4933 GLENWOOD AVE 2016-01-01 MF Import

Jordan Construction JN 00284 July 25, 2000 Page 6 to the above lateral soil pressures. lNhew sloping backfili is desired behind the walls, we will neec to be given the wall dimensio�s 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 he�ght of a wall, unless the walls are designed for the additicnal 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 walis from being overloaded by the higher soil forces that occur during compaction. Retaininq Wall Backfill Backfill placed behind �etaining 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 tl�e 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 buiid-up of hydrostatic pressure behind the walL lhe top 1Z to 1S inches ot the backtfll should consist of a compacted, relatively impermeabie soil or topsoil, or the surface should be paved. The ground surface must also slope away from backfilled walls to reduce the potential for surface water to percolate into the backfill. The sub-section entitled PERMANENT FOUNDATION AND RETAINING WALLS contains recommendations regarding the placement and compaction of structurai fill behind retaining and foundation walls. If moist conditions or some seepage through the walls are not acceptabie, 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 asph2lt emulsion is not considered waterproofing, but wiil 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 nat be made near property boundaries or existing utilities and structures. Based upon Washington Administrative Code (WAC) 296, Part N, the soil type at the subject site would be ciassified 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 recommendation is for the dense glacial tiil encountered approximately 6 to 7 feet below ?he existing grade. The soii type for the looser weathered and fill soils above the densP -j//�� % GEOTECH CONSULTANTS, INC. � _