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Kennedy/Jenks ConsuFtants Section 6: Proposed Activities - Vadose Zone Monitoring Network 6.1 Suction Lysimeter Evaluation The suction lysimeters installed beneath the Title 27 ponds are model 1920 series porous ceramic cup lysimeters manufactured by Soil Moisture Equipment Corporation. The lysimeters are intended to have a small amount of moisture in the ceramic pore space, but it is possible that they have dried in the unsaturated conditions at the Site. Average annual rainfall is 12.2 inches (RWQCB 2005) and average annual evaporation is approximately 53 inches, so it is reasonable to conclude that the lysimeters may have dried out. According to the manufacturer (Soil Moisture Equipment Corporation, 1997), if the ceramic cup dries out, the lysimeter will not hold a vacuum. The device must be rewet in order to make a measurement of soil conditions. The following procedure developed by the manufacturer will be used to evaluate the functionality of the 37 suction lysimeters currently installed beneath the Title 27 ponds. The procedure is as follows: • Open both pressure/vacuum and sample hoses for the sampler • Attach pressure side of pump to the pressure/vacuum hose. Use pump to force air into the line and through the lysimeter. Feel and listen for air coming out of the sample hose; this will determine whether the hoses and lysimeter are intact. • Seal the sample line and apply a vacuum of 50-85 centibars. Inspect the exposed hoses for any signs of leaks. If the lysimeter holds a vacuum, no further servicing is required and the sampler can be used for measurements. If the lysimeter does not hold a vacuum, proceed to the next steps for re-wetting the ceramic cup of the sensor. • Use a peristaltic pump to pump at least 250 milliliters of distilled water down the sample hose. Both pressure/vacuum and sample hoses need to be open. • Wait at least one hour, then apply pressure to the pressure/vacuum line (with sample line open). This will purge excess distilled water. • Crimp the sample hose and apply a vacuum of 50-85 centibars to the pressure/vacuum hose. Record initial vacuum. Crimp pressure/vacuum hose while still attached to pump to preserve vacuum inside lysimeter. • Wait at least one hour(to one day) and return to the lysimeter. Prior to uncrimping the pressure/vacuum hose, attach it to the vacuum side of the pump. Uncrimp pressure/vacuum hose, read and record residual vacuum. Following the rewetting procedure, two outcomes indicate that the lysimeter is functioning properly. Either a)the lysimeter holds a vacuum, or b) the vacuum is zero but there is water in the lysimeter. If the lysimeter loses its vacuum and does not collect water, further evaluation will Work Plan for Improved Detection Monitoring Program Page 17 Musco Family Olive Company, Tracy, California a` .e�a�o�m�wewznzomam_m �w.n9,.wn.wua 27_dW" d..�mUepolt text-09-26.doc