4935 GLENWOOD AVE 2016-01-01 MF Import

Jordan Ccnstruction JN 00284 July 25, 2000 Page 6 to the above lateral soil pressures. Where sloping backfill is desired behind the walls, we will need to be given the wall dimensions and the slope of the backfill in order to provide the appropriate design earth pressures. Heavy construction equipment should not be operated behind retaining walls, foundation walls, and existing rockeries, within a distance equal to the height of a wall, unless the walls are designed for the additional lateral pressures resulting from the equipment. The wall design criteria assume that the backfill will be well-compacted in lifts no thicker than 12 inches. The compaction of backfill near the walls should be accomplished with hand-operated equipment to prevent the walls from being overloaded by the liigher soil forces that occur during compaction. Retaininp Wall Bac�ll Backfill placed behind retaining or foundation walls should be coarse, free-draining structural fill containing no organics. This backfill should contain no more than 5 percent silt or clay particles and have no gravel greater than 4 inches in diameter. The percentage of particles passing the No. 4 sieve should be between 25 and 70 percent. For increased protection, drainage composites should be placed along cut slope faces, and the walls should be backfilled with pervious soil. The purpose of these backfill requirements is to ensure that the design criteria for a retaining wall are not exceeded because of a build-up of hydrostatic pressure behind the wall. The top 12 to 18 inches of the backfill should consist of a compacted, relatively impermeable soil or topsoil, or the surtace should be paved. The ground surface must also slope away from backfilled walls to reduce the potential for surface water to percolate into the backfiil. The sub-section entitled PERMANENT FOUNDATION AND RETAIN/NG WALLS contains recommendations regarding the placement and compaction of structural fill behind retaining and foundation walis. If moist conditions or some seepage through the walls are not acceptable, waterproofing should be provided. This typically includes limiting cold-joints and wall penetrations, and using bentonite panels or membranes on the outside of the walls. Applying a thin coat of asphalt emulsion is not considered waterproofing, but will only help to prevent moisture, generated from water vapor or capillary action, from seeping through the concrete. EXCAVATIONS AND SLOPES Excavation slopes should not exceed the limits specified in local, state, and national government safety regulations. Temporary cuts to a depth of about 4 feet may be attempted vertically in unsaturated soil, if there are no indications of slope instability. Vertical cuts should not be made near property boundaries or existing utilities and structures. Based upon Washington Administrative Code (WHC) 296, Part N, the soil type at the subject site would be classified as Type B. Therefore, temporary cut slopes greater than 4 feet in height cannot be excavated at an inclination steeper than 1:1 (Horizontal:Vertical), extending continuously between the top and the bottom of a cut. This recommendati�n is for the dense glacial till encountered approximately 6 to 7 feet below the existing grade. The soil type for the looser weathered and fill soils above the dense GEOTECH CONSULTANTS,INC. �5