Cape Wind Energy, LLC has proposed to build a wind turbine farm on Horseshoe Shoal in Nantucket Sound. This site has been evaluated in a previous study (Swanson et al., 2005). An alternative site, 9 km (5.6 mi) southwest of Tuckernuck Island, is also being evaluated for comparison purposes. The project will consist of 130 wind turbine generators (WTG), an electric service platform (ESP) and a series of cables connecting the WTGs to the ESP and a pair of cables from the ESP to shore at Yarmouth. Each WTG is either mounted on a monopile or a quad-caisson, consisting of four piles, depending on water depth. Concerns have been raised by regulatory agency review as to the cumulative environmental effects of the WTG pile array on waves and currents and ultimately on sediment transport in Nantucket Sound.
Cape Wind Associates LLC contracted with Applied Science Associates, Inc. to perform an analysis to estimate the expected changes in waves and currents from the placement of the WTG pile array both at the primary site at Horseshoe Shoal and the alternative site southwest of Tuckernuck Island, which is the subject of this report. The study used both a hydrodynamic model, HYDROMAP to calculate currents in the area and wave data collected from the Martha’s Vineyard Coastal Observatory (MVCO) to provide input information for the analytic approaches used to estimate the zone of influence of the WTG piles.