In the mid-20th century, wastewater plants started importing silver carp and bighead carp. They thought these fish would clean up the water and solve an ecological problem since they were good at consuming algae blooms.
However, it became a much bigger problem.
The carp made their way into the wild, and they started outcompeting local fish species. Near Peoria, Illinois, the carp make up 95% of the fish biomass in the Illinois River. They destroyed the local natural ecosystem.
Let’s look at what is happening in Chicago to prevent these predators from entering the Great Lakes and destroying that ecosystem.
Why Was the Chicago Sanitary and Ship Canal Built?
Before 1900, the sewage from Chicago flowed down the river into Lake Michigan. Because the city’s drinking water was offshore, there was a fear that it could become contaminated and cause disease outbreaks.
City officials decided to dam the river and reversed the flow so that the sewage and wastewater would move in the opposite direction away from Lake Michigan. They built the 28-mile-long Chicago Sanitary and Ship Canal to provide a passageway to Lake Michigan.
The canal also replaced the smaller Illinois and Michigan Canal. The Chicago Sanitary and Ship Canal is 202 feet wide and 24 feet deep, providing a larger passageway for ships to navigate. Due to its historical significance, on December 20, 2011, the canal was listed on the National Register of Historic Places.
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Why Does the Army Electrify the Canal?
The carp must travel through the Chicago Sanitary and Ship Canal to get from the Illinois River to the Great Lakes. The Army Corps of Engineers installed an electric fence underwater to prevent the invasive carp from passing the barrier.
The Great Lakes has a $7 billion fishing industry and a $16 billion recreational boating industry. If the carp get through and enter the Great Lakes, these industries would collapse, and the results on the economy of this region would be disastrous.
The main invasive carp population in this part of the Illinois River has remained about 70 kilometers from the canal. This is a positive sign that the population hasn’t moved closer. The electrification is working.
How Do the Barriers Keep the Carp From Traveling Through the Canal?
Electric bars extend 21 feet deep into the water. DC electric current pulses into the water, similar to a speed hump on the road, to create a voltage gradient.
The barrier of electricity at sites 2A and 2B is 2.3 volts per inch, and the border of electricity at site 1 is 6.0 volts per inch. Like an electric fence keeps dogs in someone’s yard or prevents outsiders from entering someone’s private farm, this underground electric fence keeps fish from swimming any farther.
What Happens If a Fish Travels Into the Voltage Gradient?
Often, fish turn around when they get close. Fish in the area have learned what happens if they travel too far down the canal. Other fish who haven’t yet understood or feel brave will be stunned if they enter the voltage gradient.
Once a fish is stunned, they float downstream and wake up elsewhere.
What Happens When a Barge Comes Through the Canal?
When a barge comes through the canal, the amount of voltage that has to be sent into the water for the electricity to be effective at deterring the carp has to go up dramatically.
The smallest fish tend to escape through the canal because of the drop in effectiveness. Barges have an angled rake in between two barges, which provides a water space where a small fish can remain for miles traveling along a river.
This is a weakness of the electrical barrier.
What Would Happen If a Person Got Into the Water?
A Navy dive team did a study on the electricity in the water and found that there’s a greater than 50% chance that someone in the water would have a heart attack and die. There are warning signs and fences all around the canal to keep people out and alert them to the dangers of swimming, diving, or fishing in this area.
The Coast Guard has also established specific rules for the canal to ensure personal safety. No private watercraft like jet skis or kayaks can go through.
All barges must use steel cables, and all staff on the barges must be inside instead of on deck when they pass through the canal.
What Happens During a Scheduled Maintenance?
Multiple barriers are in place because of maintenance. One barrier always operates when another barrier receives care. This layer of defense is similar to night security guards who might rotate shifts.
One person stands to watch for a few hours while another gets some sleep. Then they rotate. However, the scheduled maintenance doesn’t happen often. All three layers of barriers usually operate together to form a strong defense against invasive carp.
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Why Isn’t the Canal Closed to Prevent Carp Traffic?
Theoretically, the canal could close, and they could reroute the water down the river to prevent the invasive carp from reaching the Great Lakes. However, officials would have to re-engineer all the sewage and wastewater systems to send waste elsewhere.
The canal is also a flood defense for Chicago. It would be a hugely expensive project to undertake.
In addition, the canal is a significant route for shipping today. Millions of dollars of goods pass through on barges yearly. Rerouting these barges would increase truck traffic, increasing air pollution and congestion.
The Chicago Sanitary and Ship Canal is a vital waterway for the shipping of goods to the Great Lakes region.
This doesn’t mean some people don’t believe the canal should close. In December 2009, Michigan Attorney General Mike Cox filed a lawsuit with the Supreme Court seeking the immediate closure of the canal to keep the carp out of Lake Michigan.
He argued the Great Lakes tourism, sport, and commercial fishery impact all the states along the Great Lakes and Canada, and the invasive carp threaten their economies.
However, in January 2010, the Supreme Court rejected the request for a preliminary injunction.
Protecting the Marine Life Of the Great Lakes By Keeping Carp in the Illinois River
If you’re looking for a good fishing location, head to the Illinois River near the canal. The increasing carp population has led to a substantial new carp fishing industry. The electrification project is working. However, the Army Corps of Engineers is constantly perfecting the process.
They’re tweaking the voltage and looking at other options like light, sound, or CO2 that might also deter the carp. This project must be successful. Otherwise, the marine life in the Great Lakes could potentially end up like the marine life in the Illinois River, wholly overtaken by carp.
Did you know the Chicago Sanitary and Ship Canal was electrified? Tell us your thoughts in the comments!
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