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I I Quarterly Monitoring Report - First and Second Quarters 2003 ' C" of Stockton - FIRE STATION#2 110 West Sonora Street, Stockton, California ' 1.0. INTRODUCTION AND SCOPE OF WORK ' At the request of the City of Stockton,Advanced GeoEnvironmental, Inc (AGE) has prepared this report for corrective action activities conducted at 110 West Sonora Street, Stockton,California(the site) The location of the site and its surroundings are illustrated in Figure 1 Structures and well ' locations associated with the site are depicted in Figure 2 The soil vapor extraction and air-sparging system was re-mobilized on 15 January 2003 and operated ' since that date This report documents 1) soil vapor sampling events on 16 January, 06 February, 24 April and 13 May 2003, 2) installation and development of monitoring well MW-6 on 03 March and 24 April 2003, respectively, and 3) a ground water monitoring event on 23 and 24 April 2003, ' and presents the results of laboratory analysis of soil-vapor and ground water samples ' 2.0 PROCEDURES '• Field procedures for ground water sampling are described below All field work was performed in accordance with Central Valley Regional Water Quality Control Board(CVRWQCB)guidelines for the investigation of underground storage tank (UST) sites 1 21 SOIL-VAPOR EXTRACTION MONITORING A soil vapor extraction/in-situ air sparging system (IAS/SVE) has been in operation since mid January 2003 The system was monitored monthly, except March and inspected or maintained ' weekly during operation During each monitoring event,measurement o f the SVE flow rate,vacuum (potential),concentrations of hydrocarbons in the extracted soil-vapor and collection of a set of soil- vapor samples were conducted by AGE personnel Due to low hydrocarbon concentrations within ' the SVE stream, carbon canisters were not utilized The flow rate of extracted soil-vapor was measured using a direct measure flow meter after the SVE ' blower, a magneheiic vacuum gauge was used to measure the vacuum potential at the 2-inch influence line The organic vapor concentrations in the extracted soil-vapor stream was measured before entering the blower (vapor stream) using an organic vapor meter (OVM) equipped with a ' photo-ionization detector PID(Thermo Environmental 580B, 10 OeV,calibrated to isobutylene 100 ppb) Field measurements, recorded at regular intervals between January and May 2003, are ' summarized in Table 1 Soil-vapor samples were collected to document trends in concentrations of hydrocarbon vapor in the ' soil-vapor extracted by the SVE network Soil-vapor samples from the discharged stream were Advanced GeoBnvironmental,Inc