The City of Durham and McKim & Creed, Inc. have received a 2020 Engineering Excellence Grand Award for creating and implementing a Water Age Abatement Program that reduced water usage by 25 percent, reduced staffing effort by 75 percent, slashed overtime by 92 percent, and was implemented for 20 percent less than the most recent temporary disinfection changeover process. The award was presented on November 19, 2019 by the American Council of Engineering Companies of North Carolina.
Each spring, Durham’s Department of Water Management implements a temporary water disinfection changeover program. This is required by state and federal regulations. The program temporarily transfers from a chloramine disinfection process, Durham’s primary treatment process, to a chlorine-only disinfection process. This precautionary measure ensures the City’s water distribution system is appropriately maintained.
To facilitate the disinfection changeover process, the City conducts a system-wide fire hydrant flush. The flushing disperses chlorine throughout the system and improves water quality, water age and service.
Prior to 2019, the flushing process required 12 staff members, working six days a week, 12 hours a day for four weeks. The flushing process lacked formal hydrant selection and data collection procedures to determine program effectiveness. It also did not consider possible impacts to the rest of the system. City staff ended the process overworked, exhausted and unable to evaluate the effectiveness of this large investment of time, money and unmetered water.
The City teamed with the McKim & Creed to develop a more effective water age abatement process. Using hydraulic modeling, McKim & Creed identified 60 target hydrants—out of a possible 8,000—that should be flushed to improve water age within the City’s system. The model was also used to determine the target flow rates that would most effectively flush the system without affecting overall water pressure, impacting system storage requirements, or negatively affecting fire flow availability in emergency situations.
Three crew members flushed ten hydrants each week for six weeks, thereby completing the changeover process and flushing the system. This approach dramatically improved the water age in the system and reduced financial and staff resources required to complete the program. The more than 280,000 people in the City’s service area were positively impacted by this successful water age abatement program.