INDIANAPOLIS — Fall Creek is a gem that flows through the heart of Indianapolis. On any given day you'll find bluegill and blue herons, turtles and trillium, butterflies and bass along the creek and its winding trails. It also provides drinking water to thousands of central Indiana homes.
So it might be concerning to see a thick, black sludge pouring into a waterway that sits right alongside Fall Creek.
"What is this at Keystone and Fall Creek? It's been flowing for hours?” wrote a concerned 13News viewer, who sent video of the black substance to 13 Investigates. “It looked too gross to not report."
Passing joggers, bicyclists and motorists have been curious about the liquid -- and with good reason. At first glance, it looks like crude oil flowing into the waterway. So 13 Investigates visited the site to figure out what the black substance is, and to determine where it’s coming from and where it is going.
Impurities in the water
It didn’t take long to find the discharge pipe that triggered concerned Indianapolis residents to send e-mails to 13News.
We saw a steady stream of black sludge pouring from a hole in a concrete structure and into a narrow channel of water tucked between Fall Creek (the creek) and Fall Creek Parkway (the road). Nearby, a sign hanging on a barbed-wire fence warned of strong currents in the channel. The fence also had “No Trespassing” signs posted by Citizens Energy Group, a clear indication that the channel -- and the black liquid pouring into it -- are part of the utility company’s Fall Creek Water Treatment Plant located just across the busy street.
13News contacted Citizens Water, which said the black liquid is harmless and added to the water intentionally.
"The black substance in question is activated carbon. It is part of the water-purification process and is only used as water conditions in Fall Creek require," explained Laura O’Brien, a spokeswoman for Citizens Energy Group.
Activated carbon (also known as activated charcoal) is a very common and effective substance used to absorb impurities in water. If you have a water purifying system attached to your home water tap, it likely contains activated carbon. It’s also used in large home fish tanks.
Citizens Energy tells 13News it adds the carbon to water it collects from Fall Creek to eliminate bad tastes and smells caused by algae that grows in the water during warmer weather.
“Many times during the summer months, there are algae blooms in Fall Creek and other area waterways that Citizens utilizes for water supply,” O’Brien wrote. “Some algae blooms can produce compounds that can give the water an earthy or musty taste and odor that is objectionable to customers. During these times, Citizens must supplement our normal water treatment process with activated carbon to neutralize taste and odor problems the algae can create in our finished drinking water.”
How it works
Activated carbon is effective in removing impurities from water because it has an incredibly high surface area to absorb organic material. A single pound of granular activated carbon has more than 35 acres of surface — that’s equivalent to almost 100 football fields!
Last year, Citizens Energy said it poured about 50,000 pounds of activated carbon into the water flowing through its Fall Creek Treatment Plant.
The black substance is added to water in the collection channel, where it is circulated to absorb impurities before the water flows inside the nearby treatment plant for further processing. The activated carbon is then filtered out of the water before it is pumped to your home as drinking water.
O’Brien said the carbon poses no health or environmental concerns, but Citizens Energy acknowledges it does look kind of gross.
“We have received some inquiries about the carbon, as well, and are currently working on signage to post near the outfall,” O’Brien wrote.
If you see something unusual that you’d like 13News to investigate, send us an e-mail at 13Investigates@wthr.com.
