National Wind Watch: Wind Energy News » New method of decommissioning wind turbine concrete bases with water jets

Wind farms have about a 30-year life, and decommissioning the giant turbines is an art in itself.

One TransAlta employee whose job includes decommissioning giant turbines on wind farms is Wayne Oliver of Pincher Creek, a former high school teacher, who finished up his career, teaching shop, to work for TransAlta.

“I had to take an apprenticeship to become a journeyman to teach shop, so I apprenticed, working on wind energy, and found I liked the work. I had to finish two years teaching. I’ve been with TransAlta ever since. It’s been a good career.”

One question consistently asked during public hearings on wind farm development applications is how these wind farms are decommissioned at the end of their life.

Oliver, in an interview outside council chambers, said tenders for decommissioning the oldest Cowley Ridge wind farm included a bid from a Vancouver company that proposed to blowing up the base of each one.

“Can you imagine that?” Oliver said. “Boom, boom boom, and you’d have these towering wind turbines hit the ground, whump, whump, whump, one after the other.”

Oliver said the cleanup would have been extensive, with bits of fibreglass and broken metal spread over a wide area.

He showed a video on his cellphone of a new technique used once a wind turbine tower has been brought down safely, piece by piece, in the reverse order it was constructed, leaving only the deep concrete reinforced base left in the ground.

The reinforced base is placed deep in the earth as there are so many stresses on the base with the turbine turning for decades.

With this new removal technique, the top metre of the base is removed.

A backhoe digs a hole around the concrete base once the tower is removed. Then an automated high-pressure water jet is set up to fire a jet of water up close and rotate around the concrete base, directing the thin, high-pressure stream of water, cutting deeply into the base, slicing both the concrete and the rebar inside. The water jet rotates around the concrete pillar firing the high-pressure water jet until it is done. The top metre of the top of the concrete pillar is then lifted off.

The company demonstrating the procedure has done this sort of work before, to cut away below-ground metal casings used in oil patch drilling.

Members of the Municipal Planning Commission, while impressed with the procedure, were concerned about the remaining concrete left deep in the ground, with only the top metre removed.

Chairman Glen Alm said having a long concrete pillar below ground could become lost information once the land changes hands a few times.

“This would be a big surprise to anyone trying to dig water line,” Alm said.

Alm recommended GPS location of all remaining deep concrete pillars be recorded with the Municipal District of Willow Creek and other land record keepers so future land owners of a property where these pillars are below ground will know where they are.

MPC members unanimously approved the recommendation.