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Danish study says offshore projects pose few risks

Wind power lessons in the North Sea paved some of the road to a proposed 200-turbine wind farm off Delaware’s shoreline.

One of the most important findings recently shared from offshore projects in Denmark: Big wind farms can operate with few environmental risks to birds, fish and other aquatic creatures “under the right conditions.”

“Appropriate siting of offshore wind farms is an essential precondition for ensuring limited impact on nature and the environment,” the Danish Energy Authority reported in November.

Denmark released its report after plugging in what is now the world’s largest offshore wind operation: Two sites with 152 turbines located up to 12.4 miles offshore.

“Appropriate” is the key word to Susan Nickerson, a Massachusetts environmentalist who attended a conference in Denmark to mark release of the report last year.

“The big discussion that’s unfolding here is: How much data do you need preconstruction, and how much should this concept of ‘adaptive management’ be relied upon,” Nickerson said.

Nickerson referred to calls for monitoring and modification of environmental protection systems before and after wind farm construction. The Marine Minerals Service, due to release environmental impact requirements for wind farms next month, has stressed the same approach.

“Data collection in the offshore environment is a bit of a pipe dream,” Nickerson cautioned. “How do you measure effectiveness when you have no way to know if birds are colliding?”

Bluewater Wind said in its application in Delaware that most birds traveling near the proposed offshore sites would fly above or around the turbines, and would face little risk because of the relatively slow speed of the blades.

Nevertheless, the company acknowledged that “bird/turbine and bird/monopole tower collisions are likely to be a major issue.”

In New Jersey, state officials last year proposed lifting a moratorium on new offshore wind projects, but only to allow construction of up to 80 turbines in a test aimed at sounding out public support and working through environmental concerns.

Studies in Denmark estimated that 41 to 48 birds would have a fatal meeting with rotors at the 72-turbine Nysted complex each autumn out of 235,000 that flew past, or up to two one-hundredths of 1 percent. But researchers were unable to develop monitoring systems to actually detect a collision.

The systems also tend to spook some species of diving ducks and other water birds, easing them out of areas around the wind farm entirely. But populations of bottom-dwelling creatures such as crabs, shellfish and worms rose by up to 150 percent because the windmill foundations created a patchwork of artificial reefs to anchor aquatic creatures that find sandy bottoms too unstable for regular housekeeping. That food-chain alteration created a small boom, in turn, for larger species.

“When they’ve done environmental studies they’ve found essentially an increase in aquatic life,” said Guy Dauncey, an author and industry watcher in British Columbia. “I don’t see any fundamental problems.”

Turbines used in Denmark would match the ones proposed for Delaware, although Bluewater Wind’s design would put the generator hubs more than 30 feet higher, at about 262 feet.

Tips of the blades on each big mill would sweep up to a height of 392 feet, or nearly as high as the main towers of the Delaware Memorial Bridge, which are 417 feet.

The blades would spin at about 16 rotations per minute, far slower than the shorter, smaller, lower-power systems of the past that in some cases have whacked birds and bats with savage and distressing regularity.

Bluewater hired Holland-based Ballast-Nedam as its partner for engineering, procurement and construction. The same company recently finished a 36-turbine windfarm off the Netherlands in waters roughly the same depth and distance from shore as the larger complex proposed for Delaware.

By Jeff Montgomery
The News Journal

11 February 2007