(WBIR) Knoxville, like every city in America, is dealing with aging infrastructure. The American Society of Civil Engineers rated the country's infrastructure a D+ in 2013.

Last month, Knoxville Utilities Board (KUB) proposed rate increases for the next three years to help replace older mains from the city's system.

The board will consider annual residential rate increases for fiscal years 2015-2017:

  • Electric: $1 per month for three years ($3 total for 2015-2017)
  • Water: $2 per month, followed by $1 per month in both 2016 and 2017 ($4 total for 2015-2017)
  • Natural Gas: $1 per month for three years ($3 total for 2015-2017)
  • Wastewater: $3 per month for three years ($9 total for 2015-2017)

That money goes into KUB's Century II program which started in 2007. The program has been phasing out cast iron pipes from the city's system since its inception.

"Part of the challenge is just being able to time it right. You don't really know when exactly the right time to replace this older pipe is," said Bill Elmore, KUB chief operating officer.

In April, a large water main break in Downtown Knoxville caused several streets to close. The main that broke was a 1927 cast iron pipe. Cast iron pipes can last 100 years but some of it in the city's system is reaching the end of its shelf life.

KUB provided 10News with a map showing cast iron mains in the city's system, 12 inches and larger, installed before 1940. KUB has sectioned them into 14 areas for replacement (see Map 1).

"In the next 15 years, we plan on replacing one mile of pipe per year. By 2030 all the larger diameter older cast iron will be removed from the system," said Julie Childers, KUB vice president of engineering.

Crews removed the first four miles through Century II funding. According to Childers, they have 15 miles left to replace. In 10 years, the city will have a third of the old piping left.

KUB is also replacing four miles of the smaller diameter cast iron main until 2030. After that, they will replace five miles each year.

"It can't all be replaced over night and shouldn't be all replaced over night. So part of it is having a long term replacement plan and more importantly, a long term financial plan," Elmore said.

Crews are replacing the cast iron with ductile iron. Ductile iron has an expected life of 125 years, 25 more year than cast iron.

"When we look at pipes to replace, we have a lot of different factors we use in prioritization. One of which is age, the other if we've had a problem on the line with leaks or breaks in the past, or maybe there's an upcoming paving program that we need to get ahead of. We don't want to replace a line right after a street's been freshly paved," Childers said.

The Lyons View Pike project is one example of a time when KUB decided to address more than one utility. Elmore said they noticed that besides the wastewater system, the project was in need of an update to its gas and water systems.

KUB's next Century II project will start this July in Downtown Knoxville. Crews will remove cast iron pipe starting at N. Gay St. and W. Jackson Ave., through S. Central St (see Map 2).

"It's important that we replace pipes in a timely manner and we don't necessarily just run everything to failure," Elmore said.

While the focus is on larger cast iron pipes, they hope to have all cast iron removed by 2070.

KUB spends about $5 million each year replacing the aging water pipes.

The board will vote on next year's budget and the proposed rate increases within the next month.

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