909 51ST PL SW Geotech Report 2022-10-25

Geotechncial Engineering Evaluation Garcia Property Additions Everett, Washington NGA Project No. 1040218 June 22, 2018 Page 10 recommendations for minimum hammer size and refusal criteria is essential for obtaining a successful outcome. Our explorations encountered loose undocumented fills within the planned development area. Since large objects and debris are present within the fill, there is a substantial possibility that this material may obstruct some piles at shallow depths. There should be contingencies in the budget and design for additional/relocated piles that may be obstructed by possible debris in the fill. Final pile depths should be expected to vary somewhat and will depend on the nature of the underlying soils. The pin piles should advance a minimum of 12 feet below current grade and also meet the above refusal criterion in order to provide the recommended design capacity. This should be determined in the field by the contractor under the supervision of NGA. Piles that do not meet this minimum embedment criterion should be rejected, and replacement piles should be driven after consulting with the structural engineer on the new pile locations. The piles should be spaced a minimum of three feet apart to avoid a grouping effect on the piles. Due to the relatively small slenderness ratio of pin piles, maintaining pin pile confinement and lateral support is essential in preventing pile buckling. Pin piles should be suitably embedded into the reinforced concrete. The structural engineer should design the connections of the piles to the foundations. We should be retained to review final plans and to monitor installation of the pin piles during construction. Structural Fill General: Fill placed beneath foundations, pavement, or other settlement -sensitive structures should be placed as structural fill. Structural fill, by definition, is placed in accordance with prescribed methods and standards, and is monitored by an experienced geotechnical professional or soils technician. Field monitoring procedures would include the performance of a 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 prior to beginning fill placement. Sloping areas to receive fill should be benched using a minimum 8-foot wide horizontal benches into competent soils. 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 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). Some of the more granular on -site soils may be suitable for use as structural fill; however, this will be highly dependent on the moisture content of the soil during construction. The use of the on -site soils as structural fill during wet weather will be very difficult, if not impossible. We should be retained to evaluate all proposed structural fill material prior to placement. NELSON GEOTECHN/CAL ASSOCIATES, INC.