The small foothill communities of Alta and Colfax are located roughly 29 and 16 miles northeast of Auburn, respectively. These small communities receive water deliveries from Placer County Water Agency (PCWA), which has invested in improvements to these systems, including performing soil identification studies, traditional leak detection surveys, and system monitoring. Additionally, they PCWA has created base maps. Now PCWA, with the communities of Alta and Colfax, will install a network of correlating leak detection data loggers to reduce water losses in the treated-water distribution systems.
Information-gathering efforts have shown that Alta and Colfax are located on cobbly loam soils that readily absorb water from leaking, treated-water lines typically without any above-ground indications. PCWA’s metering system allows the agency to observe when water usage trends change, but these changes often do not become evident for several months, and some may have been present for years. In 2007, PCWA analyzed the District’s water losses utilizing the American Water Works Association’s (AWWA) water audit worksheet and discovered approximate annual treated-water losses of 38.3 percent in Alta and 28.1 percent in Colfax (55.2 and 170.6 AF, respectively).
The project will allow PCWA to identify previously undetected leaks with increased accuracy and decreased labor and materials costs by using leak detection data loggers. Rather than having to perform a time- and labor-intensive traditional leak survey with a ground microphone and correlators, the proposed system will allow PCWA operators to remotely identify leaks with great accuracy (typically to within one foot of the leak). Once the network of correlating leak detection data loggers are installed, the loggers detect noises in the system on a nightly basis, log the information, and notify operators if leaks are “heard.” The estimated annual treated-water savings associated with this project is 80 AF/year.
Current Status (September 2016)
The Alta-Colfax Leak Detection and Repair project will be completed in November 2017.
The work effort has progressed through an initial sequence of tasks: initiation and completion of easement determinations; evaluation of and confirmation of monitoring locations, calculations of existing water use and loss in both Alta and Colfax; purchase of loggers for installation; and programming and initial deployment of a selected number of loggers in the communities of Alta and Colfax.
Prior to deploying the loggers a leak detection and repair program was developed to prepare for the construction of monitoring stations and the deployment of the data loggers. As a result, GIS maps of the water system infrastructure were finalized and an installation plan for the data loggers and monitoring locations was completed.
PCWA has current base maps of the Alta and Colfax treated water distribution systems and the metal water mains have been identified. The total lengths have also been estimated; 20,888 feet in Alta and 12,393 feet in Colfax. Locations of existing valves attached to the metal mains were identified on these maps and additional monitoring locations marked. These additional monitoring locations are needed to provide near optimal spacing of the loggers on the water mains in those locations where there are great distances between valves, or locations where a section of metal pipe bounded by non-metal pipe.
An initial group of 58 loggers was installed in the two areas (20 in Alta and 38 in Colfax). This phased installation was deemed appropriate to enable initial problem-solving and development of procedures and monitoring protocols. The final 58 loggers will be installed in early 2016, so the lessons learned and system refinements accomplished over the initial year of operation can be integrated into the overall monitoring procedures and protocols. The GIS mapping for the initial installation is complete.
In order to effectively track specific information about each logger, the placement of the loggers, the distances between them, and the pipe material and size at each logger location was recorded while the loggers were being deployed.
Once deployed and set-up, the loggers began “listening” to the metal water mains during times when the water pressure is highest and noise from traffic and other sources are quietest, generally between 2am and 4am. Initially an operator downloaded each of the loggers every two weeks, beginning with this installation of the first set of loggers. However, limitations on staff time due to the emergence of drought-related needs reduced the initial monitoring to less frequent intervals.
As an indicator of the immediate utility of the loggers, a leak was detected shortly after installation of two correlated loggers. The leak was measured at 5 gallons per minute. During the 45 days that it took to verify the reading and deploy staff to repair the leak, roughly 256,000 gallons of water were lost. As the leak never surfaced or gave any physical indication of its presence, that leak would have (pre-loggers) gone on for an indefinite period of time – potentially wasting millions of gallons of water before it was detected. It is expected that future logger installations will identify pre-existing leaks, as well as newly emerging leaks.
An ongoing program of evaluation and reporting to determine the impact of the installed loggers has been initiated. Using the free AWWA software performance indicators of “gallons per day per service connection” and “gallons per day per mile of water main” an evaluation of leak reports to determine the efficacy of the program has been initiated. The performance indicators are the gallons of loss per service connection per day and gallons of loss per mile of water main per day.
Reports for each repair have been created identifying the location of the leak, estimated leakage rate, pipe material, type of leak (e.g., water main, service lateral, meter connection), date leak was repaired, estimated water loss, and the labor and materials required to repair the leak. These incidental reports will be summarized in an Annual Leak Repair Report (ALRR), which will be prepared in the first quarter of 2017. The ALRR will serve as an important source for planning future infrastructure projects, analyzing the effectiveness of the project, quantifying the water saved, and as a model for agencies contemplating the suitability of the data logger network in their own district.
Placer County Water Agency
Randy Cox, Water Management Specialist, (530) 823-4850, email@example.com
Measurable Physical Benefits
Water Supply , Water Quality