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coverage over the land. This coverage was selected based on review of the <br />development of vegetation on the natural landscape adjacent to the site, and is <br />considered typical of the native vegetation in the area. <br />The additional vegetation values listed below were also specified in the final <br />cover analyses. <br />VARIABLE SPECIFIED VALUE <br />Wilting point -1500 Kpa <br />Root Flow Resistance 1.00 <br />Root Condition Mature <br />4.3 VARIABLE SENSITIVITY ANALYSIS <br />The following discussion addresses the sensitivity of model results to changes in <br />the critical variables discussed above, and also includes a brief analysis of several <br />less sensitive input variables. A summary of this sensitivity analysis is included <br />in Table 3. <br />4.3.1 COVER THICKNESS <br />As shown in Table 3, negative flux potential decreases as the cover section thins. <br />Due to the borrow material properties and their excellent geotechnical <br />is characteristics all alternative final cover designs (three, four and five-foot thick <br />sections) outperform the prescriptive design. Since a thinner 3 -foot thick cover <br />section is unlikely to be accepted by the regulatory agencies; due to erosion and <br />dessication distress, a proposed final cover thickness of 4 -feet was selected for the <br />Forward Sanitary Landfill alternative final cover design. <br />4.3.2 SATURATED HYDRAULIC CONDUCTIVITY <br />As shown in Table 3, net infiltration is calculated to vary only slightly over the <br />range of weathered saturated hydraulic conductivities measured from the existing <br />interim cover soils. In analyzing the sensitivity of other variables within this <br />section and for long-term modeling of the alternative final cover system, the <br />median saturated hydraulic conductivity of 3.3 x10"6 cm/sec was used. [It should <br />be noted that while the available soils are expected to yield this performance over <br />time, a prescriptive maximum hydraulic conductivity of less than 1x10"6 cm/s will <br />be established as the minimum criteria for initial final cover construction.] <br />4.3.3 WATER APPLICATION RATE <br />For modeling purposes the rainfall magnitude and duration (the application rate) <br />was estimated in a fashion believed to conservatively represent typical anticipated <br />conditions. Calculated net flux through several modeled profiles showed only <br />M <br />C:\2003-033\EDOM HILL ALTERNATIVE COVER.DOC\6/16/2005 <br />Geologic Associates <br />