LEAK DETECTION: A Step Toward Accountability

Accountability is defined by Webster’s Dictionary as “Responsibility to someone or for some activity; the state of being accountable; liability to be called on to render an account; Syn: answerable, liable, responsible.” Accountability is an important word, and commitment, in the distribution of potable water.
Developing a proactive leak detection program is one of the most important steps that a community can take toward a goal of accountability and reduced water loss. But there is even more that can be done, and one northeastern community has created a city-wide proactive water maintenance program that addresses seven critical components of a comprehensive performance testing program.    

A water main break located on Anna Street in Worcester. The break was not surfacing or showing any signs of leaking but was found by using the Primayer Enigma correlator during the yearly survey ADS completes for the city. This was an 8-in. main with a circular break that had an estimated water loss of 100,000 gallons per day.

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The City of Worcester, Mass., is a member of the Massachusetts Water Resources Authority. As such, they are obligated to conduct leak detection as a means to assess water accountability on over half of their water distribution system every year. This is just one of the reasons they have implemented an aggressive, proactive leak detection program. The other is just good practice. The City of Worcester is working to reduce unaccounted for water, or water loss. Having ADS Environmental Services Pitometer Water Group as its partner in this effort, helps assure they are using the most efficient, results-oriented equipment, technology and practices. This performance analysis and accountability program has been very beneficial in reducing the amount of unaccounted for water in the city.

Components of this proactive maintenance program include Meter Testing: testing master meters for accuracy and validating supply statistics; Pump Efficiency Testing: computer modeling of performance curves to help determine the most efficient operation of pumps for optimum cost-savings; Water Accountability/Leak Detection: systematic investigations of leakage, sometimes accomplished by measuring the consumption more than 24 hours of a divided geographical district; Loss of Head Testing: determining potential pressure problem areas, water main replacement construction priorities, and creating calibrated computer models; Hydraulic Gradient Measuring: determining the hydraulic grade lines, water circulation and carrying capacity; Fire Flow Testing: determining the water available for fire fighting purposes; Monthly and Final Reporting: detailing the results of all field tests, district measurement results and leakage location and loss estimates.

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Officials for Worcester’s water operations believe that a comprehensive program that incorporates all of the above components is essential in managing and understanding its water distribution system. Not all of these services are performed on a routine basis. Some, for instance, the pump efficiency testing and hydraulic gradient measuring, are performed on an as-needed basis. In addition, meter testing is performed twice a year on all master meters in the system.

It is important to the success of the overall program to be certain that meters are accurately measuring what comes into the system and what goes out. Three or four years ago, the city increased meter testing to twice yearly and this has further reduced the unaccounted water. It is critical to understand where all the water in the system is going. This starts with knowing how much water is coming into the system and includes a thorough understanding of non-revenue water utilization, such as hydrant usage (legal and illegal), water main breaks, usage by the fire department and underground building construction activities, etc.    

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The Water Accountability/Leak Detection component of this program is the most significant and important aspect in the reduction of water loss. One of the goals of Worcester’s water operations is to repair all water distribution system leaks found in a timely manner. In order to tackle the city’s 620-mile water system, the system is divided into three sections. The Super High Service Section is 51 miles of pipe and includes all the pump systems in the network. The other two sections are both combined gravity and pumped systems. The High Service Section is 379 miles of pipe and the Low Service Section is 190 miles of pipe. ADS conducts leak detection on the Super High section every year. Since this is a pump system, any leaks that are found and corrected save energy and water. The other two sections have leak detection performed every other year.
All hydrants in the other service section are checked each year during the annual service contract. Reports are generated on any suspicious or potential leaks. The loss of Head Tests and Fire Flow Tests help determine carrying capacity and fire flow capability of various sections of water mains within the distribution system. These tests help the city determine if mains are suitable for the intended usage and demands of the community they serve. In particular, the city is interested in how the amount of water available compares with ISO’s need for fire flow values in that area. They also help the city make design and rehabilitation decisions. 

Solving Long-Term Leakage Problems

The leak detection equipment used on this project has superior listening capabilities to improve the ability to pinpoint leaks. An example of this is the problem that residents on Pine Brook Lane were experiencing for years before ADS utilized their listening techniques in 2008 and 2009. Residents in these eight- to nine-year-old homes, located at the base of a slope, were registering complaints with the city that their grass was dying and their yards were water logged and unusable due to soggy soil, odors and mosquitoes.

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The problem was thought to be groundwater and the city was investigating to try to determine if any city water was involved. The city could not identify any leaks and could not determine the source of the problem. In 2008 and 2009, during leak detection of the 800 ft of pipe on High Rock Lane and Moreland Green Drive (these streets are uphill from Pine Brook Lane), multiple leaks on the water service pipes were identified. It was determined that the use of substandard pipe and backfill materials by the private contractor involved in the subdivisions’ construction were the cause of the multiple leaks that were causing problems at the lower elevations.

The large number of leaks on these streets never surfaced or caused problems at the higher elevations and if not for the systematic testing of the entire network, the leaks might have gone undetected for many more years. A contractor was hired to replace all the water service pipes and the city is now employing stricter oversight techniques during underground construction.

The amount of money that the city saved in this one instance is considerable. A few leaks had been detected and repaired but no improvement to the problem below was realized. At $300 an hour, the city might have continued making repairs one at a time without solving the problem. Proactive leak detection that eliminates problems reduces repair and maintenance costs tremendously. Since the city replaced the leaky water services pipes, it has not had to make a single repair.

Sophisticated Listening Techniques

Another specific issue that the city had to address was on Coburn Avenue where the city had conducted their own fire flow testing in 2009 with very low flow results. The hydrants were determined to be basically useless because there was no water with which to fight fires. The city thought there was a broken valve or shut valve that was restricting the flow but could not find anything conclusive.

The city asked ADS to conduct Loss of Head Tests/C-factor Testing. Through these tests, it was determined that the pipe was so rusted internally, that it couldn’t provide any water for fire fighting purposes. The pipe was a 2,300-ft, 8-in. main that dated back to the late 1800s, early 1900s. The city replaced the pipe, resolving both the safety and water quality issues.     

In both cases, it is due to the proactive nature of this leak detection and performance testing program that the city was able to control the leaks and minimize the damage and risk of potential problems. There are other communities in the Northeast that manage their water systems in a similar, proactive manner, but it is a small percentage. So, when talking about accountability and the quality of life in the communities that are served, the City of Worcester has a program that has set an example for other cities to emulate.

Mike Daigneault is the assistant director of water operations for the Department of Public Works for the City of Worcester, Mass. Scott Neesen is a field technician for ADS Environmental Services.

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