That problem is very common with hand dug wells in my area too (Githunguri). Our well is 140ft (42m) deep and was done in the early 90s (~1993).

What they do is dig for a maximum fifteen minutes a day. They also leave the well open throughout and throw some leaves inside (I believe this has something to do with photosynthesis i.e. CO2 + Water (in the presence of light) = Oxygen + Glucose.

I just can't find a sustainable better way of doing this water mining in the rural areas. Options are;

i. Make the well very wide (5m diameter) - The project would be very costly

ii. Buy those scuba diver oxygen tanks for the diggers - Cost may go up. Also, you don't want to add a load to the person down there,

iii. Mechanize the process - Cost may be a problem. You would need a heavy bit (Tarimbo) been dropped down and lifted continuously. Just ensure that the tarimbo does not snap when someone is inside removing the broken rocks.

iv. Abandon the project and instal a water pump direct from the river. For sustainability, incorporate solar systems.

#Just_My_2_Cents

Ngai baba!! Guka!

You see at 100 feet below the surface the surrounding temperature in the hole is slightly higher (somewhere between 30 to 35 degrees centigrade. At this temperature and due to presence of wet soil the air inside that hole is pretty humid and this constitutes the water vapour gas.

The so called gas in those shallow wells is mostly carbon dioxide and water vapour/humidity. The combined density of the gas mixture is close to 1.3 kg/cu.m. The air at the surface has a density equal to 1.2kg/cu.m which explains why there is no conventional air circulation in the hole and the denser gas mixture still remains in the hole. So, pumping in air will not displace the denser mixture in the hole, but rather the other way round.

In Kenya, the various geological surveys that have been carried out that i am aware of have not confirmed any presence of mineral gases on the surface. Here, I say surface because 100ft compared to 21,000,000ft(distance to centre of earth) is negligible. Only areas around Longonot, Nakuru and Marigat where those gases (mostly hydrogen sulphide and traces of sulphur dioxide) are found in very small amounts at more than 4000ft below the surface.

Back to the hole...At 100ft (30 metres) below the surface you have added another column of 30m above the normal atmospheric pressure...This may affect your breathing by making it a little difficult for you to breathe out.

Hii mambo ingine ya sijui ya testing the gas ni pang'ngá tupu.

very clear.you took over from mukiva

A possible way out for me would be to have two air pumps..one to suck out the denser CO2/water vapour and another(hose higher that the other one)pump in surface air i,e both pumps running..
How were the wells having depths of 95-120 ft dug?I would dread a worker(s) dying down there..

There is no gas, at that depth there is no sufficient oxygen. A guy in a well with a diameter of approx 1.5 metres easily exhausts the available oxygen supply.

Try Rift Valley Machinery Serives and/or TransAfrica Water

@Majimaji. Did you succeed in getting the pump? I am interested

I got one, made in Ukraine, Greece or some country where they use that funny alphabet. It was cheap 6500/=. Then I installed it and it was working but the vibration against the rocks in my well wore the base metal, a soft alloy and the thing went kaput...