schematic of contaminated soil

The construction stormwater permit may prohibit infiltration practices on properties where existing contamination in groundwater or soil is present. The permit requires permittees proposing stormwater infiltration to analyze their specific site to determine if infiltration is appropriate. This page explains the minimum assessment required in order to demonstrate compliance with the permit at sites with potential or known soil and/or groundwater contamination.

Permit language (item 16.15)

"Permittees are prohibited from constructing infiltration systems where high levels of contaminants in soil or groundwater may be mobilized by the infiltrating stormwater. Permittees must either complete the MPCA's site screening assessment checklist or conduct their own assessment to determine the suitability for infiltration. The assessment must be retained with the SWPPP."

MPCA's screening assessment tool

Guidance

Access guidance on Stormwater infiltration and contaminated soils and groundwater

For more information on how to determine if high levels of contamination exist at a site, link here.