Nearly 20 miles downstream from Atlanta, the water in the Chattahoochee River was strangely dark and musty-smelling when Chattahoochee Riverkeeper’s Jason Ulseth launched his boat at dawn in late May.
Then, he saw the fish.
Thousands of them of every size, all dead and dying. As he motored upstream in the growing light, Jason could see that the river’s banks were coated with thick, black mud, releasing a foul odor, as flotillas of dead fish drifted downriver in the current.
Immediately, Jason knew there had been a disaster upstream, likely an overflow from the City of Atlanta’s sewage and stormwater management facilities. The black muck on the shoreline was decomposing organic matter in oxygen-depleted (hypoxic) water. Without enough oxygen in the river, the fish and other species had suffocated. It was a heartbreaking catastrophe.
Thirty-six hours earlier, a sudden, torrential rainstorm had hit Atlanta in the midst of a severe drought, flooding the 14 lanes of the city’s Downtown Connector. An inch and a half of rain fell in just thirty minutes during the extreme event, followed by several more inches.
Describing the storm and its impacts in Forbes, Dr. Marshall Shepherd, a leading expert in weather and climate, noted: “Intense rainfall and impervious surfaces are a recipe for urban flash floods. Now consider a stormwater removal system [gutters, drainage inlets, pipes, and culverts] that may be impeded by blockages or engineering assumptions for last century’s rainstorms.”
REPORT: 45,000 fish killed in Chattahoochee River to combined sewer overflow
Clear Water to a Black River
Jason reported the situation to state emergency responders, and then contacted Atlanta’s Watershed Commissioner Greg Eyerly. Within an hour, the commissioner arrived at the river to meet the Chattahoochee Riverkeeper (CRK) team. With monitoring equipment onboard, they continued upstream in the black water to the confluence of Peachtree Creek and the river.
A week before, the river had been extremely low and clear when CRK took a group of college students to observe this section of the Chattahoochee, where the city withdraws its drinking water and, a short distance downstream, discharges treated wastewater and treated stormwater after rain events.
Dirty Stormwater and Sewage
A few hundred yards up Peachtree Creek, there is an emergency spillway for the West CSO (combined sewer overflow) tunnel: a massive storage chamber designed to hold and eventually treat as many as 177 million gallons of combined stormwater and sewage during large rain events. The vast majority of this volume consists of stormwater that has flowed across pavement and rooftops, picking up contaminants and heat in warmer seasons. In May, these hard surfaces were scorching-hot from weeks of drought and high temperatures. Heated water (thermal pollution) reduces dissolved oxygen in a river, increasing biological stress for fish and other species.
Jason suspected that the West CSO facility had experienced problems during the high-intensity, isolated storm on May 20. He was correct. An overflow had taken place for the second time in the 18 years since the stormwater infrastructure – a component of the consent decree that settled CRK’s lawsuit against the city in the 1990s – was completed. The other overflow occurred in 2009, when historic flash floods virtually paralyzed the city for days.
What triggered this recent catastrophe? The city, state and federal environmental agencies, and CRK are actively pursuing answers to this question. An independent engineering firm has been hired by Commissioner Eyerly to conduct an evaluation and make recommendations. The situation appears to have been a convergence of multiple negative factors; in other words, a perfect storm.
A Perfect Storm
Those negative factors include a climate-influenced drought, urbanization, an inadequate and aging stormwater system, and infrastructure deficiencies caused by poor maintenance and minimal investment.
Beginning last fall, the severe drought in the Atlanta region sucked moisture out of the ground and hardened the soil, causing rain to run off immediately instead of seeping into the ground. Also, the drought-impacted Chattahoochee was extremely low at Peachtree Creek and the water was hot. Aquatic species were likely struggling to consume enough dissolved oxygen. Longer, more intense droughts are a sign of a changing climate, as are unpredictable, intense, and localized downpours.
Flooding and polluted stormwater have increasingly plagued the city of Atlanta. Its poorly maintained and undersized stormwater system includes 900 miles of storm pipes and other components, most designed for the type of storms that occurred fifty years ago. Planning and engineering must consider the weather and climate of the present with the future in mind — not the past.
Finally, the West CSO tunnel did not function as designed. According to the city, the tunnel was not draining properly prior to the deluge. When the downpour occurred, it was already holding too much water and debris, thereby reducing its capacity to contain the storm’s runoff. The consent decree requires an annual cleaning of the tunnel; however, it appears that maintenance has not occurred in the past year. Other operation and maintenance issues likely contributed, as have staff turnover across the years and poor oversight by overburdened and/or inexperienced managers.
Stormwater Utility Needed
More than 40 other local governments in metro Atlanta raise funds to manage rain runoff and flooding to protect public health, safety, and welfare through a dedicated fee system called a stormwater utility: a mechanism used successfully in thousands of cities since the 1970s. While Atlanta officials have invested in some notable stormwater control projects, they have kicked the utility creation can down the road for decades, while professing to be “studying” the measure. It’s past time to demand leadership and action from Mayor Dickens and the Atlanta City Council.
On the Chattahoochee, weeks after the storm, CRK’s water monitoring shows that the river is slowly healing itself from the man-made catastrophe. Fish and other creatures are beginning to move into the 20-mile section that became septic during the May deluge. It will take time – who knows how long – for this part of the river to return to its previous abundance.
