Barry Stenger sweated under a warm sun Saturday as he weeded, mulched and collected trash among native live oaks and cottonwood trees at Barry Place, a small nature preserve along Sausal Creek in Oakland.  At 75 years old, he is the fourth generation of his family to live by the creek. Years of clean-up efforts have made people more aware of the creek and its rainbow trout, he said. But  a history of illegal dumping and pollution from trash and runoff…