ARCHIVED REPORTS_XR0005278 - Laserfiche WebLink

Home Browse Search

ISA INA Working To Restore Nature Soil sample SP-SB2-5' exhibited the highest level of petroleum analytes during this investigation with a TPHg concentration of 8,300 ppm However TPHg was not detected in the sample collected at 11 feet below grade (SP-SB2-11') These data suggests the relatively low porosity of soils has impeded the vertical migration hydrocarbons at the site and confined impact to a limited depth In samples collected from soil boring S133 only trace levels of toluene (0 0080 ppm)and xylenes (0 0070 ppm) were detected at 5 5 and 8 5 feet below grade, respectively Analytical results for soils are summarized in Table 1 Laboratory data sheets and chain-of- custody documentation are presented in Attachment 2 CONCLUSIONS/RECOMMENDATIONS Soils Field observations and analytical data indicate that vertical migration of contamination did not extend beyond approximately 11 feet in depth and that lateral migration was not extensive Previously collected analytical data indicated that the main area of concern was soil in the . vicinity of the former gasoline product line leak Analytical results of soil boring samples indicate a zone of impacted soils remain between approximately 3 and 8 feet below grade directly beneath the sidewalk and building of the police facility Assuming that this zone beneath the facility is uniformly 5 feet thick, a maximum of approximately 57 cubic yards of impacted soils remain beneath the side walk and police facility Of this total, 19 cubic yards contain petroleum hydrocarbons between 8,300 and 1,000 ppm, 10 cubic yards contain petroleum hydrocarbons between 100 and 1,000 ppm, 13 cubic yards contain petroleum hydrocarbons between 10 and 100 ppm, and 15 cubic yards of petroleum hydrocarbons less than 10 ppm The remaining contaminated soil beneath the high voltage concrete encased electrical lines (which transversed the July 1992 excavation) is estimated to be limited to a depth of 1 5 feet below the lines, with a width of approximately four feet Based upon the low concentrations of hydrocarbons in soil samples collected from beneath the electrical lines, less than one cubic yard of impacted soil remains beneath the lines, and the volume of gasoline is negligible Figure 3 shows the maximum estimated extent of contaminated soil that remains beneath the site The volume of gasoline in the soil was calculated by determining the average value of TPHg concentrations for each interval shown in Figure 3 and assuming the average TPHg - -- concentrations are uniform throughout depth interval Approximately 225 pounds (34 gallons) of gasoline is estimated to be the maximum amount remaining in the soil OW01481ReportslLR-20294 FWL 4