The Blue Lake turbines are carrying all of Sitka’s electrical load, as the Green Lake hydroelectric station is out of commission. (KCAW file photo)
While the Green Lake power station remains closed, all of Sitka’s energy needs are being met by the Blue Lake Dam.
Utility Director Bryan Bertacchi updated the Sitka Assembly on the town’s power situation during its regular meeting this week (10-25-16). The Green Lake plant was shut down on October 17th, when an intake gate failed during a routine inspection. Bertacchi said that if electricity stays at current levels, the Blue Lake power plant can carry the city. But he may have to switch the city to diesel fuel if usage increases.
“Diesel generation may be required if we get a really strong cold snap before we can return Green Lake to service. Because of the potential for diesel generation, any delay if we had to start operating diesel could easily cost us $50,000 a week. So we all should be thankful that we’ve got the Blue Lake hydro expansion because at this point, Blue Lake is carrying the entire town,” Bertacchi said.
The failed hydraulic ram, at the bottom of a 160 ft shaft at the Green Lake power plant. The ram – which is essentially a water-powered pump – failed while the Green Lake Tunnel was being drained for a planned inspection. (File courtesy of Utility Director Bryan Bertacchi)
As acting city administrator while Mark Gorman is on leave, Bertacchi authorized an emergency procurement of $60,000 to buy a replacement hydraulic cylinder for the Green Lake intake gate.
That’s not the only infrastructure issue facing the Electric Department. In August, staff discovered small areas of cavitation corrosion on the Blue Lake turbines. The turbines are two years old, made by an English-manufacturer called Gilkes.
Bertacchi told KCAW by e-mail that this kind of corrosion – which erodes the surface to look like swiss cheese – is minor. He compared it to corrosion on a boat propeller in a marine environment. He assured the Assembly of the same.
“If 10 is the worst and 1 is the least of a risk concern for the community, this is a less than 1 item. And Gilkes has been here twice, sent people over from England. They also spent over $100,000 with a third party contractor so we could clean the area up, put some coatings on it, and we’re running a series of twelve 100 hour tests to identify exactly why and how this problem is occurring. And it seems to be focused on the fact that we’re running the turbines at such low levels,” Bertacchi said.
Bertacchi added that he expects the issue to be fixed within the next 12 months.
