Can the Town Board assign to the Highway Superintendent the duty of collecting trash? If so, it that a Highway or General Fund Charge?

Yes, the Board can assign this duty if they do not interfere with the performance of his regular statutory responsibilities. The costs of collection of the trash would be a General Fund charge. If any scrap is sorted and sold, the revenue would go back into the General Fund. However, if the Highway Department sells scrap from highway-related activities, the revenue would go into the Highway Funds.

Reference

Opinion from the State Comptroller
Town of Wirt Audit OSC (includes a discussion of the sale of scrap materials)