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Biological Resources, MONK&ASSOCIATES Impacts and Mitigations Tracy Facility Expansion Site 5.1 Corral Hollow Creek Protection Corridor Corral Hollow Creek and a buffer area around this creek would not be mined at any time during the life of the mining project. The creek corridor is set-aside from the mining plan in a protected area that ranges from approximately 500 feet wide on the western one-third of the creek alignment,to 300 feet wide on the eastern portion of the creek alignment. The total protected area within Corral Hollow Creek includes the 4.40-acre streambed plus a 10.58-acre set-aside within the steam channel. The total protected area would be 14.98 acres, minus the width of a temporary road crossing that would be installed and removed each year during a two-year period beginning the first year of excavation. Accounting for the road crossing,the total protected area in Corral Hollow Creek would be approximately 14.70 acres. 5.2 Site Perimeter Set-Back ter of the project site. The around the entire perimeter A 50-foot set-back has been designated p p J perimeter of the project site would not be mined,however,it would be used as an access road during the mining operation: The total acreage in the-perimeter set=back-equals 10.$8 acres'. 5.3 Excavation Plan Although much of the site has been previously mined and much of the topsoil was removed during those previous mining activities,there are still some isolated pockets of topsoils that vary in thickness up to two feet in depth. Those topsoils would initially be excavated and separately stockpiled within setback areas for later use during reclamation of the project. After removal of topsoils, excavation would proceed to remove the sand, gravel, and interbedded lean clays. General mining procedures would include creating temporary excavation slopes that would be p constructed at a gradient of 3/4 to 1 (horizontal to vertical) as allowed by the geotechnical slope stability analysis prepared by Kleinfelder(this slope stability study is available upon request). Final slopes of the mined site would be contoured 1.5:1 or flatter. .The maximum depth of excavation would be approximately 80 feet deep,which is well above the water table. During slope stability studies, test bores were drilled and water was not encountered in any of the test bores to depths of 125 feet. The exact depth of excavations would terminate upon reaching a thick natural clay layer that is present underneath the aggregate deposits at various depths. 5.3.1 EXCAVATION OF THE NORTH SITE Initial excavations on the project site would begin on the north side of Corral Hollow Creek in the year 2000 and proceed southward. Mining would be completed in this area by approximately the year 2001 and reclamation would be completed by the year 2002 (Table 1). The buffer of the north bank of Corral Hollow Creek would not be mined below elevation 240 and would form a barrier to water flows from Corral Hollow Creek into the northern reined site, even during 100- year plus"storm events. Where necessary a berm-would be constructed-to prevent flooding(this berm is shown in Appendix A, Figure 4). Mining would occur over a one to two-year period. I After the north area is mined,reclamation would include the re-spreading of topsoil into the 4