High-Water Warning

A new wireless system is helping Seattle prevent wastewater overflows.

by / August 8, 2002
Seattle relies on wireless technology to monitor wastewater levels and warn officials of potential discharges from relief valves scattered throughout the city.

The innovative system collects rainfall and wastewater data, then wirelessly transmits it to a dedicated, interactive Web site. That information helps Seattle, which averages 30 to 40 inches of rainfall annually, predict and respond to discharges from what are known as combined sewer overflows (CSOs).

The system sends early warnings, as wastewater rises to critical levels and sends secondary alarms as actual overflows occur. Alarms can be sent via cell phone, e-mail, pager and fax, allowing city staff to mitigate or avoid wastewater overflows.

"It shortens the response time, and then you can quickly get to the location and investigate the site to stop or prevent the dry weather overflows," said Hirad Mousavi of the Seattle Public Utilities' Resource Planning Division.

Although Seattle currently uses data generated by the system internally, the Web site eventually could be opened to the public, said Tim Croll, director of the Seattle Community Services Department.

"My vision was that people could check out a map online and see if there has been discharge from any of the CSOs. Windsurfers could check it before going out. Red means a discharge and green means all is OK," Croll said. "We don't have that yet, but we're going in that direction."

Wireless reporting is done via cellular digital packet data. The system uses standard Internet communication protocols (ICP) that can support sophisticated decisions based on environmental input. It's also programmed with smart logic, enabling the technology to cross-reference wastewater levels with an automated rainfall-data-gathering system to predict, measure and identify overflows.


The project has received national attention, earning honorable mention in Public Technology Inc.'s 2001 Solutions Award program. And although the system still isn't finished, it has met a number of objectives, according to city officials:

- Cost savings. A low-voltage power supply and localized street-level antenna eliminated all hardwiring requirements and significantly reduced installation and data collection costs. The estimated savings over two years exceeds $3 million.

- Durability. The system operates underground within a harsh environment and can accurately monitor wastewater flows.

- Reliability. Wastewater events are confirmed by two independent devices before an alert is generated, significantly reducing operational and maintenance response costs by minimizing false alarms.

- Efficiency. The system helps the city use limited resources more effectively by allowing it to send crews to a potential overflow site before such an event actually occurs.

This allows for a shared data management platform that is available to all city personnel and the general public.

Wireless technology was vital to the system's cost-effectiveness, according to Croll.

"Wireless was driven largely by economics," he said. "We could have dropped the big bucks and paid for a hard phone line -- the rental of it -- into every one of these sites. That would have been very foolish economically.

"The Web-based [design] just makes it a lot easier," he added. "We can access it; it's in one place and I think it gives us the most potential to move to the next iteration of having a Web-based public notification system. That's the ultimate vision."

Effective Solution

Seattle officials say the system helps the city cost-effectively comply with the conditions of its permit for CSOs. The permit requires Seattle to report wastewater discharge locations, times, durations, volumes and related weather information to the Washington Department of Ecology (DOE) each month. Dry weather overflows are prohibited and must be reported to DOE within 24 hours from the time Seattle becomes aware of them. Furthermore, the city must take corrective action immediately.

The technology also responds to increasing public concern over the CSOs and their impact on water quality, recreation and public health. These concerns have triggered growing demand for timely and accurate wastewater information and analysis.

Mousavi said the logic built into the new system, which isn't on many older monitoring systems, helps keep things intact.

"The benefit of this is that the operation crew will trust more of the alarms they receive, and they respond much quicker to everything," Mousavi said. "If they receive five or seven false alarms out of 10, the next time they receive an alarm, they won't get that serious about it."

But the city is serious about the health of its residents. Signs on the CSOs explain what a CSO is and say to avoid the area when it rains and several days after it rains. There is also a phone number to the Seattle Health Department for people to call with questions.

But if someone calls and wants to know whether there has been a discharge at CSO 17, for example, the Health Department has to call the Community Services Department, which then has to check the data. That means keeping someone available throughout the day to see if there has been a discharge. "It's a clunky system but better than what we had before," Croll noted.