Abstract: The present invention comprises a self-contained, modular unit and method of using the same for evaluating the mobility, dissipation and degradation of chemicals and their degradates through a soil matrix. The self-contained, modular unit comprises at least a soil matrix vessel for containing the soil matrix and a leachate collection vessel communicating with the soil matrix vessel for collecting and storing the leachate from the soil matrix vessel. The leachate collection vessel is designed and connected to the soil matrix vessel in such a manner that the collected leachate is observable and removable at ground level, thus eliminating the necessity of digging a trench to view or retrieve the leachate as prior art units required. The preferred embodiment of the self-contained modular unit further comprises a runoff collection vessel which communicates with the soil matrix vessel and collects the runoff from the soil matrix vessel.