What exactly would Enerdu change here in Almonte?

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by Brent Eades

There’s much controversy over Enerdu’s proposed creation of a new powerhouse on the banks of the Mississippi here in town.

How will it affect the look of the river as it flows through town? What impact might changing water levels have on the river towards Appleton, where trees are dying off in great numbers? Will the proposed construction disrupt tourism and drive away visitors?

(See map below.)

I don’t have clear answers to these questions. But I can present my take on the plans and drawings recently released by Carp’s OEL-HydroSys firm in their final report on the Enerdu proposal. (I stress that I’m neither an engineer nor an environmental expert — the following is simply my own interpretation of what I’ve read about proposed construction here in Almonte.)

My summary: Enerdu wants to dredge out a 50 metre-long section of the riverbed near Menzies House, in order to “improve hydraulic behaviour upstream of the intake canal”, which will “result in decreased water velocity and head losses at the intake canal and dam junction, improving both hydroelectric production and the discharge capacity of the dam.”

In other words, dredging the riverbed would create a deeper channel, which would make the water less turbulent as it approaches the planned powerhouse.

An Obermeyer weir gate in India.

The existing wooden weirs visible from Riverwalk behind the old Town Hall would be replaced with modern concrete equivalents, which again would help direct the river’s flow towards the powerhouse as required. These would be topped with inflatable “Obermeyer weir gates.” Enerdu would also excavate a section of riverbed above and below the weirs.

The OEL-HydroSys report states that “following consultation with concerned members of the public, [Enerdu] redesigned the original plans to the new weir in order to preserve the first set of falls.” This appears to be the case — the falls will remain, but somewhat altered in appearance.

Just below the train bridge Enerdu would build a new ‘intake canal wall’, which would further direct flow towards the proposed new powerhouse (adjacent to the current Enerdu building.)

The new powerhouse

The new powerhouse would be large, make no mistake about that. Its proposed size is 34 metres by 15 — about 110 feet by 50. Its height would be about one story.

Would this change the ‘classic view’ of Almonte? Well yes, of course it would. Would that be a disaster? Maybe not — if enough care were given to its design, perhaps the powerhouse could in time blend in. Hard to say.

Below the powerhouse, Enerdu wants to deepen the ‘tailrace’ in the riverbed, again so as to improve the flow of water through the turbines.

I suggest you read the final Enerdu reports so as to draw your own conclusions. And certainly visit the Mississippi Riverwatchers site for another point of view.

The map below is a composite taken from the OEL-HydroSys reports, with my own colouring and annotations added. I don’t guarantee its precision, but I think it’s reasonably close.

UPDATE: Thanks to Al Seaman for pointing out that my initial map showed only one phase of the proposed riverbed excavation. I’ve revised the map accordingly.

 

This drawing shows the proposed powerhouse.