At a site where the water table is shallow or where you will have to do a lot of excavation in a rainy season, make sure that you figure out your costs for dewatering. In some cases where the soil is polluted, you will need to treat this water too. Or arrange special vacuum trucks to remove it. This will have scheduling impacts too as it will slow you down. Make sure you coordinate this well in the field as far as where this will take place especially at a site with tight access.