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, I 2.26 lune 14, 2001 Discovery of Free-Floating Hydrocarbon During routine quarterly groundwater monitoring activities in June 2001 , ASE personnel discovered free-floating hydrocarbons on the groundwater in monitoring wells MW-5, MW-6 and piezometer P-4 Historically, only monitoring well MW-5 contained a measurable thickness of free-floating hydrocarbons and MW-6 had previously contain a sheen However, since the installation of the groundwater remediation system, the product i n MW-5 had reduced to an unmeasureable thickness Since the discovery of the free-floating hydrocarbons, ASE has b e e n measuring and bailing the free-floating hydrocarbons from the three wells on a weekly basis The free-floating hydrocarbon thickness has increased in monitoring well MW-6 and piezometer P-4, and decreased slightly in monitoring well MW-5 A more aggressive means of free-floating hydrocarbon removal, such as use of a vacuum truck, is planned for the site in the immediate future It is ASE's understanding that, based on an analysis of the floating hydrocarbons, it has been determined that the product is several years old, and not the result of a recent spill, release or leak from the station's UST or dispensing system 3 . 0 DISCUSSION REGARDING REMEDIATION AT THE SITE Significant groundwater contamination is present both on and off-site Free-floating hydrocarbons have also been recently discovered on-site The shallow groundwater flow at the site is to the north and numerous domestic wells north of the site have been impacted by MTBE Only the shallow water-bearing zone has been impacted significantly both on-site and on the north shoulder of West Yosemite Avenue Deeper water- bearing zones become impacted on the property north of West Yosemite Avenue The shallow sediment beneath the site is sandy Although high concentrations of hydrocarbons have generally not been detected in soil samples collected beneath the site, ASE believes that soil remediation is necessary since very strong hydrocarbon odors are present in the soil and the sandy soil does not provide a matrix for hydrocarbons to adhere to, thus providing misleading results Based on this information, the most significant points regarding the development of a remediation strategy are as follows • Soil remediation is necessary at the site Frank's One Stop Remedial Action Plan — August 2001 -12-