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Title 27 allows for alternative methods of collection of unsaturated zone data. The extraction of soil pore gases is an alternative method of unsaturated zone data. Attempts at the collection of soil pore liquid samples have proved to be very difficult with the use of suction lysimeters in the Central Valley. This is likely do to the fact that the FSL is in near desert conditions of 18-inch of annual rain fall. Such low rain fall conditions do not allow for the build-up of enough soil pore liquid to allow that limited amount of liquid to be drawn by suction into a lysimeter. However, the vacuum extraction of soil pore gases have proven to be viable for the measurement of vadose zone conditions. Although VOCs may be present in the soil pore gases, they are not exacting indicators of groundwater impact. • Several of these vadose monitoring wells are paired with groundwater monitoring wells; SG-119/MW-6, SG-120/MW-4, SG-9/MW-2R, and SG-1/MW-3. Soil Gas Well SG-8 Work Plan Vadose zone well SG-8 was abandoned and removed because it was in the expansion area of Area 2, and excavation for that Area is below the bottom elevation of that well. It is proposed that existing vadose zone monitoring well SG-119 be used as a replacement for SG-8 as shown on Figure 2. SG-119 is located at the southern edge of Area 2 and functions as an appropriate replacement for SG-8. Groundwater Monitoring Well Work Plan An additional groundwater monitoring well MW-6 is proposed to be installed as shown on Figure 2 at the Point of Compliance for Area 2. The location of this well will pair it up with vadose zone monitoring station SG-119. New well MW-6 will be constructed to the same details as existing well MW-5. The County's monitoring well construction procedures and a typical ' monitoring well detail is contained in Appendix C. This well will be monitored in conformance with WDR No. R5-2003-0020. Landfill Gas Monitoring Plan The LFG monitoring plan for FSL will consist of the following: • Collection of VOC and LFG data from the proposed seven (7) vadose zone monitoring wells. ® Collection of LFG and vacuum data from the LFG extraction system in Areas "I" and 1. t • Collection of LFG data from the LFG-to-Energy Plant or destruction data from the LFG flare. Foothill Sanitary Landfill 8 Department of Public Works/Solid Waste Engineering Feasibility Study County of San Joaquin—August 2014