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"is unreasonable and unnecessarily burdensome and will cost substantially more than alternatives which meet the criteria in § 20080 (b)" 1.2 PURPOSE The purpose of this report is to evaluate the feasibility of constructing a prescriptive final cover in conformance with 27 CCR Section 21090(a) over the Phase I final closure area of the FSL but then allowing the cover to weather over time. As a result of the anticipated weathering, the final cover section is expected to evolve into an alternative final cover hosting a relatively deep rooting plant community and exhibiting a saturated hydraulic conductivity in excess of the prescriptive minimum standard. As such, this report presents an evaluation of whether the performance of the proposed alternative final cover performance is consistent with the performance goals addressed by the prescriptive standards,by yielding equivalent or superior protection against water quality impairment. 1.3 SCOPE OF WORK Work completed during this study included: 1. Collection of bulk soil samples from the proposed borrow source adjacent to the FSL (Figure 1); 2. Collection of in-situ ring samples from the existing cover soils; 3. Determination of the thickness of the existing cover over the North and Northwest slope closure footprint(Figure 1); 4. Laboratory testing and evaluation of existing interim cover and potential borrow soils in accordance with ASTM standards; 5. Selection of representative characteristics of soils derived from the on-site borrow source and the existing cover; 6. Obtaining local climatological data for the area of the FSL; 7. Selection of a computer program to simulate unsaturated flow through the soil profile; 8. Computer modeling of the proposed non-prescriptive cover system using the laboratory soil test results and historic local climatic data; 9. Preparation of this report and the attached CQA Plan(Appendix D). 2.0 FIELD INVESTIGATION In early May, 2005, GeoLogic Associates, Inc. (GLA) conducted a field investigation of the on-site borrow source and existing interim cover over the proposed closure footprint of the North and Northwest slopes of the FSL. During these investigations, the thickness of existing interim cover was measured (Figure 1) and representative soil samples were collected from each of the areas (Figure 1, Appendix A). The soil samples collected were tested to identify the input parameters necessary for modeling the infiltration performance of these soils when used in final cover construction at the site. -2- C:\2005 0082\FORWARD/FonvarJCOVER.DOC\7/13/2005 GeoLogic Associates