It is more appropriate to take footing deeper and sump may be placed over it with some cushion layers of sand between footing top and sump bottom.

In beam design, flexure n shear are the most governing parameters and the respective max. values of can be easily captured by defining an envelope load combination. The primary advantage of envelope is to reduce the design time. However, in case of beams having significant torsion the envelope approach may lead to a slightly uneconomical design.

For columns we have to check each and every load combination as design moment at top and bottom for particular load case will change the formulation. This moment will be different for different load combinations, hence we should check all the load combinations for the column design.

Envelope should be used with caution. It gives minima and maxima of forces and moments individually. Envelope can be created as a combination to assess the behavior. We Use it to understand the deflection, sway etc. We should Never use it as load combination for designs.