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the planned basin footprint, construction of access roads, and installation of security fencing around the site ' s upland perimeter , The second phase will include containment basin construction and related earthmoving operations and the installation of outlet structures and other design features . This phase, subject to the scheduling and budget priorities of the Jacksonville District Corps of Engineers, may not immediately follow completion of the first phase. However, perimeter fencing and in- place security procedures will secure the site before excavation , grading, and dike construction begin . The remainder of this section discusses each site preparation element in more detail . 2. 2. 1 Clearing and Grubbing The first phase of facility construction begins with clearing and grubbing of site vegetation . Although adding significantly to the initial facility construction cost, the removal of all woody vegetation from the basin interior will promote efficient settling within the basin . The trees and other woody vegetation that dominate the upland areas of Site IR- 14 (Figure 2 .2), if allowed to remain , would constrictor channelize flow through the containment basin . Cutting the trees, but allowing the roots to remain , would preclude the uniform excavation and grading of the basin interior . Either omission would necessarily restrictthe required excavation to the perimeter of the basin interior and thereby result in short-circuiting, reduced retention times, resuspension of sediment through increased flow velocities, and the deterioration of effluent quality . Moreover, a failure to clear existing vegetation will make the periodic removal of the dewatered dredged material more difficult. Therefore, clearing and grubbing the area within the containment basin footprint, as well as the areas of the access and perimeter service roads ( Section 2 . 3 . 5) and the perimeter ditch (Section 2 . 3 . 6) , should take place before construction . 2. 2. 2 Excavation and Grading The second phase of site preparation includes all earthmoving operations required to construct the containment dike and basin to the design geometry . Preliminary site design ( Figure 2 . 1 ) specifies excavating the containment basin interior to obtain the material required for initial dike and ramp construction . Excavating to an average elevation of - 0 .4 ft NGVD, or 4 . 1 ft below the existing mean grade elevation within the basin footprint (+3 . 7 ft NGVD ; Figure 2 . 3 ) will provide the needed 56 ,612 cy . Excavation set back 20 ft from the interior toe of the dike will ensure dike foundation stability . Excavation of the perimeter ditch 11