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' 07 October 2003 AGE-NC Project No 95-0121 Page 6 of 7 ' stand alone treatment for impacted soil and ground water due to a reduction of the thickness of the impacted vadose zone and an increased thickness, and volume, of impacted soil(and ground water) in the saturated zone The impacted soil is primarily fine grained within sand units,which may make ' the upward and lateral path of sparged`air through the saturated zone unpredictable and stripped ; hydrocarbons unrecoverable The limited overall effectiveness and reliability of IAS technology to remediate deeper and saturated impacted sand unit and ground water likely will require a re- evaluation of the method to remediate ground water and reduce the hydrocarbon mass Additionally, the vertical extent of hydrocarbon-impacted soil and ground water had not been fully ' assessed when the CAP was developed The mass of adsorbed hydrocarbons now known to be within the saturated zone is significant,mostly due to the elevated ground water table At the time the CAP was prepared,the vertical assessment was not required by the SJCEHD However,current California Health and Safety Code regulations (H&S 25295)require the assessment and continual,monitoring of the vertical-margin dissolved hydrocarbons Additional evaluation of soil and groundwater below 30 feet bsg is required to documented concentrations of dissolved and adsorbed hydrocarbons, Irequired for mitigation and ultimately closure 5 0 RECOMMENDATIONS Based upon data collected during June 2003, AGE recommends • Continued ground water monitoring events at the site, however, collection of ground water samples from wells MW-1 through MW-9 (deeper screened monitoring wells) should be alternated between monitoring events with shallow screened wells VW-1 through VW-9 The next two ground water monitoring events are tentatively scheduled for September and December 2003 ' IIn accordance with Califorriia Underground Storage Tank Regulations, Article 5, Section ' 1 ~2655, free-phase petroleum product should be monitored and mitigated immediately If I additional petroleum product is encountered during the monitonng, than manual bailing activities should commence until the product is no longer visible Weekly monitoring of VW-1 should be continued until free-phase floating petroleum product is no longer encountered Additionally,free-phase petroleum product should also be monitored for at well EW-1 due to the,previous detection of product at this well IA work plan addendum for four (4) cone penetrometer testing soil borings were submitted to the SJCEHD on 18 June 2003 and approved by the SJCEHD by letter on 25 September 2003 (Figure 2) i f Advanced GeoEnvironmental,Inc I c