April 28, 2026 • 8 mins
Gram Butchers looks at whether detainment bunds are practical or just another farming cost.
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Speaker 1 (00:08):
Graham, Butcher Farine consultant joins us once again on the
muster and studio as he usually is, kid A Graham Afternoon.
You're deeing this in Indian summer almost.
Speaker 2 (00:18):
Well, I think it probably is. I mean it's temperatures
are pretty good. We've had one half decent frost, I suppose,
and it's nearly May, so I think people are starting
to get into winter mode now. But I think there's
been a lot of natural flushing with the conditions we've had,
so anticipating some pretty reasonable sort of scanning results.
Speaker 1 (00:36):
And just looking at these so temperatures is still staying
towards a double digits mark and pretty yeah, Lesbians minus
three frost is getting up there. We're not, I suppose
we're not used to it.
Speaker 2 (00:48):
Though, just getting soft.
Speaker 1 (00:49):
Andy, you're the one. We're in the jacket, they aren't.
We going to talk about the pavement bats today now.
I had John Patterson on the shar a couple of
weeks ago in relation to some work happening regarding the
Palmer Harker water Care group. You went along to that field.
Speaker 2 (01:03):
Day, Yeah, I did. It was really interesting. The reason
I went along is I thought detainment bunds might be
some sort of substitute or help ease the requirements around
critical source areas. So that was the big thing on
my mind as well. I went to go now detainment bonds?
Did John actually explain what they were?
Speaker 1 (01:22):
And it told about them in a little bit of
detail because it's not something you really come across every day.
Speaker 2 (01:27):
Detainment bonds are a bit different from sediment traps. Sediment
traps are set up with a continuous sort of flow,
so water comes in, nutrients, sediments trapped, and water flows
out operates all the time. Detainment bonds are difference. They're
really designed to catch storm surges a lot of water
coming off, so you basically build a dam plug in
(01:49):
the bottom plug the plug for heavy rainfalls coming through.
You close the plug and catch the water. Critical bit
is that water needs to stay still for three days
for settle for sediment to settle, So you trap the
storm surge still water for three days, sediment settles, let
it go into the river. So sounds quite simple for
(02:14):
every hecta that well, well, the first thing it comes
down to a design of the whole thing. So you
look at your farm and here's a catchment. It might
be thirty hectares, it might be fifty hectares, it might
be one hundred hectares. But in that catchment water flows
down through a point and at that point you've got
to decide where you put your your bund, your dam,
and that that's the critical part of the design program. Now,
(02:38):
all the Southland has been contoured in the light program.
They finished that about two thousand and twenty four, I
think it was with Environment Southland. So that's a very
good resource. You can see where all your contours are.
So choosing where you put the bund is a critical
part of how much is it going to cost? Now
the one out at Alistairs he had a thirty five
(02:59):
hecta catchment and for every hect here you need one
hundred and twenty cubic meters of storage. That to me
sounded like quite a lot, but that's only twelve mili
per hectare runoff, so you get twelve mills if it
all runs off, you've got one hundred and twenty cubic
meters of water that's off a hectare. Staggering really, So
(03:19):
for every hectare, the standard design thing is one hundred
and twenty cubic meters. So Alistair had a catchment area
of thirty five hectares. So he's got a bund with
a capacity of four thousand, two hundred cubic meters. Right,
so storm surge comes through. Plug the hole in the bottom,
catch the water, let it settle, sediment disappears, pull the
(03:39):
plug out, she goes sounds quite simple. The cost is
a reasonably important factor for the whole thing. Alistair mentioned
it costs about thirty grand to put his in three
years ago. If we say if you did the same
thing today, it was going to be thirty five. There's
one thousand dollars a hectare, so that's getting up now.
(04:01):
John did make the point if you've got areas on
the farm that suit where you put your bund, it
can be significantly cheaper, which was good to hear because
I thought a thousand dollars a heac there is actually
a bit over the top of it.
Speaker 1 (04:15):
It's a lot of money.
Speaker 2 (04:16):
It's a lot of money. So at the field day
they went through a whole lot of design issues. How
you build it. You have an overflow race, you have
a riser, and if a whole lot of water comes through,
it goes down the riser and soaks away, so if
you get a really bad storm surge, it's not going
to overflow the dam or wash things away. So they
(04:36):
work pretty well. But a thousand dollars a heck there
got my interest. So I asked the question, is this
a way of easing the critical source area restrictions that
we have, because critical sauce areas can be a real
pain on some farms. They can take up a significant
part of a paddock and they can make it they
(04:57):
can just about make it unreasonable to because if you
put crop on it, you're going to have a real
funny shape crop and it gets hard defense and all
that sort of carry on. The other thing that crossed
my mind was critical source areas it's got to be
in grass. You're not allowed to graze it, so it's
going to get long. It's going to be a pariana
nursery area, because that's the conditions that paranha like over
(05:18):
the summer, just long grass, ungrazed, no sunlight perfect. So
that's a bit of an issue. So I was a
bit disappointed to hear John say that it would have
been his worse nightmare to think that critical source areas
would disappear as well. So yes, I'm in two minds.
