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3.Project Description extended as the pit becomes farther from the plant. No processing of material is planned in the pit bottom. Setbacks, Slopes and Depth Temporary slopes, other than along Blewett Road, Koster Road, and South Costa Ranch Road would be mined to a 3/4:1 slope. The mining areas along Blewett Road, Koster Road,and South — Costa Ranch Road and next to Hospital Creek would be mined to a 2:1 slope for slope protection near the Delta Mendota Canal and Hospital Creek and the two perimeter roads.Within two years after mining has been completed within a phase, the slope will be backfilled to 2:1 using overburden and interbeddedI clays. San Joaquin County Surface Mining Ordinance 9-1415.3k requires final slopes over 50 feet in vertical distance to have terraces and terrace drainage. Minimum final slopes may be 1 1/2:1. In lieu of this requirement,the applicant is requesting to build final slopes to a fully engineered 2:1 (horizontal to vertical) using overburden and interbedded clays with track-walk topsoil on the surface. Chapter 9-1415.3 of the San Joaquin County Ordinance for Quarry Excavations requires that slopes in excess of 50 feet have terraces with a maximum distance between terraces of 50 feet. Although stability has been demonstrated (see Section 4.7 Geology, Soils,and Seismicity), the project does not propose terraces and may _ need a variance or text amendment from San Joaquin County. It is proposed that all existing topsoil would be stockpiled and reused in final reclamation,with a _ waste shrinkage factor of 10 percent. This would result in 800,000 cubic yards of topsoil available, which would equate to 6 to 9 inches in depth of topsoil over all final slopes and pit bottom. The slopes would be hydroseeded with an appropriate seed mix for erosion control at a — time that would maximize vegetation growth for erosion protection. Hospital Creek Hospital Creek borders the southern boundary of the site and crosses the southwest comer of the site after passing over the Delta-Mendota Canal in a box culvert. Two options are proposed for _ mining near Hospital Creek, as follows: • Mining Plan Option 1: Leave Hospital Creek in place, mining both sides with a — 100-foot setback from the centerline of the creek to the top of the mining slope. Refer to Figure 3-3 (Mining Plan Option 1). • Mining Plan Option 2: A 100-foot high berm would be constructed out of both on-site and off-site materials along the line between the Phase III and Phase V areas and between the Phase VI and Phase VII areas. Refer to Figure 3-4(Mining Plan Option 2). This would create a large retention basin. The inlet and outlet would be — modified to become a spillway and an overflow. Hospital Creek would then be mined out within the project boundaries and the creek would flow directly into the large retention basin through a concrete spillway. The retention basin would be able to _ hold a maximum capacity of 18,000 acre-feet of water. If the basin were to completely fill up with water it would be discharged back to Hospital Creek at the RMC Pacific Vernalis Quarry Mining and Reclamation Project 3-20 ESA/203015 Draft Environmental Impact Report May 2006