California Water District Saves $24,000 per Year and Improves System Reliability With Data-Linc Radio Modems

Approximately 26,000 people in Southern California's central Ventura County rely on the Camrosa Water District for their water service. The District, which encompasses 31 square miles, produces approximately 30% of its water supply through five wells and purchases the remaining 70% from water agencies via meter stations.

Back in 1995, Camrosa was using a SCADA system for the remote monitoring and automated control of its 11 tanks, six pump stations, four sewer lift stations and 12 meter stations which are spread over a seven-mile radius. The system, which was installed and programmed by an RTU vendor, required the use of analog phone lines for communication among the remote locations – the charges for which totaled nearly $24,000 a year. Any time one of the phone lines malfunctioned, Camrosa was at the mercy of the phone company to repair the problem, waiting hours and sometimes days for service. In the meantime, Camrosa was also incurring significant labor charges from sending its own technicians to the remote sites to investigate the phone line problems.

Tony Stafford, superintendent of operations for Camrosa, explained that the District resolved to replace the existing SCADA with an HMI/PLC system to eliminate the monthly leased phone line charges, reduce labor charges and increase reliability. Just as importantly, the District also wanted to gain in-house control of the system.

In 1995, Camrosa began developing and installing its new HMI system, which is powered by Rockwell’s WinView TM software (soon to be upgraded to RSView TM ), using Allen-Bradley Variable Frequency Drives (VFDs) and self-contained SLC 5/03 PLCs. The District operates the PLCs using DF1 protocol at a baud rate of 19200.

Camrosa then installed two Data-Linc SRM6000 radio modems to serve as Masters at its central office, splitting its east and west remote locations between two serial ports on the Master HMI PC to speed communications. Because the office is situated in a valley, Camrosa also installed four SRM6000s, which use Smart Spectrum TM frequency hopping technology, to act as Repeaters to negotiate obstructions and maintain connectivity with all modems throughout the hilly terrain. Next, the District began installing SRM6000s at each of its remote locations one at a time over a year and a half span- systematically replacing each RTU and eliminating the phone lines.

One advantage of Camrosa’s new self-designed HMI is that if the Master PC crashes, the PLCs are programmed to operate as stand-alone units. Through the use of PC Anywhere software, the District’s field technicians can also dial into to the HMI system from any laptop and monitor the PLC status and radio communications on-line- without having to travel to the remote sites.

In spite of some concern in the industry that the 902-908 MHz spread spectrum employed by the SRM6000 is becoming over saturated, Stafford said that Camrosa has never experienced any problems- and the district is located near a military base which generates a tremendous amount of RF. Two years after the new HMI has been up and running, Stafford believes that Camrosa has achieved all of its original objectives. "The new HMI has greatly enhanced our communication reliability and increased system operating efficiency, and we've eliminated all phone line charges and reduced our labor costs."

Download the complete three page pdf article (120 K) "Taking Back Control: Most common way to implement a SCADA system is to go outside, but is it the best way?" from ISA's Intech Magazine, July 2002.

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