4. A ten-story steel-frame office building with a 200 ft x 200 ft footprint is to be built on a site underlain by alluvial sands and silts. These soils are fairly uniform and probably have good engineering properties. The building will have one 12-ft deep basement and will probably be supported on either a mat foundation located 5 ft below the bottom of the basement, or a deep foundation extending about 60 ft below the bottom of the basement. The groundwater table is about 30 ft below the ground surface and bedrock is several 100 ft below the ground surface. There are no accessibility problems at this site. a. How many exploratory borings will be required, and to what depth should they be drilled? 10 Points b. What type of drilling and sampling equipment would you recommend for this project? 10