The results of environmental testing at the Windsor Mill on Union Street have forced the city to consider its next steps.

The Berkshire Eagle  reports  the city announced last month that an architect's plan to redevelop the mill at 121 Union St. — which is listed on the National Register of Historic Places — had been abandoned more than a year after it was first proposed.

Simeon Bruner's Cambridge Development Corp. submitted the winning bid for the Windsor Mill when the city issued a request for proposals on the property in 2017.

Though Bruner's offer of $465,000 was less than the $500,000 bid submitted by the New York-based investors who bought the Dowlin Block on Main Street, he won the support of then-Mayor Richard Alcombright followed by the City Council.

But the environmental conditions of the site proved to be an obstacle.

Several soil samples contained coal and coal ash above concentration levels at four locations at the mill property.

The mill was the home of Windsor Print Works and then the Consolidated Textile Company from 1872 until the 1950s. The city has operated the mill since the 1980s as a multiuse business park, the tenants of which now include B&B Micro Manufacturing and a host of others.

City officials have discussed what options it has to address the contamination, including via brownfield remediation funds.

The breadth of necessary cleanup, if any, remains unclear for now.

The city does not believe the contaminants pose a risk to the mill's current occupants.

The Windsor Mill is one of several city-owned properties that former Mayor Alcombright, and now Bernard, have worked to sell to private developers.

The city was also confronted with environmental contamination at its former Department of Public Works headquarters on Ashland Street, which is currently under a purchase and sale agreement with Cumberland Farms.