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Drilled Piers <br /> Dead end structures and bus structures may be supported on drilled piers. The piers may be designed <br /> using the CAISSON computer program with input parameters shown in Table 3 of this report. The drilled <br /> piers should extend into native soils in the vicinity of where on-site infiltration is planned. <br /> Retaining Walis <br /> Retaining walls will be built at the site as a part of this project. Many variations in wall design may be ; <br /> applicable including cast-in-place concrete cantilevered walls, soldier pile walls, and MSE walls. Gravity <br /> walls, such as Gabion, crib-lock, and ecology block walls may also be used. MSE walis having a vegetated <br /> face, such as Tensar's SierraScape� retaining wall system, may be desirable adjacent to open spaces. <br /> Vegetated reinforced steepened slopes, such as Tensar's Sierra� Slope retention system, may also be <br /> desirable along the Interurban Trail near the northwest corner of the 115kV yard. Although not a <br /> structural wall, rockeries may be used for grade changes across the site, typically if less than 4 feet high. <br /> Below grade walls and retaining walls should be designed with adequate drainage. We recommend the <br /> following equivalent fluid weights for design of cast in-place concrete cantilevered walls: <br /> ■ Allowable passive: 350 pounds per cubic foot(pcf) <br /> ■ Active: 35 pcf <br /> ■ At rest: 55 pcf <br /> � Infiltration <br /> I <br /> The 115kV and 230kV yards may be designed to infiltrate water from incidental (passive) rainfall and by <br /> engineered (active) systems. Stormwater infiltration should not be directed to the substation yard where <br /> structures will be supported on the old fill as water infiltration may induce settlement of loose soils, such <br /> as under the central and eastern areas of the 115kV yard. A_passive_design infiltration_rate,of no more _ <br /> -- . __.�_,__...�._ <br /> ' than 0.25jn�h�s�er,hour (,�it1�.�1d_�veathe,re_till and not more than 0.1 inches per hour (dense to very <br /> v--.�.�_._._. _ ----_ __ _ <br /> dense glacial till) may be used within the planned 115kV and 230kV yards, as shown on the Site Plan, <br /> ` Figure 2. A..dPci n anfiltrat�e_rate of_no more_�h.a�p,9�5_inches hour in_weathered ti.11 and Q 1 in�es�2�r. <br /> : ,_/. ...__ <br /> I hour in,.��wPathe�ed.�iU.�na�.�e_�d for design of stormv�a�-#�iJiti�s.l8r,��ed���ide_ e sub�iig.�1� <br /> ya rds. <br /> _�—�-- <br /> GEOENGINEER� October24,2014 Page ES-3 <br /> Fle No.0482-027-02 <br />