DETROIT LAKES — Developers have cut way back on the amount of material they seek to remove in a controversial gravel-mining operation in Lake Eunice Township, in the Cormorant Lake area. Prairie Lake Investments LLC asked the Becker County Board on Tuesday, June 2 to reduce the amount it can mine at the housing development site from 350,000 cubic yards of gravel to 50,000 cubic yards of sand, with no gravel crushing allowed. Developers would als…