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Associate

Join Date: Sep 2010
Location: Dubai
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Construction

11/11/2015 2:45 AM

Hi Gurus.

I want to start a small dam construction project for my community in africa as a way of trying to save the little runoff from the rainy seasons to come.

This I am doing as a way to reduce the effects of global warming induced drought. I want more information on how to save more water in the dam for small scale horticultural irrigation, what is the more durable material to use for the dam wall?

As a community we had suggested to use stone and cement for the dam wall ,and steel for reinforcement.

The gorge is just 10m wide and 25m deep at the proposed dam wall site. Help me with more ideas for a successful project.

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Guru
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#1

Re: Construction

11/11/2015 5:26 AM

I applaud you as a leader in your community! I don't have much to help you, as I am not a civil engineer. I think though, that you will get some very good replies here. Just stick around so you can answer questions that they will have. And they will!

Welcome to CR4 SIR G!

Mike

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#2

Re: Construction

11/11/2015 6:58 AM

Maybe you can get away with doing that on your own in Dubai but it would never fly here in the States.

Do you have any idea how the new dam will impact the environment that will now be subject to submersion and erosion or what effects your dam will have on the environment and people downstream who will now be cut off from the rain water the environment has depended on for millennia?

Why don't you just import a mating pair of North American Beavers and let nature take its course?

If you are going to go for it though, for that small of a dam you may consider prefabbed steel sections that can be assembled at the dam site.

Droughts come and go, always have and always will. If your environment is not suitable to sustain life, perhaps you should consider changing your location instead of trying to change your environment.

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#12
In reply to #2

Re: Construction

11/12/2015 10:18 AM

Droughts come and go, always have and always will. If your environment is not suitable to sustain life, perhaps you should consider changing your location instead of trying to change your environment.

Don't let the global warming doomsday supporters hear you say that. They prefer to assume we are a stupid species and will stay put when conditions get too difficult for life, and just die out. Even the deer, squirrels, and racoons around here know enough to move when food supplies get low. Haven't seen a blinkin one near my house in 6 months, when I am usually over run with them.

Not debating the warming issue - just saying proponents get a bit hysterical about outcomes based on current geographical positions of cities and towns.

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#14
In reply to #12

Re: Construction

11/12/2015 10:58 AM

"They prefer to assume we are a stupid species and will stay put when conditions get too difficult for life, and just die out."

You looked at California lately? Several years of drought, water rationing, a fault line that could drop the populated half of the state into the ocean with one good quake, and people are staying put, even encouraging others to come join them.

And let's not forget Centralia, PA, with a current population of ten, stubborn senior citizens. (Okay, one is only in his 50's, but he's the outlier in the bunch.)

Or am I just 'cherry-picking' my data, bringing up the extremeists to make my case. Let's look at Middle Africa. Say there is a drought hitting Uganda very hard this year, Where are the Ugandans supposed to go? Do they abandon their family farms, the only thing of any real value that they have and migrate en mass to the Democratic Republic of the Congo in hopes of better living conditions?

"Even the deer, squirrels, and racoons around here know enough to move when food supplies get low."

Yes, they move to a new area, and then they are competing with the critters who were already there over the used-to-be-enough-with-the-old-popilation food supplies, until one or both sides die off from starvation or fighting so that the remaining food is enough for the remaining critters.

"Not debating the warming issue - just saying proponents get a bit hysterical about outcomes based on current geographical positions of cities and towns."

And when was the last time you tried relocating an entire town? Chicago and New York are a little too big to budge, and even the tiny town of Centralia, PA cannot be successfully relocated. they started in 1984, and they probably won't get everyone out until 2055. 71 years to evacuate a town due to a coal fire? Not really a model of efficiency there.

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#16
In reply to #14

Re: Construction

11/12/2015 11:22 AM

So your opinion is - we are a stupid species?

Seems the Syrians have it figured out - just ask Eastern Europe.

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#17
In reply to #16

Re: Construction

11/12/2015 12:29 PM

"So your opinion is - we are a stupid species?"

Yes and no. The answer isn't simple because the question has hidden depth to it.

I think Tommy Lee Jones said it best in that movie about guys in dark suits: "The person is smart. People are dumb, panicky, dangerous animals, and you know it!"

The individual can work on logic and reason, the group will work on emotions (mostly fear) and rumors, unless they set up some way to enforce rational thought. Unfortunately, the way to enforce rational thought in a group is bureaucracy, which enforces literal interpretation of the rules, with NO room for any emotional factor. An unstructured group is a scared, angry, violent mob; a structured group is an emotionless, heartless sociopath of a 'synthetic gestalt person.'

Small groups of around a dozen or less can break this pattern, as long as they have good internal communication, and can decide and act free of any influence from an overly large 'mother group.' Small groups can also work in concert with other small groups, as long as either, good communication is maintained between liaisons' of each group, or each group has clearly defined goals within the larger project, so they aren't accidentally working at cross purposes.

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#3

Re: Construction

11/11/2015 8:20 AM

25 m deep is an 8 floor building, I think this thing is huge not small.

You need and a civil engineer.

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#15
In reply to #3

Re: Construction

11/12/2015 11:10 AM

I did one in West Africa (Cameroon) when I visited Peace Corps volunteer friends between oil patch jobs.

Look around. What equipment and materials do you have? For example, they had some dynamite left over from a mining operation near by that was used to blast the sides of their gorge (around 40 meters deep) to build the boulder back bone of the dam during the dry season, then seal the upstream face with massive amounts of palm thatch ballasted with smaller boulders. The hardest part was getting the mining equipment in position downstream from the gorge to dig the penstock back to the reservoir before the gorge was blasted.

Every site and situation is different, but the astute of local resources is the best approach instead of assuming you need to build an Aswan High Dam or the like.

