ARCHIVED REPORTS_2007_14 - Laserfiche WebLink

Home Browse Search

6.4 DRAIN GAUGE LYSIMETERS As discussed earlier,Drain Gauge lysimeters were installed at each monitoring location as illustrated on Figure 2. No infiltration has been recorded in either lysimeter to date. 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 alternative final cover soil properties similar to those used in the original design report (GLA, 2004). The soil moisture content and moisture flux calculated are summarized on Figures 12 and 13 respectively. 7.1 MOISTURE CONTENT As indicated by a comparison of monitored Figures 3 and 4 with modeled Figure 12,the pattern of moisture content variability resulting from modeling is consistent with the overall over-all 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 moisture content 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. The summer increase in moisture content observed at the Met station is not reflected in the modeling data because LEACHM accounts for only liquid phase moisture migration. The introduction of vapor phase (or oxidation created water)would create a pattern similar to that observed at the Met Station. This suggests,that at the Met Station, moisture from the waste itself may be responsible for much of the soil moisture response at this location. 7.2 MOISTURE FLUX As indicated in Section 5.2 above,no water migration through the bottom of the cover has been measured by the on-site lysimeters. In addition, as discussed in Sections 5.1 and 5.2 a consistent upward moisture and suction gradient has been observed within the final cover section. These results are consistent with the model results (Figure 13)which indicate negative flux (long-term drying)through the final cover system over the monitoring period. 8.0 DISCUSSION The monitoring data described above exhibits a soil moisture response that is similar to the pattern of moisture predicted by both the initial modeling and the revised (one-year) modeling. That is,the final cover is exhibiting a muted response to rainfall. The longer-term seasonal patterns are also generally consistent. One exception to this generally consistent pattern is noted at the Met Station during the summer of 2007 when an increasing moisture trend, unrelated to Geologic Associates