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Chu%roll I'i odul-t-r C.onop 1;1) 2 Chevron St-man N9-8612 575 Or ant I nae Ro id i ruv (,111101111 a No«mlly 21 2000 slightly impacted soil was aerated to nondetectable levels and reused onsite Groundwater was encountered during excavation activities at approximately 8 feet below ground surface (bgs) In August 1994, the waste-oil UST and sump excavations were over-excavated until soil exhibiting low to nondetectable levels of oil and grease were encountered Approximately 150 to 200 cubic yards of oil and grease impacted soil was removed and hauled offsite In May 1995, wells MW-1 through MW-4 were installed at the site Maximum concentrations of TPHg and benzene in wet soil were reported in the area of the former pump islands (boring MW-3) at 7,600 mg/kg at 6 5 feet below ground surface (bgs) and 24mg/kg at 6 5 feet bgs, respectively Groundwatei monitoring has been perfoi med quarterly since September 1995 Third quarter 2000 analytical data indicated maximum concentrations of total petroleum hydrocarbons calculated as diesel (TPHd) at 410 parts pei billion (ppb) (MW-3), total petroleum hydrocarbons calculated as gasoline (TPHg) at 2,400 ppb (MW-3), benzene, toluene, ethylbenzene, and xylenes (BTEX) at 220 ppb (MW-4), 9 2 ppb (MW-4) 83 ppb (MW-3), and 150 ppb (MW-3) respectively, and methyl-tertiary-butyl-ether (MtBE) at 2,100 ppb (MW-3) Gioundwater flow has been reported consistently to the northwest at gradients ranging from 0 001) to0 02 tt/ft • A SECOR woik plan for the installation of off-site groundwatei monitoring well MW-5 was approved by SJCEHD on February 1 1, 1999 The installation of MW-5 is currently pending PROPOSED SCOPE OF WORK The scope of work proposed for this assessment includes the drilling, installation, and sampling of four onsite gi oundwatei remedial wells, and a dual phase extraction feasibility test to select possible futile remedial alternatives Groundwater is anticipated to be encounteied at approximately 6 to 7 feet bgs based on recent data The specific scope of woi k is di-,cussed below • Well installation and Sainplitig One of the proposed remedial wells will be installed in the area of the former UST pit and another will be installed in the area of the southern most former dispensei island (Figure 2) The two remaming remedial wells will be installed along the northern edge of the property, and along the eastei n edge of the pioperty (Figure 2) to investigate possible hydiocarbon concentrations at the site boundai ies Soil samples will be collected at five-foot intervals during the drilling of the wells Z he wells will i 1Ch,vronM632T,port,'Wl'R t 2 3 4 imt ill dog