How are MPA groundwater tests conducted?

Samples are collected in accordance with the EPA “Consensus
Method for Determining Groundwaters Under the Direct Influence
of Surface Water Using Microscopic Particulate Analysis (MPA).”
Two sampling events are recommended, one during a dry period and
a second during a wet period.  Turbidity, temperature, rainfall and
stream flow records, and conductivity etc. may be used for guidance
for when to test.