Constructing a septic tank in Chennai - Can we leave base of septic tank uncemented? Will it affect the soil or water quality?

Hi all,

We are constructing a new house in Chennai. Our contractor says that we can leave a partial portion of the the base of the septic tank without cement flooring so that the water will get absorbed into the soil and we can have the tank cleaned once in 4 - 5 years.

Is the method of leaving the base of a septic tank without cement flooring advisable? Won’t it affect the soil and gradually won’t the contaminated water get mixed with the bore well, which is just about 15 feet away from the septic tank.

Please advice.