10901 27TH AVE SE Geotech Report 2025-07-29

Subsurface Exploration, Geologic Hazards, and Proposed James Monroe Elementary School Replacement Revised Geotechnical Engineering Report Everett, Washington Design Recommendations 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 95 percent of ASTM:D 1557 and is firm and unyielding, 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 on- site, 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. The exposed ground should be recompacted to 95 percent of ASTM:D 1557. If required, ' structural fill may then be placed to achieve desired subbase grades. Upon completion of the recompaction and structural fill, a pavement section consisting of 21/2 inches of asphaltic concrete pavement (ACP) underlain by 4 inches of 11/4-inch crushed surfacing base course is the recommended minimum in areas of planned passenger car driving and parking. In heavy traffic areas, a minimum pavement section consisting of 3 inches of ACP underlain by 2 inches of 5/8-inch crushed surfacing top course and 4 inches of 11/4-inch crushed surfacing base course ' is recommended. The crushed rock courses must be compacted to 95 percent of the maximum density, as determined by ASTM:D 1557. All paving materials should meet gradation criteria contained in the current Washington State Department of Transportation (WSDOT) Standard ISpecifications. Depending on construction staging and desired performance, the crushed base course material may be substituted with asphalt treated base (ATB) beneath the final asphalt surfacing. The substitution of ATB should be as follows: 4 inches of crushed rock can be substituted with 3 inches of ATB, and 6 inches of crushed rock may be substituted with 4 inches of ATB. ATB should be placed over a native or structural fill subgrade compacted to a minimum of 95 percent relative density, and a 11/2- to 2-inch thickness of crushed rock to act as a working surface. If ATB is used for construction access and staging areas, some rutting and disturbance of the ATB surface should be expected. The general contractor should remove affected areas and replace them with properly compacted ATB prior to final surfacing. 15.0 PROJECT DESIGN AND CONSTRUCTION MONITORING Our report is based on project plans that were current at the time it was written. We recommend that AESI perform a geotechnical review of the plans prior to final design completion. October 5, 2009 ASSOCIATED EARTH SCIENCES, INC. DWG/Id-KE09031243-Project Page 19 i