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#4

Re: Construction

11/11/2015 9:01 AM

It might be better to make a series of small dams rather than one large dam...here is a guide that may help...

http://www.fao.org/docrep/012/i1531e/i1531e.pdf

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#7
In reply to #4

Re: Construction

11/11/2015 5:16 PM
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#8
In reply to #7

Re: Construction

11/11/2015 5:36 PM

What's another name for a contraceptive diaphragm?

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#5

Re: Construction

11/11/2015 9:40 AM

Good idea!

There is a very high level of hydraulic pressure exerted on the upstream side of the dam that must be taken into consideration.

This requires that the dam is much wider at the bottom than at the top.

This also requires that the builder fully understand the design mathematics and structural requirements required to install a dam that meets and maintains structural integrity during worst case water inflow from abnormal storm events.

Choosing a dam site where there is enough competent soil and bedrock to withstand the forces applied by the weight of the dam and the stored water is crucial.

Ensuring that the dam has properly designed overflow paths that allow release of stored water without suffering damage to the toe of the dam is very critical.

Design and installation of a dam is normally done by a team of engineers from multiple disciplines. (Mechanical, civil, structural, geological, environmental, and hydraulic.)

An in-depth, competent study of dam site selection and dam design requirements for the site selected is required in order to be successful in building a safe dam that will last for a very long time.

There are world organizations that provide technical support for these types of projects which have volunteer personnel that can provide much needed technical support for your project.

If you have not done so, I suggest you start by contacting your local government and find out if you are allowed to build the dam and if so, obtain a copy of their requirements and regulations.

Many of the dams built in the USA were constructed by the federal government Army Core of Engineers and all of the site studies and structural plans are public records which are available for viewing via the internet.

Studying several of these dams will enlighten you immensely on the dam requirements as well as the risks of building a dam.

I would suggest you carefully consider building a dam that allows downstream flow to mimic normal conditions so that the water stored in the dam does not become stagnant and the downstream areas do not environmentally suffer from the dam construction.

Storing storm water behind a dam and providing a constant source of water flow could be very beneficial not only to humans but also to the wildlife and to the land if designed and constructed properly.

If installing a dam is not feasible it would be a good idea to pursue drilling wells and utilizing solar or wind power to pump the water.

A combination of both would be optimal.

Good luck and please keep us informed on your progress.

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#6

Re: Construction

11/11/2015 10:09 AM

An admirable project, but based on your dimensions, this would not be a small dam.

While researching the viability of a new undertaking, it is wise to learn about previous attempts and how they failed. I suggest researching about previous dam failures, starting here:

https://en.wikipedia.org/wiki/Dam_failure

And this is not to discourage you, but rather to validate the potential impact your project could have if done incorrectly. Rather than helping the local communities, it could wipe them out.

From there, due to the scope of this project, I would recommend reaching out to large civil engineering firms who might be willing to donate assistance, it's a tax write-off for them and expert judgment for you.

An alternative in the meantime is construct some cisterns and divert some of the flow to them. This will provide some benefits over the years it would take to correctly develop a dam project of this magnitude.

Good Luck

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#9

Re: Construction

11/12/2015 2:21 AM

I have thought about this particular need myself, and my thoughts on this are: rather than build a dam, consider digging as large, and as deep a hole as possible at the bottom of a large sloped drainage. Maybe even several smaller holes for simplicity and ease of construction. Two other things to consider is to build an open air structure with a roof over the well, which limits direct sunlight to ameliorate evaporation; AND, line the wells with fired tiles, or clay to prevent as much leakage as possible. I realize there is probably not much good old orange Georgia clay in Africa; but, depending on how much money you can raise it might be worth considering importing a few barges of the stuff. As for the actual application of the lining, someone else here probably has that expertise. It would probably require digging the holes in a parabolic shape, so that the lining material on the walls won't have a tendency to collapse in on the center.

If you planed on moving dirt anyway, you have to do something with the dirt from the wells; so, the higher, and wider you can make the drainage field, the more water will go where you want it.

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#10

Re: Construction

11/12/2015 4:58 AM

Kempe's Engineers' Yearbook, any edition, has dam construction as part of one of its chapters on Civil Engineering. The important thing is to make sure the wall can withstand the thrust provided by 25m of water. Get reading!

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#11

Re: Construction

11/12/2015 9:36 AM

I think it's funny, actually sad, that even in a remote, part of the world that the faulty thinking of "global warming impact" has spread.

These people who have promulgaed this hoax of global warming are masters at marketing.

I do applaud SIR G for wanting to utilize the resources available and to think ahead, being proactive, rather than just taking what is given at the immediate time. Living life with intention and proactivity is always better than being reactive in nature.

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#13

Re: Construction

11/12/2015 10:49 AM

As some others have mentioned there are organizations that can help you with this. Two of them are Engineers Without Borders and Water for People (more likely to help build a well than a dam). I personally do not do a lot of dam related projects so I am not much help. This is a rather large project and I expect you will want to have an experienced professional to help.

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#18

Re: Construction

11/13/2015 3:42 AM

Thank you guys for your good advice and suggestions.I will keep you updated on the developments on the project.I have a team of engineers who are part of the community and former students of tha community school.This project is 100% community oriented.Its in Zimbabwe in southern Africa.Some might be curious to know where exactly in Africa.The project will commence May 2016 finishing August 31st 2016.

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#19

Re: Construction

11/19/2015 7:37 AM

These may make you think long and hard

https://www.whatdotheyknow.com/request/the_initial_report_on_the_glebe

http://www.bbc.co.uk/history/domesday/dblock/GB-420000-372000/page/19

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#20

Re: Construction

01/12/2016 12:11 AM

Though I'm not a civil engineer, I would recommend studying dam FAILURES, especially of the size and type you plan.

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