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Ultramar Inc./ Beacon #474 page 2 <br /> 3440 E. Main Street, Stockton. <br /> wells for this site that have groundwater in them to be sampled and analyzed for <br /> all petroleum compounds that the groundwater from the monitoring wells are <br /> being analyzed for. <br /> Purging the vapor wells prior to sampling them may be at the discretion of the <br /> sampler and should be based on the well's ability to recharge adequately. <br /> Enclosed please find the PHS-EHD policy for analyzing groundwater samples for <br /> fuel oxygenates by EPA Method 8260. This procedure is to begin <br /> immediately for all samples collected from the monitoring wells and "wet" <br /> vapor wells associated with this site and is to continue on a quarterly <br /> schedule thereafter until re-directed by PHS-EHD. <br /> Prior to approving remedial proposals for underground storage tanks (UST) sites, <br /> the vertical and lateral limits of the soil contamination must be identified. PHS- <br /> EHD is concerned that the center of this site's groundwater plume is located <br /> twenty-five feet north of any potential source. The closest source to the current <br /> groundwater plume's center is the dispenser and island area. With only very low <br /> levels of soil contamination detected onsite above 65 feet below ground surface <br /> (' bgs) and relatively high levels of contaminated groundwater still present at this <br /> site, PHS-EHD has concluded that the "source" of the impact to groundwater has <br /> not been identified. <br /> PHS-EHD will require an additional soil investigation in the island and dispenser <br /> area that will define the vertical and lateral limits of soil contamination noted <br /> during the vapor well installations of September 1997. <br /> In addition, USTs that were on sites when depth to first groundwater was deeper <br /> (drought conditions, Fall 1978)) are required to investigate the soil and <br /> groundwater to that vertical depth. The San Joaquin County Flood Control <br /> Department records indicate "drought" depth in this site's area was at 105 'bgs. <br /> In addition to other soil sampling requirements, PHS-EHD will require'discreet <br /> soil and groundwater samples to be collected from this depth and analyzed for <br /> TPH-G, BTEX, and all of the oxygenates. Conclusions reached for soil vertical <br /> delineation shall be supported by laboratory data from two consecutive five foot <br /> soil samples that are "non-detect" for petroleum and the oxygenates. <br /> An addendum that addresses the above noted concerns is to be submitted to <br /> PHS-EHD for review. PHS-EHD recommends that borings placed in or around <br /> the dispensers or island area have an option for conversion into a groundwater <br />