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FROM Ground Zero Analysis PHONE NO. 209 839 9ee3 Feb. 15 2000 05:00PM P4 Mr-Harlin Knoll February 15,20o0 Page 3 of :F the former USTs to the south and west. Residual co itamination in the sail appears to atenitate rapidly, as no contamination was detected in any soilsimples colleeW from 15 feet bgs or below, ! An estimated 1,300 cubic yards of soil between the d hs of approximately 6 and 13 feet bgs has been impacted beneath the site. The estimated area of oil coiytan-dnation is shown on figure 3. a 3.2 Groundwater Conmmination Co-oundwater beneath the affected soil has been impacted by petroleum hydrocarbons and the oxygenated fuel additive WME. The lateral extent of shallow groundwater contamination beneath � the site is largely defined to the north and the south,,but has not been fully defined to the west or Ehe r east. The estimated extent of dissolved petroleum lWdroczrbon constituents in groundwater is shown on Figure 4. 4.0 'WORKPLAN q We propose using an excavator to remove residual soil contamination from the approximate area 0 depicted on Figure 3. Excavation will continue laterally until field evidence indicates that the majority of contaminated soil has been removed. Excweaflon will pro=cd vertically to an estimated depth of approximately 13 feet. :E Soil excavation will be performed by Oil Equipment Service, a Division of Keith A. 'T'allia, Inc. Ground Zero anticipates that approxamdely 1,100 cubir. yards of clean overburden soil will be removed prior to excavating contaminated soil. The Mean soil will be stockpiled separately from ilie contaminated soil and confirmation soil samples Will be collected at a frequency sof orte 21 composite sample per 100 cubic yards of excavated SQL Documented clean sail will be utilized as backfill- The anticipated stockpiling location is shawrr n f igure 5. Approximately 1,100 cubic yards of contarninated soil is expected to be removed. The i contaminated sail will be temporarily stockpiled on son 6-roil plastic sheeting aM confirmation soil samples will be collected at a frequency of one 2 1 composite sample per 100 cubic yards of i excavated soil. Contaminated soil will be aerated wider a permit for uncontrolled soil aeration �! iissued by the San Joaquin Valley Unified Air Pollutio i Control District (APCD). The anticipated area for soil aeration is shown on Fi;ure 5. Ground Zero anticipates collecting 12 confirmatit5n soil. samples from the sidewalls and floor of the 'f excavation to document the removal of impacted soil. In a,ddidor►,one groundwater sample will be caollectecifnnm the excavation pit. Samples will be analyzed for benzene,toluene,ethylbenzene, and xylenes (ETEX) using EPA method 8020, tots] petroleum hydrocarbons as gasoline (TPHG) and diesel MUD)using EPA 8015 modified,and gasoline oxygenate additives using EPA 8260. Upon completion of the excavation, Oil Equipment Service will line the bottoni and the sides of the excavation with Typar filter fabric prior to ba,ckfrl ing the excavation with gushed rock to 6pproximately one foot above the static groundwater level- Another layer of fabric will be placed � on trip of the crushed rock prior to placing and mechanically compacting the remainder of the Q%DwaGRoUNDZE104AN6SPW crVrAvriwwp.doc U