304 SE EVERETT MALL WAY PANERA BREAD Geotech Report 2025-07-25

KA No.092-12004 August 24,2012 Page No. 8 Seasonal rainfall, water run-off, and the normal practice of watering trees and landscaping areas around the proposed structures, should not be permitted to flood and/or saturate footings. To prevent the buildup of water within the footing areas, continuous footing drains (with cleanouts) should be provided at the bases of the footings. The footing drains should consist of a minimum 4-inch diameter rigid perforated PVC pipe, sloped to drain, with perforations placed near the bottom and enveloped by 1-inch sized washed rock in all directions and filter fabric to prevent the migration of fines into the drain. Resistance to lateral footing displacement can be computed using an allowable friction factor of 0.35 acting between the bases of foundations and the supporting subgrade. Lateral resistance for footings can alternatively be developed using an allowable equivalent fluid passive pressure of 250 pounds per cubic foot (pcf) acting against the appropriate vertical footing faces (neglecting the upper 12 inches). The allowable friction factor and allowable equivalent fluid passive pressure values include a factor of safety of 1.5. The frictional and passive resistance of the soil may be combined without reduction in determining the total lateral resistance. A 1/3 increase in the above values may be used for short duration,wind and seismic loads. Deep Foundations—Pin Piles: Alternatively, it may be feasible to install a deep foundation system to transfer the building loads through the undocumented fill and soft/loose soils to be supported on the dense to very dense native glacial soils. The deep foundation system could be used to limit excavation at the site. Steel pin piles with a 4-inch diameter should be driven using a track-mounted hydraulic hammer,with an energy rating of at least 1,100 foot-lb. For this pile and hammer size, we recommend a design capacity of eight tons for each pile driven to refusal. The refusal criterion for this pile and hammer size is defined as less than one inch of movement during 20 seconds of continuous driving. The above design capacities for the 4-inch diameter piles are based on theoretical numerical pile driving analysis. If higher pile capacities are desired, we recommend that a minimum of one pile load test be performed to verify the higher design values. We recommend that the piles be loaded to at least 200 percent of the design capacity, and that we be retained to observe the pile load test. A factor of safety of two could be used to reduce the ultimate capacity achieved from the pile load test to a design capacity. Actual pile load test procedures could be discussed with your contractor at the time of testing. We do not recommend using a design capacity of more than 10 tons for 4-inch pin piles, regardless of the outcome of the pile load tests. We should be retained to review final plans, monitor installation of the piles, and evaluate pile refusal as well as pile load tests. Final pile depths should be expected to vary somewhat and will depend on the actual depth of the existing fill and nature of the underlying competent soils and ground water conditions. The pin piles should penetrate a minimum of five feet into the dense or better native soil in order to develop the design capacity. Piles that do not meet this minimum embedment criterion or piles that are obstructed on debris in the fill should be rejected, and replacement piles should be driven after consulting with the structural engineer on the new pile locations. Krazan&Associates,Inc. Eleven Offices Serving The Western United States