The Lake Erie Energy Development Co. has assembled an international team of engineers to figure out if the non-profit company can use a new, lower cost foundation for the six turbines it wants to build in Lake Erie, about 8 to 10 miles offshore. The team is drilling the Lake bottom 24 hours a day this week.
CLEVELAND, Ohio --The Lake Erie Energy Development Corp., or LEEDCo, is finally getting to the bottom of a question that must be answered before anyone can build wind turbines in Lake Erie.
That question -- what kind of earth lies below the sandy Lake bottom -- is being answered this week one core sample at a time and one pressure test at a time.
Two 12-man crews are working around the clock about 10 miles offshore, said Lorry Wagner, president of LEEDCo.
Working in 12-hour shifts on the 200-foot crane barge, the Farrell 256, one team of drillers and geotechnical engineers is drilling 60 to 75 feet into the material under the Lake bottom and pulling out dozens of cylindrical "cores" of sand, clay and rocky aggregate for careful analysis.
The cores tell the story of the land under the lake, said Beau Marshall, drilling crew chief for DOSECC Exploration Services, land that has remained undisturbed for thousands of years. The cores will also enable the engineers to figure out what kind of foundation the proposed wind turbines will need to be stable.
Another team is simultaneously running a kind of pressure test on the Lake bottom to figure out the overall mixture of the material at the bottom,up to 75 feet below it and even deeper into the shale rock below that.
The teams were on course by mid-week to wrap up the job by Tuesday, Sept. 8, if the good weather and calm seas hold.
The core samples are being assayed immediately and then packed up for a more detailed analysis later, some of which will be done at the Civil Engineering department at Case Western Reserve University laboratories.
The pressure tests, called "cone penetration tests," push instruments into the Lake bottom under enormous pressure at a steady rate. The point? To get a picture of how the sediments are layered and to calculate just how much weight the soil below can support.
The tests and drilling for core samples are being done at six sites about three-quarters of a mile apart in a straight line where LEEDCo has proposed building the six-turbine pilot project. The single line of turbines, if built, will stand eight to 10 miles offshore, northwest of downtown Cleveland.
David Karpinski, an engineer and LEEDCo's vice president of operations, said knowing the composition and strength of the soils is critical because the company is not planning to drive piles deep into the shale rock below.
Instead, LEEDCo is planning to use a "mono bucket" foundation developed over the last decade by Universal Foundation, a Danish company,
The "Mono Bucket foundation" is an all-in-one steel structure -- a monopile shaft attached to the bottom of a large-diameter bucket, measuring about 45 feet in diameter.
The bucket would be is sunk and placed open-side down on the lake bottom with the pole extending toward the surface of the water.
And when engineers pump out the water trapped in the inverted bucket, the structure sinks itself into the sea or lake bottom, said Karpinski.
The big steel bucket could be made her, said Wagner, would be less costly than sinking piles into the rock and less environmentally destructive than digging into the soil.