1901 MERRILL CREEK PKY 2018-01-01 MF Import

Concrete Cantilever Retaining Walls Reinforced concrete cantilever retaining walis could be used in cut slope or fitl embankment areas. This type of retaining structure is relatively settlement-sentitive and suitable foundation support is impo�tant. We anticipate that native soils found in the projcet area will provide � adequate foundation support for concrete cantilever retaining walls. ' Construction of cantilever retaining walls require excavations having a width approximately equal to 1/3 to 1/2 of the wall height. As mentioned previously, temporary cut slopes will likely � be on the order of O.SH:1V to 1H:1V depending on the soil type. If ezisting slopes or other constrainu preclude accomplishing an open excavation for construction of retaining strucmres, r: temporary shoring, possibly consisting of soldier beams and lagging, can be considered to temporarily support the excavation. Structural Eenh Watls "Structural ear[h wall" is the generic name used by Wazhington State Department of Transportation(WSDO'I)for retaining walls that utilize reinforr.ing msterials such as metal strips, polymer grids, or geotextiles that are attached to a facing element and embedded in a portion of the retained fill behind the wall. The reinforcing material interacts with conttolled granulaz fill � material behind the wall to provide resistance to horizontal loads. Numerous snuctural earth wall systems have been developed to date,most of which aze proprietary(Keystone,Reinforced Earth, �,� Hilfiker, Cornerstone, and others). Ezperience with these systems in Washington State and �' around the United Stata indicates that they are a cost effectivo retention system for fill i..; embank �ents. We could develop detailed design drawings of a st�uctural earth wall if this is a , prefettec, r. .aining wall system. Struc�ural earth walls could be used ro retain any of the fill embantanents currently planned . for the development. Thae types of walls may be used in cut slope areas as well, although they require additional excavation behind the wall face for placement of r�inforcing materials. We utimate that the width of the ezcavation that will be required in glacial till cut slope areas will be less than 6 fat for wall heights up to 12 feet. Permenent Shoring Walls There may be some local cut slope sections where slope heights and proximiry to planned structures do not leave su�cient space to construct either a gtavity ot cantilever ataining structure. For these casa, some type of Qermanent shoting wall could be cot�sidered. Petmanent shoring walls often consist of soldier beams, lagging, and possibly tiebacks, depending on the height of the cut. Treated timber, concrete or other suitable material is used as a facing. This rype of structure involva the least amount of disturbance to the ground surface behind the wall. PAVEMENT RECOMMENDATIONS We recommend that the pavement section in automobile parking areas consist of a minimum of 2 incha of Class B azphalt concrete over a minimum of 4 incha of crushed rock. The G e a E n { i n e e r s l4 File No.1�60-006-77•11�O/l 11297