The Coast Guard has given conditional approval to the Cape Wind Associates plan to build a wind turbine farm on Horseshoe Shoal in Nantucket Sound.

In a conference call Friday morning, Capt. Raymond Perry, captain of the port for southeastern New England, said his analysis of a study of the impact of the 130-turbine array on navigation shows those effects could be mitigated.

Captain Perry said the wind turbine array, which would be built in shallow water, could be treated as islands by vessels passing by in nearby channels.

The captain said the wind farm would pose more of a problem to boats actually inside the area, such as boats fishing on the shoal.

Mark Rodgers, communications director for Cape Wind, said the company had no comment on the Coast Guard's findings.

Glenn Wattley, president of the Alliance to Protect Nantucket Sound, a not-for-profit organization that opposes the wind farm, said the Alliance was disappointed at what he calls a rushed decision.

The Coast Guard, which held an initial workshop on the navigation issue in October, had anticipated that another workshop would be held in December to discuss the findings of a $100,000 study of the issue commissioned by the service.

But Wattley said the Minerals Management Service, the federal agency scheduled to rule on the wind farm's proposed use of federal waters, requested that the Coast Guard move more quickly, so as to include its findings in the service's ruling on the project.

The MMS reportedly plans to make a decision on Cape Wind by the end of the year, before the changeover from the Bush to the Obama administration.

The decision had been anticipated as early as today, Friday, Dec. 5, but no ruling came down. A decision around Christmas now looks more likely.

The Coast Guard held a workshop in October in Falmouth on the wind farm's potential effect on navigation, with another workshop anticipated later in December.

Wattley said the Alliance was surprised to receive an e-mail yesterday evening, informing the organization of a conference call on the issue scheduled for Tuesday morning. Given the short notice, Wattley said, the Alliance wasn't able to arrange for two of its witnesses at the October workshop to participate in the call.

The public, he said, isn't getting an opportunity to comment on safety issues that continue to arise about the wind farm.

Richard Elrick, president of Clean Power Now, a non-profit organization that supports the proposed wind farm, said CPN is pleased that the Coast Guard found no incompatibility between navigation and the proposed project.

Elrick said that while a study commissioned by the Coast Guard found that vessels could sometimes lose turbines as targets on their radars, vessel operators could compensate for that in other ways.

Clean Power Now's biggest concern, Elrick said, was that the Coast Guard would require Cape Wind to reduce the number of turbines or rearrange them, which the organization feared could affect the viability of the project. But the Coast Guard didn't do so.

Cape Wind Associates has proposed a number of measures to address navigation safety at and near the project. They include day beacons, signs, signals and lights at the perimeters of the wind farm, and sound signals; specially marked traffic lanes and recommended vehicle routes; the establishment of a control center with staffling and equipment to monitor activity at and near the wind farm; and working with the Coast Guard and other entities to educate mariners on navigation safety issues related to the wind farm.

Wattley said the Coast Guard review remains a work in progress. He said the Alliance plans to submit letters stating the organization's concerns, and is looking for allies such as U.S. Rep. James Oberstar of Minnesota, who Wattley said wants to see an adequate comment period on Cape Wind.