Portland's new water pipes expected to last 250 years
In recent years, American infrastructure has sometimes been characterized as crumbling and out of date.
According to the American Road and Transportation Builders Association, four out of 10 bridges in the United States need to be replaced or repaired, including one in three bridges on the Interstate Highway System, at an estimated cost of $41.8 billion.
One place where infrastructure replacement is ahead of the game is Portland and its water pipes.
Clean water and sewage are very different animals in Portland. The Portland Water Bureau provides drinking water in its pipes — even if that water can be used for other things, such as flushing toilets or cooling machinery.
The Bureau of Environmental Services, a different city bureau, manages sewage and stormwater. Their pipes carry sewage — never drinking water. BDS maintains its own pipes, and the Water Bureau maintains its own.
Water Bureau pipes are usually smaller in diameter and closer to the surface. They are under pressure, and to prevent cross-contamination, they are kept well away from sewage and stormwater pipes, which are laid deep in the ground and are gravity-fed.
When the COVID-19 pandemic struck, Water Bureau work crews switched to 10-person teams who worked together exclusively, with limits on sharing equipment and vehicles and other statewide restrictions. According to the Water Bureau, the Maintenance & Construction (M&C) Division broke a record for new pipe installation in fiscal year 20/21.
Crews proactively replaced 31,700 feet of pipe. The prior record, set two years ago, was 28,000 feet of pipe replaced. In the last decade, the average was approximately 23,000 feet of proactively replaced pipe. These figures do not include what's going on at reservoirs, such as in Washington Park.
The water bureau's Asset Management Division says the expected useful life of the type of cast iron pipe Portland's water system was built on is around 125 years. The city was founded in 1851 but between 1900 and 1930, the city's population tripled from nearly 100,000 to 301,815. So, much of that iron pipe is coming due to be replaced.
Today the Water Bureau replaces cast iron pipe with ductile iron pipe, designed to last 250 years in Portland's soil conditions. Some reasons pipes must be replaced include cracking under pressure as soil moves, corrosion (rust), nodules forming inside the pipes (which slow flow), and population density increase, which requires more water for drinking and firefighting.
Ty Kovatch, director of maintenance and construction at the Portland Water Bureau, explained to the Business Tribune that they would ramp up pipe replacement to reach a pace of approximately 40,000 feet each year over the next five years.
"In 2019, the Water Bureau recognized that we needed to ramp up the pace of installation of new water main, to get in front of a cohort of pipe that was installed in the early 1900s, through about 1940," Kovatch said. "It was a big chunk of our system was all installed during that window, so it's all going to reach the end of its useful life within a 20-year span."
He added, "There aren't enough resources to go and fix all that pipe all at once — 20 years from now — so we want to knock the top off of that. So that's what we started doing this year, and we were able to successfully get there in our first year of trying."
The Bureau uses a computerized maintenance management system to look at break history. Then engineers decide if a water main needs total replacement or just a local repair.
If the analogy were capillaries, veins and arteries, the capillaries would be the "service" pipes that come from the street to your home. The veins would be the water "mains," the high-pressure pipes that run down the middle of the street. (This is called "distribution.") And the arteries would be the "arterials" that come from the reservoirs and wells. (This is called "transmission.")
Not that thirsty
For all the talk of drought in Oregon, Portland is not running short of water.
"One of the blessings of the city of Portland is we have the Bull Run watershed and the temperate rain forest that has served this community very well for a long time. And we have a secondary source of supply of water which is the Columbia South Shore groundwater wells system that helps us supplement during drier years and later in the summer. We encourage our customers to just be responsible users of resources, but we don't have a shortage."
Portland has 150 to 200 water main breaks every year. That pace has been steady for decades, and Kovatch says it is relatively low compared to jurisdictions around the country. Portland soil is neutral and therefore less corrosive, and the mild climate limits freeze-thaw action.
Failure can be severe: On March 16, 2019, a 30-inch diameter main burst at Northeast 23rd Avenue and Skidmore Street, releasing millions of gallons into the streets.
"When we got down to look at that pipe (from 1924), it was in really good condition, but it had been damaged by a construction project," Kovatch said. "Our engineers didn't see any reason why the rest of it needed to be replaced other than the section that failed, which was the result of construction, where they probably nicked it."
The Bureau also replaced 337 hydrants this year, which is on the normal pace. Some get damaged by vehicles, and some are just old. Some Portland fire hydrants in the inner southeast and northeast have their manufacture date, 1895, in the cast iron. Over time, the Bureau converts them to a compression hydrant, which features a big screw that opens at the top. It is easier to maintain and less likely to fail. The Bureau tries to have a fire hydrant within 500 feet of every structure in the city, and no more than a tenth of a percent of hydrants inactive at any one time. Hydrants are used for flushing sediment from the system, not just for firefighting.
Like many homeowners who lost income and were unable to pay their bills, the Water Bureau lost revenue during the pandemic. While downtown office buildings sat empty, thousands of toilets and sinks weren't being used in the city. Most likely, those users were at home consuming water in the suburbs and therefore not contributing to Portland Water Bureau revenue.
Consequently, maintenance work is being done with current staff.
"We are not in a position to add staff at the moment."
But Kovatch concluded, "From our engineering staff who designed it to our crews who installed it, it takes a lot of coordination and effort, and despite many hurdles presented by the pandemic, the Water Bureau had its most productive year of pipe replacement ever."
Portland Water Bureau
The Portland Water Bureau's 600 employees, who work on everything from water treatment to customer service, provide water to almost a million people in the Portland area. Portland's water system includes two vast water sources, 53 tanks and reservoirs, and 2,200 miles of pipes.
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