Solution
BPU has enlisted Burns & McDonnell for several years to provide engineering and environmental support as needed while it implements the optimization study for Section 316(b) compliance efforts at its generation facility. As part of that broader program, we were asked to evaluate the compliance technology options for Nearman Creek.
Intake structures are unique, so each solution must evaluate and accommodate local needs. We collaborated with the client and determined a modified traveling screen with fish return trough offered the optimal potential solution at the plant.
We applied multidisciplinary talents to designing the fish return system, combining engineering experience with biologists who understand the affected species and their anticipated survival. To avoid expanding the plant's footprint and complicating permitting for the project, the design included suspending the return trough off of the existing cooling water intake structure. Suspending the large superstructure eliminated the need for a new foundation for a separate structure.
Permitting with the U.S. Army Corps of Engineers, U.S. Fish and Wildlife Service, and U.S. Coast Guard was streamlined by avoidance of flood plain disturbance, no extension beyond the existing facility over the river, no construction in the river, and consideration given to protected species.
There were existing exit points in the building that needed to be used and limited space inside the intake building. Creative, innovative thinking helped resolve challenges like these, as well as the complex matter of designing the trough that would return fish to the river, given the height of the intake. Calculating and designing the slope of the trough and the height of the drops to safely return fish to river level required significant effort. The sloped trough included drops of up to 4 feet along the trough and a final drop of up to 32 feet during low-level river conditions. The trough design needed to account for water flow at the upstream side and retaining sufficient water level in the trough to safely transport the fish and other organisms.
Construction was successfully completed in last summer 2019. Subsequently, Burns & McDonnell designed and implemented a two-year impingement optimization study of the system. Training, oversight and quality control was provided by our biologists. The study measured and analyzed impingement survival over different operating conditions, including fish spray and removal pressure, fish trough flow, and screen rotation speed.
The optimization study had relatively little precedent to inform its design, especially given challenges like the height of the intake and fluctuating river levels. A temporary sampling system was developed to collect fish and shellfish from the modified traveling screens using a series of diversions, troughs, piping, valving and tanks to assess latent mortality.
