WORK PLANS - Laserfiche WebLink

Home Browse Search

FIELD SCREENING OF SOILS EXCAVATED AND EXCAVATIONS Upon removal of the product dispensing piping and the three underground storage tanks (UST's) the native soils will be field screened using a photo-ionizing detector (PID) with a 10.6 ev bulb. i This detector is sensitive to volatile organic compounds that have an electron potential of or greater than 10.6 e.v. Gasoline vapors are readily detected with this detector and it is the preferred field- screening instrument for screen soils at suspected gasoline-contaminated sites. The excavator will obtain soil from the base of the excavations and from the sidewalls in areas of suspected contamination (i.e. soil staining, odor etc,). There will be no entry into the excavation by personnel. The geologist will then screen the entire bucket of the excavator with the PID, placing the highest responses into a ziplock bag and sealing the bag. The bag will be allowed to warm in the sun, or if foggy near the exhaust of an engine. Heating the soil and releasing vapors into the headsP ace of the sealed baggy. The geologist will then peal the seal of the baggy just enough to introduce the sample port of the PID into the bag,to obtain a reading of the vapors inside the bag. If the readings are in excess of 50 ppmv (parts per,million vapor) a decision will be made to excavate thatarea. Some high readings are the result of water vapor entering the detector and can result in false positives. E EXCAVATED SOIL HANDLING All excavated soils will be placed on and covered with plastic liner. Samples of the excavated soil will be obtained after completion of the excavating. Once laboratory results have been received (approximately five working days) the clean soils will be used as compacted backfill in the j excavated areasand any contaminated soil will be profiled into an accepted landfill. It is anticipated that the soil will be clean and non-hazardous and non-hazardous manifest transported for disposal to Forward Landfill, Stockton, California. The frequency of the samples will adhere to Forward Landfill and San Joaquin County Health requirements. The removed pea gravel will not be used as backfill and will be disposed of and soils excavated will be used as compacted backfill in the UST excavation. Cleaned soils are those that have been remediated and will"not leach gasoline compounds into the groundwater. Update Status Report #53 dated October 9, 1998 contained Tier 2 RBCA in calculated the Soil Leaching Appendix G which g to Groundwater concentrations for Benzene, rr Toluene, Ethylbenzene, Xylene isomers and MTBE indicate the following concentrations as Site Specific Target Levels (SSTLs) that can be left in the soil: Compound mg/Kg Compound mg/Kg Benzene 0.49 MTBE . 2.1 Toluene 340 Ethylbenzene 160 Xylene isomers >500 Gasoline >500 Confirmation soil boring S134 drilled and sampled on June 4, 1997 showed that the vapor extraction remediated the soil near the UST area. The fifteen foot depth (bgs) below ground surface sample 4 R-603 UST WP 2/23/99