Please define the type of waste materials (from decomposition solid or liquid materials). then try to measure at the uncontaminated areas and at the contaminated areas and compare between both.
As you know basically the medium you are measuring should be sensitive to resistivity variation. For example the saline water body is denser than the fresh water and hence reflected as more conductive than the fresh water. Whether it is hospital waste contamination or something else does not matter.
You should be study about type of contamination in first. After this I have a question: do you have any dissolved material that can be affected Ec and TDS in ? If you have such material you can use geophysics and spicially geo- electric methods. You may be extracted electrical conductivity in both dry and wet session. You need background water saturation of surface soil, depth of bedrock, aquifer thickness, and water table location.
With prescribed data set you can study soil, groundwater and aquifer contamination that created with goal wastes!