1. Dig a rectangular pit having dimensions of say 20m by 30m. This pit should be approximately 4 meters deep from the earth surface.
2. On this pit, take dimensions of say 19.5m by 29.5m unto which you shall compact the soil to attain stability. After compaction, you can add some hardcore of small stones on it and then fill the voids with murram.
3. Then put meshwork fibres as form of reinforcement followed by dump proof membrane which shall hinder water from rising up the structure. Also lay reinforcement bars of specification D12.
4. Then prepare concrete in the coarse aggregate:fine aggregate: cement ratio of 1:2:5 which is preferably known as M15 and pour it on the surface.
5. On the corners of this structure, prepare some four columns of specification M15 class of concrete and reinforcement bars of D8 which shall be 1.5m high.
5. Then using burnt clay bricks construct a wall around the structure using mortar ratio of cement:sand ratio of 1:3. It is important to note that the type of cement to be used is sulphate resistant and the type of sand to be used is pit sand. Also to one side of wall at the bottom, a void of 30cm by 30cm can be left for installation of pipes which shall be used to draw water from the tank and also another pipe which shall be used for intake of water to this tank.
6. Then do the internal finishing by plastering the surface and walls of the underground tank to make the surface smooth and avoid water loss which can happen due to bricks absorbing some water. This is achieved by using waterproof cement. Also for external walls, rendering can be done.
7. Then you can have the top cover of the tank which in this case can be precast. It is important to understand that the precast top cover has to be reinforced. The precast top cover shall have a space of 50cm by 50cm upon which lid cover shall be installed for the purpose of inspecting the water levels during particular period of time.
8. Then install the pipes for intake of water and also for obtaining water from the tank. These pipes should run up to the ground surface and also the sub structure having lid cover should be erected to the surface.
9. Then fill the trench left after the construction is done and cover the whole structure with soil leaving only the pipes and lid cover exposed to the ground surface.
10. On the top of the underground tank, you can install a generator which shall be used for pumping water from the underground tank and also have a simple structure having iron sheets which shall have rainwater pipes and gutters to ensure that the rainwater is directed to the underground structure when it rains.
11. On the other hand, you can cultivate some crops on the top part of underground tank since it is covered with soil.
12. When these crops are ready for the harvest, they can be harvested and consumed at the homestead and the surplus sold out to gain some money which can be used to cater different needs.
13. Also, when dry season comes the water can be drawn for commercial purpose. That is, it can be sold. When this water is sold it can generate some income.
Thus in this way, a small piece of land has been put into maximum use and hunger can never be a story of the day.