Heavy rains pushed more than 187 million gallons of partially-treated sewage into the Flint and Saginaw rivers last weekend, according to updated reports filed by wastewater officials in Flint, Saginaw and Bay City.
The discharges, treated with disinfection and some settling, were also heavily diluted by rain and melted snow, according to reports filed by the three cities with the state Department of Environment, Great Lakes and Energy.
Flint, Saginaw and Bay City each have combined sanitary and storm sewers, which means runoff from rain ends up at sewage treatment plants that have retention basins but limited capacity. Once that capacity is reached, the overflow is released to prevent sewage backups. More