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Report:Groundwater-quality Monitoring—July 27,2004: 7500 West Eleventh Street, Tracy, CA. Page 18 ; ] 6.0 RECOMMENDATIONS The leakage of fuel hydrocarbons to the subsurface from tanks and piping associated with the former fueling station at 7500 West Eleventh Street in Tracy, California, was first detected in December 1998, when the underground storage tanks there were exhumed (Dietz Irrigation 1999a). Since April 2002,when SJC was permitted to implement the full scope of a site characterization program (The San Joaquin Company Inc. 2002c) that had originally been developed and presented in a formal work plan by a California-registered ,i Professional Engineer in June 1999 (The San Joaquin Company Inc. 1999), there has been a major expenditure of effort and public money via the California Underground Storage Tank Cleanup Fund in response to a variety of directives issued by numerous SJCEHD case officers and other staff. Unfortunately, those efforts and expenditures have lead to no significant change in understanding of the characteristics of the plumes of affected groundwater emanating from the site, nor have any alternate cost-effective methods for remediation or management of the affected area been illuminated, beyond those that have been long advocated by SJC. SJC now strongly recommends that to conserve public funds and to provide a means for cost-effectively bringing the site to l "closure,"the following procedures be implemented. 6.1 Closure of Wells in Deep Aquifers Groundwater-quality Monitoring Wells MW-3A, MW-3B and MW-12A should be closed. The closure should be scheduled so that it can be cost-effectively performed during the next round of groundwater-quality monitoring in late October 2004. As is documented in Table 2, analyses of samples recovered from those wells have shown �< consistently that they contain no detectable components of fuel hydrocarbons. As SJC has pointed out in previous recommendations, their continued existence if of no technical importance to the characterization or management of the site and, as long as they remain open, they pose a risk of contamination to the pristine aquifers in which they are screened should hazardous or noxious material enter the wells from surface spillage or other accident. 6.2 High Concentrations of Hydrocarbons along North Side of West Eleventh Street From the time Monitoring Well MW-7 was installed in April 2000,it has been obvious to an experienced engineer that there are high concentrations of fuel hydrocarbons in its vicinity and in an area to its east and west along the north side of West Eleventh Street. In fact, when that welt was left un-purged for a sufficient period to permit the thickness of LNAPL floating on the surface of the groundwater to be adequately monitored, the floating product in the well reached apparent thickness of up to 0.58 ft. As is typical of floating product behavior in such wells, even after an extended program of periodic purging, since January 2004, the concentration of gasoline in Monitoring Well MW-7 has been rising steeply. By June 27, 2004, it had reached 37,000 µ1L, with associated high concentrations of the BTEX compounds. sic