902 PINE ST NORTH SOUND BEHAVIORAL HEALTH TREATMENT CENTER 2025-11-04

GeoTest Services, Inc. November 16,2018 North Puget Sound Behavioral Health—Treatment Center Addition Job No. 18-0770 the structure is level in the direction of movement for a distance equal to or greater than I twice the embedment depth. The recommended value also assumes drained conditions that will prevent the buildup of ' hydrostatic pressure in the compacted fill. Foundations should include a drain system constructed in general accordance with the recommendations presented in the Foundation and Site Drainage section of this report. In design computations, the upper 12 , inches of passive resistance should be neglected if the soil is not covered by floor slabs or pavement. If future plans call for the removal of the soil providing resistance,the passive resistance should not be considered. I An allowable coefficient of base friction of 0.35, applied to vertical dead loads only, may be used between the underlying native soils or imported granular structural fill and the base of the footing. If passive and frictional resistance are considered together, one half the recommended passive soil resistance value should be used since larger strains are required to mobilize the passive soil resistance as compared to frictional resistance. We do not recommend increasing the coefficient of friction to resist seismic or wind loads. Utilities It is important that utility trenches be properly backfilled and compacted to reduce cracking or localized loss of foundation, slab, or pavement support. It is anticipated that excavations for new shallow underground utilities will be in dense native glacial till. I Trench backfill in improved areas (beneath structures, pavements, sidewalks, etc.)should consist of structural fill as defined earlier in this report. Outside of improved areas, trench backfill may consist of re-used native fill provided it can be compacted to the project specifications. Trench backfill should be placed and compacted in general accordance with the recommendations presented in the Fill and Compaction section of this report. I Surcharge loads on trench support systems due to construction equipment, stockpiled material, and vehicle traffic should be included in the design of any anticipated shoring system. The contractor should implement measures to prevent surface water runoff from entering trenches and excavations. In addition, vibration as a result of construction activities and traffic may cause caving of the trench walls. Actual trench configurations are the responsibility of the contractor. All applicable local, state, and federal safety codes should be followed. All open cuts must be monitored by the contractor during excavation for any evidence of instability. If instability is detected, 1 the contractor should flatten the side slopes or install temporary shoring. If groundwater or groundwater seepage is present, and the trench is not properly dewatered, the soil within the trench zone may be prone to caving, channeling, and running. Trench widths may be substantially wider than under dewatered conditions. Utility Trench Backfill Considerations I The native till on-site has the potential to be suitable for use as backfill material provided it is placed at or near optimum moisture contents. It should be noted, however, that the silt content within till soils are variable, and if the native soils are over optimum moisture, GTS anticipates that this native soil may require significant moisture conditioning to reduce moisture contents to a near optimum condition. Page 12 of 17