The Minnesota Pollution Control Agency has come up with a plan and a price tag to clean up or cover up three more of the legacy contaminated sites in the Twin Ports harbor.

The PCA plan, announced Tuesday, would spend $22 million in state and federal funds to clean up the AGP/Northland Pier Slip, the AZCON/Duluth Seaway Port Authority Slip and the ponds behind Erie Pier.

Engineers will now design the remedies for the highly polluted sites with construction set to begin next summer.

The contamination is the result of a century of industrial and shipping activities and continues to threaten public health as well as fish and other aquatic life if left unchecked. The cleanup is part of the massive Great Lakes Restoration Initiative to clean up or cover toxic hotspots, restore fish and wildlife habitat, prevent new pollution from farms and cities and thwart invasive species.

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Cleanup plans in the AGP/Northland and Azcon/Duluth Seaway Port Authority slips call for removal of the most highly contaminated sediments and installing caps of clean material and armor stone. The projects already received state funding from the 2017 Legislature. The PCA is awaiting approval of a federal grant from the Environmental Protection Agency to cover the rest of the estimated $6.2 million cost.

The “ponds” behind Erie Pier will be dredged, and contaminated sediment removed and disposed of in a landfill at an estimated cost of $15.8 million and won't start until 2021 at the earliest.

All three projects will involve environmental review and permitting processes that provide opportunities for public comment.

Several similar cleanup/cover-up projects already have been completed in the St. Louis River estuary and Twin Ports harbor — including Radio Tower Bay, Minnesota Slip, Kingsbury Creek and Slip 3 — with many more still on the list. The goal is to restore the estuary to a more natural state and get it off the list of 43 contaminated hotspots across the Great Lakes.