September 20, 2013

Wind turbines

Guthrie Center Times | September 19, 2013 |

Thursday, assistant Guthrie County attorney Tim Benton briefed county supervisors regarding a second case of major road damage to county pavement F63 (310th Road) caused by massive cranes used for installing and repairing turbines at the Eclipse wind farm located north of Adair.
In March, Benton reached a settlement regarding road damage caused in 2012 during initial wind farm construction. At that time, MidAmerican Energy, owner of the wind farm, agreed to pay the county $1.1 million for road damage in the entire construction area, but most notably for damage on a 3.5 mile stretch of F63 pavement.
County engineer Josh Sebern subsequently contracted repair and repaving of the road with Henningsen Construction. Preparation patchwork has already been completed with repaving scheduled for October.
However, during early morning, August 26, residents on 310th Road reported a “huge crane” driving on F63. Sebern and supervisor Cliff Carney, a turbine owner who lives in the area, were called to investigate.
According Benton, the crane involved weighed approximately 800,000 pounds. It did not have a permit to operate on the road, nor would it have been granted one due to its excessive weight.
Carney stated he could easily see everywhere the steel-tracked vehicle had driven, as it left tracks up to three inches deep. He indicated at one point it stopped at a bridge, decided not to cross, and backed up. He opined the driver made the correct decision, as the bridge would not have supported the weight.
The crane incident further damaged an already deeply scarred road.
The October repaving contract originally called for patchwork repair of crack damage followed by asphalt overlay.
However, according to Sebern, given the additional damage, simple patchwork with asphalt overlay will no longer suffice. Now the road will have to undergo “modified rubblization,” where the existing pavement is actually broken into small pieces prior to repaving.
Sebern stated preliminary estimates add an additional cost of $400,000 to the road repair.
The crane, owned by Mountain Crane, Salt Lake City, UT, was working under contract with Siemens Energy, manufacturer of the wind turbines.
Siemens contracted Mountain Crane after massive, nearly brand-new 173′ blades fell from wind turbines on two separate occasions, one at Eclipse on April 4, and another east of San Diego, CA at the Ocotillo Wind Project on May 16.
After the blade failures, both involving B53 blades, Siemens curtailed the use of nearly 700 turbines worldwide until an engineering analysis was completed to determine the root cause of the failures.
A June 25 a Siemens press release stated, “…the fractures happened as a result of adhesive bonding failure between pre-cast root segments and the fiberglass laminate of the main blade.” According to Siemens, the bonding of metal to a composite is a delicate procedure, and it appeared contractors hired by them had done “insufficient surface preparation” leading to the adhesive bonding failure.
As a result of the worldwide inspections, numerous blades were identified for replacement, including 11 at the Eclipse farm.
In addition, Tina Pothoff, spokesperson for MidAmerican Energy, stated Monday that seven turbines at Eclipse (21 blades) underwent additional modifications which were completed last week.
Those modifications, according to Siemens, were to “provide an extra level of protection through an incremental enhancement of the bond between pre-cast root and the fiberglass laminate.”
Speaking of the new damage to F63, Benton summed up the situation. “At this point, we’re right back to where we started from eight months ago.”
He recommended, given massive cranes will be in and out of Guthrie County for years repairing wind turbines, that supervisors consider a clear set of weight restrictions for all roads and bridges in the county.
He concluded, “I’d like to see the board get proactive, because these crane repairs are not going away.”

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