A long-awaited federal report on the proposed wind farm in Nantucket Sound says the project would do little or no harm to fish, birds, and the surrounding seafloor, and would not drive down local property values -- all key findings as Cape Wind Associates seeks final approval to start construction next year.
The 4,000-page draft environmental impact statement by the Army Corps of Engineers will be formally released tomorrow. But a detailed 26-page executive summary obtained by the Globe seems to undercut opponents' arguments that the 130-turbine wind farm would cause deep, lasting damage to the environment.
Specifically, the draft says the estimated 420-foot-tall turbines could kill as many as 364 birds per year -- about one a day -- but notes that number is unlikely to affect endangered species or specific populations of birds. In predicting the project's impact on shellfish and fish populations -- a concern of environmentalists as well as fishermen -- the report says any effects would probably be felt only during construction.
Still, the report noted that visual impact from the country's first proposed offshore wind farm would be ''adverse" for some historical areas, such as the Kennedy Compound and the Nantucket Historic District.
The report's release marks the beginning of a 60-day public comment period, after which the Army Corps will continue studying the issue before giving final approval or rejection, probably sometime next year.
Opponents of the project said last night they had not seen the report, but they repeated concerns that consultants who provided much of the data were hired by Cape Wind and would be expected to find little negative impact. Federal law requires developers to pay for data collection, and the Army Corps has said a wide range of other agencies and groups contributed to the draft.
Cape Wind owner Jim Gordon, who has seen the report, said last night that its release was a large step forward.
Because no federal standards exist on, for example, how many bird deaths are acceptable at a wind farm, the Corps has wide discretion in weighing the costs and benefits that drive its decision.
Among the findings in the executive summary:
Nearby homes' property values are not likely to drop, based on government-funded studies at other wind farms. (The executive summary did not name other wind farms studied.) The area would see economic benefits, according to the report summary, because the wind farm would create jobs and could increase tourism.
Navigation, a concern of the many recreational boaters and commercial fishermen who use the waterway, would not become more hazardous, although boaters would have to take extra care during poor weather navigating near turbine towers spaced more than a quarter-mile apart over the roughly 24-square-mile area.
The project would improve public health by generating energy without emitting pollutants. The report estimates the public health savings each year at $53 million.
The project would not adversely affect some historic properties, such as the Oak Bluffs Christian Union Chapel and the Martha's Vineyard Campground Historic District. But in addition to affecting the Kennedy compound and Nantucket's district, the wind farm would alter the character and setting of four other historic Cape districts and 10 historic properties.
As part of the environmental review, the Army Corps looked closely at four possible alternative sites for the plant, including a land-based site at the Massachusetts Military Reservation on Cape Cod. But neither the executive summary nor the report is designed to make conclusions about whether those sites are preferable.
''We feel we worked 34 months putting together a document which we believe has the integrity we promised the public," said Larry Rosenberg, chief of public affairs for the New England district of the Army Corps of Engineers. ''When this is released to the public, we hope they read it, digest it, and comment to us so we can make an informed decision on this application."
The report's release promises to intensify the controversy over the wind farm, which has been a political flash point since it was proposed three years ago.
Although other offshore wind farms have been proposed around the country, such as one off Long Island, Cape Cod's is the largest and the first to go through the federal permitting process. Elsewhere in the world, offshore wind farms are becoming more popular, especially as residents fight to exclude wind turbines from scenic mountaintops. The draft is the first official indication of how the project will be received by the federal government.
The project already has weathered opposition from several local and national politicians, including Senator Edward M. Kennedy, Democrat of Massachusetts. Last month, a Virginia senator was unable to add language to a defense bill that would have delayed the project indefinitely. In recent weeks, a high-level Pentagon official delayed public release of the report to conduct a closer review of it. The draft has not changed because of that review, Army Corps officials have said.
The report is unlikely to satisfy opponents' concerns over the aesthetics of the project, or over a series of environmental issues such as the potential for an oil spill from an electric service platform.
''Cape Wind essentially wrote [the draft report], so it is not surprising it is headed toward building the project," said Susan Nickerson, executive director of the Alliance to Protect Nantucket Sound, the main opposition group to the wind farm. ''We will begin our own analysis" once we get a copy of the report, she added.
Gordon, meanwhile, called the release of the report ''a big step towards greater energy independence, lower energy costs, new jobs, and a healthier environment."
Four public hearings will be held on the project: Dec. 6 in Oak Bluffs, Dec. 7 in West Yarmouth, Dec. 8 in Nantucket, and Dec. 16 in Cambridge.
Beth Daley can be reached at email@example.com.