GPR’s Site Design for Two 1.5 MW Wind Turbines


By: Cal Goldsmith, VP

Way back in 1984 the Town of Princeton, Massachusetts became one of, if not the first state in the US to build its own wind farm for the generation of electrical power for its residents. That wind farm consisted of eight 40 kilowatt (KW) wind turbines mounted atop towers about 100’ tall. The eight turbines combined to produce something less than 10% of the town’s power, yet it was an extraordinary thing for a town to do. How far ahead of the curve this town’s leaders were! Over the next 22 or 23 years, the wind turbines produced power, but also slowly declined, until they reached the end of their useful life and were removed in 2007.

Yet the ‘green’ spirit of 1984 lives on in Princeton. Under the expert guidance and unflagging determination of the Princeton Municipal Light District Commissioners, and its manager, Mr. Jonathon Fitch PE, wind turbines have once again sprouted on the flanks of Mount Wachusett. But this time, instead of eight turbines there are only two. And these two 1.5 megawatt (MW) turbines will provide on the order of 40% of the town’s power requirements, owing to their substantially larger size and efficiency over their earlier brethren.

Each of these 60 ton turbines manufactured by Furhlander in Germany, sits atop a 230’ high monopole tower, anchored to the bedrock by a 40’ across hexagonal, 20’ deep cast-in-place concrete foundation reinforced by an intricate, incredibly dense tangle of steel rebar, and anchored into bedrock with eight 50’ long rock anchors each. Harnessing the wind is accomplished by three 130’ long 6 ton fiberglass and steel blades, the tips of which will reach some 360’ into the sky to snag the wind from one of the few inland areas in Massachusetts blessed with such strong, sustained wind speeds.

GPR was the site engineer for these turbines, designing the access roadway in, the substantial construction areas needed for the blades, turbines and cranes, and the turbine sites themselves. GPR worked with Jonathon Fitch, Methuen Construction (the site contractor), Community Energy (the energy broker first involved in the project, but no longer) and Hallamore Cranes to determine all the relevant design criteria for the siting of the turbines and the design of the construction pads for both the cranes’ and the wind turbines’ assembly operations.

The large areas around the cranes were very necessary during construction. The 600 ton crane used to erect the towers and float the 60 ton turbine and 20 ton blade assembly into the air itself took a week of work and another smaller crane to assemble. The monster crane was delivered on a series of 20 trucks, and disgorged its pieces onto the layout pad next to the tower sections awaiting the construction. The crane, while mobile, moves only very slowly, and only on relatively level ground, in deference to its 350’ height and the inherent stability challenges associated with such a machine.

The relatively steep access road through the dense woodland in to the site proper had to be straight and smooth, as the blades each came in on trailers long enough to accommodate their 130’ length, which cannot turn or tolerate irregularities in the road surface without getting hung up. The steepness of the access grade in required a large rubber tired crawler to assist the delivery trucks the quarter mile up the hill to the site proper, especially when hauling the massive turbines.

But it all came together last week for the first turbine. Aspiring wind developer Mike Bedard of Bedard Realty in North Attleboro, MA and I watched the $6.5 million Hallamore monster crane in action as it lifted first the towers, and then the nacelle (turbine) and then the completed blade assembly into place. The second turbine should be completed by now as well. What a spectacular sight, on a spectacular site overlooking eastern Massachusetts all the way to the Boston skyline. Take a minute to check out the links to PMLD on our website and read more about the project. Its worth a look!