9300 W MALL DR 2018-01-01 MF Import

� G & M Investments P-3161 November 11, 1993 Page 8 desired behind the walls, then we will need to be given the wall dimensions and slope of the backfill in order to provide the appropriate design earth preseures. Heavy construction equipment should not be operated behind retaining and foundation walls within a distance equal to the height of the wall, unless the walls are deaigned for the additional lateral pressures resulting from the equipment. Plavement and compaction of retaining wall backfill should be accomplished with hand-operated equipment. Retaining Wall Backfill Backfill placed behind retaining or foundation walls should be free-draj.ning structural fill containing no organics. This backfill shou].d r_ontain no more than five (5) percent silt or clay particles and have no particles greater than four (4) inches in diameter. The percentage cf particles passing the No. 4 sieve should be between 25 and 70 percent. The purpose of these backfill requirements is to ensure that the design cr.iteria for the 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 relatively impermeable soil o: topsoil, or the surface should be paved. The sub-section entitled GENFRAL EARTfiWORK AND STRUCTURAL FILL contains recommendations regarding placement and compaction of structural fill behind retaining and foundation walls. EXCAVATIONB AND SLOPES In no case should excavation slopes be greater than the limits specified in local, state, and national gavernment satety regulati.oas. Temporary cuts to a depth of about four (4) feet in unsaturated soils may be attempted vertically. Based upon Washington Administrative Code (WAC) 296, Part N, the soil type at the site would be classified as Type B, and therefore slapes greater than four (4) feet cannot be excavated steeper than 1:1 (Horizontal:Vertical). GEOTECH CONSULTANTS, INC.