2621 ROCKEFELLER AVE Geotech Report 2022-10-25

! 1 la Foundation Settlement 11 We estimate that the total postconstruction settlement of footings founded on the dense to very dense glacial soils or structural fill extending to the dense to very dense glacial soils, as recommended above, should be less than 3/4 inch. Differential settlement between comparably loaded column footings or along a 25-foot section of continuous wall footing should be less than %z inch. We expect most of the footing settlements will occur as loads are applied. Loose or disturbed soils not removed from footing -- excavations prior to placing concrete will result in additional settlement. Construction Considerations Immediately prior to placing concrete, all debris and loose soils that accumulated in the footing excavations during forming and steel placement must be removed. Debris or loose soils not removed from the footing excavations will result in increased settlement. If wet weather construction is planned, we recommend that all footing subgrades be protected using a lean concrete mud mat or crushed gravel. The mud mat or gravel layer should be placed the same day that the footing subgrade is excavated and approved for foundation support. 11 Lateral Resistance Lateral loads can be resisted by passive resistance on the sides of the footings and by friction on the base of the footings. Passive resistance should be evaluated using an equivalent fluid density of 350 pcf where footings are poured neat against native soil or are surrounded by structural fill compacted to at least 95 percent of MDD, as recommended. Resistance to passive pressure should be calculated from 1 the bottom of adjacent floor slabs and paving or below a depth of 1 foot where the adjacent area is unpaved, as appropriate. Frictional resistance can be evaluated using 0.4 for the coefficient of base friction against footings. The above values incorporate a factor of safety of about 1.5. ifIf soils adjacent to footings are disturbed during construction,the disturbed soils must be recompacted, otherwise the lateral passive resistance value must be reduced. Footing Drains 11 We recommend that perimeter footing drains be installed around the proposed apartment building. The perimeter drains should be installed at the base of the exterior footings, as shown on Figure 3. The perimeter drains should be provided with cleanouts and should consist of at least 4-inch-diameter 11 perforated pipe placed on a 4-inch bed of, and surrounded by, 6 inches of drainage material enclosed in a non-woven gedtextile fabric such as Mirafi 140N (or approved equivalent) to prevent fine soil from migrating into the drain material. The footing drain pipe should be installed at least 18 inches below the 11 top of the adjacent floor slab. The drainage material should consist of washed 3/8-inch to No. 8 pea gravel or "Gravel Backfill for Drains" per Section 9-03.12(4) of the 2006 WSDOT Standard Specifications. We recommend that the drainpipe consist of either heavy wall solid pipe(SDR-35 PVC, ` or equal) or rigid corrugated smooth interior polyethylene pipe (ADS N-12, or equal). We also recommend against using flexible tubing for footing drainpipes. The perimeter drains should be sloped to drain by gravity, if practicable, to a suitable discharge point, preferably a storm drain. We recommend that the cleanouts be covered,and be placed in flush mounted utility boxes. Water collected in roof downspout lines must not be routed to the footing drain lines. j' File No.12547-001-00 Page 11 February 3,2006 GEOENGWEER