SCOPE 10 Saving City's Sewer System

INFRASTRUCTURE SERIES

By TIM SINIARD
Posted 11/7/19

(Editor's Note: This is the third in a two-week series exploring existing infrastructure and future needs in the Cleveland and Bradley County community).

 

Cleveland residents driving …

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SCOPE 10 Saving City's Sewer System

INFRASTRUCTURE SERIES

Posted

(Editor's Note: This is the third in a two-week series exploring existing infrastructure and future needs in the Cleveland and Bradley County community).
 
Cleveland residents driving down the city’s patchwork of streets might not be aware there could be a camera threading through a sewer pipe directly beneath them.
 
It’s not a security camera or a webcam, although it could be considered that in some ways.
 
The camera is part of Cleveland Utilities’ massive SCOPE 10 project, a sewer rehabilitation project that began in 2012 to prevent unwanted groundwater from seeping into existing cracked or broken sewer lines.
 
The project is focused on mitigating excessive amounts of stormwater in sewer systems, which can result in manhole overflows, as well as health hazards to the community caused by flooding.
 
Cleveland, as well as most cities across the United States, is required to embark on the multi-year project to meet regulations set forth by the Clean Water Act, enacted in 1972 and amended over subsequent years.

Cities such as Chattanooga, Nashville and Memphis are in the same boat, spending millions of dollars to bring their wastewater systems into compliance.

Knoxville is set to spend up to $1 billion on its sewer rehabilitation project, according to CU Wastewater Rehabilitation Manager Greg Clark.

“They've been working on their project for almost 15 years,” he said.

It will be a never-ending process as pipes age over the next decades, requiring additional rehabilitation. However, CU Water and Wastewater Division Vice President Craig Mullinax and Clark said the extent of future work required in years and decades to come will hopefully not be as extensive as the SCOPE 10 project, which has had to rehabilitate sewer lines and manholes that are up to 80 to 100 years old.

In a nutshell, the project consists of locating broken sewer pipes that allow stormwater to enter the system, causing overflows. To locate the damaged sections, CU hires a contractor to snake a camera through pipes to determine which sections need repair.

As the camera works its way through a section of pipe, broken shards of clay pipe come into focus, allowing groundwater, as well as soil, to enter CU's wastewater system.

The pipes are damaged due to a myriad of causes including age and root intrusion, as well as other sections that were damaged when lines from homes and businesses were hooked up to the sewer.

“A long time ago, they would just hit the clay pipe with a hammer and hook up a line to the sewer,” Mullinax said.

The result is an unsealed connecting pipe that allows stormwater to enter the system from around the loose-fitting junction.
 
Instead of digging up the pipe in the sewer main, sometimes a section of pipe is inserted into the damaged portion to seal it. Other methods include using an epoxy resin that essentially seals the entire interior surface of the pipe, eliminating leaks.
 
The work, which may focus on several hundreds of feet of sewer pipe at a time, can be time-consuming, as well as costly.
 
The SCOPE 10 project was budgeted to cost $30 million over 10 years, primarily paid for by low interest loans from the Tennessee State Revolving Fund. So far, CU has spent approximately $15 million.
 
However, the project timeline will surpass 10 years. Why? It’s a huge undertaking.
 
According to Clark, there are 370 miles of sewer mains within the collection system, accompanied by 7,200 manholes. Some of the manholes are also decades old.
 
Most of the infrastructure was listed on decades-old maps.
 
“We started this program with probably one of the biggest challenges,” Clark said. “We had some maps, we had some knowledge of the system, but it was actually getting in and doing an asset-management part of this system.”
 
At that point, CU had to conduct sewer evaluation surveys to determine the condition of its sewer mains, many of which are made of clay and dating back to the early to mid-20th century.

Also problematic were  heavy rain events that caused Cleveland's sewer system to become overwhelmed, requiring the use of a 10-million gallon tank, located near Tinsley Park, where excess water is pumped and stored.

“There are some times when it might rain for days and days and days and days, and then you'll have a really big rain and it just overwhelms the system and fills the tank,” Mullinax said.

When the tank is filled to capacity, CU must shut down the pump, resulting in a nearby manhole overflowing.

However, since the project was launched, CU is seeing fewer such events.

“We're trying to spend enough money to keep the overflows from occurring … to spend the money wisely where it needs to be spent to make the repair work,” Mullinax said. “We can see improvements there ... there's one area that was an overflow that is completely gone. And so, we can see we're making a difference, but it's a slow process.”

One such area is along Wildwood Avenue, where overflows have been reduced significantly.

The SCOPE 10 project, according to Mullinax, will help the city grow since wastewater systems will be able to function more efficiently. With less stormwater and leaks intruding into the system, it will be able to accommodate new users such as residences and businesses.

“It means you can develop more because there's more capacity in the sewer,” Mullinax said. “You’re taking out unwanted rainwater or groundwater, and it's  freeing up waste that used to go to the [wastewater] plant.

Mullinax said making the repairs delays wastewater treatment plant expansions because there is less water to treat due to an improvement of the sewer system’s self-containment and efficiency.

“So, it is allowing for extended operation of our plant without having to expand it,” he said.

Despite the cost and labor intensive aspects of SCOPE 10, Mullinax said it is repairing problems that were not considered priorities based on assumptions at the time.

“I could tell you stories of pipes that were plumbed down into the creek,” he said. “That’s just the way it was years ago; nobody thought any more about it. It wasn’t wrong or right. That's just the way it was, but when the Clean Water Act came along, they set a bar of what you need to do. So our goal … my goal — maybe before I retire — is at least to see that manhole [near Tinsley Park] doesn’t overflow anymore and we don't have to put any water in our tank anymore.”

Mullinax said the project is making a difference.

"We think we're positioned pretty good to show and demonstrate the EPA that we are doing it the right way," he said. "We may have to spend more money, but our rate increases on the wastewater side have been between 4% and 5%, so we haven't had huge increases and our sewer rates are still in the middle of the pack.”

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