Mr Dauda had the choice of buying a plot of dry land in Agbara, a Lagos suburb. But he opted to buy two plots in a water-logged land at Onireke near Ojo Barracks. Two factors affected his choice, which are the cost of the two plots and their proximity to the Badagry express road. The water-logged parcel of land was by far cheaper than the dry land at Agbara. It is closer to the road which will aid him to resume early in his work place.
Mr. Dauda started to work on the site without engaging the services of the environment professional to conduct soil tests. He later learned that he had made a wrong choice. The cost of sand-filling the could have taken him far if he had bought the dry land. When Mr Daudu ran out of funds, he decided to abandon the project. His plight is synonymous to what many Lagosians go through on regular basis. This is because most parts of the city are water-logged and marshy. Some of those who succeeded to erect shanties have to share it with wild life.
What are Swamps
Swamps are wetlands with a forest in and on it. They are often found near rivers or lakes and have mineral soil that drains very slowly. But unlike marshes, they have trees and bushes. They may have water in them for the whole year or for only part of the year. Experts conclude that the constru ctions of houses on swamps require special attention. The marsh soil is removed and strengthened by suitable means after ascertaining its (soil) properties. Building houses in challenging terrain like the swamps requires special attention when compared to construction in a normal dry soil. This is because swamps or marsh lands are periodically and at times permanently inundated by water.Against these conditions, it is expertly advised that those who have bought swamp land ensure that the foundation of their buildings rests on sound soil; so that when the super structure (building) is completed, the weight would be evenly spread.
How to Build on Swamp
One of the first steps to take is to excavate the marsh and sand-fill so that it would become firm. When this is done, you should put a raft foundation to carry the building. It is not in all cases that raft foundation will be effective. “Sometimes, the swamp or what we call potopoto will be too deep that using the raft foundation will not solve the problem. In that case, the building engineer can go for a pile foundation.
There are two types of pile foundation, which are, end-bearing pile foundation and friction pile foundation. However noted that in a place like Lagos where it is becoming increasingly difficult to get dry land to build, you cannot run away from building on swamps. What can be done is to apply engineering methods and techniques to get nature to suit our building purpose.
The most of Lekki and Ajah were swamps that have been turned into highbrow residential neighbourhood. But still suffers flooding because the area is below sea level and the foundations in most building were not raised to accommodate future disasters as these. However to effectively utilise a swampy land it requires soil investigation. Where the water table is high, one needs to determine its capacity. Once these have been determined, the builder would now be left with the choice of the type of foundation that will be suitable on the land. The choice is between the raft foundation and piling. Builders are advised to equally take the future level of the road around the premises into consideration.
If the level of the road is higher than the level of the foundation, the house will have drainage challenges. Water from the ground will also pose a challenge to the building. So any developer should use water resisting membrane to check dampness of the walls and avoid clay materials or soil when filling water logged areas. This is because when the water table diminishes, the clay will shrink thereby creating a space underneath the slab and causing cracks on the building in future. In constructing the fence round the building, concrete must be used on the lower part of the fence above the proper floor level.