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August 15, 1996 Is • <br /> Mr. Michael Infuma <br /> submerged due to the record rainfall in recent years. It should be noted that between <br /> 1990 and 1994, the water table was appropriately within the screened interval of the <br /> site monitoring wells and data generated during this timeframe should be considered <br /> representative of aquifer conditions. UNOCAL believes it would be premature to <br /> replace any existing wells at this time until the groundwater elevations stabilize (as <br /> your letter implies) and proper placement of the well screen intervals can be <br /> determined. We will also address the need (if any) to install additional monitoring <br /> wells for plume characterization at that time. <br /> It is interesting to note that your agency will not consider the use of ORC socks to help <br /> mitigate elevated hydrocarbon levels in wells MW 11 and MW 12. Our proposal to use <br /> ORC was never intended to suggest full scale remedial efforts for groundwater <br /> cleanup, nor as a"most feasible option". Rather, we had hoped to achieve some level <br /> of mass reduction by increasing the biodegradation rate in the most heavily impacted <br /> monitoring wells. We had thought that some effort at moving toward this goal would <br /> have been welcomed by your office, but it appears that you would rather see no effort <br /> initiated in this regard. We, therefore, will forego further consideration of the use of <br /> ORC at this site. <br /> UNOCAL would like to consider RBCA options for groundwater cleanup and is <br /> currently awaiting further direction and policy guidance from the SWRCB which is <br /> anticipated to be published during 1997. Until then we will continue our joint <br /> monitoring efforts with Montgomery Ward and will pursue information on the well <br /> construction details for a reported irrigation well at the nearby Delta College. <br /> UNOCAL has instructed our consultants to continue quarterly sampling activities and <br /> to include the analysis of MTBE into our monitoring program. However, we request <br /> that San Joaquin County reconsider our proposal to reduce the monitoring and <br /> sampling program to semi-annually as it is still unclear what additional information <br /> and benefit is gained from obtaining quarterly data at this site. <br /> If you would like to discuss this case in more detail, please call me at 510-277-2321. <br /> Sincerely, <br /> Tina Berry <br /> Senior Geologist <br /> Project Manager <br /> 3 <br />