and "B" zones. The compliance wells are sampled quarterly to monitor concentrations following the anticipated initial spike in concentrations from operation of the ozone remediation system. An initial spike of concentrations was anticipated to last up to one year, and concentrations of petroleum hydrocarbons and MTBE within observation wells were anticipated to increase by one to two orders of magnitude over historical concentrations. The initial spike period was expected to extend through fourth quarter 2005. In accordance with the contingency plan originally presented in SECOR's June 27, 2003 Response to CRWQCB Letter Dated May 9, 2003 And Addendum to Corrective Action Plan