Constructing Septic Tanks On-Site Using Ferrocement

  • USAIDssd
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Constructing Septic Tanks On-Site Using Ferrocement

In the urban slums of Abidjan (Cote d’Ivoire), delivering precast concrete septic tanks is often not feasible due to narrow roads that could accommodate a crane truck. Costs of plastic or fiberglass tanks are generally too expensive for the local population to afford.
Read more here www.psi.org/publication/constructing-sep...e-using-ferrocement/




Dana Ward MBA, MPH
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  • goeco
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Re: Constructing Septic Tanks On-Site Using Ferrocement

Thanks for this Samira, looks great. The pdf provides some construction details, but could you provide material costs and labour hours for the unit in the photographs?

cheers
Dean

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www.go-eco.co.nz
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Re: Constructing Septic Tanks On-Site Using Ferrocement

Thanks for sharing this! Looks like you need a massive excavation for it though.

Maybe it would be more efficient to cast a few round smaller tanks above ground and lower them after curing (and leak testing) with a tripod or so into much smaller excavations? Afterwards they can be interconnect with PVC pipes like commonly done with prefabricated FRP septic tanks.

One of the big strengths of ferrocement is also that it easily allows for round etc. forms that should be significantly more resistant to inside and outside stresses that might cause leakages after a while.

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  • Ashok
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Re: Constructing Septic Tanks On-Site Using Ferrocement

Many similar structures have been made in the past.
This, though, strictly speaking, is NOT ferrocement. For ferrocement the covers are specified to be about 3-5 mm on either side. With single reinforcement cage with two wire meshes, the overall thickness should not be more than 25 mm in any case. This will further reduce the cost.
Moreover, it is feasible to precast the floor, walls and lids and assemble the tank at site either inside the hole (for which a much larger whole is to be made) or outside on ground and lower the septic tank into the hole. I am attaching a photograph which is self explanatory. About 500 such ferrocement precast tanks were made in 1992 and are still functional in India.
The super structure is also in precast ferrocement.
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  • USAIDssd
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Re: Constructing Septic Tanks On-Site Using Ferrocement

Thanks All - for your comments/questions.

We hope this video can help throw more light on the brief:


Dana Ward MBA, MPH
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  • Ashok
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Re: Constructing Septic Tanks On-Site Using Ferrocement

In my reply yesterday, the attachment did not appear.

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  • shaji
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Re: Constructing Septic Tanks On-Site Using Ferrocement

Dear Ashok,

Did you check for any leakages from the system after installation.
We did find ground water contamination due to leakages from the pits in some cases.
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  • shaji
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Re: Constructing Septic Tanks On-Site Using Ferrocement

How did the person who is doing the plastering inside the tank come out ?
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  • Ashok
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Re: constructing septic Tanks on-site using ferrocement

Dear Shaji,

The ferrocement components were 20 mm thick, precast and cured prior to installation. No leakages were found. The users are satisfied even today. To my understanding, if ferrocement is made thicker than required, it will crack.

Ashok

PS: A current photo is given here under: There are septic tanks on both sides in two rows, one for every house. The persons on the right are actually sitting on a septic tank. The temple in between the septic tank is a proof that there is no foul odour, mosquitos or fly. This photo is dated April 11, 2014.


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  • AjitSeshadri
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Re: Reply: Constructing Septic Tanks On-Site Using Ferrocement

How does a man come out.. opening like a boiler man hole is given.. 30 yrs back..it used be eliptical opening 300x450mm.. 12by18".. now its 450x450 circular..or more.. many types of openings are possible.. hand holes.. 150x150mm. and smaller ones for sensors etc.. w wshs..
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  • USAIDssd
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Re: Constructing Septic Tanks On-Site Using Ferrocement

Hi Dean,

The material costs was approximately CFA 310,000 (USD 499), and we used a total of 14 workers who worked approximately 8 hours/day for 14 days...so approximately 112 labour hours.

cheers - Samira

Dana Ward MBA, MPH
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Re: Reply: Constructing Septic Tanks On-Site Using Ferrocement

Workers went in and out of the metal cage with the help of two wooden ladders placed against each other, as in these attached photos.






Dana Ward MBA, MPH
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PSI Country Representative
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