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i II r „f ,rr. � 't t ENSR Acquired FugrorI'Aronmental Services an January 1997 Consulting• Engineering• Remediation , , 1050 Melody Lane May 1, 1997 ;2 15 Suite 160 Project No 9647-0771 (8716-002) Roseville, CA 95678(916) 782-2110 Ms Pamela Lopez FAX(918) 786-7830 c/o Bob Holiday 26500 Nowell Road Thornton, California 95686 Subject First Quarter 1987 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 March 14, 1997 The monitoring event included collection of depth to ground water measurements and the collection of ground water samples at the locations of monitoring wells MW-1 through MW-3 for chemical analyses (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 east side 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 southern site boundary The subject site was j purchased by Ms Lopez 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 (TPH-g) 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 in Attachment 1 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 The third 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 TPH-g and BTEX TPH-g and BTEX were indicated at concentrations below 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 A summary of the analytical results is 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 TPH-g and BTEX The analytical results indicated the greatest concentrations were detected at the location of SBA On the basis of these results, RAH — re 11« a