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Materials <br /> Concrete <br /> Concrete shall meet all requirements for Concrete Class 4000 as specified in Section 6- <br /> 02, with the following exceptions: <br /> 1. The slump of the concrete shall be between 5 inches to 7 inches when tested in <br /> accordance with WSDOT Test Method No. 804 at the jobsite. <br /> 2. The Contractor may use a water-reducing admixture in accordance with Section <br /> 6-02.3(3), the manufacturer's written recommendations, and as directed by the <br /> Engineer in order to attain a slump of 5 inches to 7 inches. <br /> Reinforcing Steel <br /> All reinforcing steel shall meet the requirements of Section 9-07 and in accordance with <br /> the Plans. <br /> Casing <br /> 1. The casing shall be of steel and of ample strength to withstand handling stresses <br /> and the external pressure of the caving soil and/or water. <br /> 2. The casing shall be watertight, smooth, and clean. <br /> 3. The inside diameter of the casing shall provide as a minimum the specified <br /> diameter of the shaft. No extra compensation will be allowed for concrete <br /> required to fill an oversized casing or an oversized excavation. <br /> Construction Sequence <br /> All excavation for the foundations in which the drilled shafts are to be constructed shall <br /> be completed before shaft construction begins. After shaft construction is completed, all <br /> loose or displaced materials shall be removed from around the shafts, leaving a clean <br /> solid surface to receive the footing concrete. <br /> Shaft Excavation <br /> 1. Shafts shall be excavated to the required depth as shown in the Plans or as directed <br /> by the Engineer. The excavation shall be completed in a continuous operation using <br /> equipment capable of excavating through the type of material expected to be <br /> encountered. (Boring Log is available at the office of the Engineer.) The concrete shall <br /> be placed immediately after the completion of shaft excavation and cleanout without any <br /> undue delay. <br /> 2. If the shaft excavation is stopped with the approval of the Engineer, the shaft shall be <br /> secured by the installation of a safety cover. It shall be the Contractor's responsibility to <br /> ensure the safety of the shaft and the surrounding soil and the stability of the sidewalls. <br /> A temporary casing should be used if necessary to ensure such safety and stability. <br /> 3. Where caving conditions are encountered, due to soft soils or water intrusion, no <br /> further excavation will be allowed until the Contractor selects a method to prevent <br /> ground movement. The Contractor may elect to place a temporary casing or use other <br /> methods approved by the Engineer. <br /> Swift Green Line—Corridor Stations Special Provisions SP120 <br /> May 2017 <br />