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i f ht f ' .. 95. Rationale why conditions remaining at site will not adversely impact water quality, health, or other beneficial uses. I E The plume of impacted groundwater.appears to be defined and adequately ,} characterized. Except for one anomalous detection of 0.66 µg11 of MTBE in f groundwater at MW-8A, on June'2, 2004, no gasoline compounds have been detected in the downgradient monitoring well cluster(,MW,-,8A and MW-8B) in 16 dwater collected from Irrigation Well #2 has been quarterly sampling events. Grau free of gasoline compounds for 23 consecutive quarters. r Concentrations are declining,and the plume of impacted groundwater appears to.be stable. By projecting a linear concentration trend derived from the last nine quarters U _ '1 1 of groundwater analytical results from MW-5, the concentration of MTBE in groundwater should continue Ao decline to below repo'r-ting'limits by approximately _ the fourth quarter of 2008. AArend chart showing projected concentrations for MW-5 is presented in Appendix D.-- The :The results from the RBCA analysis confirm that current site conditions do not pose H kE # excessive risk to human health:oesafety. The RBCA`'results combined with an evaluation of the site conceptual'model indicate: I The leak has been stopped''.ard remaining petroleum h,ydrocarbons and fuel oxygenates appear to be.insufficient to constituent,and ongoing source. 2 The site has been adequately1characterized to a degree that has identified the Tack of potential preferential pathways and the risk`theisite poses to sensitive receptors in the area. 3 The contaminant plume in groundwater has been demonstrated to be stable or declining in concentration over more than five years of,groundwater monitoring. 4 No other waters,of the state, water supply wells orother sensitive_ receptors are likely to be impacted by this,8Ae. L 5 Based on a RBCA assessment and site conceptual model, the site does not represent a significant risk to human health and safety Ramage Environmental recommends that the San Joaquin;County EHD and RWQCB t close the case and issue a "No Further Action Required" letter.