9512 EVERGREEN WAY 2022-08-29 - Laserfiche WebLink

May 4, 2017 HWA Project No. 2017-036-21 Municipal Code, potential landslide hazard areas include those areas defined as high and very high/severe risk of landslide hazard in the Dames and More Methodology for the Inventory, Classification and Designation of Geologically Hazardous Areas, City of Everett, Washington, July 1, 1991. Our review of this map indicates the project site is mapped as having a very low potential for landslide hazard. In No potential landslide hazard areas were identified on site during our geologic reconnaissance. 4 CONCLUSIONS AND RECOMMENDATIONS 4.1 GENERAL The results of our field investigations indicate that the project site is underlain by up to 5 feet of fill soils, depending upon location. Within the location of the proposed new building footprint, our borings indicate depth to dense till ranges from 3.5 to 5 feet (see borings logs: HH-3, HH-5). Building foundations should be founded on the very dense glacial till soils or structural fill placed over the very dense glacial till soils. Typical spread or strip footings may be used to support the new library building structure. Our recommendations pertaining to foundation design and construction are presented in Section 4.2. Seismic design considerations and parameters are presented in Section 4.3. Construction considerations are presented in Section 4.6. 4.2 LIBRARY BUILDING FOUNDATION DESIGN The proposed library structure may be supported on conventional strip and spread footings bearing directly on dense native soils, or on properly compacted structural fill, consisting of Gravel Borrow, as specified in the 2016, WSDOT Standard Specification Section 9-03.14(1). The recommended compaction level for structural fill placed under footings and grade -supported slab levels is 95% Modified Proctor maximum dry density (per ASTM D 1557). We recommend a maximum allowable bearing capacity of 3,000 psf be used for design of the footing foundations founded on weathered glacial till, non -weathered glacial till, or properly compacted structural fill. For short-term wind and seismic loading conditions, the allowable bearing pressure may be increased by 1/3 (to 4,000 psf). We recommend minimum footing widths of 18 and 24 inches for strip and square footings, respectively. Minimum footing widths may, therefore, govern footing design for this project. Footings should bear at least 24 inches below the lowest adjacent exterior grade to provide for frost protection. For development of lateral resistance to sliding, an allowable coefficient of friction of 0.5 may be assumed for spread and strip footings cast neat against properly prepared subgrade. For frost Final Geologic Assessment 6 HWA GeoSciences Inc.