(05:38):
I think we're going to hear quite a bit more
about detainment bonds. The bit I'm a little bit concerned
about if it's not going to help ameliorate critical sauce
area restrictions. If regional counsels jump onto this and say
here's a tool that farmers can use and it works
its way into legislation, could be a bit of an
(05:58):
issue because of the cost.
Speaker 1 (05:59):
Issue printical for the average khaki.
Speaker 2 (06:02):
If you've got the right area to put it, and
I think Alistair's one, I can't remember the woods of
the thing. It must have been must have been one
hundred hundred and twenty meters long. I suppose that you've
got to have clay, so you've got to you've got
to key it into the subsurface. You've got to use clay,
(06:23):
cover it with soil. And one of the theories is
that you only hold water for three days, let the
water train away, and you'll always have grass so it's
always grazable. I'm not too sure how important that part is.
Maybe it's better to go for a bigger dam, have
it in water all the time, let it drain away.
Occasionally and use it for firefighting or stockwater or something
(06:44):
like that. So I think that's probably in my book,
a bit more work to do on whether we should
use or whether we can use attainment bonds and use
them economically.
Speaker 1 (06:53):
One hundred and twenty cubic meters of water storage behind
a bund for every hect year of catchment.
Speaker 2 (06:59):
That's exactly what I say. Don't please you saw that there?
Speaker 1 (07:02):
Yeah, I suppose we can get off them.
Speaker 2 (07:04):
It's surprising. I mean, one hundred and twenty keeping meters
of water twelve mill run off on a heck there,
that's that's a lot. And I think the height of
Alistair's bund was about two meters and he made the
point when you get water under pressure, but it behaves
quite differently when you pull the plug and you've got
to use gaskets and all sorts of things in the day.
(07:25):
But that's that's the practical thing you get to when
you design your whole thing anyway, So it's going to
be interesting to see what develops entertainment buns.
Speaker 1 (07:33):
And the Palmerhaka Water Care Group give them a shoutout
as well. They're doing some more some work there.
Speaker 2 (07:40):
They certainly are that postabley of water management in New Zealand?
Speaker 1 (07:44):
I think, yeah, I're doing a great job there. Good
on your grant. You stay warm so afternoon.
Speaker 2 (07:48):
I certainly will.
Speaker 1 (07:52):
Graham Butcher farm consultant based here and Gore Kelly Buckingham
is up next from darien Zed. Before the end of
the hour McCleary the great Man from Sheerwell on New Zealand.
He catches up
Graham, Butcher Farine consultant joins us once again on the
muster and studio as he usually is, kid A Graham Afternoon.
You're deeing this in Indian summer almost.
Speaker 2 (00:18):
Well, I think it probably is. I mean it's temperatures
are pretty good. We've had one half decent frost, I suppose,
and it's nearly May, so I think people are starting
to get into winter mode now. But I think there's
been a lot of natural flushing with the conditions we've had,
so anticipating some pretty reasonable sort of scanning results.
Speaker 1 (00:36):
And just looking at these so temperatures is still staying
towards a double digits mark and pretty yeah, Lesbians minus
three frost is getting up there. We're not, I suppose
we're not used to it.
Speaker 2 (00:48):
Though, just getting soft.
Speaker 1 (00:49):
Andy, you're the one. We're in the jacket, they aren't.
We going to talk about the pavement bats today now.
I had John Patterson on the shar a couple of
weeks ago in relation to some work happening regarding the
Palmer Harker water Care group. You went along to that field.
Speaker 2 (01:03):
Day, Yeah, I did. It was really interesting. The reason
I went along is I thought detainment bunds might be
some sort of substitute or help ease the requirements around
critical source areas. So that was the big thing on
my mind as well. I went to go now detainment bonds?
Did John actually explain what they were?
Speaker 1 (01:22):
And it told about them in a little bit of
detail because it's not something you really come across every day.
Speaker 2 (01:27):
Detainment bonds are a bit different from sediment traps. Sediment
traps are set up with a continuous sort of flow,
so water comes in, nutrients, sediments trapped, and water flows
out operates all the time. Detainment bonds are difference. They're
really designed to catch storm surges a lot of water
coming off, so you basically build a dam plug in
(01:49):
the bottom plug the plug for heavy rainfalls coming through.
You close the plug and catch the water. Critical bit
is that water needs to stay still for three days
for settle for sediment to settle, So you trap the
storm surge still water for three days, sediment settles, let
it go into the river. So sounds quite simple for
(02:14):
every hecta that well, well, the first thing it comes
down to a design of the whole thing. So you
look at your farm and here's a catchment. It might
be thirty hectares, it might be fifty hectares, it might
be one hundred hectares. But in that catchment water flows
down through a point and at that point you've got
to decide where you put your your bund, your dam,
and that that's the critical part of the design program. Now,
(02:38):
all the Southland has been contoured in the light program.
