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PUBLIC HEALTH SERVICTS <br /> SAN JOAQUIN COUNTY <br /> ENVIRONMENTAL HEALTH DIVISION <br /> Karen Furst, M.D., M.P.H., Health Officer <br /> 304 East Weber Avenue, Third Floor • Stockton, CA 95202 `'FORS <br /> 209/468-3420 il 7 <br /> KAREN PETRYNA <br /> C/O EQUIVA LLC <br /> PO BOX 6249 MAY 2 6 1999 <br /> CARSON CA 90749-6249 <br /> RE: SHELL STATION SITE CODE: 1058124 <br /> 620 W CHARTER WAY <br /> STOCKTON CA <br /> San Joaquin County Public Health Services Environmental Health Division (PHS/EHD) and the <br /> Underground Storage Tank Cleanup Fund (USTCF) have recently reviewed the tiles associated with the <br /> site referenced above. Although groundwater monitoring is continuing, the plume is undefined as <br /> indicated in correspondence from PHS/EHD dated October 14, 1997. Data from monitor well installations <br /> at this facility fail to characterize the vertical component since soil samples below the groundwater <br /> interface were not commonly provided at fuel leak sites in the early 1990's. However, field-screening <br /> notes during the installation of most boreholes (see MW-1 through MW-10 borehole logs) clearly <br /> document the existence of contaminants at depths greater than 40 feet below grade surface (bgs). A <br /> November 24, 1997 workplan was approved by PHS/EHD on December 4, 1997. The responsible parties <br /> at this site have failed to implement the approved workplan and are out of compliance with corrective <br /> action regulations. <br /> The responsible party is now directed to modify the November 24, 1997 workplan considering the <br /> following comments. The amended workplan must be approved and implemented within 90 calendar <br /> days from the date of this letter. <br /> Data from cumulative tables indicate that ground water in monitor wells MW-1, 5, 7, 8, 9, and 10 exceed <br /> the screened intervals.No field data was available to indicate depth to water,gradient,or groundwater flow <br /> direction for the First quarter of 1999 (see April 9, 1999 QMR by Cambria). The monitoring wells at this <br /> Underground Fuel Tank (UST) leak site are inadequate and insufficient to properly locate and define the <br /> extent of contaminant distribution in the saturated zone as evidenced by the vertical and horizontal <br /> variations of contamination observed at this site. Historic depth to water in this area has been documented <br /> by the San Joaquin County Flood Control Department in excess of 80' bgs during the operational period <br /> for this facility. Please be aware that fuel hydrocarbon contamination has been documented in soil and <br /> groundwater at depths in excess of 100' below grade surface at sites in this area. Commingled contaminant <br /> plumes are also suspected in this area. <br /> Boreholes shall be completed as monitoring wells with appropriate screen intervals to locate and <br /> effectively define the plume (soil and groundwater). At least two boreholes should be continuously cored. <br /> Each continuous core borehole should be located near known contaminant source areas (i.e., former tank <br /> cavity). All wells installed and surveyed shall be referenced to an appropriate and designated benchmark. <br /> Well screen intervals shall not exceed 20' in total length and should not create a potential vertical conduit. <br /> 1 <br /> A Division of San Joaquin County Health Care Services <br />