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ChevronTexaco—Vernalis Pump Station,Vernalis,CA. Project No. 06-6102-00-6369-201
<br /> June 29,2004 Page 3 of 7
<br /> were detected in all borings except SB-18. The maximum concentration detected was 39,000
<br /> mg/kg. Low concentrations of BTEX and PAHs were detected in various soil samples collected
<br /> from these borings. Geomatrix Consultants collected grab groundwater samples from soil
<br /> borings SB-15, SB-17, SB-18, and SB-21. TPHg and BTEX were not detected in any of the
<br /> groundwater samples analyzed. However, TPHd and PAHs were detected in all the grab
<br /> groundwater samples analyzed.
<br /> ARCOSPROPERTY
<br /> 2003: October—Geomatrix conducted a preliminary soil and groundwater investigation at the Arcos
<br /> property,which was part of the Former Vernalis Pump Station,but was not under environmental
<br /> investigation prior to 2003. The preliminary site investigation included review of public records,
<br /> historical maps, aerial photographs,the geophysical survey, evaluation of current property
<br /> conditions, and subsurface investigation. Between October 20 and 28,2003, Gregg Drilling and
<br /> Testing,Inc.,under the supervision of Geomatrix, advanced 12 soil borings,ASB-1 through
<br /> ASB-12, on and around the Arcos property. TPHc were detected in borings ASB-1,ASB-2, and
<br /> ASB-4 at a maximum concentration of 17,000 mg/kg. TPHc were not detected in any other
<br /> borings. Low concentrations of BTEX and PAHs were sporadically detected in several soil
<br /> samples. Geomatrix collected grab groundwater samples from soil borings ASB-1,ASB-5
<br /> through ASB-8,ASB-10,ASB-11, and ASB-12. TPHd were detected in grab groundwater
<br /> samples collected from borings ASB-1,ASB-5,ASB-6,ASB-7, and ASB-11, at a maximum
<br /> concentration of 2,900 gg/L.
<br /> Based on the previous soil and groundwater investigations,petroleum-affected soil and groundwater has
<br /> been delineated vertically to a maximum depth of approximately 80 feet bgs. The RWQCB approved the
<br /> delineation results in their letter dated March 19,2004. However,the lateral extent of affected soil and
<br /> groundwater has not been delineated beneath the site. Furthermore, soil and groundwater appears to be
<br /> affected down gradient and off site and additional delineation was requested by the RWQCB in the east-
<br /> northeast direction. Groundwater beneath the site has been encountered between approximately 31 to 37
<br /> feet bgs. Based on the data from previous reports, groundwater flow direction beneath the site varies
<br /> northeast to east. Detailed Historical Soil and Groundwater Analytical Results are presented in tables
<br /> attached as Appendix B.
<br /> SCOPE OF WORK
<br /> The scope of work outlined below is being proposed to collect data required by the RWQCB to delineate
<br /> the lateral extent of affected soil and groundwater down gradient of the former heater house,boiler house,
<br /> and pump house;the northwest portion of the Bellini property; and east of the Arcos property. SAIC
<br /> proposes advancing nine primary soil borings(SB-22 through SB-30, and SB-36),possibly five additional
<br /> contingency borings(SB-31 through SB-35), and installing five groundwater monitoring wells (MW-5
<br /> through MW-9). The majority of the borings and wells would be installed down gradient,northeast and
<br /> east of the site. Two borings, SB-30 and/or SB-31,would be installed in the northwestern portion of the
<br /> site on Bellini property,and two borings(SB-22)and one well(MW-5)would be installed on the Arcos
<br /> property. In addition,one soil boring(SB-36) is being proposed to delineate the lateral extent of soil and
<br /> groundwater west of the former heater house. Soil borings and monitoring well locations are shown on
<br /> Figure 2. Contingency borings would be drilled only if intervals of affected soil were encountered in the
<br /> primary borings. SAIC also proposes to initiate quarterly groundwater monitoring and sampling of the
<br /> newly installed wells and existing wells, and to perform a search of Department of Water Resources
<br /> (DWR) files to identify domestic, irrigation, or municipal wells within 2,000 feet of the subject site.
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