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John Cody gravatar image
RedR

You could try a circular pit, with linings made from stone, brick or sandbags, depending on the mass of your slab. We recently used circular pits with wooden slabs supported by 3 beams, with a gobe plaster (clay, fibre & dung) for a sanitary seal. A heavier slab will require a ring beam. Depending on the target life time of the latrine wood or wicker could be used.

The slab needs to be raised at least 300 mm above ground level. Use compacted spoil from the pit to hipped against the edges of the slab to provide a sloping edge away from the pit to prevent run off entering. Also provide drainage channels or bunds (constructed from pit spoil) to prevent standing water around the edges of the pit. Where light weight slabs are used allow approx 200 mm bearing surface from the circular sides of the pit. If you must use a ring beam ensure that it is raised above ground level.

Depending on your programme parameters it is likely that a larger number of low volume pits (1 m usable diameter to 2 m depth) is preferable to larger volume pits to mitigate the risk of collapse. In Nepal we faced similar challenges to those described in you mail. As the context was humanitarian we focused on simple, low cost construction with smaller pits that were easily replicable at community level.

If you must use a rigid lining (e.g. For permanent institutional latrines) provide a sand or gravel pack between the pit lining and the excavated faces. This will accommodate differential contraction/expansion of the soil.

I agree with the comment on barrels by a previous poster. If long term latrines are required you could look at using concrete rings, again with a flexible lining in the annular space between the ring and excavated faces, to accommodate soil movements.

Hope this helps

Cody

Sent from my iPad

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No.2 Revision
KnowledgePointAdmin gravatar image
RedR CCDRR

You could try a circular pit, with linings made from stone, brick or sandbags, depending on the mass of your slab. We recently used circular pits with wooden slabs supported by 3 beams, with a gobe plaster (clay, fibre & dung) for a sanitary seal. A heavier slab will require a ring beam. Depending on the target life time of the latrine wood or wicker could be used.

The slab needs to be raised at least 300 mm above ground level. Use compacted spoil from the pit to hipped against the edges of the slab to provide a sloping edge away from the pit to prevent run off entering. Also provide drainage channels or bunds (constructed from pit spoil) to prevent standing water around the edges of the pit. Where light weight slabs are used allow approx 200 mm bearing surface from the circular sides of the pit. If you must use a ring beam ensure that it is raised above ground level.

Depending on your programme parameters it is likely that a larger number of low volume pits (1 m usable diameter to 2 m depth) is preferable to larger volume pits to mitigate the risk of collapse. In Nepal we faced similar challenges to those described in you mail. As the context was humanitarian we focused on simple, low cost construction with smaller pits that were easily replicable at community level.

If you must use a rigid lining (e.g. For permanent institutional latrines) provide a sand or gravel pack between the pit lining and the excavated faces. This will accommodate differential contraction/expansion of the soil.

I agree with the comment on barrels by a previous poster. If long term latrines are required you could look at using concrete rings, again with a flexible lining in the annular space between the ring and excavated faces, to accommodate soil movements.

Hope this helps

Cody

Sent from my iPad