Superfund arsenic clean-up set for South Minneapolis


The United States Environmental Protection Agency (not the MPCA, or Minnesota Pollution Control Agency, as was noted in our November print edition) has set a cleanup plan for the South Minneapolis Residential Soil Contamination Superfund site, which is contaminated with varying levels of arsenic from the former CMC Heartland company that produced and distributed pesticides and herbicides at the epicenter of the 1,480-acre area between 1938 and 1963.

The pollution was discovered in 2004. By the end of this year, the EPA will have cleaned up almost 200 properties. In September 2007, the EPA designated the area a Superfund site, providing more resources to evaluate, select and perform long-term cleanup work. In October 2007, following that decision, the cleanup was expanded, adding 541 more properties. (See our story here.)

Thresholds for cleanup were set at 25 milligrams of arsenic per kilogram of soil (or 25 mg/kg) for shallow soil and 95 mg/kg for soil one foot deep. Aspart of the cleanup, shallow soil with arsenic levels higher than 25 mg/kg will be removed. Afterwards, the EPA will take samples from the remaining soil to determine that only low amounts of arsenic remain. If soil one foot deep still contains arsenic higher than 95 mg/kg, workers will dig deeper, according to an overview of the plan released by the EPA in October.

Once all contaminated soil is removed, the EPA will fill in the yards with clean soil and restore the ground to its original condition, states the overview.

This fall, the EPA began contacting owners of approximately 500 targeted properties for permission to do the cleanup. The EPA hopes to begin work in the summer of 2009. The entire project will take two to four years to complete.

Public comments on the plan included concerns that the 25 and 95 mg/kg thresholds were to high, and that the cleanup would take too long, according to the EPA, which responded that the timing is an estimate, and that it has “worked as quickly as possible to clean up the site,” beginning soil removals in 2004, when the EPA first learned of the contamination.

As to the threshold levels, the EPA responded that the 25 and 95 mg/kg levels “[provide] the best balance of trade-offs between the alternatives and is considered to be the most cost-effective.”

The EPA considers exposure levels safe if the risk of cancer from toxic contamination is less than one in 10,000; that level of risk is at 25 mg/kg, they have determined.

There is little risk of exposure from touching soil or breathing particles, states the EPA. Higher-risk exposure can result from getting contaminated dirt on one’s hands and touching the mouth and/or swallowing the soil, or by eating “a lot of unwashed garden vegetables grown in contaminated soil.”

The site is centered on Hiawatha Avenue and East 28th Street, the former home of the CMC Heartland Lite Yard. Years ago, the company made an arsenic-based pesticide there. EPA officials believe that open-air procedures for mixing and unloading toxic materials allowed them to blow into nearby neighborhoods.

The Superfund site has a roughly oval shape. At its widest, it stretches along East 28th Street from 10th Avenue South to 31st Avenue South. At its longest, it runs from I-94 to East 35th Street, following a line just east of Cedar Avenue.

You can find more information and EPA updates here, and a map of the Superfund site can be found on page 3 of this document.