Michigan recently amended the requirements for response activities addressing impacted groundwater that vents into surface water. Vented groundwater is subject to groundwater/surface water interface (GSI) criteria. The amendments are aimed at addressing the great difficulty being experienced in complying with GSI criteria.

The first step in evaluating the potential applicability of GSI criteria to impacted groundwater is to determine whether there is a relevant pathway for groundwater to vent to surface water. An enclosed sewer is excluded from the definition of surface water, which means GSI criteria do not apply at the point groundwater is infiltrating a sewer. However, sewers are still part of the determination of a relevant pathway by which impacted groundwater may ultimately reach surface water. The existence of sewers and other subsurface conduits have long complicated the determination of such pathways and compliance points for GSI criteria.

In that connection, the amendments liberalize the number of ways to determine if a pathway between impacted groundwater and surface water is relevant. A person evaluating the relevance of a pathway no longer needs to use GSI monitoring wells, if other information is sufficient. The amendments also permit the use of fate and transport modeling.

If a relevant pathway is determined to exist, a responding party is now allowed to demonstrate that additional response activities are not necessary based on an alternative monitoring point. For example, such monitoring may occur in the surface water itself where the groundwater vents, beyond the water’s edge and on top of or into the sentiments. Other new monitoring-based limits on the application of GSI criteria include demonstrations that:

  • The venting groundwater has little to no effect on the surface water.
  • Compliance is technically impracticable and the source of contamination has been eliminated or contained to prevent further migration of groundwater.
  • The impacted groundwater is naturally attenuating prior to venting.  

A helpful feature of the amendments is that they streamline the application of other statutory requirements, with the goal of making site remediation more efficient and cost-effective. One such provision eliminates the need for a permit under Part 31—Michigan’s Clean Water Act—if the substantive requirements are otherwise addressed as part of State-approved cleanup actions. Another clarifies that wetlands discharge requirements only apply to the extent that particular designated uses specific to a wetland in the GSI pathway would otherwise be impaired by the venting groundwater.

Michigan’s new law is aimed at easing the burden of complying with environmental regulations and at facilitating the pace of site closures involving GSI criteria. Born from the Governor’s Regulatory Reform Initiative and the MDEQ’s Collaborative Stakeholder Initiative, and enacted over a short period of time, the GSI amendments are viewed as a promising vehicle for stimulating the remediation and redevelopment of property. Such potential progress would be a particularly welcomed development for companies looking to convert Michigan’s large inventory of impacted sites into functional infrastructure for new business.