Sewer and water utilities have long been turning to sophisticated sensors and monitoring devices designed to keep tabs on a host of information ranging from flow volumes to leaks and line integrity. How that information is transmitted to the utility is a critical decision that impacts not only the cost, but also the reliability of the data reported.

Industrial automation specialist ProSoft Technology of Bakersfield, Calif., primarily offers its clients two different remote monitoring methods — private radio frequency (RF) and industrial cellular technology — or a combination of technologies. The company has no financial interest in promoting one technology over another. Its specialty is creating communications modules and their associated software to ensure that monitoring technology of any type can communicate effectively with any of hundreds of networks and all major protocols in a cost-effective manner.

“A lot of larger companies want to focus on their core networks, but they don’t want to get locked out of a project because their system won’t talk natively to their clients’ supervisory control and data acquisition (SCADA) system,” says Jim Ralston, Product Strategy/Wireless Product manager with ProSoft. “That’s where we come in.”

Designing the project

Remote monitoring technologies are particularly useful on large water district systems that include pumps and water mains in remote locations. To help utilities design a waterline monitoring project, Ralston must first take down details on the length of the line and on how many monitoring stations the client wants to place along its length. The distance from the monitors to the company’s SCADA system is also critical.

Next, engineers will determine how much reporting data is required, for example, simple data, photographs or streaming video. How quickly the data is required and how often the monitors are polled is also an important consideration, determining the maximum data throughput of the system.

Finally, the terrain of the area will be analyzed to determine what sort of communication system will be most reliable and cost-effective, given such potential impediments as hills, valleys, buildings and other structures such as dams and pumping stations or even foliage.

Choosing a monitoring system

In the 1990s, the traditional method of transmitting waterline data was to lease telephone lines from the phone company to poll the electronic devices involved, says Ralston. However, that technology has continued to fall out of favor with ProSoft clients.

“Phone companies are reluctant to stretch their land-based systems to reach pumps and water mains located in remote areas,” he says. “The conversion from analog telephone signals to digital was also problematic, as was the cost of a host of monthly land-based phone bills. Also, with phone lines in remote areas, some of our clients were experiencing reliability issues. They received repair and troubleshooting service on a schedule well below the priority reserved for residential customers, leading to system outages and higher maintenance costs.”

The satellite option

Satellite monitoring service, on the other hand, uses satellite systems to relay monitoring data back to headquarters. This technology might suit an extremely remote site where other technologies would prove more expensive to establish. However, the third-party satellite monitoring service may also be costly, ranging typically around $200 per month per data monitoring point.

“When you add up a number of pump stations and multiply by $200, that can add up to a significant operating cost for the monitoring system,” says Ralston.

The move to RF

For a private RF monitoring system, the cost is limited almost entirely to purchasing and setting up the RF transmitter, receivers and antenna systems. Depending on the terrain, surrounding buildings and foliage, the system may also require the installation of transmission towers, which would add to capital cost. However, the long-term cost of operating the RF equipment is negligible, largely because the client owns the system and there are no recurring charges or third-party transmission costs involved.

“Also, with complete ownership of the system, they would know exactly what to troubleshoot, and how to fix any problem,” says Ralston. “In many cases, simply upgrading the RF system to something faster than might have been installed years ago provides a significant improvement.”

A case-in-point — a current project at the Padre Dam Municipal Water District (PDMWD), located in Eastern San Diego County, which serves several communities from Santee to Alpine. Relying on old radio technology, the district’s existing system employed a 4,800 baud modem to transmit data from all 70 monitoring points across 85 square miles in a less-than-blazing 90 seconds.

The radio transmitters were replaced with ProSoft Technology Industrial Spread Spectrum Radios in mid-2010.

Challenges included the site terrain, which ranges in elevation from 100 to 2,600 feet. “There are many natural and man-made difficulties, which made line-of-site an almost impossibility, even though some of our sites are on the highest points around the county,” says Rich Mellor, SCADA technician with the PDMWD. “Using some ingenuity and the radio’s repeater ability, we were able to use some of the 900 MHz radios as repeaters, allowing us to pass information through very difficult terrain.”

ProSoft’s wireless engineers assisted Padre Dam officials with a field study and helped the client create a communications system using nine 2.4 GHz radios linked in a circular pattern. This allowed the district to drive communications in any direction should one radio ever fail. The system works with local 900 MHz radio and control devices to transfer microprocessor data gathered along the line to the central office at high speeds, where it’s stored on a ControlLogix programmable logic controller (PLC).

At some of Padre Dam’s remote locations there is no AC power, so some of the RF sites were powered by solar energy and backed up by batteries. “This was a learning curve, between the size of the panels and the type of batteries,” says Mellor.

Parabolic antennas and wireless radio monitors were phased in over time to limit disruption to the water system. “We had to be careful to not interrupt operations too much,” Mellor says.

The system received an acid test more than a year ago when a motorist struck a hydrant and destroyed one of the system’s microprocessor units.

“Within a just a few seconds, we recorded an alarm of low pressure and total loss of communications with that site,” Mellor says.

Industrial cellular data

ProSoft is seeing considerable interest from large water districts in industrial cellular data technology as a method of remote polling. As cellular networks expand, more and more remote sites are covered by either Code Division Multiple Access (CDMA) or Global System for Mobile Communications (GSM) networks, providing access to 3G and 4G cellular data service.

The company’s cellular data system employs Ethernet cellular radio modems powered by 12-volt DC batteries or solar power. The units are small enough to fit into the palm of a hand, and employ external antennas for extended range.

The technology has been employed by the Cobb County-Marietta Water Authority (CCMWA) in Georgia, which currently operates three cellular radios, one of them solar-powered, to monitor water pressure at remote sites.

The utility was initially leasing a landline for one site that was costing it a telephone bill of $500 per month.

“We were considering converting to DSL (digital subscriber line) or even cable, but the service isn’t available or too costly to install at some locations,” says Craig Scheibel, process control programmer with CCMWA.

In 2010, the authority accepted ProSoft’s recommendation to move to cellular monitoring devices. The cost of the cellular line? Less than 10 percent of the cost of a landline on a two-year contract with AT&T.

The units are installed with minimal technical assistance, relying on contractors to tap the main and assist on the water side of the project.

“Once it’s installed, we log in to our firewall and verify we have a connection, and then patch the unit into the SCADA system,” says Scheibel.
With three years of cellular service under its belt, the authority plans to install an additional four cellular monitors.

“We like the system’s durability and versatility,” says Scheibel. “The modems are tough and operate in a wide variety of temperatures and climatic conditions. We’ve also learned a lot about operating the units on solar power. Even during long periods of rain and grey weather, they receive enough power to carry through. All of the four additional monitors will be solar-powered.”

Ralston notes that cellular systems aren’t limited strictly to data — they can also transmit images from a site.

He notes, however, that cellular isn’t a catch-all solution.

“Cellular isn’t necessarily as fast as a private RF network, but neither is satellite,” Ralston says. “And RF is usually near 100 percent reliable, while cellular availability may be less. Currently, RF and cellular are becoming popular, with clients usually only going to satellite if those options are ruled out.

“However, we’re finding that clients are not only interested in saving money. At the lowest price point, they’re encouraged to improve monitoring and automation of their existing water system networks.”