One of the largest electric power holding companies in the United States has provided clean, renewable energy since 1912. In 2015, the company began its Hydro Project, focusing on the protection, mitigation, and enhancement measures to select stations to ensure they continue to operate safely and reliably as it has done for more than 100 years. It also involved enhancements to water quality, recreation, fish and wildlife habitat protection and land conservation efforts.

Of the many aspects of this project included installation of fish passage facilities for American shad, American eel, and blueback herrings in the river upstream and downstream of the hydroelectrical station. American shad are migratory fish that are born in freshwater, mature in the ocean, and return to freshwater to spawn. This hydroelectric station is the first dam the fish encounter on the river as they swim upstream from the ocean. Because of this, the electric power holding company installed a trap, sort, and truck (TST) facility, as well as a downstream passage on the spillway to allow access around the dam for the juvenile fish. The goal of both initiatives is to re-establish historical populations of these fish species in the river upstream from the station.

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pipe rehab

The owner decided to create the passage using its station’s two existing 48-in. steel penstock headwall pipes. The pipes were original to the facility and were inactive. It required replacement or trenchless rehabilitation as the assets needed structural repair since they had deteriorated from their original wall thickness over the years.

With guidance from their engineer, the owner evaluated all potential methods based on factors such as safety, risk, schedule, impacts, cost and constructability. After much consideration, rehabilitation of the pipe using an epoxy coating system was identified as the best solution for the project. This trenchless rehabilitation method allowed for the pipe’s structural capacity to be quickly restored without the disruption and high costs associated with open-cut pipe installation.

Of the products considered, Warren Environmental’s aquatic safe, non-hazardous, structural epoxy system was selected. It was the only epoxy coating on the market that could be spray-applied to 500 mils (1/2-in. thick) in a single coat, providing the high build and the rapid return to service needed to maintain their critical path schedule.

Warren Environmental’s master applicator, A&W Maintenance, was chosen to apply the coating due to its previous experience using Warren’s products on similar assets for structural rehabilitation. The A&W Maintenance team mobilized to the site to prepare the steel pipe by sandblasting residue and silt until the ideal profile was created. To avoid a potential trip hazards, the crew ran their hoses and dust collection equipment vertically by dropping them 50 ft into the work area. Then 375 mils of Warren’s 301-14 high performance epoxy was spray applied to the two 23-ft sections of 48-in. pipe that had deteriorated to 50-in. with one-tenth inch wall thickness. The project spanned 10 days from the start to final inspection due to the epoxies’ single coat capabilities and fast cure times (four to six hours after being sprayed).

pipe rehab

The short coating duration enabled other portions of the work to begin immediately. This was key as the access to the pipe changed from the riverside to the courtyard side. With another product, the coating of the penstock could have ultimately delayed the project.

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Maintaining the critical path schedule was not only capable because of the epoxies’ quick cure times, but also due to its non-hazardous attribute. The schedule required for various improvements to be executed simultaneously. Because the epoxy was non-hazardous (free of volatile organic compounds, solvents, styrene, and isocyanates), it allowed the A&W Maintenance team to apply the coating while other work was conducted. There was no risk to the applicators or other workers on site. Replacement of the penstock or other epoxy products could not offer the project the same opportunity.

Another contributor to Warren’s selection is its aquatic safe attribute; its product passed rigorous lab testing with a 100 percent survival rate of fragile aquatic life. It also has a proven history of being used in fisheries in New England and other parts of the United States. The project team was confident in the product’s ability to have zero impact on the American shad and blueback herrings using the passage.

The epoxy coating system proved to provide the structural repair needed while saving significant time, money, and impacts on the larger project and the surrounding area. More importantly, the non-hazardous and aquatic safe epoxy has eliminated the harmful effects of more traditional solutions and has contributed to the electric company’s goal of increasing the native fish species’ historical populations.

Max Silva is senior project manager at Warren Environmental.

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