City of Durham, N.C., Improves Water Quality with 3-in-1 Pressure Monitoring, Sampling & Flushing

By Nathan Wiles

The City of Durham is commit­ted to providing safe drinking water to a service population of more than 289,000. The city’s Depart­ment of Water Management (DWM) ensures the delivery of water to ap­proximately 99,000 service connec­tions through 1,400 miles of water­mains. Lake Michie and Little River Reservoir are the two sources that deliver raw water to the city’s two treatment plants, using a combina­tion of gravity flow and electric and hydro-powered pumping systems. Together, these plants have the combined treatment capacity of 64 million gallons per day (MGD) with an average demand is 28 MGD.

The two facilities have onsite raw water reservoirs that store approxi­mately 135 million gallons and can sustain the city for two to three days. Like many municipalities Durham stores drinking water in covered tanks on the treatment plant sites, ready for distribution. Treated water is also stored in elevated and ground level water storage tanks located throughout Durham. Levels in the towers are monitored remotely and usually filled each evening using off-peak pumping strategies.

The towers and elevated tanks help maintain pressure in the distri­bution system so that each house­hold and business have sufficient flow. Any time pumps are part of a pressure zone or a district metered area (DMA), there is an increased risk for water surges or pressure spikes. The city has several DMA’s to control this flow, but not every zone was being monitored for pressure fluctuations. After having an average of 12 main breaks a month over the last several years, DWM’s Superin­tendent for Water & Sewer Mainte­nance, Junior Mobley, thought the city should explore ways to monitor pressure throughout its system.

At about the same time, the city was planning to upgrade its sampling stations to provide a higher level of water quality assurance and improve station locations. Over time, this would eliminate the need for staff to enter businesses to collect state-required water samples. It would also provide the opportunity to relocate and upgrade existing stations, im­proving access so that staff would no longer have to cross property lines, which often proved to be compli­cated and not always possible.

In researching the best solution, Mobley visited a Mueller Water Products’ factory in Cleveland, Ten­nessee, where he was able to meet with Hydro-Guard engineers and explain the city’s need for pressure monitoring.

“I was familiar with the Hydro- Guard flushing system from a previous job, but new to me on this visit were the additional features and technology capabilities of the Hydro-Guard [system] to also monitor pressure and water qual­ity within these units,” says Mobley. “Having a 3-in-1 solution would save time on installation, maintenance and monitoring.”

The city identified the need for 21 Hydro-Guard stations that perform a combination of flushing, sampling and pressure monitoring. Also, for short-term solutions in areas where a 3-in-1 station has not been installed yet, staff have modified the remote pressure monitoring bracket so it can be installed on fire hydrants. Currently, staff have installed 11 pressure monitors on fire hydrants throughout the system. Installation was easily performed by the city’s water maintenance staff.

“Similar to our existing setup, we just added a 2-in. wet tap with a 2-in. gate valve and then we run 2-in. copper pipe over to the station (right),” says Mobley.

The remote pressure monitor­ing units have a cellular connection allowing city personnel to see the pressure in the system anytime and anywhere using a connected device. Users can choose a set­ting which records standard state pressure readings every 15 seconds or they can choose to measure transient pressure at a rate of 256 reading per second.

“If there is a spike in the system, I get an alert and can send a crew out to investigate,” says Mobley. “This allows us to respond quicker and usually before we receive customer complaints about a hydrant being hit or a water main break.”

The combination stations will re­place all the older sampling stations. This also allows city water crews to do multiple tasks at the same loca­tion. For example, if chlorine is low at the site, operators can immediately initiate flushing until the chlorine lev­els are within the acceptable range.

“The Hydro-Guard units have giv­en us more visibility into the system with remote pressure monitoring, and improved efficiencies in water quality sampling and flushing capa­bilities,” says Mobley. With continued success, the city anticipates adding more units over the next five years.

Nathan Wiles is Hydro-Guard Territory Manager for Mueller Water Products.

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