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Musco Family Olive Company - 17 - 12 December 2006 in concentration indicating these wells are monitoring the same groundwater zone. Chloride in well MW-4 is moderately lower than chloride concentrations detected in well MW-8. The COC concentrations of both wells is lower than the interim standards and both have relative concentrations to the Regional Well when compared. However, TDS values have increased slightly over time as indicated in the Time Series Plot for wells MW-4 and MW-8. Well MW-7 , Well MW-7 is near the northeastern facility boundary of Field North 18. Field North 18 has f been spray irrigated since 2000. Groundwater in the vicinity of Well MW-7 is sulfate dominant at concentrations approximately 500 mg/L higher than detected in wells MW-4 and MW-8. Well MW-12 has similar sulfate concentrations to MW-7 and its source needs to be evaluated. TDS is elevated above the interim standards and the Regional Well when compared. Chloride and sodium concentrations are below the interim standards yet above the Regional Well concentrations. REVIEW OF BACKGROUND GROUNDWATER QUALITY As required in WDR No. R5-2002-0148, Musco submitted a Background Groundwater Quality i Report (Report) dated 30 July 2004. Kennedy/Jenks Consultants prepared the report on behalf of Musco. The Report discusses three encountered depths of groundwater beneath the site that can be segregated into: 1. A perched zone 5 to 20 feet thick encountered at a depth between 5 and 20 feet bgs. 2. An intermediate zone 10 to 40 feet thick encountered at a depth between 20 to 60 feet bgs. 3. A deep zone 50 to 110 feet thick at depths between 90 to 200 feet bgs.. The Report evaluates groundwater quality of the shallow and intermediate zone as noted by Musco's previous consultant Klienfelder. Based on current groundwater data where several on-site wells have gone dry from the uplands through the mid-slope area and lowlands, staff has evaluated groundwater as two zones:'shallow and deep. The perched zone in the lowlands area does not appear to exist and has not been observed in wells W-2 or MW-11 .for several years. Wells MW-6 and MW-9 located in the mid-slope area have been dry since 2004 and 2002, respectively. Well MW-13 in the uplands area has been dry since 2005. Therefore, the shallow zone in this memo is equivalent to intermediate zone in Kennedy/Jenks report. The focus of the Report's evaluation was to analyze whether there was or is an increasing, decreasing, or no significant change in time versus concentration trends for specific CDCs and then to attribute them to one or more of the following explanations: 1. Occurrence of constituents in upgradient groundwater conditions, 2. Occurrence of constituents in localized and cross-gradient conditions, 3. Site related activities influencing shallow groundwater.