Bouncing back: Five steps to ensure your water systems recover from unexpected disasters

In August 2017, Hurricane Harvey hit Houston, devastating the city and disrupting many of its services. Water expert, Vinoth Manoharan explains how foresight and planning kept safe drinking water flowing in Houston during this time of extreme need.

When Hurricane Harvey made landfall in Houston, it brought more than 40 inches of rain — the equivalent of almost an entire year’s worth — to parts of the city. The result was calamitous, with city-wide economic losses estimated at between US$70 billion and US$200 billion.

Yet, amongst the devastation, Houston’s drinking water system remained up and running during and after the hurricane, ensuring Houston’s residents continued to have access to safe, clean drinking water. Essential to this was the East Water Purification Plant, which is the largest of Houston’s three major drinking-water facilities, and supplies drinking water to most of the city’s residents.

So, how did the East Plant team maintain service during this record-breaking storm? The seeds of this capability were planted by the foresight of the facility’s engineers. The management team at the East Plant, working with AECOM, recognized the importance of preparing for a possible event like this, for example, planning for the care of frequently overlooked ancillary facilities, such as storm sewers, stormwater pump stations, fuel tanks and command centers, well in advance of any potential disaster.

With critical infrastructure around the world vulnerable to an increasing range of threats, such as climate change and extreme weather events, here are five steps that water treatment plant managers and engineers can take to build resilience — based on lessons learnt from Hurricane Harvey.

1/ Evaluate current function

Understanding your water system’s effectivity is the first step towards resilience. In 2010, the City of Houston and AECOM undertook a study that assessed the sustainability and vulnerability of the entire East Plant facility. The study evaluated the treatment process, hydraulic capacity, solids process and ancillary facilities, confirming the critical role that the East Plant’s interior stormwater conveyance system and pump station play in the facility’s functionality as it collects, conveys and pumps rainfall out of the plant site. Further, it was determined that without this system, the plant would flood during record storm events.

2/ Investigate risk for failure

If understanding functionality is the first step, analysis is the next. For example, the East Plant team analyzed the potential for the facility’s failure and the factors that could contribute to it. Among the observations was one stark, highly-concerning finding: the current stormwater system was inadequate in terms of its ability to handle the water resulting from a record-setting storm. The East Plant is surrounded by a levee that protects it from rising flood waters, but also traps rainfall inside the levee and within the plant’s boundary. If the stormwater system could not handle the rainfall, it was clear that the East Plant’s treatment equipment could flood and be forced to shut down and the team committed to take steps to address this issue.

3/ Pinpoint vulnerabilities

Working from the precept that knowledge is power, it is important to evaluate the impact of a potential significant storm and the exposure and risks that such a storm could present. At the East Plant, AECOM performed a hydrologic and hydraulic study to gauge the impact of a major rainfall, and followed up by identifying the improvements required to control flood waters within the plant boundary.

4/ Target solutions

Once the vulnerabilities and risks are uncovered, it is essential to work toward finding solutions that protect operations. At the East Plant, this meant: identifying and targeting ways to add pumps within the existing stormwater pump station: reserving open green space within the plant site to detain storm water; raising curb heights around critical equipment vaults; identifying critical equipment that needed to be elevated above expected flood waters; and developing redundant power sources for the stormwater facilities.

5/ Mitigate the risks identified

Once the vulnerabilities are detected, corrective actions must be quickly implemented. The East Plant is the largest and oldest drinking water facility in Houston, so it was imperative to begin immediate mitigation. After the required design and construction improvements were identified and approved by city leadership, they were implemented on an expedited schedule.For example, the engineers delivered a hydraulic and hydrologic study predicting rainfall amounts over time as well as the amounts of water flowing across the site during a storm.  Pump station improvements were designed based on these results and were ready for bid in less than three months.

The results

Taking action ahead of time can make all the difference to the resilience of critical infrastructure during and after a storm. The East Plant team’s due diligence enabled the facility to maintain its functions throughout and beyond Hurricane Harvey.

Despite experiencing unprecedented rainfall, the East Plant’s stormwater system prevailed — remaining at full capacity and suffering only minor damage. The continued successful operation of the East Water Purification Plant when disaster struck is a reminder that, often times, it is ancillary facilities that make the difference in water system resilience. And AECOM continues to work with the City of Houston and other partners to build the resilience of this and other critical infrastructure in the city.

This article is part of our ongoing series examining the top water issues that need to be solved in the state of Texas and beyond.

 

For further reading:

Making Cities Resilient: Houston Takes a Cyber Stress Test

Water in Texas: Top Five Issues We Need to Solve Now

Six alternative water sources for Texas

Safe drinking water that doesn’t break the bank

Creating more resilient flood plains in Texas

 

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