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KEOKUK, IOWA  A couple of the tall arch-shaped windows that line the powerhouse are broken. The old manual controls have been abandoned in place decades ago. And interior offices that once housed a large administrative staff are vacant and used for storage.

But what’s remarkable about the century-old Keokuk hydroelectric plant jutting into the Mississippi River near the Missouri-Iowa border is how little about the plant has changed — including its indelible ties to St. Louis.

Celebrated as an engineering marvel when it was completed in 1913, the Keokuk plant helped power St. Louis’ streetcar system. Now, a small but important part of Ameren Missouri’s generating fleet, it provides the juice for a new generation of conveniences — air conditioners, televisions, smartphones and computers.

Construction of the powerhouse and dam began in 1910 and required the excavation of more than a million cubic yards of soil and rock.

When the $25 million project was completed in the summer of 1913, it was the largest privately funded construction project in the world.

The plant supplied power not only to St. Louis but also to parts of Iowa and Illinois. Civic leaders in Keokuk thought it would transform the small Iowa city into a Midwest metropolis, according to “Keokuk and the Great Dam,” a book from John E. Hallwas that chronicles the project.

In the end, the Keokuk plant didn’t transform the city into a regional power.

“Even though the Keokuk Industrial Association promoted the town nationally as ‘the Power City’ only a few factories relocated to the community — partly because the cost of electric power was not as low as dam promoters had hoped, and partly because cities like Chicago and St. Louis still had far more advantages,” the book said.

Union Electric Co., Ameren Missouri’s predecessor, bought the powerhouse and transmission lines in 1925. The lock and dam are operated by the Army Corps of Engineers.

Much of the plant’s original equipment is still in place, including four of 15 giant cast iron turbines — the largest ever built when they were put into service a century ago.

“Most of the electrical stuff, the controls are all new,” said Warren Witt, Ameren Missouri’s director of hydro operations. But “most everything civil and mechanical is original.”

Keokuk is what’s known as a “run of the river” hydroelectric plant, meaning there’s no upstream storage reservoir. Its ability to generate electricity is solely dependent on the water level in the river.

The Corps of Engineers notifies Ameren of the flow available each day, and that determines how many of the 15 turbine-generators the utility operates.

On a recent tour, about 30,000 gallons of water passed through the plant’s gates every second, spinning the huge turbines and generating electricity.

Much of the old control room where crews monitored output remains frozen in time, a relic of history, replaced by employees positioned behind flat-panel computer monitors.

A century ago, it would have taken workers a half hour to get one of the generating units up and running. Today, it takes less than 5 minutes, said Larry Weiman, the plant superintendent.

Original plans for the Keokuk project called for twice as many generating units and a railroad bridge across the Mississippi River. But those plans were scrapped amid controversy and Congressional hearings. Steamboat companies argued that the dam impeded travel on the river below Keokuk, and local leaders were disappointed that the power project didn’t reduce electricity costs.

In fact, the Keokuk project itself almost didn’t get built.

The idea for a dam across the Mississippi River between Keokuk and Hamilton, Ill., had been conceived decades earlier when Gen. Robert E. Lee, then a lieutenant in the Army, reportedly surveyed the area for the War Department in the 1830s and proposed a dam to help tame the Des Moines rapids, an 11-mile stretch of river that falls 22 feet and made upstream navigation all but impossible.

Local leaders sought Congressional help for a dam decades later, and President Theodore Roosevelt signed a bill in 1905 that gave developers exclusive rights to construct a dam at the location if they began work within five years.

Hugh L. Cooper, a renowned engineer who had overseen construction of a hydroelectric plant at Niagara Falls, agreed to take on the project. But it didn’t move forward until 1910 when the Keokuk and Hamilton Water Co. secured contracts to deliver electricity to three St. Louis customers: Union Electric Light and Power Co., Laclede Gas Co. and United Railways Co., which operated streetcars in St. Louis.

Those contracts also posed another engineering challenge: No one at that time had ever transmitted electric power more than a few miles. Sending power from Keokuk to St. Louis meant the first use of high-voltage transformers and transmission towers.

Today, Keokuk remains a valuable source of electricity for a few reasons. It’s inexpensive, cleaner than burning coal or even natural gas. And although the amount of electricity it can generate is limited by the flow of the river, a unit can be started in minutes, providing needed power in case of a system emergency.

“If a big unit trips somewhere, someone’s got to pick that up,” Weiman said.

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