While ExxonMobil and government officials worked Saturday to clear a ruptured pipeline underneath the Yellowstone River of any residual oil, a small group of boaters began their own weeks-long survey of the river in an effort to document areas affected by the spill.

Called the Oily River Rendezvous, the group consisted Saturday of two kayakers and a pair of canoers from Montana and Arizona who plan to float the Yellowstone and its backwaters at least to Miles City and compile data as they go.