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REMEDIATION TESTING AND DESIGN July 1, 1993 Vacuum Extraction Feasibility Testing A limited vapor extraction feasibility test was conducted utilizing vapor probe P-2 as the extraction point . Prior to conducting the test, an air discharge notification letter was sent to the San Joaquin Valley Air Pollution Control District . A copy of the regulatory correspondence is contained in Appendix A. Probe P-2 was extracted from for a period of 20-minutes . Vacuum extraction was conducted using the RTD vacuum extraction testing unit (VETU) consisting of : a Sutorbilt Model 3ML positive displacement blower capable of displacing 100 standard cubic feet per minute (scfm) at a vacuum of 15 inches of mercury ( "Hg) directly driven by a Kohler 12-horsepower gasoline engine; a 55-gallon water knock-out device and; two drums in series, each containing 175-pounds of vapor phase activated carbon. A clear, flexible PVC vacuum hose was connected from inlet port of the VETU to an airtight fitting at P-2 . Standard vacuum extraction was conducted for a period of 20-minutes . RESULTS Soil Gas Screening Results of the SGS are presented in Table 1 . FID field screening at all probe locations showed no detectable hydrocarbons . Generally, the probes exhibited moderate to good sample flow characteristics, with an average sample flow rate through the sample pump of 13 standard cubic feet per hour (scfh) , with an average vacuum of 9 inches of mercury ( "Hg) . Probe installation difficulties were encountered beyond approximately 12-feet . Beyond that depth, the probes went down very slowly. Probes P-3-deep and P-10 could not be driven beyond the 15-feet depth interval due to inpenetrable soil conditions encountered at these locations . All probes were very difficult to remove . Probes P-10 and P-12 could not be removed. These two probes were pounded 1-inch below grade and filled with a neat portland cement slurry to grade . Vacuum Extraction Feasibility Testing Table 2 contains VEFT field data for extraction screening from probe P-2 located at the east end of the UST area. The results of this test exhibited that there was no flow from the probe and that a maximum vacuum of 22 . 0 "Hg was recorded. Probe P-2 was originally thought to be located in the UST backfill material , but based on VEFT results (not characteristic for higher permeability backfill material) was probably located in the less permeable native soils . Based on the poor flow rate and high vacuum, influence at the surrounding probes was not recorded during the VEFT. 2 -