U.S. Department of Energy - Energy Efficiency and Renewable Energy

Wind Program

Interior Department Approves Cape Wind, the First U.S. Offshore Wind Farm

May 5, 2010

Photo of a row of tall towers each supporting three, sleek blades, as a freighter sails nearby.

Offshore wind turbines such as these are proposed for the Cape Wind project. Enlarge this image.
Credit: Siemens

After almost a decade of federal study and analysis, the U.S. Department of the Interior (DOI) approved the Cape Wind project on April 21, allowing the first U.S. offshore wind farm to move ahead. Cape Wind is a 130-turbine wind power project on submerged federal lands in Nantucket Sound off the Massachusetts coast. DOI required the developer of the $1 billion wind farm to agree to additional binding measures to minimize the potential adverse impacts of construction and operation of the facility. Located in a 25-square-mile section of Horseshoe Shoal in Nantucket Sound, the Cape Wind project will have a maximum electric output of 468 megawatts (MW), with an average anticipated output of 182 MW. That's enough to meet 75% of the electricity demand for Cape Cod, Martha's Vineyard, and Nantucket Island combined. The Cape Wind developer hopes to begin construction by the end of this year. See the Cape Wind press release.

Interior Secretary Ken Salazar said that the project's public benefits weighed in favor of its approval, citing the benefits from increased energy independence, reduced pollution, and job creation. Both the Wampanoag Tribe of Gay Head (Aquinnah) and the Mashpee Wampanoag Tribe have opposed construction of the project, saying it would disturb culturally significant sites on the seabed floor and would visually interfere with their cultural activities, and the Advisory Council on Historic Preservation (ACHP) agreed. But Secretary Salazar disagreed, noting that Nantucket Sound is far from pristine, already featuring undersea power lines, communication towers along its coasts, and the visual impacts associated with aviation, shipping, fishing, and recreational boating. Those visual impacts are far greater than the impacts of wind turbines located at least 5.2 miles from the mainland, according to Secretary Salazar.

Nevertheless, DOI took several steps to minimize the visual impacts, including reducing the number of turbines from 170 to 130, reconfiguring the array to move it farther away from Nantucket Island and to reduce its breadth when viewed from Nantucket, requiring the developer to paint the turbines off-white to lessen contrast with the sea and sky, reducing nighttime lighting, and minimizing daytime lighting. In terms of seabed cultural and historic resources, DOI is also requiring a detailed marine archaeological survey of the area before construction begins. In addition, a "Chance Finds Clause" in the lease requires the developer to halt operations and notify DOI of any unanticipated archaeological find. See the DOI press release, the Record of Decision (PDF 20 MB), the Cape Wind fact sheet (PDF 108 KB), the project site map, and Secretary Salazar's reply to ACHP (PDF 3.6 MB). Download Adobe Reader.

In approving Cape Wind, DOI noted that there are other offshore wind power proposals in neighboring northeastern states, all seeking to tap the region's estimated offshore wind power potential of 1 million MW. To help advance that process, DOI issued a Request for Interest (RFI) on April 21 for renewable energy development off the coast of Delaware. Delaware officials have approved a proposal by Bluewater Wind Delaware, LLC for the construction of a 200-MW offshore wind farm, but the company is still required to apply to DOI's Minerals Management Service for an offshore lease, which may entail competing with other companies. The area covered in the RFI is in federal waters between the shipping routes for Delaware Bay, with the closest point to shore located about 7.5 miles due east from Rehoboth Beach. Responses to the RFI are due by June 25. See the DOI press release, the RFI (PDF 62 KB) as published in the April 26 edition of the Federal Register, and the DOI's map of the proposed leasing area (PDF 486 KB).