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i Consulting - Engineering - Remediation 10324 Placer Lane Suite 200 September 23, 1997 Sacramento, CA 95827 Project Number 8716-002 (916) 362-7100 FAX(916) 362-8100 Ms Pamela Lopez c/o Bob Holiday 26500 Nowell Road Thornton, California 95686 Subject Second Quarter 1997 Ground Water Monitoring Report Lopez Property 26500 Nowell Road, Thornton, California Dear Ms Lopez ENSR Is pleased to provide this report documenting the results of quarterly ground water monitoring conducted at the subject site (Figure 1 - Site Location Map) on July 22, 1997 The monitoring event included the collection of depth to ground water measurements and ground water samples at the locations of monitoring wells MW-1, MW-2 and MW-3 (refer to Figure 2 - Site Map) This report is based, in part, on information provided to ENSR by Ms Pamela Lopez, and is subject to modification as new information is received BACKGROUND The site is a private residence located on the side east of Nowell Road in a rural portion of Thornton, California Adjacent to and south of the property is a Tri-Valley Growers canning facility The canning facility includes former underground storage tanks (USTs) and a forklift shop within 50 feet of the subject property Ms Lopez purchased the subject site in 1979 with an existing 500-gallon-capacity gasoline UST on the property According to the previous property owners, the UST had not been used for ten to 15 years On October 9, 1989, the UST was removed One soil sample was collected from the base of the excavation and analyzed for the presence of total petroleum hydrocarbons identified as gasoline (TPHg) and benzene, toluene, ethylbenzene, and total xylenes (BTEX) The analytical results indicated that a release of petroleum hydrocarbons had occurred The analytical results are included as Attachment 1- Analytical Results Soil and Ground Water -Previous Investigations In November 1994, three drill holes were advanced and sampled at the subject site by RAH Environmental, Inc (Figure 2) Two of the drill holes (SB-3 and SB-4) were advanced in conjunction with a subsurface investigation of the adjacent Tri-Valley Growers property and one drill hole (SBA) was advanced at the former UST location to evaluate the vertical extent of the release Soil samples collected from the drill holes were analyzed for the presence of TPHg and BTEX TPHg and BTEX were not detected at concentrations above the laboratory detection limits in soil samples collected from drill holes SB-3 and SB-4 Chemical analysis of the soil samples collected from drill hole SBA indicated that petroleum hydrocarbons were present at depths below the water table The analytical results are included in Attachment 1 Ground water samples were collected through the hollow-stem augers at the location of the drill holes and analyzed for the presence of TPHg and BTEX The analytical results indicated the i oM,jai 5G 'la a "1s 8716062 gQ