Articles & Case Studies

Kepware OPC Server Supports St. Lawrence River Eel Ladders

Posted: Thursday 25th November 2010

The St. Lawrence River is one of the largest rivers in North America. Its flow impacts both the US and Canada, including the five Great Lakes. It’s the site of massive hydroelectric power plants owned by the U.S. and Canada and also functions as a deep-water seaway connecting the Atlantic Ocean with the Great Lakes.

The production of hydroelectric energy and the establishment of a deep-water seaway have provided many benefits but also created some ecological concerns including an impediment to migration for young American eels moving from the ocean to the upper river and Lake Ontario.

American eels are extremely beneficial to the ecosystem of the area as they devour dead fish, invertebrates, carrion and insects. For the balance to continue forward, young eels need to move from the ocean to the St. Lawrence River to live out their adult lives.

The impediment to migration has been overcome by the construction of eel ladders installed by Ontario Hydro, owner of the Canadian half of the power project, and the New York Power Authority (NYPA) owner of the U.S. hydroelectric plant.

On the U.S. portion of the project, a 182-foot eel ladder provides safe passage for the American eel to navigate around the power plants located on the St Lawrence River Power Dam system during the eels’ summer migration upstream to the Great Lakes.

Engineering Challenges

While the eel ladders have proven effective, their construction was an engineering challenge – from the positioning and angle of the ladder to the water flow necessary to encourage the eels to swim upstream and finally how to safely release the eels so they would not fall back through the plant’s turbines.

A team of biologists, civil engineers, electricians and software engineers were called upon by the NYPA to assess the challenges and create a solution, gaining best practices information from other eel ladders, particularly the Ontario Hydro ladder built in the 1990’s. This eel ladder water flow application was very mission critical as flows had to be kept at a certain rate to allow the eels to successfully migrate.

The eels’ migratory period begins in July and ends in October. Migration begins upstream just after dark when personnel are not always present. Throughout the evening, the eels are moving up the ladder system with the aid of water flows. In addition to the angle of the ladder, the size of the pipes off of which the eels push themselves upward, the length of the ladder, the distance of depository in the river above, the depository method, all of which have optimum ranges, the most critical aspect is the rate of the water current against which the eels swim. The American eel requires a steady stream of water to encourage them to continue up the eel ladder and that flow rate must be maintained within a range of a few gallons per minute. If the flow rate is too aggressive the eels will tire or not attempt to continue up the ladder. If flow rates are too low the eels will abandon the ladder or become stranded. The flow rate must be steady and exact.

Once up the ladder, there’s a depository system that prevents the eels from slipping back toward the dam and its turbines. Once the optimum distance from the dam was identified, it was found that having the eels continue to swim against a steady current increased their success rate instead of flushing them out.

Meeting the Challenges

The construction company had specifications for pumps and controls systems and software. They called upon Deadline Solutions, an engineering services company headquartered in Syracuse, NY, to devise the control system strategy and implement that aspect of the system. Deadline Solutions is known for its extensive experience with control systems and software development for unique applications. In turn, Deadline Solutions turned to Kepware Technologies, Inc., of Portland, Maine, for the continuous communications aspect of the control system.

Deadline Solutions customized a .NET Windows application that monitors the eel ladder water flows and provides access for pump control logic using a PLC (Programmable Logic Controller) and a PC (Personal Computer). This customized application then leverages Kepware Technologies’ KEPServerEX solution for communications between the PLC and the PC. Via the KEPServerEX, the customized .NET Windows Application accesses and distributes the data to designated recipients.

As the water flows are so critical to the success of the project, alarms were built into the system via the custom Windows application, which sends alerts to the designated recipients if there is an alarm condition that requires immediate attention.

Using the Kepware Modbus Protocol and KEPServerEX

KEPServerEX was a proven solution as Deadline Solutions had used it in previous applications. According to Mike Silliman, Software Engineer at Deadline Solutions, “Kepware was the most robust communications technology we could find. It enabled us to track some of the internal events such as system level monitoring, for example, which could set an alarm if PLC communication was lost.” Now running successfully for four years, the communications is handled through fiber optics to remote I/O blocks.

“The KEPServerEX is straightforward and easy to set up and does not require a lot of leverage to make it work,” Mike continued. “You install the software, address the device and right away you’re collecting data, proving out the base system for retrieving information.”

Kepware’s ‘out of the box’ approach saved time configuring the I/O. And Kepware’s licensing scheme allowed Deadline Solutions to fully develop and test out the system prior to implementation, thereby streamlining the business aspect of the project and ensuring success upon delivery.

“I can download, build tags and know what I’m getting right out of the gate,” added Mike. “When I arrive at the customer site, it’s just a matter of turning on the licensing switch. This guarantees our success at the customer site, maintaining a high level of efficiency across the breadth of the project.”

Tracking Results

Biologists located at the power dam track flow data to ensure enough, but not too much water is being fed into the eel ladder system. Via the KEPServerEX, NYPA is able to record the data accurately and reliably throughout the unmanned evening hours. Eel counts and water flows are analyzed the following day and recorded for future reference as dictated by federal regulatory requirements.

This system also enables the NYPA to report to regulatory agencies that the water flows are constant and “eel migration friendly.” With so many variables contributing to the safe passage and successful migration of the eels, it’s important that the water flow reports are constant and reliable; to insure that hat part of the system meets federal guidelines.

“This was a truly collaborative effort between the New York Power Authority and the U.S. Fish and Wildlife Service to design a ladder that would enhance the conservation of American eels without reducing any power to NYPA’s customers,” said Michael Thabault, assistant regional director of Ecological Services, U.S. Fish and Wildlife Service. “This eel ladder utilizes state-of-the-art techniques to pass American eels upstream at the Project. This structure will help our efforts to conserve the American eel by passing more juveniles upstream where they may live to be 30 years old before returning to the ocean to spawn. The monitoring data resulting from daily eel counts at the ladder will provide the Service with very valuable information about the numbers and timing of the migrations of this catadromous species.”

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