Hewett Fork in Raccoon Creek, Ohio was a large source of acid mine drainage (AMD) to the main stem of Raccoon Creek, impacting the biological community for several kilometers. To reduce this impact, the AMD treatment was implemented in the Hewett Fork subwatershed to treat water from the largest mine drainage source in the watershed near the village of Carbondale. From prior to installation of wetland treatment in 2000 and installation of the lime doser in 2004, the pH of the mine discharge has been raised from about 4 to about 9, which greatly improved biological communities in Hewett Fork and Raccoon Creek. During the summer of 2010, the doser was off-line for approximately 2 weeks. While the chemistry of Hewett Fork showed little lasting change due to non-treatment, biological surveys show the effect of temporary non-treatment. In the year and a half since the doser was off-line, surveys have shown that the fish community was seriously impacted due to non-treatment and it has not yet recovered; the macroinvertebrate community, on the other hand, showed little impact due to non-treatment, and has shown no lasting effect of non-treatment.