3620 BROADWAY VERIZON 2019-01-11

Geotechnical Engineering Evaluation NGA File No.983917 Stadium Flowers Addition March 10,2017 Everett,Washington Page 7 We recommend that construction take place during the drier summer months if possible. However, if construction takes place during the wet season, additional expenses and delays should be expected due to the wet conditions. Additional expenses could also include the need for placing a blanket of rock spalls on exposed subgrades and construction traffic areas. The anthropogenic on-site soils will be very difficult to compact to structural fill specifications in wet conditions. We should be retained to evaluate proposed structural fill materials prior to construction. Temporary and Permanent Slopes Specific grading plans were not available at the time this report was prepared. Temporary cut slope stability is a function of many factors, including the type and consistency of soils, depth of the cut, surcharge loads adjacent to the excavation, length of time a cut remains open, and the presence of surface water or groundwater. It is exceedingly difficult under these variable conditions to estimate a stable, temporary, cut slope angle. Therefore, it should be the responsibility of the contractor to maintain safe slope configurations since they are continuously at the job site, able to observe the soil and groundwater conditions encountered,and able to monitor the nature and condition of the cut slopes. The following information is provided solely for the benefit of the owner and other design consultants and should not be construed to imply that Nelson Geotechnical Associates, Inc. assumes responsibility for job site safety. Job site safety is the sole responsibility of the project contractor. For planning purposes, we recommend that temporary cuts in the on-site soils be no steeper than 2 Horizontal to 1 Vertical (2H:1V). This assumes that the site can be effective dewatered. If significant groundwater seepage or surface water flow were encountered, we would expect that flatter inclinations would be necessary. We recommend that cut slopes be protected from erosion. The slope protection measures may include covering cut slopes with plastic sheeting and diverting surface runoff away from the top of cut slopes. We do not recommend vertical slopes for cuts deeper than four feet, if worker access is necessary. We recommend that cut slope heights and inclinations conform to appropriate OSHAIWISHA regulations. Permanent cut and fill slopes should be no steeper than 3H:1 V. However, flatter inclinations may be required in areas where loose soils are encountered. Permanent slopes should be planted and the vegetative cover should be maintained until it is established. We should review plans and visit the site to evaluate excavations for this project. NELSON GEOTECHNICAL ASSOCIATES, INC.