Ann Arbor has approximately 12 miles of gravel roads which are graded three times per year. Some gravel roads are graded more often to control erosion. Three times per year the City also applies a liquid calcium chloride treatment to control dust. These treatments are spaced out during the summer months to maximize effectiveness and reduce over application/runoff. Treatments do not occur during the winter or in the rainy seasons.
There are many reasons why we don't treat gravel roads more often during the summer. The current treatment frequency is considered industry best practice and is the standard throughout Washtenaw County. In a normal precipitation year, 3 treatments are sufficient. Weather also plays a role as treating before a rain storm will simply result in chemicals being washed away. Finally, frequent treatments mean more chloride in the storm water system, which can have a negative impact on water quality.