Posts Tagged ‘main break’February 14, 2014
Despite an aggressive preventative maintenance program in Central Iowa, water mains around Des Moines are breaking at a record number, Cold weather and corrosion of pipes have teamed up to cause pipe failures. The extreme drop in mercury drives frost penetration to a greater depth. Deeper frost penetration causes the corroded water mains to break. With expected warmer temperatures in the coming days, it can cause the frost line to move quickly and cause breaks as well.
The American Society of Civil Engineers’ 2013 grade for America’s drinking water infrastructure was a D, which is no surprise considering Des Moines Water Works has repaired a record number of main breaks in one month: 122 breaks in January. To date, Des Moines Water Works crews have repaired 200 main breaks, with as many as 12 in a single day.
The 10 year average for total main breaks in a year is 290. On average, half of the main breaks occur in the three winter months of December, January and February. The total number of main breaks in 2013 was 342. The highest number of breaks in one year was 365, set in 1988.
The average cost of a main break is around $5,000-7,000 for labor, materials and equipment. This does not account for the loss of water at a main break. The 2014 budget for emergency repairs is approximately $1.5 million. So far in 2014, Des Moines Water Works has spent approximately $1 million in repairing water mains. Any impact of this year’s main break experience will be analyzed when determining the 2015 water rates.
Though largely out of sight and out of mind, Des Moines Water Works operates and maintains more than 1,300 miles of underground water mains distributing finished drinking water to homes and business in Des Moines and surrounding communities. The pipes in the distribution system are made from cast iron, concrete and plastic and also vary in size, from half-inch diameter service lines to 48-inch diameter transmission mains. Pipes installed between 1940 and 1960 are leading to most of the main breaks in Des Moines. The oldest pipe (circa 1900), which can be found in Downtown Des Moines, is some of the best in the distribution system.
“While every main break is different, fixing it quickly and safely are top priorities,” said Bill Stowe, CEO and General Manager, Des Moines Water Works. “Our goal is to minimize disruption to our customers who live, work and commute in the area.”
Des Moines Water Works invests millions of dollars each year in infrastructure improvements. The 2014 capital improvements budget includes $2.2 million for water main replacement within the Des Moines water distribution system. These funds will be used to replace water mains that have reached their useful life expectancy – water mains with a high occurrence of breaks.
Finding leaks early helps reduce the level of damage that a larger main break might cause. Leak detection also helps keep production costs down, which in turn has a positive impact on our customer’s water rates.
DMWW began its leak detection program in 1983. At the start of the program, DMWW’s unaccounted for water (total pumpage minus billed) was at 15 percent. Today, DMWW’s unaccounted for water is 7-9 percent.
Water Distribution’s staff performs an annual leak survey of the distribution system. In addition, leak survey and follow-up activities are conducted for other metro area communities, plumbers, contractors and property owners.
The leak detection team uses a highly sensitive electronic sounding device to listen for leaks. The leak surveyor systematically works his or her way through the distribution system sounding valves, blow-offs and hydrants, searching for leaks. When a leak sound is discovered, the leak surveyor records the leak in DMWW’s geographic information system (GIS) software. These leaks can be as small as pinholes in the pipe or as large as a split main.
Follow-up involves sounding the structures where a leak sound was found during the survey. The Field Service Technician must determine if the leak is actually on the valve, hydrant, or the main. A leak correlator and outstation sensors are used to run scans on the water main to pinpoint the location of a leak. The leak can usually be pinpointed within one to two feet of its actual location. Identified leaks are then turned over to a repair crew.
Advance pinpointing of leaks and main breaks saves Des Moines Water Works $30,000 to $50,000 each year in labor costs.
As cold weather draws near, water main breaks become more common. The months of December, January and February bring the highest number of water main breaks. Des Moines Water Works crews repair an average of 300 water main breaks each year. Although DMWW has a proactive and aggressive main replacement program, underground water mains can break for a number of reasons including corrosion, frost heave, and pressure fluctuations.
