The City’s water distribution system, much of which dates to the mid to-late-1800s, experiences substantial leaks (15 to 20 percent of total water treated and distributed through the system), many of which go undetected for extended periods of time.
A variety of types of leaks currently occur throughout the City, including service line and valve leaks. Initial evaluation completed in late 2014 and early 2015, confirms that a key aspect of controlling water waste in the City is associated with the gate valves installed throughout the system – many of these valves are over 50 years old. The gate valves are in many cases either inoperative or have deteriorated to the point where the valves themselves leak. The ability of the City to shut off selected zones in the City while executing repairs is greatly reduced by the presence of so many inoperative or faulty valves. Frequently, over half of the City must be shut down (and drained) to enable repairs in one isolated street. This can result in substantial water loss, as well as inconvenience to water customers.
However, in most cases, the largest portion of unaccounted-for water is lost through leaks in supply lines. The material, composition, age, and joining methods of the City distribution system components have influenced leak occurrence, along with other underlying factors.
Leak detection was delayed due to two primary factors: 1) the soils in the area are sufficiently porous that leaks do not immediately surface but instead drain through the fractured bedrock; and 2) the City is currently unable to correlate metered information and data with projected loss profiles. Due to costs involved, the City has been unable to purchase the necessary equipment to execute a systematic leak detection and repair program.
To enable the City to engage in future planning, to capture the improvements included in all the infrastructure projects, and to support ongoing system operations and maintenance, a detailed GIS-based map of the City’s entire water treatment and delivery infrastructure will be prepared which will include the locations of all existing and new infrastructure, and will be updated as each project component is installed.
Purchase of leak detection technology will enable the City to institute a systematic program of leak detection and prioritized repair. This task includes purchase of equipment, training of staff, and an initial increment of detection and repair.
The benefits to the City of minimizing leakage in the water distribution systems include:
- Improved operational efficiency
- Reduced water loss
- Lowered water system operational costs
- Reduced potential for contamination
- Extended life of facilities
- Reduced potential property damage and water system liability
- Reduced water outage events
- Increased system data
Status Update (September 2016)
The overall Leak Detection and Repair project will be completed by November 2016.
In the first quarter of 2013, the City contracted with Nevada City Engineering to compile a comprehensive data base of the entire water distribution system. The CAD-based mapping effort has progressed in stages with the mapping of larger infrastructure being completed first and the more detailed mapping of system components occurring second. The maps were completed by the end of December 2015 and will be augmented as required to reflect new grant-funded projects completed prior to the end of the grant timeline (December 2017).
In late 2015 an early 2016, the City installed 38 gate valves at locations across the City that had been identified as a result of field work and system mapping. These valves enable to the City to establish a number of ‘zones’ which allows repair teams to isolate leaks without requiring the draining of the entire system. This simple installation will save millions of gallons of water in the future, as the City repairs leaks across the City without having to drain the entire downtown zone.
Work on developing a Leak Prevention, Detection and Repair Program (LPDRP) was delayed because of limited staff availability resulting from operations and maintenance issues associated with the drought. Staff evaluated available leak detection equipment in early 2015. The appropriate equipment was ordered in March and received in April 2015. Staff has initiated training activities which will continue through the end of 2015.The LPDRP will be the subject of ongoing refinement in response to the completion of the City’s Capital Improvement Plan and the results from the ongoing training and use of the purchased technology. The LPDRP will consider: repairs of leaks detected by the new equipment, repair of observable leakage (i.e., leaks which ‘surface’), and leaks and system management issues associated with gate valves located throughout the distribution system. Repair of detected leaks will continue throughout 2016, ending with expiration of the grant in December 2017.
Current Status (June 2017)
City of Nevada City
Catrina Olson, Assistant City Manager, (530) 265-2496 x134, email@example.com
Measurable Physical Benefits
Water Supply , Water Quality