Straight from the Tap

Winter Recap: Implementing Lessons Learned & Planning for the Future

03/28/2019

According to the calendar, spring is officially here. And as the cold temperatures finally subside, we’re taking a look at the impact this winter had on our infrastructure.

Water Main Breaks

Every fall, Cleveland Water begins preparations for an increase in main breaks that is common during cold weather. Each winter brings a different challenge as exact weather events can never be anticipated – and this year was no different.

While we didn’t quite reach the severity of last year, one of the harshest winters our crews have had to contend with in the last 10 years, a polar vortex during the last few days January was enough to cause a jump in frozen pipes and main breaks.

Last winter, the highest one month total for main breaks was 510 in January. This winter, the highest was 317 – closer to the expected winter average of 7 to 10 breaks daily. Most noticeable, were breaks on two large transmission lines, one on Engle Rd. in Middleburgh Heights and one on Clark Ave. near West 14th St. in Cleveland.

The late January cold stretch was an opportunity to implement lessons learned from last year. The main break data collected in Cityworks from last winter helped us to better recognize early warning signs of a sharp increase in main breaks and respond more quickly, limiting the backlog. One metric we paid close attention to was pumpage rate. An increase in the volume of water pumped from our treatment plants through the distribution system can occur before many leaks surface, making it an early indicator of a spike in main breaks.

Winter Main Breaks
     2017-2018   2018-2019
November   178   160
December   255   206
January   510   317
February   205   302
Total   1148   985

 

The data collected both this winter and last also suggests that successive bad winters can have an effect on break rates. As we continue to invest $26 million a year to renew and replace mains, this data will help us target projects to improve system resiliency as we face future extreme weather events.

Frost Sensors

This winter we installed new temperature sensors to help give us a better idea of what exactly was happening below ground. Two, ten-foot-long temperature sensor arrays, each with 21 temperature probes spaced six inches apart, collected ground temperature data with the goal of better understanding the impact that frost can have on main breaks.

The data collected showed that a spike in breaks occurred when frost depth was still relatively shallow, between 6 and 12 inches. This would indicate that the increase in downward pressure caused by frost does not have to be high as originally thought to affect water mains.

Our engineers will continue to analyze the data for conclusions along with the help of Case Western Reserve University graduate students who are also studying the physics of loads on mains from frost. But as is often the case with pilot programs, the biggest lesson is what improvements can be implemented for next year.

Planned upgrades include increasing the number of temperature probes at shallower depths; measuring pressure, moisture content and groundwater level in addition to temperature; and conducting an accompanying study to look at the effect that dry ground during summer can have on mains.