Two chronic problems are linked to Nevada City’s water system’s storage tanks: 1) users at higher elevations experience low pressure during peak periods due to the gravity feed system, and 2) water is wasted by due to system inadequacies associated with the tanks. As operated, all three storage tanks cannot achieve full storage capacity because of the absence of altitude valves. In other words, in order for Nevada City’s supply tank system to run at peak capacity, water wastage has to occur.
Additionally, the City has limited capacity to identify and resolve operational problems due to the dependence on visual inspections and/or meter reading to identify problems, with a subsequent interpretation of data. This further relies on a currently irregular meter-reading schedule. Therefore, anything other than catastrophic leaks could continue undetected for substantial periods of time, and the capacity of the City to pinpoint the leaks is further compromised by the lack of leak detection equipment.
Initial evaluations concluded that installation of altitude valves with an integrated Supervisory Control and Data Acquisition (SCADA) system at the three storage tanks would significantly increase system reliability, decrease water wastage, and enhance the efficiency of the entire Nevada City water distribution system.
A flow control valve or altitude valve is used to regulate or monitor the flow of a liquid through a system and, in the case of Nevada City, to respond to pressure changes within the supply tank system by opening or closing, thus maintaining a desired water level depending on individual tank design parameters and peak water needs of the service area.
Installation of a SCADA system will enable automated data collection, eliminate the need for recording and evaluating manual meter readings, allow for the download of data on a regular and predictable basis, improve the management capacity of the City, and alleviate water losses due both to system efficiency and leaks or system failures. With a SCADA system water losses will be automatically determined by conducting a periodic water balance in defined sections of a water network. The system thus provides a guide to how much water is lost as a result of leakage from the network and how much of the water loss can be attributed to other reasons.
Substantial cost savings will accrue to the City due to elimination of spillage and increased efficiency of existing personnel. In addition, the ability to monitor water levels so closely will reduce the need to buy additional treated water from NID.
Current Status (September 2016)
The installation of system components was completed in December 2015, with ongoing field testing and system refinement through June 2016.
The work effort for the altitude valves with Integrated SCADA Systems has progressed in three distinct stages: 1) contracting with an engineering consultant to develop design options, 2) contracting with a lead consultant to finalize the system design, and 3) installing and testing the system components.
- Contracting with an engineering consultant to develop design options: the process of preparing bid materials, advertising the project, reviewing the submitted bids, selecting a consultant and initiating contracts began in November 2013 and was completed in February 2014, with award of a contract to Stantec Engineering. Stantec and the project team collaborated through December of 2014 to determine altitude valve design options.
- Contracting with a lead consultant to finalize the system design: Between January and March 2015, the City solicited a proposal to finalize design and install the SCADA control system, based on design recommendations developed with Stantec and the project team. The proposals were received and an award made in March 2015. The City finalized the contract with XIO (the selected firm) while continuing work refining the final mechanical/electronic specifications the system. Following refinement of the work plan (as a result of input from XIO), the project has been segmented into two phases: Phase 1 is final design and installation of the control system (SCADA) and Phase 2 is the design and installation of the mechanical systems which support SCADA.
- Installing and Testing System Components: The designs, specifications and contracts were completed in April and May for Phase 1, with equipment ordered in June 2015. The selected equipment has been delivered to the water plant, with installation completed in 3rd Quarter 2015. Phase 2 (mechanical systems testing, refinement and monitoring) was completed by June 2016.
City of Nevada City
Catrina Olson, Assistant City Manager, (530) 265-2496 x134, firstname.lastname@example.org
Measurable Physical Benefits
Water Supply , Water Quality