4626 HARBOR LN 2018-01-02 MF Import

Geotechnical Engineering 1?valuation NGA File No.853512 Fox Residence Underpinning and Retaining Wall Design August 3, 2012 Everett, Washington Page 10 representative number of in -place density tests to document the attainment of the desired degree of relative compaction. The area to receive the fill should be suitably prepared as described in the Site Preparation and Grading subsection of this report prior to beginning fill placement. Sloping areas to receive structural till should be benched prior to fill placement to key the fill into the slope. the benches should be Icvel and have a minimum width of six to eight feet. The benches should be constructed by cutting into the native sloping ground, then fill can be placed on the level benches. Materials: Structural fill should consist of a good quality, granular soil, free of organics and other deleterious material, and be well graded to a maximum size of about three inches. All-weather structural fill should contain no more than five -percent fines (soil finer than U.S. No. 200 sieve, based on that fraction passing the U.S. 3/4-inch sieve). The use of some of the on -site soils as structural rill may be feasible, but will be highly dependent on moisture and organic contents of the material at the time construction takes place. We should be retained to evaluate proposed structural fill material prior to placement. Fill Placement: Following subgrade preparation, placement of structural fill may proceed. All fill placements should be accomplished in uniform lifts up to eight inches thick. Each lift should be spread evenly and be thoroughly compacted prior to placement of subsequent lifts. All structural fill underlying building areas and pavement subgmde should be compacted to a minimum of 95 percent of its maximum dry density. Maximum dry density, in this report, refers to that density as determined by the ASTM D-1557 Compaction Test procedure. The moisture content of the soils to be compacted should be within about two percent of optimum so that a readily compactible condition exists. It may be necessary to over -excavate and remove wet soils in cases where drying to a compactable condition is not feasible. All compaction should be accomplished by equipment of a type and size sufficient to attain the desired degree of compaction. Site Drainage We recommend that all drains on the property including roof downspout drains, footing and yard drains, the existing drain under the walkway, and the new drain associated with the new retaining wall be directed to a main catch basin located at the approximate location indicated on Figure S. A pipe should be tightlined from the catch basin down to a relatively level area north of the residence to a level spreader. NELSON GEOTECHNICAL ASSOCIATES, INC.