U.S. Coast Guard 150′ High Communications Tower ($300 Thousand Dollar Project)
Merit Engineering provided full scale geotechnical engineering services for this project. The project involves a 150 feet high telecommunications tower for U.S. Coast Guard at Whidbey Island and an office building for U.S. Navy at Marysville, Washington. The tower is one of the largest at Whidbey Island Naval Air Station supported by three legs, 28 feet apart. The tower has the following loading conditions: 360,000 pounds in compression and 330,000 pounds in tension on each leg; 55,000 pounds in shear between each leg and its foundation; and 8,200,000 pound-foot overturning moment.
Merit Engineering conducted site exploration for foundation designs by test boring investigations. During these investigations, Merit discovered a high plasticity clay in the area that is “sensitive” to dynamic load. During a seismic event, there is a high potential for the clay losing strength. We have evaluated the feasibility for both footing and pier foundations. Merit recommended the foundation for the tower should not be placed either in or above this soil stratum and recommended an innovative foundation and footing design, thus saved the tower from potential disaster. We successfully designed a pier foundation for both vertical load and lateral pile analysis using a FEM (finite element method) computer model.
As a team member for this Design-build project, Merit Engineering worked closely with other team members such the structural engineer and the contractors, as well as provided prompt response and assistance to the general contractor to select a responsible pier installation contractor. Merit Engineering also provided construction observation services to assure the quality control and quality assurance in the earthwork and foundation installation.