|
ChevronTexaco—U.S. Can/Welty Road, Vernalis, CA. Project No. 06-6102-00-5394-101
<br /> March 10, 2004,2004 Page 3 of 6
<br /> 2002: May 20 and 21 —Gregg Drilling,under the supervision of Geomatrix Consultants,advanced three
<br /> soil borings(GMX-8, GMX-9, and GMX-1B) for additional soil samples. TPHc were detected in
<br /> borings GMX-8 and GMX-1B at maximum concentrations of 8,000 mg/kg and 5,100 mg/kg,
<br /> respectively.
<br /> 2003: August 4 and 5—Gregg Drilling,under the supervision of Geomatrix Consultants, advanced three
<br /> soil borings (GMX-10, GMX-11, and GMX-12) for soil and groundwater samples. TPHc were
<br /> detected in the soil sample collected from a depth of 41.5 feet bgs from boring GMX-12 at
<br /> concentration of 15,000 mg/kg. TPHd were detected in all groundwater samples collected from
<br /> GMX-10, GMX-11, and GMX-12 at concentrations of 210 pg/L, 3,600,ug/L,and 110,ug/L,
<br /> respectively.
<br /> Based on the previous soil and groundwater investigations,petroleum-affected soil northeast of GMX-12
<br /> has not been laterally defined off site. Furthermore,groundwater appears to be affected in the vicinity of
<br /> borings GMX-10, GMX-11, and GMX-12 and has not been laterally defined downgradient of the subject
<br /> site. Groundwater beneath the site has been encountered between approximately 25 and 39 feet bgs.
<br /> Based on the data from previous reports, groundwater flow beneath the site varies from the northeast to
<br /> southeast.
<br /> SCOPE OF WORK
<br /> The scope of work outlined below is being proposed to collect data required to delineate soil northeast of
<br /> soil boring GMX-12 and groundwater down gradient of the subject site. SAIC proposes advancing five
<br /> soil borings (SB-13 through SB-17) in the vicinity of former borings GMX-6, GMX-7, GMX-10,GMX-
<br /> 11, and GMX-12 at the locations shown on Figure 2. A sixth soil boring(SB-18) located approximately
<br /> 200 feet northeast of GMX-12 is also being proposed if a significant interval of affected soil is
<br /> encountered in the boring northeast of GMX-12. SAIC also proposes to initiate a quarterly groundwater
<br /> monitoring and sampling program, and perform a search of Department of Water Resources(DWR)files
<br /> to identify domestic, irrigation, or municipal wells within 2,000 feet of the subject site.
<br /> Previous sampling and chemical test results summarized and presented in the most recent Report of Off-
<br /> Site Soil and Groundwater Investigation (Geomatrix,2003)indicated the presence of residual petroleum
<br /> in the soil to depths ranging between 20 and 45 feet(see tables in Appendix B). Based upon this
<br /> information,the soil borings will be advanced to a target depth of approximately 45 to 50 feet bgs. SAIC
<br /> will attempt to collect soil and groundwater samples from the depths that coincide with affected intervals
<br /> observed in previous borings in accordance with the Second Draft Revised Technical Approach to Site
<br /> Evaluation and Decision Making, Old Valley Pipeline Sites (Geomatrix,2002).
<br /> TASK 1 —PRE-FIELD ACTIVITIES
<br /> Prior to conducting field activities, SAIC will obtain boring permits from the San Joaquin County Public
<br /> Health Services(SJCPHS), and obtain an encroachment permit from Caltrans, if warranted. Proposed
<br /> boring locations on WFS property will require an access agreement, to be secured by ChevronTexaco.
<br /> Prior to advancing the proposed borings, SAIC will conduct a site visit to mark the proposed boring
<br /> locations and perform a high-level site reconnaissance noting any potential above-ground or below-
<br /> ground obstructions. SAIC will also subcontract with a private utility locator to perform an underground
<br /> utility clearance at each boring location. Following SAIC's initial site visit and utility clearance,
<br /> Underground Service Alert(USA)will be notified 48 hours in advance of field activities. If necessary,
<br /> ChevronTexaco will notify and obtain a right-of-entry access from UPRR and KM prior to starting
<br /> fieldwork.
<br /> If an encroachment permit is required from Caltrans, SAIC will prepare a traffic-control plan in general
<br /> accordance with Caltrans guidelines for work along Welty Road and Highway 33. The encroachment
<br />
|