Site investigations get started for a variety of reasons. At some sites, like Superfund sites, Michigan Department of Environment, Great Lakes, and Energy (EGLE) staff have been overseeing environmental cleanup efforts for many years, and may add PFAS sampling to ongoing sampling if PFAS was known or suspected to have been used at the site. EGLE staff also conduct routine monitoring of rivers and lakes. If a sample exceeds water quality standards, staff work upstream until they find the site contributing to the PFAS. Other sites were sampled due to historical information, such as Carl's Retreading, which was where tires burned for many days and firefighting foam containing PFAS was used. PFAS investigations are also being conducted by responsible parties under various programs overseen by EGLE.
On August 3, 2020, the groundwater cleanup criteria became PFOA of 8 ppt and PFOS of 16 ppt. On December 21, 2020, five additional PFAS compounds became effective and enforceable groundwater cleanup criteria: PFNA (6 ppt), PFHxS (51 ppt), PFHxA (400,000 ppt), PFBS (420 ppt), and HFPO-DA (370 ppt). EGLE staff use all 7 PFAS criteria to guide groundwater investigations, protect public health, and identify MPART PFAS sites.