1020 N BROADWAY EVCC STUDENT HOUSING Geotech Report 2022-10-25

Proposal for Geotechnical Engineering Services Proposed Apartments: 1020 North Broadway, Everett, Washington September 27, 2017 Table 2—Capillary Break Gradation Sieve Size Percent Passing 3/4-inch 100 No. 4 0- 10 No. 100 0—5 No. 200 0—3 The capillary break should be placed on the subgrade that has been compacted to a dense and unyielding condition. A 10-mil polyethylene vapor barrier should also be placed directly below the slab. Construction joints should be incorporated into the floor slab to control cracking. 4.4 RETAINING AND BASEMENT WALL DESIGN PARAMETERS Retaining and basement walls should be designed to resist the lateral earth pressures exerted by the soils behind the wall. Proper drainage provisions should also be provided behind the walls to intercept and remove groundwater that may be present behind the wall. Our geotechnical recommendations for the design and construction of the retaining/basement walls are presented below. 4.4.1 Lateral Earth Pressures Cantilever walls should be designed for an equivalent fluid pressure of 35 pcf for a level backfill condition behind the walls assuming the walls are free to rotate. If the walls are restrained at the top from free movement, such as basement walls with a floor diaphragm, an equivalent fluid pressure of 45 pcf should be used for a level backfill condition behind the walls. Permanent walls should be designed for an additional uniform lateral pressure of 7H psf for seismic loading, where H corresponds to the buried depth of the wall. The recommended lateral pressures assume the backfill behind the walls consists of a free draining and properly compacted fill with adequate drainage provisions. 4.4.2 Surcharge Surcharge loads, where present, should also be included in the design of retaining walls. We recommend a lateral load coefficient of 0.3 be used to compute the lateral pressure on 17-233 1020 North Broadway Page 8 PanGEO,Inc.