SIOUX CITY | If it seems like more Sioux City water mains were breaking this winter, that's because they were.
In a rough start to 2018 for its water infrastructure, the city reported 39 main breaks in the first nine weeks of the year, or an average of about four per week. That number was up from 24 breaks during the same period last winter and 22 the year before.
Going back to the start of the city's fiscal year on July 1, the city has counted 106 water main breaks as of last week. With more cold weather forecast for this month, that's on pace to surpass the 107 breaks tallied during the previous fiscal year, according to statistics from the city's Underground Utilities Division.
City underground utilities superintendent Jon O'Brien said deeper freezing and other soil conditions are often the culprit for main breaks, with the number varying from year to year and hard to forecast.
"You can't really predict what year and in what main you're going to have issues," he said. "It depends on the soil conditions and what's around it that causes a main break."
This year is on pace to be the second in a row that the number of breaks has increased, although the number of breaks has the past two years been far below much higher numbers experienced earlier in the decade, such as the 184 counted in FY2013, 152 in FY2014 and 133 in FY2015.
Among the highest-profile breaks this year was a Jan. 17 water main break on an access road near West High School that temporarily closed West High and West Middle and led to a more than two-day boil advisory for many west side residents.
With 474 miles of water mains in Sioux City, the city averaged around 22 main breaks per 100 miles last year. That is below the estimated national average of 25 to 30 breaks per 100 miles.
Sioux City and some other cities around the country face aging water infrastructure and the rising costs of fixing and replacing the underground pipes. The city's budget for the fiscal year beginning July 1, approved last week, does not forecast to decrease the age of the water mains but does expect to keep pace in order to prevent their collective age from increasing.
Currently, more than 30 percent of the city's existing water mains are more than 60 years old, the age at which the city's utilities department says mains are typically in need of replacement. Fourteen percent of the pipes are 94 years old or more.
O'Brien said each year, the city tries to identify which replacement projects will carry the largest benefit for the city.
"It's an ongoing battle," O'Brien said. "We're a large city with a lot of water mains in the ground."
City Utilities Director Mark Simms said the city takes into account the frequency and location of the water main breaks as it lays out its capital improvements projects.
"We look and see if we have breaks occurring in the same area on the same line, and that might force us to change the focus of our CIP (capital improvement program) to respond to a certain area sooner," he said.
Simms pointed to the overall drop in water main breaks over the past few years as a positive trend and credited the current City Council's emphasis on infrastructure repair.
According to a report of water main breaks from Jan. 1 to Dec. 31 last year, the average age of the mains that broke was 72 years old, although the breaks included several newer mains, including four from the 1990s, one from the 2000s and two from the 2010s.
O'Brien said winters with deeper freezing will typically cause more water main breaks than lighter winters, although breaks occur year-round and are hard to predict. The way a main is installed in the ground and how it sits in the soil will also play a role, he said.
The average cost per water main break last budget year was nearly $7,000.