Any good alternatives for Cape Wind?

ProjoHow disingenuous can the Alliance get?

CHARLES W. KLEEKAMP, Sandwich MA

SOUTH OF TUCKERNUCK Island that is. How disingenuous! A recent article in Cape Cod newspapers notes that the Alliance to Protect Nantucket Sound is hiring a firm to assess the viability of other offshore wind-energy locations as a diversion from Cape Wind’s optimum site, on Horseshoe Shoal, which is a few miles off the coast of Osterville.

Charles Vinick, president of the alliance, and Susan Nickerson, its executive director, mentioned in particular the south-of-Tuckernuck alternative site, which has already been examined in both the Army Corps Draft Environmental Impact Study and in new federal Minerals Management Service (MMS) documents. Indeed, several alternative sites have been examined.

However, it appears the alliance has no intention to actually build a wind farm south of Tuckernuck (five miles south and west of Nantucket Island) or anywhere else. But we’ll see if it applies to the MMS for a permit with an expanded Environmental Notification Form (ENF), including a pilot project the group mentions. And we’d welcome the alliance with open arms if it would become the second (or third) organization to construct a wind farm in New England waters. Otherwise, the alliance is just blowing mist.

Here’s a quick comparison of the two sites:

Horseshoe Shoal site:

  • Average wind velocity: 19 mph
  • Water depth: 8 to 55 feet 
  • Extreme wave height: 17 feet
 The site is out of marine navigational channels and instrument-flight- rules-regulated air-traffic approaches.

The site is close to the mainland’s shoreline, allowing alternate-current transmission cable to be used. This means much much less power loss than with such further-out sites as the south-of- Tuckernuck location.

The subsurface on Horseshoe Shoal is ideal for maintaining structural stability and it would be relatively easy to install monopile foundations there. These monopiles are the most cost-effective and environmentally sensitive design alternative.

South-of-Tuckernuck-Island site:

  • Average wind velocity: 19.5 mph
  • Water depths: 15 to 100 feet 
  • Extreme wave height: 52 feet
Half the area is over 60 feet deep, requiring expensive quad-caisson (four-legged) turbine foundations.

The wind-turbine array there would be within the flight path of two of three established low-altitude instrument-flight-rules-regulated airplane routes that serve Martha’s Vineyard and Nantucket Island.

The extreme wave height of 52 feet is three times higher than that found at Horseshoe Shoal.

The long interconnection distance would likely require a very expensive direct-current transmission system.

In comparison with Nantucket Sound, the south-of-Tuckernuck alternative represents a considerable challenge to maintain year-round, especially during winter. The winter is when the most electricity production is likely to occur because of high average wind speeds, exacerbating the impact of lost production for this alternative.

Both the Army Corps and the MMS in their permitting documents have already identified many more alternative offshore sites for comparison purposes. Those off Massachusetts in federal waters include, besides the south-of-Tuckernuck site: south of Martha’s Vineyard, off Cape Ann, east of Nauset Beach, on Nantucket Shoals, on Monomoy Shoals, in the Boston Harbor vicinity and in the New Bedford Harbor vicinity. And within Nantucket Sound: Monomoy Handkerchief Shoal, Tuckernuck Shoal, and the proposed site of Cape Wind — Horseshoe Shoal.

Each site is evaluated on environmental aspects as well as such criteria as wind speed, water depth, wave height, transmission-cable costs, and avoidance of shipping lanes and aircraft-landing corridors.

The purpose of an agency’s examination of alternatives in the permitting stage is to help determine if the proponent’s site is a reasonable choice. The permitting agency, the MMS in this case, has only three options in their final determination, called a Record of Decision: deny the permit, approve the permit, or approve the permit with conditions. The agency cannot direct the proponent to another site.

Let’s all be patient and let the permitting process work. There will be ample opportunity for public comment this spring on the MMS draft environmental-impact statement on Cape Wind.

As the price of oil and natural gas continue to rise, some of these alternative sites that have lesser attributes may well become locations for the next wind farms. Would the alliance build one of them?

Charles W. Kleekamp is a retired engineer and vice president of Clean Power Now, a pro-Cape Wind group.  This appeared today in the Providence Journal.

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