Duncan Berry, from Infrastructure and Environment, said: “This is a pinch point, and with climate change, and if we put more houses on, it means that is a point where we will get more flooding.
“If we get high flows during heavy rainfall, it will come out on to the roads [and] sewers will surcharge.
“It will ultimately mean that people cannot flush their toilets in the area.”
He said it was unlikely waste stored in the tank would cause unpleasant odours because it would be transferred to treatment works quickly.
The storage tank would not use the whole site and the rest of the field would be returned to local farmers, he added.