There appears to be a mine under the reservoir. Says Miner
About 47% of the runs covering the 36 acres of skiing territory at Hidden Valley are difficult while 58% of the runs are easy. Skiers love Hidden Valley; it's a good ski mountain. There is a total of 12 runs at close by Hidden Valley; this ski mountain gets 6 feet of ice cold snow every season. There are 4 ski lifts at Hidden Valley, and the vertical drop is 620 feet. This lake is so wonderful.
Take a side trip to Kanouse Brook, and going for a horse ride at close by Smoke Rise Farms is always a fun thing to do. Life's too short to enjoy all the exciting things in the vicinity of Charlotteburg Reservoir.