Oakland County water commissioner briefs Birmingham on combined sewers, retention basins and flood drivers

At a Sept. 8 workshop of the Birmingham City Commission, Oakland County Water Resources Commissioner Jim Nash and his staff outlined how combined sewer systems and regional retention/treatment basins work, described why regulators sometimes close outflows to downstream systems during storms, and urged cities and residents to coordinate on aging pipes, stormwater changes and funding.

Why it matters: Birmingham lies inside multiple drainage districts that send combined sewage and stormwater to different county retention/treatment basins. Decisions about whether to store stormwater in local basins or convey it to regional systems affect where overflows occur, how often basements back up and who pays for capital and operating costs.

Nash said the county oversees large assets and operations for many communities. “My name’s Jim Nash. I’m the Oakland County Water Resources Commissioner,” he told commissioners as he introduced a team of engineers and legal staff. He said the county operates 433 county drains and hundreds of miles of enclosed storm drains, and manages retention/treatment basins built to capture combined storm and sanitary flow for later screening, settling and disinfection.

Oakland County staff described the historical reason for combined sewers — many streets and home drainage systems were enclosed as communities urbanized — and the regulatory response. “Back in the day the combined sewage would just run straight to the river,” said Gary Nigrove, a county manager, describing earlier uncontrolled outfalls. Under state and federal rules, discharges to surface waters require NPDES permits and oversight by EGLE (the Michigan Department of Environment, Great Lakes and Energy).

County staff explained two common responses to combined flows: (1) retention/treatment basins (RTBs) built to store and partially treat excess flow during storms, and (2) separated…