Six inches. That was the key measurement on the 24.6 MW Eva Creek Wind Farm, the largest wind project in Alaska.
That was the total clearance available to get components of 12 wind turbines to a project site across an existing railroad bridge in Ferry, Alaska. The bridge over the Nenana River quickly became one of the most significant aspects of the project.
With the exception of gravel and sand for road improvements and concrete production, every tower, blade and crane - not to mention construction equipment and workers – had to cross it.
Detailed planning was crucial months in advance of construction. Initial site-clearing and grubbing was done from August to November 2011 before work shut down for winter. Construction resumed in April when the weather broke and wrapped up in October, just as Alaska’s winter weather arrived.
Getting equipment and material to the work site was a colossal task. Most material, and all vehicles and pieces of equipment, were taken by truck from Fairbanks or Anchorage to Healy, 14 miles southeast of Ferry, Alaska.
Equipment included lattice-boom cranes, hydro-boom cranes, scrapers, haul trucks, excavators, loaders, graders, rollers, dozers, tractors with specially designed trailers, portable batch plant, a rock crusher, drill rigs and ready-mix concrete trucks. The largest piece of equipment was our Manitowoc 16000 crane, which was broken down to 42 pieces and shipped by barge and rail to Healy from a recently completed project in California.
The equipment and material crossed the bridge and were offloaded at a rail siding. From there, the crew members, with all equipment and material, faced about a 10-mile drive up a mountain road at grades as steep as 10% to get to the turbine sites. The turbines were installed in two strings. The road was built specifically for the project and will remain there in order to provide access to the turbines.
Prior to being assembled, the REpower cold-climate-version MM92 turbine parts included 36 tower sections, 36 blades, 12 hubs and 12 nacelles. The blades were shipped on railcars from Arkansas to Healy.
However, to get to the project site, engineers and components alike needed to cross the narrow bridge to Ferry.
To get from the man-camp to the work site, crew members needed to either walk or take a four-wheel, all-terrain vehicle on a half-mile trek across a narrow walkway attached to the railroad bridge.
Planning and preparation were critically important to accommodate the job's tight schedule. All supplies needed to be carefully ordered and shipped to the site. Ferry is a remote town with about 30 residents and no retail outlets. If supplies were needed on the fly, only a limited amount was available at an auto parts store in Healy. Other parts would need to be shuttled in from Fairbanks, about 100 miles away, or Anchorage, 250 miles away.
Of course, wind farm construction in Alaska would not be complete without mentioning the weather. Work was completed on a tight timeline in a narrow window carved out by the arrival of Alaskan spring in April and snowfall in early October. During the seven-month work span, temperatures ranged from highs of 72 to lows of -20 degrees F. Winds often exceeded 70 mph and topped out at 84 mph. Record amounts of rain in June damaged an access road, which was rebuilt with more aggressive erosion-control measures.
The land of the midnight sun did provide some extra working hours. During the peak of summer, it was light nearly 24 hours a day. Although our crews worked one shift, some subcontractors opted to run two each day during the longest days. In spring and fall, there were only about seven hours of daylight.
The project received $13.4 million in state grants. It will meet Golden Valley’s goal of having 20% of the system’s peak load generated by renewable resources in 2014.
In total, the project included 13 miles of upgraded or new access roads; 12 REpower turbines; 12 concrete spread foundations; a 5-mile underground collection system installed in permafrost, rock and arctic conditions; a 230 kV substation; two operations buildings; two communications towers and one meteorological tower. Two meteorological towers were also relocated.
The turbines were commissioned in early November and are now generating electricity.
Author's note: Jill Badzinski is a marketing and communications specialist for Brownsville, Wis.-based Michels Corp., which has 4.1 GW of wind farm experience in the U.S.
Caption: A train moves along a narrow rail bridge that separated Ferry, Alaska from the project site.