1010 N BROADWAY EVCC 2018-01-01 MF Import

PROPOSED LIBERTY HALL,EVERETT COMMUNITY COLLEGE '? Everett,Washington EXECUTIVE SUMMARY This report contains the results of our geotechnical engineering services for use in the design of the proposed Liberty Hall at Everett Community College. The project consists of constructing a new 3-story, 70,000 square foot building, located west of Broadway and south of the Student Health and Fitness Center currently under construction. The project will require demolition of the existing Royal Motor Inn and the Triangle parking lot. Subsurface Conditions The subsurface conditions at the site were evaluated by drilling seven borings in the vicinity of the proposed building footprint. Based on our explorations,the near surface soils generally consist of fill overlying soft to hard silt (Transitional Bed deposits) and dense to very dense silty sand (Advance Outwash deposits). The depth to the dense native soils is variable across the building footprint. Dense soils will exist at footing subgrade elevation under the west end of the building, but are up to 12 feet deep under the east end of the building. Loose fill and/or soft native soils exist over the dense native soils under the east end of the building. Perched groundwater was encountered in six of the seven borings. Seismic Design In accordance with the 2009 International Building Code(IBC),the site is classified as Site Class D. Reuse of On-Site Materials The on-site soils are not suitable for reuse as structural fill. For planning purposes,we recommend that imported Gravel Borrow be used for structural fill on the project. Recycled concrete and asphalt pavement from the existing parking lot may be reused as structural fill on the project except under building foundations and in future landscaping areas. Temporary Cut Slopes Excavations for the first floor level will require cuts up to about 9 feet deep in the western portion of the building footprint. These cuts can be made as temporary open cut slopes depending on site constraints. Temporary unsupported cut slopes more than 4 feet high may be inclined at 2H:1V (horizontal:vertical)maximum steepness. Foundation Support Unsuitable soils below the building footprint should be improved by either (1) removing compressible fill and silt/clay soils from below the building foundations, (2) installation of drilled aggregate piers and placement of a 2-foot thick layer of gravel-borrow between the floor slab and aggregate piers,or(3) using deep foundations to support foundations. Foundation Design(Shallow Foundations) The building can be supported on conventional spread footings bearing on properly placed and compacted structural fill or on drilled aggregate piers. Footings bearing on undisturbed dense glacial soils within Zone 1 (see Figure 3) may be designed using an allowable soil bearing value GEOENGINEERSg June 10,2010= Page ES-i File No.5835.010.00