Wednesday, November 21, 2012

Making of SST #2 : Random Rubble Irrigation Tank

Last month, we concluded the cultivation and development of Phase 2. This consisted of several dozen acres of Mango UHD and Melia Dubia (15x15 ft). During Phase 2, we also decided to proceed with inter-cropping of fodder crops. The large acreage required another sub-surface tank (SST) for irrigation.

Last year, we constructed our first tank. In case you missed reading that posting, you can find it here . This time around, we decided to use random rubble instead of bricks. The former has a significant cost advantage over bricks.

The new tank is 22 ft x 22 ft x 10 ft which translates into approx capacity of 1.35 lakh litres.

Steel reinforcement grid 8"x8" being laid to contain the hydrostatic pressure from the bottom of the tank















Construction of the side walls with random rubble.
















Walls erected up to the ground level..















Tank ready, drip system installed!















Initial testing of tank at half capacity.



















Last time around, inner and outer sides were plastered which led to budget overruns. This time, we did not plaster the walls, instead suffered from several leaks due to gaps and partially due to poor workmanship. Subsequently, we ended up plastering the exterior sides which seems to contain the leaks. 

Due to different material and design, we were able to save considerably even though cost of cement and labor has increased in the last one year. We hope to be able to service the entire plantation between our two SST tanks including future Phase 3 needs.

18 comments:

  1. Thanks for the update..

    may i know what is the comparative costs i.e.forsimilar capacity of tank using brick howmuch did it cost and for this current design how much did it cost?

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    Replies
    1. Tank constructed with RR was approx about 15% cheaper (in spite of higher labor and material cost, more than a year later). Depending on the season, bricks can get expensive, moreover the volume of RR is almost 2-4 times that of bricks, which in turn translates into savings in cement and labor.

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  2. Thanks for the update, looks nice.

    I think this Random rubble (irregular shaped stone bricks) costs much more than brick, isn't it?

    Could you tell us the cost please?

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    Replies
    1. RR cost ranges from Rs 7 - 10 but then this can vary depending on your location from the quarry. RR is more expensive per piece but it is definitely much cheaper per unit volume.

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  3. Looks Good.

    Which are the fodder crops you are growing?

    Fodder do u sell it or u have dairy farm to use it?

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    Replies
    1. Planning on agathi, lucerne, planning on starting a goat farm soon.

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  4. Hi,

    Reading about the earlier SST, the cost is about Rs 1-2 per liter. However, you have made an attempt to reduce cost in this second SST.

    Since cost is a major factor, I was wondering why you didn't go for plastic film lined pond. Life of plastic lined pond is only about 5-6 years, but then subsidy is available and the cost can reduce to 6 to 12 paise per liter. ( http://www.ncpahindia.com/articles/article21.pdf )

    The governments reasoning for promoting plastic film lined ponds is that, despite their shorter life, the farmer should be able during that period to become profitable and afford a permanent tank at the end of the period.

    Obviously, govt claims to be taken with a pinch of salt. But seriously, why did you reject plastic film lined pond apart from shorter life issue?

    Vernon
    PS: are you growing papayas also?

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    Replies
    1. We considered plastic lining. However, there were many problems we faced.
      Firstly, the mfg was in Bombay and there was no clarity on the design. The delaer in Madurai was not sure of the design aspects as well and it just seemed that there would have been problems during execution.
      Secondly, the surface area in plastic lining ponds is more (due to 45 degree slope). Place like Sivaganga is hot most of the year and we wanted to control the evaporation losses (hence we went for a smaller surface and deeper tank this time).
      Thirdly, the preparation work involved is tremendous. The entire bottom and side surfaces need to be smooth and clay needs to be applied in order to avoid 'punctures'. The location of this tank is fairly rocky and getting a smooth surface would have been a challenge.
      Fourthly, shorter life coupled with potential maintenance problems like leaks was a deterrent. That is why we went with a permanent solution. I am not aware of 6-12 paise per Litre figure.

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    2. No, we are not growing papayas.

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  5. Kaustubh - can you tell us what is the purpose of this reservoir. I mean, why not irrigate with groundwater directly. What aim does the tank serve.

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  6. There was a comment by Manu Sharma which I do not see any more "Kaustubh - can you tell us what is the purpose of this reservoir. I mean, why not irrigate with groundwater directly. What aim does the tank serve."

    This tank was constructed in our phase 2 for the precisely the same reasons as in the last phase. Reducing risk in case any of the borewells go dry in future. In a large acreage, you need to have borewells spread across the plot (which may not be possible always due to non availability of the source). This time around, the borewells are not as good as the previous ones, hence it was imperative to have a centralized source of irrigation, rather than a localized one.

    Additionally, discharge of SST pump is about 780 LPM compared to borewell discharge of 220 LPM, which implies larger acreage can be irrigated in a shorter duration of time.

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    Replies
    1. From tank size it looking like a holding arrngement for irrigation. It does not appear to be a reserve storgae as its size is very small and can possibly meet irrigation of 20 acres maximum if by drip irrigation.

      Could you tell us how many days of irrigation the water will serve if ground water is insufficeint?

      Rajan

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    2. Currently, we irrigate approx 6000 plants by this tank. Water in the tank is replenished every 1-2 days depending on the usage.

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  7. I am planning to build the same kind of tank, could you reveal the cost of this tank? please.

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  8. I have seen farmers pump the small amt of borewell water in to their existing open wells (Have no water), and using the motor in their open they connect to drip system.
    Is your tank do the same function as that of the open well.

    Pls provide your opinion. If my question is not appropriate also explain. Thanks a lot.

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    Replies
    1. Yes, the tank is doing a similar function..

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  9. Great efforts!
    After two years now how is the leakage? any cracks in the wall?
    We are planning to build similar one in our farm. Your suggestion is much appreciated. Many thanks.

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