When Tonya Bechtler put her kayak in the Yellow River, near the Georgia International Horse Park in Conyers, and began paddling downstream recently, she ran into a troubling obstacle — the biggest pile of trash she’d ever seen on a river. Containing massive amounts of plastic bottles and a fair share of discarded sports balls along with a refrigerator and 55-gallon drum, the trash pile, mixed in with lots of logs, forms a barrier across the entire width of the river. Bechtler and other members of the Newton County-based volunteer group Yellow River Water Trail are planning a river cleanup