Fecal colitbrm (FC) disappearance studies were conducted in Ford Lake during the summer of 1979. Ford Lake, an artificial impoundment at the lower end of the Huron River drainage basin belov, ~ Ypsilanti, Michigan, receives all upstream flow (2072 km: of drainage). During dry weather an overall daytime FC disappearance rate of 0.4 (h-t) (K base e) was measured using dye tracer for timed collection. assuming a first order equation of the Chick type. Sedimentation was demonstrated as important in the overall FC disappearance in the upper end of the lake. Rooftop studies showed light level to affect daytime disappearance. Two types of wet weather conditions were documented: (1) where a substantial increase in flow occurred due to an isolated upriver storm; and (2) as a result of two different storm events in the Ford Lake area itself. In both cases, Ford Lake was effective in substantially reducing the large FC contribution.

Michigan area affects the bacterial indicator organism quality of the Huron River. Investigations during the 1985 summer period involved sampling during dry and wet periods with parallel determination on each sample for fecal coliforms, fecal streptococci, E. coli and enterococci. Wet weather bacterial indicator densities were statistically significantly higher than dry weather levels, and downstream densities were statistically significantly higher than upstream densities. The FC/FS (fecal coliforms/fecal streptococci) ratios for the storm drains were low and suggestive of more animal than human sources. The geometric mean EC/FC (E, coli/fecal coliforms) ratios were in the range of 0.82-1.34, well above the ratio of 0.63 calculated using the U.S. EPA recommended level for E. coil of 126/100 ml to the presently accepted level for fecal coliforms of 200/100 ml. If the intent is to maintain the currently accepted illness rate, additional results from other areas are necessary to refine the E. coil and enterococci levels for water quality standard development purposes. In general, physical-chemical observations reflected the source of the sample.