10632 7TH AVE SE Geotech Report 2025-07-28

I June 6,2008 Serenity Meadows IAA Job No. 8A017 Page 11 constructed in lifts not more than 12 inches untilit is brought up to at least 6 inches above the groundwater table. This crushed rock base should then be topped with a 8-inch-minimum layer of filler and leveling course, consisting of 2-inch-minus crushed rock, compacted to a non- yielding state with a vibratory mechanical compactor. The construction of soil structural fill may then proceed over the filler and leveling course. UNDERGROUND UTILITY IN UNSTABLE SOILS Underground utility installation may encounter loose, unstable organic soils along the fringe of the wetland buffer zone. These unstable soils coupled with high groundwater, if encountered, may cave suddenly without warning. Trench blocks should be used, as required, for trench deeper than 4 feet in areas of unstable soils to prevent trench caving if the trench walls are not to be sloped back sufficiently to maintain slope stability. Loose fill and organic soils should be thoroughly removed from the utility trenches down to firth bearing soils. If encountered, groundwater in utility trenches should be directed into sump pits dug 2 to 3 feet deeper than bottom of the trenches,from which water can be pumped out of the trenches. The pumps should be housed in perforated metal or plastic pipes/barrels placed in the ' sump pits backfilled with washed gravel. The sump pits should be spaced closely enough to sufficiently lower the groundwater level and allow the trenches to be excavated to its finish grade. The sump pits should be filled with gravel or crushed rock after they are no longer needed for dewatering. The bottom of the trenches should be compacted with a vibratory compactor to a non-yielding state, and the trench lined with a layer of non-woven filter fabric to prevent fined- ' grained soils being washed into the more permeable trench backfill material. After the utility lines are laid, the trenches should be backfilled with 5/8-inch crushed rock or free-draining, granular soil to within about 12 to 18 inches of the finish ground. Crushed rock, if used, should be densified to a non-yielding state with a hoe-pack or a concrete vibrator. Granular soils, if used, should be compacted in lifts and to density per recommendations in the STRUCTURAL LIU & ASSOCIATES, INC.