While California contemplates new dams for its thirsty future, it’s also thinking about taking out old ones. Along with advancing plans to demolish three dams atop the Klamath River, there’s a movement to rethink and possibly take out a water and power dam in the Mendocino County back country. Pacific Gas and Electric Co. is walking away from the Potter Valley project and Scott Dam, built east of Ukiah in 1922. A new federal license will be costly and the utility has plenty to do working its way out of wildfire-caused bankruptcy. What’s coming next is intriguing: A coalition of local agencies and a dedicated fishing group, California Trout, are talking up a takeover of the dam.