202 ALDER ST Geotech Report 2025-07-30 (2)

Proposed View Ridge Subsurface Exploration, Geologic Hazards, Infiltration Potential, Elementary School Replacement and Preliminary Geotechnical Engineering Report Everett, Washington Preliminary Design Recommendations previously discussed. We recommend that an allowable bearing pressure of 3,000 pounds per square foot (psf) be used for design purposes, including both dead and live loads. An increase of one-third may be used for short-term wind or seismic loading. Higher foundation soil bearing pressures are possible for foundations supported entirely on undisturbed advance outwash. For foundations supported entirely on undisturbed advance outwash, an allowable foundation soil bearing pressure of 5,000 psf may be used. For structures that are supported by a combination of existing fill and undisturbed native sediments, the lower allowable foundation soil bearing pressure of 3,000 psf should be used for all foundations. Perimeter footings should be buried at least 18 inches into the surrounding soil for frost protection. However, all footings must penetrate to the prescribed bearing stratum, and no footing should be founded in or above organic or loose soils. All footings should have a minimum width of 18 inches. It should be noted that the area bound by lines extending downward at 1H:1V from any footing must not intersect another footing or intersect a filled area that has not been compacted to at least 95 percent of ASTM:D 1557. In addition, a 1.5H:1V line extending down from any footing must not daylight because sloughing or raveling may eventually undermine the footing. Thus, footings should not be placed near the edge of steps or cuts in the bearing soils. Anticipated settlement of footings founded as described above should be on the order of 3/4 inch or less. However, disturbed soil not removed from footing excavations prior to footing placement could result in increased settlements. All footing areas should be inspected by AESI prior to placing concrete to verify that the design bearing capacity of the soils has been attained and that construction conforms to the recommendations contained in this report. Such inspections may be required by the governing municipality. Perimeter footing drains should be provided, as discussed under the "Drainage Considerations" section of this report. 11.1 Drainage Considerations Foundations should be provided with foundation drains. Drains should consist of rigid, perforated, polyvinyl chloride (PVC) pipe surrounded by washed pea gravel. The drains should be constructed with sufficient gradient to allow gravity discharge away from the proposed buildings. Roof and surface runoff should not discharge into the footing drain system, but should be handled by a separate, rigid, tightline drain. In planning, exterior grades adjacent to walls should be sloped downward away from the proposed structures to achieve surface drainage. The site has the potential to experience a perched ground water layer within the existing fill, above the underlying advance outwash. These conditions have the potential to result in poor September 22, 2010 ASSOCIATED EARTH SCIENCES, INC. BWG/tb-KE700255A2-ProjectsL201002551KEtWP Page 18