MI SB1090

Allows persons to demonstrate compliance with groundwater venting response activities using generic groundwater-surface water interface (GSI) criteria, variances, mixing zone-based criteria, site-specific criteria, ecological demonstrations, or modeling demonstrations.

Permits use of alternative monitoring points beyond GSI monitoring wells if they meet specified standards including reasonable identification of venting locations, representative sampling of hazardous substance concentrations, and use of sentinel monitoring points.

Requires persons to proceed under section 20114b for response activities involving acute toxicity endpoints, bioaccumulative chemicals, coldwater fisheries, or outstanding resource waters.

Establishes notification and response procedures when GSI criterion exceedances occur, requiring notice to the department within 7 days and response actions or alternative proposals within 30 days.

Exempts venting groundwater contamination from requiring part 31 permits and allows natural attenuation as an acceptable remediation method; permits retroactive application to existing cleanup orders and agreements.