By William Ekwelu
10ft is big, to save on materials it can be reduced to 8ft, and it will take you very many years before emptying it . For excavating there are three methods you pay per feet , per cubic metre or per metre. Most local casual Labour want to charge per feet that is 25000/= per feet , so calculate how many feet’s you have and multiply by 25000/=.
Second method per Cubic metre
10ft = 3m, assuming depth is 2.4m ,so you get 3by3by 2.4m = 21.6 cubic metres
After that you can decide to multiply those cubic metres with between 4k to 8k depending on your ground nature.
Let us assume 6k or 6000/= Ugandan shillings
So 21.6 multiply 6k = I believe it will give you 129600/=. Just excavation. So it is better you decide how much you are paying each cubic metre but someone to give you a round figure that it is this amount without looking at that ground nature it may help you little.
Alternatively get a professional let him visit the site and let him make quotations . a rough estimate will be 500,000/= but remember you have to dig a soakpit too which may be of relatively similar size . if you get a good casual labour who can excavate it may take not more than 1.2m. Well, 10ft is better and reasonable in the engineering point of view if you expect to have usage capacity of 50 users but it may require you to have short columns like six of them if the soils are loose or weak . so you need to consider some things too. Another thing you look at the size of soakpit and the trip of hardcore it will swallow.
Mine costed about 1.8m including soak pit, labour and materials.