Until recently, climate change was something water infrastructure engineers in the United States were preparing to face 30 to 60 years from now. But the threat has become more immediate as severe weather occurs in more areas of the country with greater frequency, from prolonged droughts in the West to severe storms and flooding in the East.
This is adding stress to a water infrastructure already burdened by old age, particularly in well-established metropolitan areas like New York, Washington, D.C., Los Angeles and Chicago.
Utilities are responding as best they can, but it is a challenge. The risks of climate change are still hard to measure, and climate scientists can only provide rough predictions of what to expect in the future. At the same time, municipalities do not have the luxury of spending more on reinforcing infrastructure than is absolutely necessary.
An important first step in addressing the problem is looking around the country at the risks water utilities are facing in terms of how the physical infrastructure ? water mains, sewage pipes, storm drains and treatment plants ? are faring under severe weather. For instance, are they failing under the effects of extreme heat? Are they able to manage the massive amounts of excess water from flash flooding and prolonged rain storms?
Western states such as California, Nevada and Texas have been plagued by severe drought. In California, this has led to water rationing that is causing main blowouts due to water pressure buildup that occurs on days when water bans are in place. In Texas, extremely hot temperatures are causing more pipes to distress and break.
The mid-Atlantic area has been battered by severe storms over the last few years. Storms on the scale of Hurricane Irene and Superstorm Sandy are more common. During Hurricane Irene, an astonishing 400 million gallons of sewage overflowed the Washington, D.C. area?s treatment plants. Additionally, flash floods and heavy rains are occurring more often and are causing higher-than-average rainfall that easily overwhelms water systems.
Freezing temperatures are posing challenges, too. Prolonged periods of cold (below 37 degrees) cause mains to break more frequently due to water freezing and expanding in the ground. The winter of 2014 was one of the most bitter in recent memory. Nearly 600 water mains of the Washington Suburban Sanitary Commission (WSSC) broke or leaked that January. In December 2010, a record 645 breaks and leaks occurred. The extreme rise and fall of temperatures placed stress on the pipe walls, causing them to expand and contract.
Miami is facing some of the toughest conditions. Its porous limestone bedrock allows water from rising seas to enter and backup the storm drain system, releasing ocean water onto the streets and sidewalks on sunny days. The situation has become so serious that the city has earmarked $300 to $400 million toward short-term solutions, including installing pumps that are powerful enough to remove flood waters. They also are retrofitting 300 outflow values to include plugs that will prevent sea water from flowing into storm drains.
All of these developments mean that utilities must begin addressing these issues on a larger scale much sooner than was anticipated even five or 10 years ago. Efforts across the country vary according to environmental risk factors of the area, resource constraints and political considerations, but we?re seeing some trends emerge in the approach. They can be simplified into four categories: proactive condition or vulnerability assessments, redundancy, green infrastructure and additional storage.
Proactive Condition Assessments
Proactive condition assessments provide an accurate view of the vulnerability of storm drains, sewage pipes, water mains and water treatment plants. The assessment provides a much-needed warning before critical pieces of infrastructure fail on a large scale.
When conducting this assessment, utility managers should think about which assets are the most critical. Consider the density of population served by each main, the areas that serve critical infrastructure like hospitals and operations of first responders, and how weather-related risks in your area make them more vulnerable.
These assessments should be done proactively and regularly, ideally on a three, five or 10-year schedule depending on the condition of the system and the risks it faces.
Establishing Redundancy
Utilities are establishing redundancy to maintain service in the event a large main break. If there is not a way to establish redundancy, then the pipe is reinforced or replaced so it is stable and reliable. Treatment plants have backup power so water continues to be pumped and treated in the case of a widespread power outage. Not having access to water only creates more chaos and difficulty in an already strenuous rescue and restoration effort.
Green Infrastructure
Many cities are also making use of green infrastructure to manage excessive flows of stormwater. Green infrastructure has been shown to reduce the burden to buried assets by using natural hydrologic features to manage stormwater rather than collecting and piping the water. This includes rain gardens, green rooftops, as well as permeable pavement. The U.S. Environmental Protection Agency (EPA) has done some demonstration projects in this area and cities such as Washington, D.C.; Portland, Ore.; and New York have launched projects. Washington, D.C. conducted a demonstration green roof project that greened 121,200 sq ft of city rooftops, resulting in an estimated stormwater retention of 1.8 million gallons per year.
Additional Storage
To manage excessive flows, more utilities are installing storage tanks or deep rock tunnels in areas where flooding occurs regularly. Columbus, Ohio, Indianapolis and Washington, D.C. have all installed such systems to manage excess sanitary flows. Miami is also considering it as part of a long-term climate response plan. The Philadelphia Water Department recently constructed an underground storage basin capable of holding over 4 million gallons of water that will be used to store excess flow until it can be diverted to the water plant for treatment.
Public education and outreach are also a large part of any major infrastructure initiative, and there are a couple of good resources that provide guidance in this area. The U.S. Environmental Protection Agency?s Climate Ready Water Utilities (CRWU) has released a framework for utilities that provides six elements to consider in becoming climate ready, which includes guidance on engaging the community, aligning with applicable state and federal regulations, and building strategic partnerships. Another resource is the Water Research Foundation?s Climate Change Clearinghouse, which provides good background information on climate change science and its impact and case studies related to vulnerability assessments, long-term planning, flood management and other areas. The American Water Works Association also provides a clearinghouse of information on climate change tools, resources and news.
The topic of climate change and water infrastructure is not new, but the urgency that water utility managers are facing to take concrete action has increased substantially in recent years. Citizens are more aware of the impact of severe weather and are looking for answers and action. Public officials are desperate to provide solutions and demonstrate results. Resource constraints often mean projects that might have prevented some of the impacts were placed on the back burner until now. It is a difficult position for utility engineers, but one positive outcome is that infrastructure projects that have long been neglected due to lack of funding or public support will now perhaps see the light of day.
John Matthews, Ph.D., is a principal research scientist with Battelle Memorial Institute.?
