Archive for Sunday, November 15, 2009

City checking up on weathered water lines

November 15, 2009


They’re old warriors that lurk beneath the ground.

They’re pieces of cast iron that somehow have fended off the wear and tear and the corrosive elements that are a big part of the Lawrence soil. They’re the city’s water lines.

And some of them are pretty old.

A main transmission line running from the Kaw Water Treatment Plant, for example, dates back to 1886, if the city’s records are correct.

Double-checking those records is part of a major new project the city’s Utilities Department has undertaken to measure the age and condition of the city’s water lines. Thus far, the results are better than some expected. The preliminary analysis has found that 60 percent of the 423 miles of water mains in the city have been installed since 1980.

“When I saw that, I was surprised by the amount of replacement we’ve had in recent years,” Mayor Rob Chestnut said.

But still, there’s the other end of the spectrum, which includes some lines that have been providing water since the days when a family’s horse may have been as likely as anybody to drink from the city’s well.

The report, which is still in a draft stage, doesn’t provide details on what percentage of the city’s water lines date back to before 1900. But the report does include a map that shows several areas where the water lines are old. They include:

• A major line along Indiana Street from Second Street to Eighth Street is pre-1910.

• A line along Mississippi Street from Fifth Street to Ninth Street is pre-1920.

• A line along Tennessee Street from Sixth Street to 10th Street is pre-1920.

• A section of line on Delaware Street from Eighth Street to Ninth Street is pre-1910.

Age just one factor

City leaders said determining the age of pipes is important but it is not the only criteria used when determining whether a pipe should be replaced.

“As we get older, we realize the fact that something is old doesn’t mean that it is obsolete,” said City Manager David Corliss. “But clearly, age is one of the criteria that we look at.”

Other factors include the size of the line, the number of breaks that have occurred on the line, and the importance of the line to the overall system.

That last point means the 1886 line will get a thorough review by city utility engineers. The cast iron transmission line supplies large amounts of water to the entire system, said Dave Wagner, the city’s director of utilities.

Although Wagner doesn’t want the line to break, he said Lawrence is in a better situation than most communities if a major failure occurs to a key water line. That’s because the city also operates the Clinton Water Treatment Plant in western Lawrence. Either the Kaw or the Clinton Plant has the capacity to serve the entire town by itself, although if the break occurred during the summer it could cause the need for restrictions on some lawn and garden watering.

Old lines, though, aren’t the only ones on Wagner’s mind. The City Commission last week gave Wagner permission to begin soliciting a new study of the city’s concrete water transmission lines. The city has about 13 miles of the concrete lines, which were built in the 1950s through 1970s. The lines generally are monsters, ranging in size from 16 inches to 36 inches in diameter. In other communities, there’s been a history of some major failures of concrete lines, and the city’s Utilities Department doesn’t have as much ability to quickly repair those type of lines as it does with traditional cast iron or plastic lines.

New technology — such as electromagnetic, acoustic-wave and video devices — allow engineers to examine a pipe without digging it up.

Rating factors

Newer cast iron pipes also are being watched by city engineers. Until the last few years, much of the cast iron pipe being installed in the city was not being wrapped with a protective coating, Wagner said. The coating is important, Wagner said, because data from the Natural Resources Conservation Service has shown that Lawrence soils have elements and minerals that can be significantly corrosive to cast iron pipe.

For about the past five years or so, since the time Wagner came on as the department’s director, the cast iron pipe has been wrapped in a protective coating. The department also uses some plastic pipe, but prefers cast iron in major rights-of-ways where the pipe is at risk of being struck by an excavator or other construction equipment.

Corliss said the city’s efforts to get a good inventory of all its water lines should help the city greatly in determining what lines need to be replaced in the future. He said the process is similar to what the city has been doing with a system that gives a condition rating to every mile of street in the city.

Wagner said thus far, he’s pleased with the early results. The inventory so far has tracked the number of water main breaks from 1998 through 2006. During that time period there were 672 breaks, which Wagner said is about half the number of breaks per mile that many other cities experience.

“In a lot of ways, we’re looking pretty good, but we also always remember that it takes just one bad break for us to have a really bad day,” Wagner said.


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