1400 W MARINE VIEW DR WATERFRONT PLACE APARTMENTS Geotech Report 2022-10-25

• Settlement The ground improvement should be designed to limit static settlement to less than 1 inch and to limit seismic differential settlement to less than 2 inches over a distance of 50 feet. For shallow foundations bearing on improved ground,the static settlements will occur rapidly,essentially as loads are applied.Static differential settlements between footings is estimated to be half of the total settlement. Note that smaller settlements will result from lower applied loads. Lateral Resistance Lateral foundation loads may be resisted by passive resistance on the sides of footings and by friction on the base of the shallow foundations. For shallow foundations supported on improved ground,the allowable frictional resistance may be computed using a coefficient of friction of 0.35 applied to vertical dead-load forces. The allowable passive resistance may be computed using an equivalent fluid density of 300 pounds per cubic foot (pcf) (triangular distribution). These values are appropriate for foundation elements that are surrounded by structural fill. The above coefficient of friction and passive equivalent fluid density values incorporate a factor of safety of about 1.5. Foundation Drains We recommend that perimeter foundation drains be installed around the proposed buildings. The drains • should consist of 4-inch-diameter perforated collector pipe enveloped within a minimum thickness of 6 inches of gravel as described in the "Structural Fill" section of this report. The gravel backfill should be wrapped with a geotextile filter fabric meeting the requirements of construction geotextile for underground drainage (Section 9-33 of the 2016 Washington State Department of Transportation [WSDOT] Standard Specifications). We recommend using either heavy-wall solid pipe (SDR-35 polyvinyl chloride [PVC]) or rigid corrugated polyethylene pipe (ADS N-12 or equivalent) for the collector pipe. We recommend against using flexible tubing for footing drainpipe. The pipes should be laid with a minimum slope of 1/2 percent and discharge into an appropriate outfall. The pipe installations should include a cleanout riser with cover located at the upper end of each pipe run. We recommend that the cleanouts be covered and be placed in flush-mounted utility boxes or monuments. The foundation drainpipes should be located near the base of perimeter strip footings where discrete spread foundations are used. Permanent drainage systems should intercept surface water runoff at the top and/or bottom of cut and fill slopes to prevent runoff from flowing in an uncontrolled manner across the site. The finished ground surface adjacent to new and existing buildings should be sloped so that surface water runoff flows away from the structures and the nearby slopes. Roof drains should be tightlined to an appropriate discharge point and should not be connected to the footing or wall drains. • GEOENGINEERS� May31,2017 Page9 File No.22360-003-00