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Geotechnical Engineering Evaluation NGA File No.961916 Mason Residence Addition and Deck August 24, 2016 Everett, Washington Page 11 I'2,S estimate a stable, temporary, cut slope angle. Therefore, it should be the responsibility of the contractor to maintain safe slope configurations since he is 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 2.0 Horizontal to 1 Vertical (2.0H:1V). 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 OSHA/WISHA regulations. Pin Piles We recommend that the proposed basement addition and deck foundations within the vicinity of the top of slope be supported on 4-inch pin piles to transfer foundation loads to the underlying native competent materials found below the fill. Due to potential site access constraints for the larger equipment needed to install the 4-inch pin piles, it may be necessary to support the southern upper deck foundations on 2-inch pin piles that are installed with hand-held equipment. Our explorations did not encounter any significant debris within the existing fill, however there is a possibility that some obstructions within the fill may impede some of the piles. There should be contingencies in the budget and design for additional/relocated piles to replace piles that may be obstructed by debris. We also recommend that excavation equipment be available on site during pile installation so that shallow obstructions can be removed from the planned pile locations. We recommend that the four-inch pipe piles be utilized and should be driven using a tractor-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 15 seconds of continuous driving at a rate of 550 blows per minute or higher. We recommend using galvanized schedule 40 pipe for the 4-inch pin piles. Maintaining these recommendations for minimum hammer size and refusal criteria is essential for obtaining a successful outcome. NELSON GEOTECHNICAL ASSOCIATES, INC.