Several water-main breaks in the city this year prompt people to ask questions.
What causes the breaks? What are the main pipes made of and how old are they? How are the breaks fixed and when do problems indicate the need for replacement?
The Journal reported breaks along Ninth Street Jan. 14 and Feb. 4. Another break happened in the 100 block of South Wasson Lane Feb. 5.
City Administrator/interim utilities director Scot Simpson said about the water-main breaks: "Unlike electrical outages, it's not as easy to pinpoint what the problem is."
Simpson calls the process for finding the cause of a water-main break, "a lot more speculative." In all the cases, said Simpson, crews found actual broken pipes.
Some, including experts, insist weather affects the mains -- extreme cold or a rapid rise or fall in barometric pressure can do it.
Others insist that buried rocks move. Some of it's due to the materials used, method of construction or installation, weak pipe joints or movement within the earth.
"There is lots of speculation about this area of town and about the rock," he said.
Simpson said the age of the Ninth Street pipe is about 50 years; the Wasson Lane pipe was laid in 1971, and both are made of cast iron. The pipe would typically be expected to last a total of about 70 years.
"Both of these areas have experienced an unusually high number of breaks over their life," the administrator said. "We believe that is due to poor bedding of the pipes at construction and movement of rocks in the soil."
Water-main pipes before the mid-1970s were made of cast iron. The newer material is still iron but more flexible than those of cast iron.
The Ninth Street main affects the middle school's water supply because unlike some more modern 'commercial' buildings, MMS cannot be serviced from any other line -- only the neighborhood pipe along Ninth Street.
He agrees the pipe seems to be problematic, but it isn't obvious why. Simpson said replacement of the pipe was in the city's work plan for 2016, but it's now a priority project slated for 2013.
Crews will replace the water main in conjunction with other construction work happening at MMS.
Finds, fixes, facts
Simpson explained that when a water main breaks, it normally affects only about a block's worth of homes and a dozen or so customers. He said a commercial main, for example, would cause worse disruption.
Water running or spraying may be the most obvious clue there is a problem, but the water doesn't always come out at the point where the pipe broke. Simpson said the city also monitors and compares usage to actual gallons billed in order to catch any undetected leaks.
River Falls responds to a water-main break by first trying different valves to see if it can cut supply to the broken main. The city calls a consultant that uses sonar-like sensor tools to determine where the underground break is located.
Simpson said then a local excavating contractor does the digging. Depending on how the pipe is broken, the city might slip a sleeve over it and or use a variety of clamps and fittings to repair it.
"When you have a break," he said, "you're going to saw and put something new on or use some kind of sleeve to fix the pipe."
He says the city water staff does not have the capability to do the digging and fixing, but a staff member remains on scene throughout the repair. The diameter of water-main pipes would typically be six inches or more.
When repair work will be performed, the city water staff looks at a map to see what homes will be affected then goes door-to-door telling people about the planned repair and service disruption. If nobody is home, the staffer leaves a hang tag on the door.
Most water-main breaks are repaired within four-to-six hours, and Simpson said they are not usually dramatic events. The breaks along Ninth Street drew much attention since they caused classes to be cancelled at the middle school.
Simpson said the pressurization of water helps keep contaminants out of the system. Before any repairs can be made, the pieces being installed must be disinfected with bleach and water, a process made challenging by winter's bitter cold. He said while the city doesn't do the actual repair work, an important part of its job is making sure the water is safe to drink.
Simpson said even the number of breaks seen this year isn't that high considering that River Falls has about 71 miles of water-main pipes beneath its streets.
He says the city has averaged less than four water-main breaks per year over the past three years. The American Water Works Association (AWWA) conducted a survey that revealed an average of one emergency main break per year for every 3.7 miles of pipe, which translates into 19 breaks a year per 70 miles of main.