4730 COLBY AVE YMCA Geotech Report 2025-04-14

Subsurface Exploration, Geologic Hazard, and Snohomish County YMCA Geotechnical Engineering Report Everett, Washington Design Recommendations 13.1 Passive Resistance and Friction Factors Lateral loads can be resisted by friction between the foundation and the natural soils or supporting structural fill soils, and by passive earth pressure acting on the buried portions of the foundations. The foundations must be backfilled with structural fill and compacted to at least 95 percent of the maximum dry density to achieve the passive resistance provided below. We recommend the following allowable design parameters: • Passive equivalent fluid = 250 pcf • Coefficient of friction=0.35 14.0 PAVEMENT RECOMMENDATIONS Pavement areas should be prepared in accordance with the "Site Preparation" section of this report. If the stripped native soil or existing fill pavement subgrade can be compacted to a firm and unyielding condition as determined by the geotechnical engineer, no additional overexcavation is required. Soft or yielding areas should be overexcavated to provide a suitable subgrade and backfilled with structural fill. The pavement sections included in this report section are for driveway and parking areas onsite, and are not applicable to right-of-way improvements. At this time, we are not aware of any planned right-of-way improvements; however, if any new paving of public streets is required, we should be allowed to offer situation-specific recommendations. For driveways and private paving serving passenger cars, we recommend a paving section consisting of 3 inches of Class 1/2-inch Hot Mix Asphalt (HMA) underlain by 4 inches of crushed surfacing base course (CSBC). Alternatively asphalt treated base (ATB) or Class 3/4-inch HMA could be used for construction access followed by repair of any construction damage and final surfacing. If this alternative is used, we recommend a minimum of 2 inches of CSBC to serve as a working surface and a minimum of 3 inches of ATB. Final surfacing should consist of 2 inches of Class 1/2-inch HMA after any construction damage has been repaired. Paving for heavy traffic areas, such as bus lanes, fire lanes, and access for garbage and food service trucks, should consist of 4 inches of Class %-inch HMA above 6 inches of crushed rock base. If an ATB section is desired, we recommend a 2-inch-thick working surface of crushed rock, topped by 4 inches of ATB and 3 inches of Class %-inch HMA. Alternatively, a rigid pavement section consisting of 6 inches of CSBC under 5 inches of concrete pavement with reinforcement may be used for heavy traffic areas. February 26, 2018 ASSOCIATED EARTH SCIENCES,INC. AWR/ms-170671E001-2-Projects12 01 706 71\KEIWP Page 16