Well rehabilitation after the floods

Now that the floods waters are beginning to recede, the important task is to start rehabilitating the open wells that have been over-run by the flood waters. This is critical as the contamination of the wells by human and animal faecal wastes have rendered them quite toxic for human use.

We are starting the slow process of well disinfection in the Baray vicinity as the wells become uncovered. The following describe how such disinfection can be carried out. It is not a precise method but is probably adequate, and better than doing nothing. We used similar methods in the 2000 flood, and found it quite effective.

Equipment needed:
Pump 5.5hp pump with 10m of tubing
Chlorine powder S70 (calcium hypochlorite ~70%) - be careful as concentrated chlorine can be corrosive
Large pail
Knotted rope at 10cm intervals
Long pole
Plastic sheet
2 or 3 helpers

Method:
1. Pump out as much well water as possible. The less water remaining, the less chlorine you will need. It will not be completely drained as water will continue to accumulate while you pump. Just do the best you can.
2. Measure the depth of remaining water. You can do this using a rope tied to a weight. The rope can have a painted mark, or a knot every 0.1m.
3. Estimate the amount of chlorine to be used ( according to the Table below). The amount will depend on the depth of water and the diameter of the well.
4. Mix the chlorine powder into a large pail of well water.
5. Pour the mixture into the drained well, and try and stir using a long pole if possible.
6. Cover the well with a plastic sheet.
7 Leave the well covered for about 24 hours (meanwhile, DO NOT USE THE WELL). During this time also do not try to enter the well as the chlorine fumes may be overpowering and toxic.
8. The next day. Pump and empty the well again, as much as possible. Again, be careful of chlorine fumes which have accumulated in the closed environment of the well.
9. Let the well water re-accumulate naturally over the next 24 hrs
10. The well should now be able to be used, if the strong smell of chlorine has disappeared.

The following Table gives the approximate amount of Chlorine powder to be used depending on the diameter of well and depth of residual well water. For example: if well diameter is 1.5m and depth 0.5m, it will reference cell "I10", which is approximately 16 tablespoons.