ARCHIVED REPORTS XR0000099 - Laserfiche WebLink

Home Browse Search

Request for Site Closure 2 •` Chevron U S A Products Company,2400 Airport Way,Stockton,CA_ _January 15,1996 7 ppm were reported (Versar, 1989a),these results are not discussed in this report due to Insufficient documentation regarding survey locations, results and instrument calibration Soil collected from the 20-foot depth in boring BH-2 contained 0 083 parts per million (ppm) benzene and 0 350 ppm total petroleum hydrocarbons-as-gasoline (TPH-G),while all other analyzed soil samples contained concentrations of benzene,toluene, ethylbenzene and xylenes(BTEX) and TPH-G below the laboratory method detection limits (MDL) (Versar, 1989a) In August 1989,Versar installed groundwater monitoring well MW-1 The soil sample collected at 45 feet below ground surface (BGS) contained BTEX levels below MDL and TPH-G at a concentration of 0 230 ppm,while the sample collected at 50-feet BGS from this boring contained BTEX and TPH-G at concentrations below the MDL(Versar, 1989b) Groundwater sampled from MW-1 during the first groundwater sampling event in September 1989 contained levels of BTEX below MDLs and TPH-G at a concentration of 0 032 ppm (Versar, 1989b) In February 1991, Groundwater Technology was contracted by Chevron U S A Products Company to conduct additional site assessment work which involved the installation of groundwater monitoring wells MW-2, MW-3 and MW-4 All soil samples from these borings chosen for laboratory analysis contained BTEX and TPH-G at levels below the MDLs(Groundwater Technology, 1991) The first groundwater sampling event conducted on these wells during the period December 1990-January 1991 produced samples containing BTEX and TPH-G at concentrations below the MDLs (Groundwater Technology, 1991) Groundwater Technology was again contracted by Chevron in May 1994 to provide further soil and groundwater assessment and install groundwater monitoring well MW-5 BTEX and TPH-G jll concentrations were below MDLs in all analyzed sal and groundwater samples (Groundwater Technology, 1994) Soil sample analytical results are summarized In Table 1 and Figure 3, and laboratory analytical reports are presented in Attachment 4 Subsequent groundwater monitoring and sampling conducted on MW-1, MW-3, MW4 and MW-5 have resulted in four consecutive quarters of analytical results below MDLs for BTEX and TPH-G (Table 2) Groundwater samples collected from MW-2 were below MDLs for BTEX and TPH-G from date of well installation to the third quarter of 1994 Sampling in the fourth quarter 1994 showed concentrations of 1 9 parts per billion (ppb) benzene,2 0 ppb toluene, and 1 8 ppb xylenes (Blaine Tech, 1995) These results are somewhat anomalous given the histonc trend of groundwater analyses from MW-2 Furthermore,the two subsequent quarterly sampling events produced groundwater samples below MDLs for BTEX and TPH-G,while the most recent quarterly event revealed a benzene concentration of 0 97 ppb(Blaine Tech, 1995) olssdos rpt(Chv-56) ❑E:10 GROUNDWATER ❑❑❑TECHNOLOGY g