May 2012, Vol. 67 No. 5
Features
Drought Brings Challenges To City Water Departments
Failed crops drooping over dry, rock-hard soil backed by record heat . . . dried lake beds and farm ponds . . . reservoirs falling to dangerously-low levels . . . wildfires burning tens of thousands of acres, consuming everything in their path . . .
And the list goes on.
In many areas, lack of rainfall was accompanied by intense heat that set records during the summer of 2011.
For 2012, an unusually mild winter and early spring with unseasonal storms has people wondering what the coming summer will bring.
While many effects of the drought are easily seen, the underground utility infrastructure of drought-stricken cities suffered major damage last summer as dry soils shifted, causing water mains to rupture. City crews and contractors were busy repairing water line breaks, a time-consuming and costly task.
It is not an overstatement to say utility crews and contractors pressed into service during the crisis performed at heroic levels.
For example, the city of Houston typically experiences 12,000 water line breaks a year in its 7,500-mile transmission and distribution system, said Alvin Wright, senior staff analyst and public information officer, Houston Public Works and Engineering Department. In 2011, there were17,800 breaks.
Conditions worsen
From February through May of 2011, the area experienced only 3.1 inches of rain, said Wright. The 30-year average for this period is 14.41 inches. Extremely high temperatures also were a factor. On Aug. 27, 2011, the temperature rose to 107 degrees Fahrenheit — the highest ever recorded temperature in the city of Houston.
“Typically, our department receives 50 to 60 new breaks daily and is able to repair a leak within four days,” said Wright. “However, due to the high number of breaks experienced during the summer of 2011, the number climbed to an average of 100 per day during August and September and repair time spiked to eight days.”
Wright said the types of pipe that ruptured most often were asbestos/cement (A/C), followed by cast iron and PVC. Estimated failure rates for asbestos/cement pipes were 75 percent; cast iron, 20 percent, PVC and other, 5 percent.
“A study by the University of Houston determined that pipes buried within five feet of natural ground were more likely to rupture due to changes in the moisture content of the high plasticity clay soil that is present in most of the Houston area,” Wright said. “While A/C pipes appeared to be the most vulnerable and impacted the most, fortunately most of the breaks seen on this type of pipe could be repaired using wraps and clamps. Cast iron pipes often displayed splits which were several feet in length. These types of repairs required more extensive excavation and pipe replacement.”
Houston addressed the 2011 line breaks with city crews supported by temporary employees and hired contractors. Extra equipment was rented as needed. On average, 29 city water repair crews and 25 contractor repair teams were deployed daily.
“A crew consists of a team leader and two assistants,” Wright explained. “This number may vary depending on the complexity of the job. The department has a range of non-specialty (pickups, dump trucks, etc.) and specialty equipment (cement mixers, backhoes, etc.). Typically, a repair team deploys with a heavy repair truck towing a backhoe on a 15 ton trailer. Support is provided by a roving area supervisor and other valve turning personnel riding in pickups. Dump trucks transport spoil and fill material from and to repair sites on an as needed basis.”
Cavalry
Wright said when officials recognized the circumstances required additional resources to make repairs, they reached out to the contracting community through the Houston Contractors Association.
“Emergency provisions of state procurement laws allowed the department to procure their services on an expedited basis,” Wright continued. “Informal bids allowed work to start in days instead of the usual months. Repair contracts ranged up to $1.5 million. To promote small businesses, a number of contracts in the $100,000 range were also awarded. Ten contracting companies were retained to make repairs, restore property, and provide support assistance. Typically, each repair cost between $ 3,000 and $ 4,000.”
When breaks occurred, facilities providing essential services received priority.
“Repairs at Houston’s famed medical center area are one example,” said Wright. “So were the city’s airports, sports arenas, convention centers, major shopping malls and educational institutions. One break necessitated interruption of service to a federal detention facility. The repair was scheduled during the evening hours and caused no disruption of operations at the institution.”
Overall, Houston residents seem to accept service interruptions and appreciate the task facing the utility department.
“Houstonians have come to accept the fact that during periods of drought, water line breaks increase,” Wright said. “The department has significant institutional knowledge and technical expertise to manage these types of events. The media was engaged as a partner and facts about the event were disseminated in a timely manner on radio, television and on the internet.”
OKC
Four-hundred-fifty miles north in Oklahoma City, Utilities Director Marsha Slaughter said utility employees will remember July and August 2011 as a time of record low lake levels, low water pressure complaints, the high number of main breaks and other water delivery problems.
While the drought contributed to 2011’s water line breaks, Slaughter said other contributing factors include corrosion caused by the soil and higher-than-normal pressures.
“We have various types of soil in Oklahoma City,” said Slaughter, “however the majority is characterized from clay to a clay loam. High temperatures and lack of rain caused the ground to dry, crack and shift. About the time this becomes the norm and main breaks subside, the weather may change. An abundant rain can also change the soil conditions and the pipes react. It’s the same problem we experience with freezing temperatures and ice.”
As temperatures climbed in the summer of 2011, so did demand for water.
“On July 30, 2011, water demand had reached a new high of 202.2 million gallons a day,” she continued. “The previous one-day record of 189.8 million gallons was topped eight times in two months, and water line breaks increased dramatically as treatment plants increased delivery pressure.”
Lower-priority leaks waited while line maintenance crews repaired Code 1 breaks that were losing large volumes of water or causing property damage.
“In July and August, line maintenance crews repaired 1,794 leaks, a number typically repaired in a year,” Slaughter said. “The division adjusted its operations to include mandatory overtime, 12- to 16-hour shifts, rescheduling crews to 24-hour operations and deploying wastewater crews to water.”
Slaughter praised personnel for faithfully serving the city’s customers with their usual courtesy and professionalism, despite unprecedented weather-related issues.
“Something really amazing,” she added, “is that no injuries of line maintenance crews were reported in July with a few heat exhaustion incidents in August. It was a true testament of safety in the workplace and remarkable public service. City officials, trustees, councilmen and customers noticed and applauded their efforts.”
What lies ahead
Will coming summer produce another round of water line breaks?
In February 2012, the National Oceanic and Atmospheric Administration National Climatic Data Center’s National Drought Overview classified 32 percent of the contiguous United States as being in “moderate to extreme drought categories with 13 percent in areas of severe to extreme” drought.
In many areas an extremely mild winter, followed by an early spring with heavy storms and bringing flooding in some regions, has people wondering what kind of weather the next few months will bring.
In the Houston area, Wright said rains in the months of December and January have refilled two of Houston’s three reservoirs.
“While the number of water line breaks continues to remain higher than in previous years,” he said, “the rains will ultimately reduce the number of breaks which are occurring.”
In Oklahoma City, Slaughter said there is nothing like a crisis to clearly see what needs to be fixed.
“Our utilities staff identified some proactive efforts to help prepare for future weather-related issues,” she said. “They include completion of reliability improvements at one of our water treatment plants, escalating completion of transmission system improvements that will deliver more water to far north and west areas of the city, identification of booster pump station installations in areas with seasonally low water pressure until planned permanent improvements are completed, replacing water mains with material not susceptible to corrosion, and updating the city’s Water Master Plan to reflect current water demand patterns and redistribution due to growth in new development areas.”
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