Reactive Actions for Water Distribution Systems

Reactive Actions for Water Distribution Systems

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Water Quality Improvement
Water quality isn't static; it changes over time as pipes corrode, as treatment processes change and as new undocumented dead ends appear in the system.  It changes as flow, treatment, source water and pipe conditions change.  Chlorine residuals deteriorate predictably over time and they worsen more rapidly when there is high demand for disinfectant inside the pipe, along the walls against which water flows.  Water quality changes in the distribution system over time, and in a static treatment and source water environment the change is almost always negative.

Utilities have no control over the passage of time, however, they do have limited control over the impact that time has on water quality.  An obvious way to improve water quality is to perform flushing; either unidirectional (UDF) or conventionally.  The challenge is twofold when it comes to conventional flushing.  It changes the direction of flow, stirring things up in the pipe, and for the most part it doesn't develop enough velocity to clean the pipe effectively. 

But unidirectional flushing (UDF) isn't perfect either.  In most cases, hydraulic models don't accurately reflect field conditions, mapping systems are out of date and numerous assets don't work.  This substantially diminishes the effectiveness of unidirectional flushing (UDF) by reducing velocity, reducing system pressures until they are unmanageable and it sometimes takes people out of water accidentally.  While we do have limited control over the impact time has on pipe conditions, we frequently take actions which are less than effective because of diminished operational intelligence and asset reliability.

Wachs Water Services Solution - is to approach water quality improvement from both the physical asset side and from the business systems side.  As a first step, establish asset conditions, in terms of operability, valve gate position (either open or closed), location and hydraulic connectivity.  Then, combine the physical asset conditions with business systems creating a match between the field conditions, the mapping and the hydraulic modeling system.  As a matter, of convenience intrinsically linking work orders to locations so that they can be evaluated as part of the unidirectional flushing (UDF) design.  As a final measure put control over work orders decisions in the utility's hands, make the repairs that are necessary to be successful when executing the unidirectional flushing (UDF), design the sequences and execute them checking water quality by zone prior to flushing and then again afterward to quantify the impact on water quality improvement.

Surfacing Water Complaints

This type of complaint can come in many forms; from water surfacing in basements and construction pits to it surfacing in pavement grass or asset structures.  Regardless of the form, procedurally, they pose a challenge to the utility in terms of the cost associated with assessing the complaint, pinpointing the leak and making the repair. 

The first challenge the utility faces is processing the service request.  It needs to be very clear where the complainant observed the surfacing water, especially if it isn't on their property.  Nonetheless, assessing these types of complaints can be complicated because it isn't always a leaking pipe that causes water to surface in below ground areas such as in construction pits, basements or tunnels.  In these cases, the utility will take a sample of water and determine whether it is treated water or ground water.  When there are several suspect pipes in more than one pressure zone, the utility may conduct a more extensive test of the water to determine the zone. 

For distribution sized mains - less than 18 inches - the most difficult pinpointing occurs when there are several pipes in the same zone which are hydraulically connected.  This configuration can easily lead to ambiguous results when using conventional leak detection methods and when there aren't enough listening points.  A parallel main configuration that is hydraulically connected with all of the services taken from one main will have a tendency to return the crossover connection as the leak location when the leak is on the parallel main.  In the absence of listening points on the parallel main, the utility faces potholing to determine the leak location definitively.  

Wachs Water Services Solution - To this type of complicated leak location task is to perform the survey from inside the pipe.  By using a proprietary sensor that captures video and audio simultaneously, field crews enter through fire hydrants/taps and navigate the pipe in a reduced ambient noise environment until the noise level of the leak combined with the highest frequency of its sound meet; pinpointing the leak location.  At the location of the leak, field crews examine the pipe walls to provide insight into the type of repair that is required, be that on a service connection, a pipe joint or along the wall of the pipe. This approach precipitates valuable knowledge about the course which must be taken to effect the repair.  This is a bottom line improvement to a process that now combines condition assessment technology with acoustic leak detection for "right the first time" results.

Emergency Water Main Breaks

The catastrophic nature of emergency water main breaks unconditionally demands that utilities establish a level of professionalism and a level of preparedness.  During emergency water main breaks there are very few success stories published.  The outward public face of sustainability at any given utility is the severity and frequency of emergency water main breaks -public perception is driven by news reports of the main breaks themselves.  Utilities that are lacking asset reliability, lacking operational intelligence, lacking equipment or lacking personnel are often deemed less capable of managing a sustainable level of service by the public for very good reason - they see the public face of sustainability in an exceedingly negative light.

Emergencies can be confusing, they can happen in the middle of the night when crew levels are at their lowest, when it's hardest to read maps or under the lights from a camera crew.  Emergency shutdowns can be complicated because new pavement is covering a needed valve and forcing a backup.  Emergency shutdowns can be difficult to execute because the large quantity of water increases the torque required to turn valves, again causing the shutdown to be backed-up extensively.  Emergency shutdowns can pose a wide variety of problems over and above the consequences of failure and regardless of the weather.  Each of the problems that a utility encounters during an emergency main break costs time and in this case, time is money.

The 2007 AWWARF study entitled "The Total Cost of Large Diameter Pipe Failures" from April 5th 2007 by Peter E. Gaewski, P.E. of Tata and Howard Inc. and Frank J. Blaha of the AWWARF presents a method for better understanding the cost of any main break.  The authors perform what appears to be a Tobin Model regression analysis plotting gallons of water lost against the actual cost of the main breaks.  There is a correlation 0.3426.  It isn't a perfect correlation, but there wouldn't be.  There are other costs caused by main failures on pipe with varying criticality.  We suspect that had they been able to normalize the data by criticality there would be a much better correlation.  There is nonetheless a correlation suggesting that the primary factor in controlling the cost of main breaks is controlling the response in terms of time which would reduce the quantity of water which flowed from the breach.

Wachs Water Services Solution - is to provide equipment, manpower and knowhow where utilities are lacking to help them develop asset reliability and operational intelligence levels high enough to respond quickly to emergencies.  The plan; concurrently, develop a criticality model of all pipe segments and evaluate the current methods, training, equipment and staff levels directly related to emergency main breaks.  By way of criticality, systematically establish valve asset reliability and operational intelligence to control the flow of water and limit exposure to the consequences of failure.  And finally implement staff augmentations as a stop gap measure until training, equipment acquisitions, asset reliability improvement and operational intelligence development have been completed.

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Wachs Water Services is the leading provider of water distribution system asset management solutions that significantly improve efficiency and network control. Our specialized approach combines condition assessment and rehabilitation services for valves, hydrants and water mains with the capture and integration of critical water asset GIS information. We provide the expertise, equipment and personnel to locate, assess, operate and document virtually any water asset.