If what you say is true, it must be the problem of the farm.
However, if a large amount of sewage does not seep into the groundwater layer for a long time, it will generally not cause groundwater pollution.
The soil itself also has a certain self-purification ability. However, it is best to ask a professional unit to conduct certain tests before determining.
Changyang Environmental Science and Technology Specialty Indoor Harmful Gas Purification 0371679 91KLOC-0/29 (6793256)