Mactaquac Dam: What to do with the Quac?

Taeolas · #1 Posted **Oct 2, 2014, 12:54 PM**

We have about 15 years now to decide what to do with the damn dam. NBPower is estimating that whatever is done, will cost around 5 billion dollars regardless.

Currently the options are:

1. Repair/rebuild it. Pros: It still generates power. Cons: Most expensive solution.

2. Remove the generation capacity, leave the basic dam: Pros: Cheaper, minimal impact. Cons: Still pricey, no more income from power generation.

3. Restore the river; take it all down. Pros: River is back to normal. Cons: No more power generation. Diminished control of the river during the spring.

So what should we do with the Quac? Is it worth saving or should we just go the green route and restore the river?

If we decide to take it all down (very unlikely admittedly), what impact would that have on Mactaquac and Freddy?

Mactaquac would lose most of its waterfront area which would be economically disastrous.

Would Freddy be at risk for flooding? Would we need to add ice breakers in front of Westmorland Bridge?

Woodstock would regain its river island parks, and the reversing falls (or the currents at least) would reach up to Woodstock and beyond again (supposedly)

Personally, I'm not sure where I stand on this. On the one hand, I don't think we could afford to lose Mactaquac's power generation in the years to come, unless there is a big breakthrough in the next 10 somewhere. On the other hand, part of me wants to see the Saint John opened up again, especially the above dam stretch.

But in any case, I'm pretty sure the middle solution is a nonstarter. It's pretty much the worse of both options, though if they decide to reopen the dam it would be easiest to restore from.

And I have no clue how rising sea levels and/or more extreme weather will affect the dam, or the opened river.

cl812 · #2 Posted **Oct 2, 2014, 1:25 PM**

In my opinion its a no brainer to refurbish the generating station. I understand they have to go through their due diligence and explore all options but I suspect in the end the chosen option will be to refurbish it.

Not sure the removal of the dam would be the cheapest option either, there would be significant remediation involved if the head pond were gone and not to mention the actual construction costs invlolved to the remove the spillway/concrete sections and the earthen dam (which is not expected require any work if the dam remains). It is likely this would be the most unpopular choice with the majority of the public as well. While the river would be restored to its natural state there would be significant loss of fish habitat as well as for other wildlife.

For the option to leave the dam in place but to remove the generating station would not be much cheaper either, as the spillway and concrete sections of the dam would need to be completely rebuilt, given the issues with the concrete. The only capital cost saving would be the construction of the new power house/turbines, but you lose a relatively cheap (and stable operating cost) power generation and associated revenues. Also pretty sure if the generating station were rebuilt efficiency could be improved upon and generation capacity would increase as a result.

MonctonRad · #3 Posted **Oct 2, 2014, 2:05 PM**

Good idea for a thread.

I agree with you that the middle option makes the least sense. It's almost a non decision to adopt this course. You either go big or go home.

We need the electrical generation capabilities of the dam. I would say the obvious choice would be to completely refurbish the structure. It provides a stable supply of green energy. If we do this, I wonder if there is some way of mitigating the alkali aggregate problem which shortened the lifespan of the dam the first time round??

The second choice would be to deconstruct the dam completely and return the river to it's original status. Of course, it would likely take a century for the river valley in the head pond area to begin to resemble it's former self. It takes a long time for trees to regrow and habitat to be re-established. In the meantime, the head pond would just be a long brown scar on the landscape. Also, as mentioned, any recreational value for Mactaquac Park would be lost. The electrical generating capacity of the dam would have to be replaced - perhaps by new wind farms.

I vote for option one. It might be more expensive, but it would be the less disruptive option, and should provide for lots of infrastructure jobs during the reconstruction phase of the project.

OliverD · #4 Posted **Oct 2, 2014, 2:28 PM**

Quote:

Originally Posted by Taeolas

3. Restore the river; take it all down. Pros: River is back to normal. Cons: No more power generation. Diminished control of the river during the spring.

That's a simplistic assessment of the "pros". It would take decades for the river to be back to "normal" and in the meantime it would have a huge negative effect on the people that live on the headpond.

I agree that a complete refurbishment is the only option that really makes sense. It's expensive, but it's also the only option that guarantees future revenue – a lot of revenue.

Taeolas · #5 Posted **Oct 2, 2014, 2:36 PM**

True, I agree that rebuilding the generation and keep it producing power is the only real solution; at least that one will eventually (theoretically) pay itself back.

Option 2 is a non option. And the Restore the River is probably a disaster in the making. (Though as I said in the OP, part of me is curious to see what the Saint John would be like back to what it used to be, when the tides pushed back up past Woodstock and such.)

In any case, that should be a major construction project in the decade to come when they do figure out what to do.

Taeolas · #6 Posted **Oct 3, 2014, 11:07 AM**

NBPower's preferred choice seems to be to keep it going (which makes sense).

They're now looking into a potentially cheaper method to rebuild the dam by basically rebuilding it without shutting it down.

Regardless though,

Quote:

NB Power intends to have a preferred option in front of the provincial government by 2016. Thomas said construction would likely need to start around 2020.

