The sun sets over the James River in Richmond. (Ned Oliver/Virginia Mercury)

Every time there’s a heavy rainfall in Richmond, stormwater mixed with untreated sewage overflows into the James River to keep the sewer system from backing up. In 2018, this happened more than 550 times, spilling 3.4 billion gallons of raw sewage mixed with stormwater into the river and surrounding tributaries.

Last year’s historic rainfall was the first increase in volume and number of what the city calls “overflow events” in six years — and it might not be a fluke.

Experts say climate change is causing an increase in precipitation, flooding and high-intensity storms in Virginia, and cities with combined sewer systems like Richmond’s could experience more overflows as result.

Grace LeRose, program manager for Richmond department of public utilities, said the city’s sewage system is already being impacted.

“We’re on the frontlines dealing with climate change,” LeRose said. “We’re seeing bigger and more frequent storms that are going to tax our system even more.”

Richmond’s sewer system, called a combined sewer system, contains both stormwater runoff and wastewater from homes and businesses in the same pipes. During heavy rainstorms, the mixture of untreated stormwater and wastewater is released into the James River and surrounding waterways to prevent it from backing up into people’s homes.

For the last six years, the number and volume of overflows had been on the decline, but last year’s record rainfalls halted this trend. Richmond recorded 63 inches of precipitation in 2018 — 20 inches more than the yearly average — and there were 20 days in which it rained more than an inch in one day, the second highest number on record for the city.

In May and June, the city experienced 23 inches of rain — the highest ever recorded in Richmond for consecutive months. Much of that rainfall came from several large storms that poured inches of rain in a short period of time and caused flash floods that overwhelmed the sewer system.

“We had a storm in May that dropped seven inches of rain in one day. We had another in July that was six inches,” LeRose said. “These super big storms just drop an enormous amount of water.”

During May and June, more than one billion gallons of combined sewage was dumped into the river.

The city’s combined sewer system was constructed in the late 1800s, and is one of only three cities in Virginia that have one; the other two are Alexandria and Lynchburg. Across the United States, there are more than 700 cities in the Northeast and Great Lakes regions that rely on combined sewer systems.

Combined sewer overflows contain human and industrial waste, toxic materials and debris in addition to stormwater, according to the U.S. Environmental Protection Agency. Stormwater runoff picks up pollutants like oil, pesticides and fertilizer that can further pollute the river if it’s not treated.

The recent uptick in rainfall in Richmond is part of an overall increase in heavy rain storms across Virginia. According to researchers at Environment America Research and Policy Center, there was a 33 percent increase in heavy rainstorms in Virginia, and an 11 percent increase in precipitation from the largest storms between 1948 and 2011.

Researchers at the Virginia Institute of Marine Science wrote in a 2013 report that the swell of rainfall and high intensity storms could impact combined sewer systems in the state.

“In the Virginia urban areas with combined sewer stormwater systems, changes in storm intensity could have health and environmental impacts,” the report said. “New stormwater systems should be designed to handle larger storms than we are currently experiencing.”

Climate scientists predict that precipitation levels and the amount of rainfall from heavy downpours will increase over the next century. The National Oceanic and Atmospheric Administration has warned that much of the East Coast, including Virginia, is at risk for flooding this spring.

The City of Richmond has spent more than $300 million to repair and update its aging sewage infrastructure since the 1970s, but the Department of Public Utilities estimates that several hundred million more dollars will be required to fix the problem entirely.

Right now, 63 percent of the money used for these fixes comes directly from ratepayers in the city and the rest is funded by grants from the state and the U.S. Environmental Protection Agency.

The city is currently upgrading its wastewater treatment plant to hold and treat larger amounts of stormwater. Until this year, the wastewater plant could treat up to 75 million gallons of combined wastewater and stormwater every day. The upgrade will equip the facility to take an additional 65 million gallons during wet weather, nearly doubling its capacity.

The department also has embarked on several green infrastructure initiatives to help soak up some of the stormwater and divert it away from the sewers. In 2010, the city planted a 6,000-square-foot rooftop garden on top of its wastewater plant, and in 2012, the city constructed several “green alleys” using permeable pavement to reduce stormwater runoff.

Green infrastructure projects are currently underway at the Low Line in the city’s East End, Jefferson Avenue in Church Hill and Gillies Creek.

Mayor Levar Stoney’s proposed budget for 2020 includes $15 million for stormwater facilities improvements, nearly $4 million for wastewater treatment and $2.3 million to address combined sewer overflows.

The city is also making efforts to educate and inform the public about the issue through its RVAH2O program, which has partnered with local environmental organizations on a number of public outreach initiatives.

The James River Association, a nonprofit environmental group, has worked with the city to find solutions to the overflow problem, but it’s been a slow process. The group gave the James River stormwater pollution controls a “C” rating in 2017 — an improvement from its “D” rating in 2015.

Jamie Brunkow, senior advocacy manager for the James River Association, said evidence of untreated sewage can still be seen floating in the James after heavy rainstorms, but it happens less frequently now because of the city’s recent efforts to address the issue.

“This is something the city has had to deal with for a long time,” Brunkow said. “We had a really wet year last year. It’s not terribly surprising that you’re seeing more of these discharges.”