SU0006108 SSCRPT - Laserfiche WebLink

Home Browse Search

Soil and Groundwater Investigation Report and Second Quarter 2005 Monitoring and Sampling, US Can-Welty Road October 2005 4. FIELD ACTIVITIES 4.1 PRE-FIELD GOALS The work plan for the subject site proposed five soil borings and one contingency boring to delineate soil northeast of soil boring GMX-12 and groundwater down gradient of the subject site. SAIC proposed ` advancing soil borings SB-13 through SB-17 in the vicinity of former borings GMX-6, GMX-7, GMX-10, GMX-11, and GMX-12 at the locations shown on Figure 2. A sixth soil boring was proposed as a contingency boring approximately 200 feet northeast of GMX-12. SAIC also proposed to initiate a quarterly groundwater monitoring and sampling program, and perform a search of Department of Water Resources(DWR) files to identify domestic, irrigation, or municipal wells within 2,000 feet of the subject site. ` Previous sampling and chemical test results summarized and presented in the Report of Of-Site Soil and Groundwater Investigation (Geomatrix, 2003) indicated the presence of residual petroleum in the soil to depths ranging between 20 and 45 feet(see tables in Appendix B). Based on this information,the soil borings were proposed to a target depth of approximately 50 feet bgs. SAIC planned to collect soil samples from the depths that coincide with affected intervals observed in previous borings and to collect grab groundwater samples from select borings in accordance with the CTA and the approved work plan. ` In addition to soil and groundwater samples collected for delineation, shallow soil samples (less than 10 feet bgs)were to be collected for a human health risk assessment(HHRA). Prior to drilling, SAIC initiated the process of obtaining all necessary permits required to enter onto private properties and State easements. In addition, SAIC conducted a site visit to mark the proposed boring locations and subcontracted a private utility locator to electronically clear all boring locations. 4.2 PRE-FIELD ACTIVITIES Prior to the initiation of field activities, SAIC obtained Encroachment Permit No. 1004-6SV-0479 from California Department of Transportation(CALTRANS)to perform work adjacent to State Highway 33. Soil boring permit numbers SR#0041390 and SR#0041392 were obtained from San Joaquin County ` Environmental Health Department(SJCEHD) for the installation of five soil borings and one well boring. Site access was granted by property owners of WFS to work within their property. A copy of the encroachment permit obtained for this investigation is included in Appendix C. Copies of the SJCEHD boring permits are included in Appendix D. SAIC contacted Underground Service Alert(USA)to notify utility providers within the area of the ` drilling investigation. As an additional precaution, SAIC contracted Cruz Brothers Locators (Cruz)of Scotts Valley, California to provide a supplemental underground utility survey. In March 2005, Cruz conducted the electronic survey clearing a 15-foot radius around each of the proposed borings. The boring locations were cleared for drilling and no anomalous utilities were identified within the vicinity of ` the marked locations. 4.3 SOIL BORINGS In order to evaluate the extent of residual petroleum affecting soil and groundwater adjacent to the areas identified in the work plan, SAIC supervised the installation of four soil borings (SB-13, SB-I4, SB-I5, and SB-17), and installation of groundwater monitoring well MW-5. Soil borings SB-13 and SB-17 were �. drilled on March 14, 2005 and borings SB-14 and SB-15 were drilled on March 15, 2005. On March 16, 2005, groundwater monitoring well MW-5 was drilled as a companion boring in the vicinity of SB-15. The proposed soil boring(SB-16)down gradient of GMX-6 was not installed based on evidence of a former gasoline station at the eastern corner of Welty Road and Highway 33. As discussed in the background section, a former Union Oil Service Station operated at the location from 1972 to the mid 1980s. In addition, efforts to secure access to the property were complicated by an unclear chain of title 4 From Science to Sotutionsi-