When a water main breaks, generally water comes to the surface and flows across the ground to a storm sewer or waterway. Large water main breaks can reduce water pressure in the area and the flowing water can cause damage. If you witness a main break or see water flowing in the street, please call Des Moines Water Works at 283-8772. Des Moines Water Works is committed to providing our customers with safe, quality drinking water. To honor that commitment, Des Moines Water Works crews are on call 24 hours a day, 365 days a year to respond to main breaks, ensuring that your service is restored as quickly as possible.
Once a water main break has been confirmed, the exact location of the break is determined using acoustic leak detection equipment. This equipment listens to the sound the water makes as it exits the pipe and can determine the location of the leak based on the intensity of the sound. When the location of the leak has been determined, water service in the area must be shut down so the break can be repaired. Depending on the time of day and the extent of the outage, it may not be possible to notify customers before the water is shut off. The safety of our employees and the public during a main break repair is a top priority. Special attention is given to trench safety which protects our employees and to traffic control which protects our employees as well as the traveling public. Before the water service is restored, the repaired water main is flushed and sampled to restore the best possible water quality. An average main break takes four hours to repair. You can find current water outages at www.dmww.com.
When the water comes back on, there will likely be air in your water service piping. It is a good idea to run the first water after an outage through a faucet that does not have an aerator screen, such as a bathtub. Open faucets slowly to allow the air to escape. Air will make a spurting or hissing sound as it escapes through the faucet. Once the water is flowing, allow the faucet to run for a minute or two. The first water may be cloudy due to air in the water or particles that dislodge as the pipes fill with water. This should clear fairly quickly. If water is cloudy throughout the house and it does not clear after allowing the water to run for several minutes, contact Des Moines Water Works.
If kitchen or bathroom faucets do not perform normally following a water outage, it may be necessary to remove the aerator screen. Typically, the aerator can simply be unscrewed from the faucet. Inspect the screen for small particles and rinse away any you find. Reinstall the aerator and test performance of the faucet again. If you experience difficulties such as low pressure throughout the house following a water outage, contact Des Moines Water Works at 283-8772 for assistance.
Each year, Des Moines Water Works experiences between 250 and 300 water main breaks. In some cases water does not even come to the surface of the ground, but in other cases main breaks can cause real problems. Large water main breaks, like those shown, are easy to find and the loss of water they cause is reflected on instrumentation at the water treatment plant. Unfortunately, however, Water Works receives no indication of smaller water main breaks other than from eye-witness reports. If you see water in the street (or spraying into the air), you can help stop the loss of water and limit the damage it causes by notifying Des Moines Water Works dispatch immediately at (515) 283‑8772.
Once a water main break is identified, water service in the area must be shut off. In emergency situation such as these, it may not be possible to notify customers of the outage in advance, and in fact, the break itself may interrupt water service before it is shut off. After the water main break is repaired, water service is restored. When the water comes back on, there will likely be air in your water service piping. It is a good idea to run the first water after an outage through a faucet that does not have an aerator screen. Bathtubs and hose bibs are good candidates. Open faucets slowly to allow the air to escape. Air will make a spurting or hissing sound as it escapes through the faucet. Once the water is flowing, allow the faucet to run for a minute or two. The first water may be cloudy due to air in the water or particles that dislodge as the pipes filled with water. This should clear fairly quickly. If water is cloudy throughout the house and it does not clear after allowing the water to run for several minutes, contact Des Moines Water Works dispatch for assistance.
If kitchen or bathroom faucets do not perform normally following a water outage, it may be necessary to remove the aerator screen. Typically the aerator can simply be unscrewed from the faucet. Inspect the screen for small particles and rinse away any you find. Reinstall the aerator and test performance of the faucet again. If you experience difficulties such as low pressure throughout the house following a water outage, call Des Moines Water Works dispatch for assistance.