I have to agree with Jan, I would avoid black cotton soil at all costs. The only good advice I can give is identify another site.
It's bad enough for more permanent construction which can only be realistically attempted in the dry season, but with temporary constructions, all that Jan mentions become serious show-stoppers. Water supply, water run-off and waste water disposal difficulties - all likely to lead to life threatening sanitation issues sooner rather than later. Paul K REDR expert
I agree with both Jan and Paul. There is a real danger of making a bad problem worse if the basic essential risk assessment is not followed.
Mike W. REDR Expert.
Some generally good advice (not specific to tents / refugee camps) on black cotton soils is found on http://civil-engg-world.blogspot.com/2012/06/black-cotton-soil.html. Sorry it will not help the tents themselves but may assists in some of the associated infrastructure of a camp. Again as Jan points out, more don’ts than does.
Optimum solutions are to try and keep it drained without ponding, ie drains using natural terrain and a suitable invert slope if no other choices. If you plan to be in location for any period of time and alternatives are few although available surface are is acknowledged as limited consider mass planting of grasses that absorb water (bamboo and vetiver families are found in South Sudan). Sorry cannot be more help CN REDR Expert
I'm afraid with black cotton soil there are plenty of "do nots" and not many positive suggestions of getting around the problems. Also the construction of other facilities to support a settlement can aggravate the conditions for tents/shelters if not carefully considered. So here goes:
- Siting is crucial: Avoid black cotton soil! This may seem obvious but has to be considered as an option - even if there may be no other option.
- Siting is crucial: Try to site on a gradual slope to encourage natural runoff and drying of the soil as quickly as possible following rainfall.
- Avoid digging pits close to the site to provide soil for raising floors as the pits will fill with water and become stagnant breeding grounds. Any materials for raising floors will have to be trucked in from some distance.
- Similarly, avoid placing tapstands on mounds where the waste water drains into the pits dug for raising the tapstands as the place becomes a mess. Try to site tapstands on the edge of naturally draining ground to drain water away from shelters. Depending on the weather, try to spread any runoff from tapstands so that it can dry quickly.
- I have seen some awful attempts to dig soakaways for drains in black cotton soil which clearly do not work because the pits simply fill and do not soakaway because it is impermeable clay. So this is more of a warning to be given to those who do not know what they are dealing with. It can save a lot of heartache.
- Access roads can be a problem if raised to allow drainage off the road and quick drying of the surface. It's good for the access road but clearly the runoff has to go somewhere and if tents / shelters are located close to the road then they suffer. I have seen a situaiton where an access road was constructed with no culverts (to save time) on the downhill side of a large refugee camp located on black cotton soil. The first rainstorm resulted in the road acting as a dam to create a lake which flooded the tents on the downhill side of the camp - something to be avoided.
Plenty of things to avoid. Sorry can't be more helpful.
This thread is public, all members of KnowledgePoint can read this page.