An intensive survey of Sugar Creek and tributaries in the vicinity of Robinson, Illinois in Crawford County was conducted during the period June 24 to October 8, 1986. Sugar Creek, a tributary of the Wabash River, is 14 miles long and has a watershed of 69.5 square miles. Major dischargers in the basin include the Robinson municipal wastewater facility (MWWTP) and the Marathon Oil Company refinery; both discharge to Robinson Creek. The survey was designed primarily to assess wastewater impact from these two sources upon water quality and biotic integrity of the receiving streams. Environmental quality was summarized utilizing various indices including water quality (WQI), macroinvertebrates (MBI), fish (AIBI), and habitat (PIBI). Severe stream degradation evident in approximately 9.5 miles of Robinson and Sugar Creeks was attributed to wastewater from the Marathon Petroleum Company.