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z r GeologkolTeclucicslKc. Page 2 COE-Former Arco Site Monitoring Report-VETS Project No.: 750.2 January 21,2003 .� 2.0 VAPOR EXTRACTION SYSTEM 2.1 System Installation Two vapor extraction wells were installed through the former tank pit (VEW-3 and VEW-4) and two were installed east of the site (VEW-1 and VEW-2). VEW-1 and VEW-3 were installed to a depth of 55-feet bgs and VEW-2 and VEW-4 were installed to a depth of 27-feet bgs. A vapor extraction pilot test was perforined at the site on June 12, 2000 and it showed that vapor extraction was a viable remedial method for the site. A report of this work was submitted on August 8, 2000. 1� The Authority to Construct was issued on October 18, 2001 for a vapor extraction remedial system. Geological Technics Inc. completed installation of the vapor extraction system and Internal Combustion Engine by the end of January 2002. The San Joaquin Valley Unified Air Pollution Control District (SJVUAPCD) conducted a startup sampling inspection on February 5, 2002. r 2.2 VETS Operation Since the VETS was started on February 5, 2002 it has been operated as follows: 0 The IC ran until February 27, 2002 when it was shutdown and removed from the site because it was not properly controlling emissions. • The IC was completely rebuilt and returned to the site on April 22, 2002 and restarted. --..� • The IC operated until late May when it was again removed from the site due to mechanical failure. • The IC was rebuilt again and returned to the site on June 14. The IC ran continuously since r June 14 without problems. • The IC was shut down on December 10 to perform a spike test. The IC was restarted on January 1, 2003. Samples were colleted before shutdown and again after startup. r The VETS was operated from startup to February 27, 2002 pulling from VEW-3, the deeper vapor extraction well. For the first month of operation the VETS was operated with a fairly significant amount of dilution air being added at the wellhead. This had to be done because the low levels of oxygen in the subsurface caused the IC to burn improperly. On April 22, 2002 when the IC was brought back to the site, the system was switched over to VEW-4 because of the relatively low concentrations from VEW-3. The system has been operated pulling from VEW-4 since April 22, 2002. Extracted concentrations from VEW-4 were initially relatively high but started decreasing in September of 2002 and have decreased to approximately 6 lbs of gasoline a day. Since the VETS startup in February of 2002, it has been operated for a cumulative runtime of 226 days and has removed approximately 675 gallons of gasoline. A spike test was performed at the site starting on December 10, 2002. A sample was colleted on December 10 with the system pulling from VEW-4 and then the VETS was shutdown. The system was left off for a period of three weeks, allowing the soil vapors to come into equilibrium with contamination that is still sorbed to the soil. At the end of the three-week -•� period, the VETS was restarted. Samples were collected one hour after startup and again the following day, approximately 20 hours after startup. The test was performed to see if