Workers will begin tossing dirt on conservative talk radio skeptics and 5,000 square feet of roof at the Minneapolis City Hall Saturday. That’s the first step in the long-talked about, much-ridiculed Green Roof project that was first envisioned by members of a city-county body,  the Municipal Building Commission, four years ago.

The workers will use a special dirt on the roof, which is in a courtyard inside the main building and out of sight of pedestrians. Wild grasses and prairie flowers are to be planted next week.

The project, which includes an irrigation system tied to a cistern,  is being funded by taxpayers and grants from a number of organizations.  The green roofers envision thousands of square feet of environmentally friendly green roofs throughout Hennepin County in coming years.