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Well Abandonment and Soil and Groundwater Investigation Work Plan US Can-Welty Road September 2007 indicated two domestic wells were constructed with minimum sanitary seals extending to 20 feet bgs. The well completion report of the third well did not state a seal depth. One industrial well may be located in the vicinity of the site,but its exact location was unspecified. Municipal or agricultural water supply wells were not identified during the April 2004 DWR search,but two wells were described on well completion reports as public wells and were located at the site. Both wells are sealed from the surface to 150 and 200 feet bgs,respectively. There are no domestic wells located down gradient(east)of the site. SAIC concluded that the data collected during this and previous investigations indicated that residual petroleum had affected soil between 5 and 42 feet bgs in the vicinity of SB-17,MW-1, SB-1, SB-2, SB-3, B-1,B-4 through B-7(MW-2),GMX-3,GMX-8,GMX-1B,and GMX-12. In SB-17,clay and sandy layers below 37 feet bgs appeared to be the most affected. The lateral extent of affected soil appeared to be delineated towards the south,west,north,northeast,and east. However,the lateral extent of affected soil southeast of the former OVP and TAOC pipeline ROWS and boring SB-17 was not been fully characterized. The area northeast of GMX-6 had likely been affected by a refined fuel plume as a result of a leaking UST at the former service station at the eastern corner of Welty Road and Highway 33,where a former Union Oil Service Station operated from 1972 to the mid 1980s. Second Quarter 2007 Groundwater Monitoring and Sampling(SAIC,2007c). Based on data collected during the most recent groundwater monitoring and sampling event completed on April 30, 2007,groundwater elevation at the site varied between 71.48 and 71.94 feet above MSL with a flow gradient toward the east at 0.001 foot per foot. Historically,the groundwater flow direction has been to the east-southeast,and groundwater elevations at the site ranged from 70.19 to 73.09 feet above MSL. Wells MW-1 and MW-2 were not sampled during the second quarter 2007 due to the hydrocarbon sheen on the groundwater surface in these wells. Wells MW-3 and MW-4 were not sampled due to insufficient water volume to collect a sample. Groundwater samples were collected from MW-5 and WFSMW-1 and analyzed for TPHd and PAHs. In order to assess whether groundwater was affected by San Joaquin Valley(SJV)crude or another petroleum product,a fuel-fingerprint sample was collected from WFSMW- 1 and submitted to Chevron Energy Technology Company(CETC)for fingerprinting analysis using gas chromatography/mass spectrometry (GC/MS). TPHd was detected above the WQO and ESL in WFSMW-1 at 630 µg/L. However,results of the fuel- fingerprint analysis conducted by CETC on this sample showed that hydrocarbons detected in the WFSMW-1 sample were predominantly in the gasoline range(C7-C10 at 78.4 percent). These results are also consistent with the first quarter 2007 fuel fingerprint-analysis results. This indicates that the hydrocarbons detected in WFSMW-1 represent heavier hydrocarbons within the gasoline range,and are not representative of crude oil transported in the pipeline. Samples from well WFSMW-1 have historically shown elevated levels of hydrocarbons reported as TPHd,with concentrations ranging from 66 µg/L to 970 µg/L. Historically,TPHd has not been detected in MW-5 above the WQO or ESL. The oleophilic socks in wells MW-1 and MW-2 were replaced during second quarter 2007 monitoring because they exhibited SPO staining. However,no measurable amounts of SPO were removed from either of these wells. SPO has been observed in wells MW-1 and MW-2 since 1999 with a total of 0.34 gallon of SPO removed from these wells to date. PAHs were not detected above ESLs or WQOs in any of the second quarter 2007 samples.Historically, PAHs have been detected above ESLs or WQOs in wells MW-2 and MW-3,but not since 2005. SAIC's Second Quarter 2007 Groundwater Monitoring and Sampling Report recommended the following: • Discontinue collecting groundwater samples from MW-5 since TPHd and PAHs have never been detected above ESLs or WQOs in this well. 6 W/a:: fin/ FrJ'r S'rct r.0 5;1fi;'ror:s