They finished that about two thousand and twenty four, I
think it was with Environment Southland. So that's a very
good resource. You can see where all your contours are.
So choosing where you put the bund is a critical
part of how much is it going to cost? Now
the one out at Alistairs he had a thirty five
(02:59):
hecta catchment and for every hect here you need one
hundred and twenty cubic meters of storage. That to me
sounded like quite a lot, but that's only twelve mili
per hectare runoff, so you get twelve mills if it
all runs off, you've got one hundred and twenty cubic
meters of water that's off a hectare. Staggering really, So
(03:19):
for every hectare, the standard design thing is one hundred
and twenty cubic meters. So Alistair had a catchment area
of thirty five hectares. So he's got a bund with
a capacity of four thousand, two hundred cubic meters. Right,
so storm surge comes through. Plug the hole in the bottom,
catch the water, let it settle, sediment disappears, pull the
(03:39):
plug out, she goes sounds quite simple. The cost is
a reasonably important factor for the whole thing. Alistair mentioned
it costs about thirty grand to put his in three
years ago. If we say if you did the same
thing today, it was going to be thirty five. There's
one thousand dollars a hectare, so that's getting up now.
(04:01):
John did make the point if you've got areas on
the farm that suit where you put your bund, it
can be significantly cheaper, which was good to hear because
I thought a thousand dollars a heac there is actually
a bit over the top of it.
Speaker 1 (04:15):
It's a lot of money.
Speaker 2 (04:16):
It's a lot of money. So at the field day
they went through a whole lot of design issues. How
you build it. You have an overflow race, you have
a riser, and if a whole lot of water comes through,
it goes down the riser and soaks away, so if
you get a really bad storm surge, it's not going
to overflow the dam or wash things away. So they
(04:36):
work pretty well. But a thousand dollars a heck there
got my interest. So I asked the question, is this
a way of easing the critical source area restrictions that
we have, because critical sauce areas can be a real
pain on some farms. They can take up a significant
part of a paddock and they can make it they
(04:57):
can just about make it unreasonable to because if you
put crop on it, you're going to have a real
funny shape crop and it gets hard defense and all
that sort of carry on. The other thing that crossed
my mind was critical source areas it's got to be
in grass. You're not allowed to graze it, so it's
going to get long. It's going to be a pariana
nursery area, because that's the conditions that paranha like over
(05:18):
the summer, just long grass, ungrazed, no sunlight perfect. So
that's a bit of an issue. So I was a
bit disappointed to hear John say that it would have
been his worse nightmare to think that critical source areas
would disappear as well. So yes, I'm in two minds.
(05:38):
I think we're going to hear quite a bit more
about detainment bonds. The bit I'm a little bit concerned
about if it's not going to help ameliorate critical sauce
area restrictions. If regional counsels jump onto this and say
here's a tool that farmers can use and it works
its way into legislation, could be a bit of an
(05:58):
issue because of the cost.
Speaker 1 (05:59):
Issue printical for the average khaki.
Speaker 2 (06:02):
If you've got the right area to put it, and
I think Alistair's one, I can't remember the woods of
the thing. It must have been must have been one
hundred hundred and twenty meters long. I suppose that you've
got to have clay, so you've got to you've got
to key it into the subsurface. You've got to use clay,
(06:23):
cover it with soil. And one of the theories is
that you only hold water for three days, let the
water train away, and you'll always have grass so it's
always grazable. I'm not too sure how important that part is.
Maybe it's better to go for a bigger dam, have
it in water all the time, let it drain away.
Occasionally and use it for firefighting or stockwater or something
(06:44):
like that. So I think that's probably in my book,
a bit more work to do on whether we should
use or whether we can use attainment bonds and use
them economically.
Speaker 1 (06:53):
One hundred and twenty cubic meters of water storage behind
a bund for every hect year of catchment.
Speaker 2 (06:59):
That's exactly what I say. Don't please you saw that there?
Speaker 1 (07:02):
Yeah, I suppose we can get off them.
Speaker 2 (07:04):
It's surprising. I mean, one hundred and twenty keeping meters
of water twelve mill run off on a heck there,
that's that's a lot. And I think the height of
Alistair's bund was about two meters and he made the
point when you get water under pressure, but it behaves
quite differently when you pull the plug and you've got
to use gaskets and all sorts of things in the day.
(07:25):
But that's that's the practical thing you get to when
you design your whole thing anyway, So it's going to
be interesting to see what develops entertainment buns.
Speaker 1 (07:33):
And the Palmerhaka Water Care Group give them a shoutout
as well. They're doing some more some work there.
Speaker 2 (07:40):
They certainly are that postabley of water management in New Zealand?
Speaker 1 (07:44):
I think, yeah, I're doing a great job there. Good
on your grant. You stay warm so afternoon.
Speaker 2 (07:48):
I certainly will.
Speaker 1 (07:52):
Graham Butcher farm consultant based here and Gore Kelly Buckingham
is up next from darien Zed. Before the end of
the hour McCleary the great Man from Sheerwell on New Zealand.
He catches up
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