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19 July 1996 AGE-NC-95-0109 Page 2 of 6 in air to the subsurface. The blower is commonly turned off for procedures associated with the business located at the site. Oxygen, carbon dioxide and organic vapors were measured once each month using field instrumentation. The percentage of oxygen and carbon dioxide in soil gas recovered from the vadose zone was measured using a GasTech OX02 analyzer. Organic vapor concentrations were measured in parts per million using a photo-ionization detector (PID). Air samples were collected from each monitoring point after the well had been purged for approximately three to five minutes, using an electric air pump. Air was then drawn through the field instrument and the measurement was recorded after stabilization. The results of the vapor monitoring are included in Table 3. ' On 17 June 1996 air samples were collected from MW-3, MW-4 and MW-14. Samples were I collected in Tedlar bags, after field measurements, using an electric air pump. The samples were transported under chain-of-custody to FGL Laboratories in Stockton and from there to their associate office in Santa Paula for analysis for methane, nitrogen, oxygen, carbon dioxide and carbon monoxide. 2.3. MONITORING OF GROUND WATER FOR PETROLEUM HYDROCARBONS On a more frequent monitoring schedule requirement, wells MW-14 and EW-1 were sampled, but not purged,on 25 April and 23 May 1996, On 19 June 1996, regular quarterly monitoring procedures were performed at the site, which also included MW-14 and EW-1. As during past monitoring events, wells MW-I through MW-5 did not contain enough water for sampling. 2.3.1. MONITORING WELL PURGE PROCEDURES On 17 June 1996, a Solinst water level meter was used to measure the depth to ground water in each monitoring well (Table 5). On 19 June 1996, purging and sampling procedures were conducted. Monitoring well EW-1 was purged using a 2-inch submersible pump. Monitoring wells MW-6 through MW-14 were purged using clean PVC bailers. A minimum of three well volumes of water were removed from each well. Temperature, pH and conductivity of the purge water were measured at approximately 1-gallon intervals (10-gallon intervals for EW-1) using an ICM water analyzer. Dissolved oxygen was measured in each well during purging. Monitoring well stabilization data and field sheets are included in Appendix A. The purge water was placed in DOT-approved drums and stored on-site.