MidAmerican Energy has released a time-lapse video that shows the construction of its first concrete wind-turbine tower — the company’s tallest at 379 feet — in 6 minutes. Construction of the Adams County tower took 31 weeks. With the blades extended, the wind turbine is 557 feet tall, slightly taller than the Washington Monument. The concrete prototype is 100 feet taller than the surrounding wind turbines with steel towers. The blades came from Siemens in Fort Madison, and the concrete form came from EFCO Corp. in Des Moines. Siemens Americas Onshore Wind handled the construction.