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11 May 1992 <br /> (GeoAudit CV43F3-1. 16) <br /> Page 4 of 5 <br /> retention time, the diesel concentration in the processed soil was <br /> consistently below 50 mg/kg; most of the soil was less than 10 <br /> mg/kg (ND for the required reporting limit) . <br /> Therefore, Falcon Energy considered the treated soil to be <br /> homogeneous. Under this assumption, the 485 cubic yards of soil <br /> that was processed a second time (at a higher temperature and <br /> longer retention time) was considered to be near or below <br /> detectable levels. Sampling was continued only intermittently after <br /> the SRU was correctly adjusted. <br /> Of the 40 samples collected from the treated soil, 28 contained <br /> less than 50 mg/kg TPH as diesel. The 12 samples that showed TPH asp��jp!L <br /> diesel in levels greater than 50 mg/kg were collected during the f" pV" <br /> adjustment stage. Since this soil was treated a second time it was 0 <br /> Falcon Energy's opinion that the re-sampling of this soil was <br /> unnecessary and would add cost to the remediation process. <br /> Prior to treatment, the soil showed levels of TPH as diesel between <br /> 170 mg/kg and 570 mg/kg (samples 2-6-1V, 2-6-2V and 2-6-R) . Samples <br /> collected from the original excavation indicate levels of TPH as <br /> diesel as high as 10, 000 mg/kg. Based on these maximum levels of <br /> TPH as diesel, the SRU operated by Falcon Energy was successful in <br /> reducing contamination levels in the soil by greater than 90 <br /> percent. <br /> CONCLUSIONS <br /> Approximately 2 ,400 cubic yards of soil were successfully treated <br /> by using Falcon Energy's portable SRU. Using guidelines in the LUFT <br /> Field Manual for the Leaching Potential Analysis for TPH (page 29, <br /> State Water Resources Control Board) , the maximum allowable TPH <br /> levels that can be left in place without threatening groundwater is <br /> 100 mg/kg (100 ppm) . A prepared worksheet is included in Appendix <br /> E. <br /> Based upon our findings, we feel that the excavation should be <br /> backf illed with the treated soil and site closure be requested from <br /> the RWQCB and SJEHD. <br /> LIMITATIONS <br /> Our professional services were performed using that degree of care <br /> and skill ordinarily exercised by environmental consultants <br /> practicing in this or similar localities. The findings were mainly <br /> based on analytical results provided by ana independent laboratory. <br /> Evaluations of the geologic conditions at the site for the purpose <br />