1901 W MUKILTEO BLVD Geotech Report 2022-10-25

Scriven Residence Improvements-REVISED NGA File No 974316 1901 West Mukilteo Boulevard November 29,2016 Everett,Washington Page 10 significant surface water flow is encountered during construction, this flow should be diverted around areas to be developed,and the exposed subgrades should be maintained in a semi-dry condition. If wet conditions are encountered, alternative site stripping and grading techniques might be necessary. These methods could include using large excavators equipped with wide tracks and a smooth bucket to complete site grading and covering exposed subgrade with a layer of crushed rock for protection. If wet conditions are encountered or construction is attempted in wet weather, the subgrade should not be compacted as this could cause further subgrade disturbance. In wet conditions it may be necessary to cover the exposed subgrade with a layer of crushed rock as soon as it is exposed to protect the moisture sensitive soils from disturbance by machine or foot traffic during construction. The prepared subgrade should be protected from construction traffic and surface water should be diverted around prepared subgrade. Shallow groundwater, if encountered, should be intercepted with cut off drains and routed around the planned grading area, or the groundwater should be controlled with sump-pumps or dewatering systems. Addition Foundations We recommend that the proposed addition structure be supported on 2-inch pin piles to transfer foundation loads to the underlying native competent materials found below the fill. Our explorations did not encounter any significant debris within the existing fill, however there is a possibility that some obstruction 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. For 2-inch diameter pipe piles driven to refusal using a hand-held, 140-pound jackhammer, we recommend a design axial compression capacity of two tons for each pile. The refusal criterion for this pile and hammer size is defined as less than one inch of movement during 60 seconds of continuous driving. We recommend using galvanized extra strong (Schedule 80) steel pipe. Maintaining these recommendations for minimum hammer size and refusal criteria is essential for obtaining a successful outcome. Final pile depths should be expected to vary somewhat and will depend on the depth of the loose material, the nature of the underlying competent soils, and groundwater conditions. The pin piles should penetrate a minimum of ten feet into the competent native glacial soils below the fill material in order to develop NELSON GEOTECHNICAL ASSOCIATES, INC.