Dam help

3 posts
Mon, 03/02/2015 - 20:12 #1

Member for

9 years 9 months
abalone
Last seen: 03/04/2015 - 07:41
Joined: 03/02/2015 - 19:54

Dam help

Hi ,this is my first post so forgive me if my questions sound odd??? I recently put a dam on our property 10 acre hobby farm .and although the people digging the dam were experienced my dam will not hold water.we dug down to hard clay,and put a 4 meter base narrowing to a 2.5meter top.it has been full to the top twice in the last few months.it takes about 3-5days to drain complete.there are dams further along on next doors property. And very (you could water ski on them ) large dams opposite.some of the old stagers around here are saying that it has to fill up 3-4times before it seals ?? others are saying throw bentonite in ? ?others are saying wait until it dries then furrow the bottom and force bentonite in to the soil by driving over it etc, any help or suggestions would be welcome. Larry
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Tue, 03/03/2015 - 11:36 #2
peter_marybank
Last seen: 03/08/2018 - 21:05
Joined: 02/26/2015 - 13:47

Hello Larry,

Based on what you've outlined, (and without meaning to restate the blindingly obvious) somewhere in your earthworks there is pourus material. Bentonite is a possible solution, but it is not a simple as just bringing it in and incorportaing it.  There are many "it depends" that may influence it's success (or otherwise).

A dam should seal from Day 1 - imagine if dams supplying major cities had to fill and drain 3 or 4 times before they worked - not very satisfactory.

 Can I suggest:

Contact your local Dept of Ag in your state - they often have useful "fact sheets" in fixing leaking dams. They are just a good place to start and may be also be able to assist with suitable contacts in the private sector.

If you have some good agronomists that local commercial farmers use they may be worth talking with because they will have good knowledge of your local soils.

Talk with your neighbours and get the history of their dams - this is useful in understanding how wide spread (or local) the issue is.

Talk with other earth moving contractors it is probable that they have experienced this (or similar before).

You need to find people to locate and determine the pourus material in your earth works - then you can move towards a solution.

 

Watch the cost - you already have a degree of "sunk cost" in construction. Repairing dams is sometimes simple and reasonably priced - often it can be very expensive depending on how much and how wide spread the pourus material is in your dam site.

 

All the best

Peter

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Tue, 03/03/2015 - 12:47 #3
barb
Last seen: 09/17/2019 - 18:07
Joined: 11/23/2011 - 09:38

Hi Larry,

everything Peter said is absolutley spot on. Bentonite is the usual solution if the dam is very large. However, having said that, it seems the contractor may not have extracted some of the clay at the bottom to line the walls with- a usual practice. If the walls are porous the water will not hold. As Peter said, the dam should hold water from the first time it is full. The only water lost should be from natural surface evaporation and use by the farm and animals. If the dam is not too large, there is a solution that may work, but I do not know the cost. You can buy commercial dam liners, which are made of super heavy plastic similar to VisQueen used under concrete slabs, but much thicker. Suppliers of these, often advertise in rural newspapers such as ON the Land and the Queensland Country Life. This could be another solution to the problem.

 

Cheers,

 

Barb

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