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Kennedy/Jenks Consultants Section 4: Vadose Zone Monitoring 4.1 Leachate Collection and Recovery System In accordance with the WDRs, Musco staff perform complete inspections, including visual observations for the potential presence of water, of the LCRS on a monthly basis. Liquid has been detected on only three occasions in the LCRS. Samples of the liquid were collected and submitted for analysis of total dissolved solids (TDS)and other constituents. The concentrations of TDS and other constituents in these samples were much less than constituent concentrations in the Title 27 ponds, and therefore, did not indicate the lining of the pond system had been compromised. In accordance with the WDRs,the LCRS monitoring information has been submitted to the RWQCB as part of the semi-annual and annual reports. 4.2 Vadose Zone Monitoring System Musco operates 37 suction lysimeters that were installed at the time of the construction of the Title 27 ponds. The lysimeters were installed at depths of either five feet or ten feet below the bottom of the second liner. These lysimeters have been sampled in accordance with WDRs since their installation. The results and findings have been submitted to the RWQCB in the semi-annual and annual reports. Musco staff reviewed the operator's manual (Soil Moisture Equipment Corporation, 1997; copy included in Appendix B)for these lysimeters in 2010 and became aware that they were not being operated in full accordance with the manufacturer's recommendations, namely with respect to the amount of vacuum applied to the lysimeter. Additionally, a number of lysimeters do not hold a vacuum, which indicates either that the lysimeter and surrounding soil are dry, or that the lysimeter is no longer operational. The lysimeters need to be evaluated in accordance with the manufacturer's recommendations to ensure proper operation and functionality. There is additional concern that the suction in the native soil may be greater than the suction available in a lysimeter(i.e. water cannot be pulled out of fine grained material). It is correct that the lysimeters cannot remove water held more tightly in the soil than 100 centibars,the maximum possible vacuum that the lysimeter can supply (the standard procedure is to apply 50-85 centibars of suction). In fact, when the soil suction is greater than 30-50 centibars, only very small quantities of water can be removed by the lysimeter because the water is unsaturated (also termed 'below field capacity'). At these soil suctions, the pore water cannot drain under the force of gravity (ASTM, 2008). A leaking pond would cause much higher saturation and therefore lower suction in the soil. Under these conditions, the lysimeter will yield a sample that represents moving soil water. If the lysimeter holds a vacuum and does not yield a water sample, then water cannot be extracted from the soil either by a lysimeter or by drainage. When this occurs, the lysimeter results indicate that the soil is too dry for water movement and there is no evidence of pond leakage. No logs were kept of the soils in which they were installed; however based upon the boring logs for the Title 27 monitoring wells, the soil in the upper 10 feet typically can range from a silty sand, silt, or silty clay. Page 10 Work Plan for Improved Detection Monitoring Program Musco Family Olive Company, Tracy, California 9!�9,.p�,^mpbt2DNlUW ..I..o3.pm lits 27_d.pof d.a .ntlreport text-09-26.doc