In another small but important step forward for offshore wind development in the United States, the Lake Erie Energy Development Corp., or LEEDCo, began testing the soils at the bottom of Lake Erie. The tests and drilling for soil samples are being done at the six sites where LEEDCo has proposed locating turbines for an offshore wind pilot project. The sites are eight to 10 miles offshore, northwest of downtown Cleveland. Results will help answer the question of what kind of soil lies below the sandy lake bottom and will enable engineers to design the foundations for the turbines.
LEEDCo is planning to use a “mono bucket” foundation developed over the last decade by Danish company Universal Foundation. The “mono bucket” foundation is a large-diameter steel cylinder with an open bottom and closed top, measuring about 45 feet in diameter. The bucket will be sunk and placed open-side down on the lake bottom with the smaller diameter turbine support cylinder extending toward the surface of the water. When engineers pump out the water trapped in the inverted bucket, the structure will sink itself into the lake bottom, penetrating into the soil, and creating a very stable and rugged foundation. This concept eliminates underwater excavation or the need to drive steel piles deep into the lake bottom.
LEEDCo, or its predecessor, has been exploring how to place wind turbines in Lake Erie since 2005.