Weed Instrument Helps Keep New Orleans Dry

New Orleans may be the Big Easy but keeping it dry takes hard work, good engineering, and the latest in technology. Products from Weed Instrument are playing their part, providing one of the three communication links in a system put in place after the flooding of the city in 2005. It’s all part of an effort by U.S. Army Corps of Engineers to make sure New Orleans will never go under water again.

The devastation that resulted from Hurricane Katrina prompted the Corps, which has responsibility over the city’s system of levees and canals, to install a new monitoring system on the 17th Street, Orleans Avenue and London Avenue canals. For that general contractor Prime Controls turned to Sutron Corp. of Sterling, Va., a leader in real-time hydrological and weather monitoring systems. Sutron, for its part, selected Weed Instrument fiber optic based communication modules.

“The goal of this project was to monitor meteorological parameters. They wanted to monitor if a storm was coming through,” says Faisal Al-Mtwali, an electrical engineer with Sutron. “They also were monitoring the water level in the canals.”

Such information is vital if the operation of a canal’s pumps and gates are to be automatically managed by a supervisory control and data acquisition, or SCADA, system. The control system needs data quickly, which is one reason why fiber optic communications were selected. Another reason has to do with the far-flung nature of the operation. There are 12 stations in the project, scattered along tens of thousands of feet of canals. The runs are too long for any copper wire but well within the capabilities of a fiber connection. As for why the Weed Instrument EOTec 2000 in a star network arrangement was selected, Al-Mtwali says one factor was the configuration available. “They offered modules for single mode fiber, which is what was used in New Orleans.”

Another critical selection criterion was low electrical power draw on the Weed modules. This becomes vitally important when the system goes into battery back up mode. If a hurricane were to hit and knock out region wide power, having a low power draw would be an advantage. System requirements were to be able to run on battery back up for 10 days. The system has been up and running since December 2006. Before that there was no automatic way that critical data about the situation flowed from the canals to the Corps. Thus, up-to-the minute and accurate data on weather and water levels could be scarce as hurricanes, tropical depressions, and less fearsome storms rolled through or near New Orleans. Since a great portion of the city is below the water level of nearby Lake Pontchartrain, this lack of visibility increased the vulnerability to flooding. It also made it difficult for real-time preventative steps to be taken by those charged with keeping the city dry.

As part of the infrastructure improvements implemented after Hurricane Katrina, the Corps installed monitoring stations. Since these had to work no matter the conditions, they have redundant communications capabilities. The primary telemetry path for the SCADA system was over fiber optic cable running the MODBUS industrial automation protocol.

Products from Weed Instrument play a key role in this communication. “We use the 2C10, the electrical module interface, for the RS-232/RS-485 protocol,” says Al-Mtwali The connection between SCADA, pumps, and remote gates has to be speedy. A failure by the system to react in time could transform a manageable situation into something else. Pump parameters such as oil pressure and temperature are converted to MODBUS format and transmitted, along with CCTV images of remote stations. Commands to the pumps and gates take this same path, which is through armored fiber-optic cable.

Another data telemetry conduit is through the GOES satellite, running a high data rate option to a geostationary satellite thousands of miles overhead. This path provides hourly transmission of 15-minute interval stage data of such measurements as water level, temperature, relative
humidity, rainfall, and barometric pressure, as well as wind speed and direction.

The GOES link provides wide-area dissemination of the water level data, with the information transmitted to and monitored by personnel at the Vicksburg, Miss. regional headquarters of the Corps. This connection is extremely reliable, requiring no land lines or terrestrial repeaters.

It also can automatically sound an alert if a problem is detected, explains Al-Mtwali. “The satellite would send an alarm, what they call a random transmission, to the Army Corps of Engineers, warning them that the water level is high limit.”

The final data route is through Iridium satellite phone modems, a slower and more costly link than GOES. One advantage that the Iridium channel offers is two-way voice and data communication, which can be critically important in a crisis. Iridium also offers a last ditch link, used if all else fails.

Because of the multiple channel setup, if the fiber breaks the station will still be logging and transmitting data. Indeed, so long as there is power and the antennas exist, the monitoring stations can continue to do their job. This information then helps the Corps do its job in ensuring that the levees and canals protecting New Orleans don’t fail.

To date, the system has not been subjected to a severe test. This good news is partly due to the relatively quiet hurricane season of 2007, at least as compared to the onslaught of storms two years earlier that ran through all the names in the alphabet. A related factor is that no storms have sideswiped New Orleans like Katrina since the monitoring system became operational. How long such relatively good fortune will last is anyone’s guess but steps have been taken to be ready for the next storm.

So far all the communication channels have worked well and the Corps has not encountered a problem – or even a lack of information. That good outcome is due in part to the products that Weed Instrument supplied. Al-Mtwali says of the Corps and the all important data transmission, “They’re getting their data and the fiber has been working perfectly.”