OliverD · #7 Posted **Oct 3, 2014, 1:17 PM**

This thread got me curious about the original construction of the Mactaquac dam and I found this album of photos taken between '64 and '68: https://www.facebook.com/media/set/?...1460033&type=3

Ire Narissis · #8 Posted **Oct 3, 2014, 1:58 PM**

Quote:

Originally Posted by MonctonRad

If we do this, I wonder if there is some way of mitigating the alkali aggregate problem which shortened the lifespan of the dam the first time round??

Simple: use a different kind of rock for the concrete; one that is not prone to the same issue.

I'll take my engineering consultation cheque now, please, NBPower. Thank you!

cl812 · #9 Posted **Oct 3, 2014, 3:11 PM**

Quote:

Originally Posted by OliverD

This thread got me curious about the original construction of the Mactaquac dam and I found this album of photos taken between '64 and '68: https://www.facebook.com/media/set/?...1460033&type=3

Very cool, good find.

RedBall · #10 Posted **Oct 4, 2014, 2:19 AM**

Quote:

Originally Posted by cl812

Very cool, good find.

I don't know if this was ever posted here, but, there was a research project done or is being done by UNB.

http://vimeopro.com/unbmediaservices...search-project

Bishop2047 · #11 Posted **Oct 4, 2014, 3:15 AM**

Quote:

Originally Posted by RedBall

I don't know if this was ever posted here, but, there was a research project done or is being done by UNB.

http://vimeopro.com/unbmediaservices...search-project

Good find! Original cost was 120 million, WOW! Up to 5 billion to refurbish.

josh_cat_eyes · #12 Posted **Oct 4, 2014, 2:33 PM**

I wonder if there is a way to increase its generation capacity when they refurbish it? It would increase the cost but it would help reduce the blow when they have to refurbish point lepreau again eventually.

Freddypop · #13 Posted **Oct 4, 2014, 2:50 PM**

My understanding from discussions with those on the "inside" is that to build from scratch would cost 8 billion....so a 5 billion expenditure for a refurbishment may not be so bad.

josh_cat_eyes · #14 Posted **Oct 4, 2014, 8:17 PM**

Would it be worth 8 billion if they could also increase its generation capacity by adding turbines or replacing existing ones with newer larger capacity ones.

cl812 · #15 Posted **Oct 5, 2014, 8:44 PM**

Might be able to increase gen capacity just with newer more efficient turbines. Pretty sure they only run all 6 units when the water is high and run less when the flows are lower, so not sure it would be possible to increase the number of units to increase gen ability. Since the energy produced is related to the potential energy involved from the head of water (ie height of the dam or height of the head pond) the only other way to increase the generation capabilities would be to increase the height of the dam.

josh_cat_eyes · #16 Posted **Oct 6, 2014, 12:31 AM**

Quote:

Originally Posted by cl812

Might be able to increase gen capacity just with newer more efficient turbines. Pretty sure they only run all 6 units when the water is high and run less when the flows are lower, so not sure it would be possible to increase the number of units to increase gen ability. Since the energy produced is related to the potential energy involved from the head of water (ie height of the dam or height of the head pond) the only other way to increase the generation capabilities would be to increase the height of the dam.

Well since they have to replace it couldn't they increase the height? I just hate to see them spend all this money and then get nothing more out of it then the did before!

MonctonRad · #17 Posted **Oct 6, 2014, 1:27 AM**

Quote:

Originally Posted by josh_cat_eyes

Well since they have to replace it couldn't they increase the height? I just hate to see them spend all this money and then get nothing more out of it then the did before!

If they increased the height of the dam then they would be increasing the water levels in the head pond which would mean more land expropriations and flooding.

I'm old enough to remember the debacle over flooding of productive farmlands in the area of the current head pond. There would be outrage if more farms and homes had to be abandoned or relocated.

OliverD · #18 Posted **Oct 6, 2014, 1:38 PM**

Quote:

Originally Posted by MonctonRad

If they increased the height of the dam then they would be increasing the water levels in the head pond which would mean more land expropriations and flooding.

I'm old enough to remember the debacle over flooding of productive farmlands in the area of the current head pond. There would be outrage if more farms and homes had to be abandoned or relocated.

Also, the land on the headpond is now much more valuable so expropriation would mean many millions of dollars.

Whaler · #19 Posted **Oct 7, 2014, 12:39 PM**

NB Power has their minds made up and are now just conditioning the public.
New damn will be built and started in the next few years (no choice).
Refurbishment is not a good option. Too many issues with the exisiting structure and by far out of date. Just like an old house, twice the work to remodel.
Watch the news.

Ire Narissis · #20 Posted **Oct 7, 2014, 2:09 PM**

Honestly, that doesn't bother me terribly. Provided, that is, that a new dam could increase generation capacity in order to offset its costs.

I guess the real question is whether a new dam could operate better than a refurbishment. But with the dam's concrete woes, if a new one can be built that would dramatically outlive the present one even with refurbishment, that seems like the better option.

Removing the dam altogether is, of course, right out, as people have expressed. The headpond is part of our landscape now and Mactaquac is one of our biggest stations; it's not a piece of infrastructure that can just be torn down and forgotten.