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6.5 DRAIN GAUGE LYSIMETERS Two Drain Gauge lysimeters were installed at each monitoring location as illustrated on Figure 2. These instruments have measured no infiltration to date at any location. This indicates that while the soil may wet during the winter, breakthrough (infiltration into the waste) has not occurred. 7.0 MODELING RESULTS Climatic data collected from the MET station was used to remodel the performance of the 4-foot thick alternative final cover using a combination of the actual final cover soil properties in the original design report (GLA, 2004) and the data generated during the soils re-calibration study of 2007. The original soil characteristics and results of the re-calibration have been used to model both the soil moisture content and moisture flux, and are summarized in Figures 12 and 13, respectively. 7.1 MOISTURE CONTENT As indicated by a comparison of monitored soil moisture content (Figures 8 and 9)with modeled soil moisture content (Figure 12), the pattern of moisture content variability resulting from modeling is generally consistent with the overall moisture trends observed at both the Met and Satellite stations. That is, both the modeled and monitored data indicate broad seasonal changes in moisture content with discrete soil moisture responses to individual rain events only being recorded and anticipated for the most severe events. In addition, the general tendency for deeper soils to exhibit higher moisture contents is also reflected in both the observed and modeled data. Two relatively minor discrepancies exist between the modeled and monitored data. First, individual severe rain events are observed to have a more immediate and dramatic impact on soil moisture contents than is indicated by modeling. Second, the observed late summer increase in moisture content is not reflected in the modeling data because LEACHM accounts for only liquid phase moisture migration. Both of these discrepancies should result in conservatism in the model results since, 1)the slower soil moisture response modeled allows more time for infiltration and 2)the introduction of vapor phase (or oxidation created water)would result in extraction of more water from the soil than is calculated. 7.2 MOISTURE FLUX As indicated in Section 6.5 above, no water migration through the bottom of the cover has been measured by the on-site lysimeters. In addition, as discussed in Sections 6.3 and 6.4, a consistent upward moisture and soil suction gradient has been observed within the final cover section over a majority of the year. These results are consistent with the modeled results (Figure 13)which indicate a net negative flow of moisture (long-term drying)through the final cover system over the three year monitoring period. g GeoLogic Associates