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  • From: John Thomas Naisbitt <johntnaisbitt@gmail.com>
  • To: permaculture <permaculture@lists.ibiblio.org>
  • Subject: Re: [permaculture] Rainwater harvesting pond story
  • Date: Tue, 11 Aug 2009 11:13:56 -0600

Agreeing with Brent, the slopes should be at a 1:4 gradient. A slope of
natural impose usually rests at around 1:1.5 (eath fill natural fall,
natural sluff) which is only the beginning of the initial sluff which will
occur within the first few months without a retaining wall. (Which brings up
a safey monster of its' own.) After that, the pond wall will most likely
begin to create its' own slope "Healing" process by creating its own stable
slope gradient depending on the soil compostion.

If your operator had been on top of it, he could have suggested that you
create the 1:4 slopes as it would minimize the effort of digging towards the
toe of the machine which increases the time it takes to dig the excavation
and work at a slope away from the machine, which keeps the boom of the
excavator at a comfortable distance and near the optimal swing radius for
moving material from the excavation. This is dual purpose (stacking
functions) as it allows the operator to keep his machine on the 1:4 slope
and further the depth of the excavation to reach the desired elevations,
thus opening the possibilities of reaching your goal for the desired volume
of the pond. The only real restriction to this is the space available for
the pond as this does reduce volume possibilites.....in which case, you
could steepen the slopes to 1:3 which is still safe for excavator operation
*as long as the operator is trained in woking on a slope.*

The only other thought I have is that, being made of natural soils, no
matter what slope you excavate, the pond slopes will continue to settle
until the soils find their "Happy" place. Have you considered running cows
in the pond to build up bacteria (for the pond slime), work the slopes and
pond bottom, and compact the soils? (A kind of cow "romper room to eat and
play"; or cow "mosh pit", if you will.....no stage diving please.)
**
I do not intend to be misleading as to the intentions, skills, or mindset of
your operator, the hole is there.....make the best of it and please be safe
around the edges.

John

*

* On Tue, Aug 11, 2009 at 9:38 AM, Brent McMillan <brent@gp.org> wrote:

> As someone who use to work in the engineering department of a Sanitary
> District, the slope should not exceed 1:4 (One foot of rise to four feet
> of run)
>
> Anything greater than that is unstable and will probably only collapse
> over time anyway until it gets to a slope close to that.
>
> Sincerely:
>
> Brent McMillan, Steward of Woodhaven
> Avilla, IN, USA
>
> Suraj Kumar wrote:
> > Hi Guys,
> >
> > Your questions are all valid and my ideal shaped pond would have
> > looked exactly like a bowl. Minimal surface area, maximum volume. A
> > smoothly sloping pond would be, to mathematically put it, made up of
> > an infinite number of steps. In my case, its just 3 steps.
> >
> > Each step decreases surface area of water exposed to sunlight.
> >
> > However, the JCB operator mentioned in advance that the cost of the
> > operation will be proportionally expensive and time consuming - hence
> > we had to settle with 3 steps.
> >
> >
> > Cheers,
> >
> > -Suraj
> >
> > On Tue, Aug 11, 2009 at 8:29 AM, Lisa Rollens<rollens@fidnet.com> wrote:
> >
> >> Very interesting, Suraj, and quite a well done write-up. I also do not
> see
> >> how the straight sides will stay that way. Surely they will wash into
> >> gentle slopes. Another consideration...what if someone falls in. Can
> they
> >> he/she get out or would drowning possibility be high...esp a small
> child?
> >> That would worry me. Even a dog would have a hard time climbing out
> without
> >> a slope.
> >>
> >> Just my first impressions, hope they're useful, Lisa
> >>
> >>
> >> ----- Original Message -----
> >> From: "Suraj Kumar" <suraj@sunson.in>
> >> To: "permaculture" <permaculture@lists.ibiblio.org>
> >> Sent: Monday, August 10, 2009 10:28 AM
> >> Subject: [permaculture] Rainwater harvesting pond story
> >>
> >>
> >>
> >>> Hi Guys,
> >>>
> >>> On our tiny acreage farm (1.86 acres), we recently finished building a
> >>> 3 stepped 3825 sq.ft. sized pond with a max depth of 22 ft. We had
> >>> three goals:
> >>>
> >>> 1. Store water for irrigation needs during the dry-seasons (post
> >>> monsoon and then pre-monsoon)
> >>> 2. Conserve the constructed pits / wells / dams / hedges / whatever
> >>> structure
> >>> 3. Storing run-away water / Retrieving stored water must be doable
> >>> using as little energy as possible
> >>>
> >>> We rented out a backhoe excavator (JCB-3CX) and two tipper tractors
> >>> for this job.
> >>>
> >>> http://wiki.sunson.in/rain_water_harvesting explains the design in
> >>> terms of satisfying these above three goals.
> >>>
> >>> Please feel free to let out your comments!
> >>>
> >>> Cheers,
> >>>
> >>> -Suraj
> >>>
> >>> --
> >>> "The Greatest Shortcoming of the Human Race is
> >>> our Inability to Understand the Exponential Function"
> >>> Dr. Albert Bartlett
> >>> _______________________________________________
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> >
> >
> >
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