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The recent Duke Energy spill that left more than 70 miles of the Dan River coated in 40,000 tons of toxic coal ash has created a demand for immediate inspections and repair plans for leaking pipes in all 14 of Duke Energy’s facilities, including those that have already been retired or demolished. And while most inspections are indicating that “the infrastructure is safe and performing as designed”, many leaks have already been found in riser pipes and other pipelines throughout the facilities. The Eden facility, responsible for the coal ash leak, is not the only facility in which these leaks have been found; Duke’s Weatherspoon Steam Electric Power Plant, which was retired in 2011, was found to have a crack in the riser pipe at the plant’s ash pond dam.

The Weatherspoon plant was demolished in 2013, but its 54-acre coal ash pond is still full and the cracked riser is still in use. The steel-lined concrete riser is designed to siphon the cleanest water off the top of the pond when the water rises, allowing heavier sediment and coal ash to sink to the bottom. While experts say that a coal ash leak with the magnitude of Eden’s is unlikely at Weatherspoon, they fear that the crack could cause a leak of ash-laden water to contaminate the local tributaries and rivers. Coal ash is a byproduct of the burning process that generates electricity, and it contains numerous toxic substances, including mercury, cadmium, lead, arsenic, selenium, and chromium, among others. Duke Energy has been given a July 20 deadline to provide a schedule for repairs; if they don’t, they could be fined up to $500 per day.

The Weatherspoon Plant was demolished in 2013 but its ash pond is still full
Credit: fayobserver.com

The leaking crack in the riser pipe at Weatherspoon was identified by camera inspection, which helped to determine that the condition of the riser is “serious enough to justify further engineering study to determine remedial measures”. A similar issue was identified at another of Duke’s steam plants; a 40-foot crack in the coal ash dam at the company’s Cape Fear Steam Electric Plant developed as a result of shifting earth below the dam. Over time, the shift forced a riser in that pond to bend almost to the point of cracking. Duke Energy has since fixed both the dam and riser at the Cape Fear plant, but has yet to provide plans for repair of the riser at the Weatherspoon plant.

Riser at the Cape Fear Plant’s ash pond
Credit: Charlotte Business Journal

Power Plants like Duke Energy’s utilize a circulating water system to cool steam that has been heated and passed through a turbine. The cooled steam turns back into water, at which point it can be reused to generate more electricity. Over time, the riser pipes transmitting the cooling water can corrode. Corroded riser pipes at this power plant in the southwestern US had cracked and started leaking. Two of the risers were so corroded that they could not support the operating pressure, resulting in their complete failure. The risers that were still operational had corroded all the way through to the inner steel, which was exposed. The plant wanted to reinforce 22 total risers, but only had a minimal outage window for the repair. HJ3 was asked to perform the repair with the CarbonSeal™ system.

Some of the 22 risers needing repair
A corroded riser
The riser is abraded and ready to be primed
The riser is wrapped with saturated CarbonSeal fabric
An installer applies a UV- and abrasion-resistant topcoat

Before the riser pipes could be repaired, they were excavated and their concrete diapers were removed. The exposed steel surface was prepared to near white metal and primed. The CarbonSealTM high modulus paste was applied, and saturated CarbonSealTM fabric installed. The carbon fabric is protected by an abrasion and UV-resistant topcoat. Steel sleeves were applied at the base of the repair, which was enclosed by new concrete diapers. The repaired risers were painted to meet the client’s aesthetics. In total, all 22 steel riser pipes were reinforced within a limited window, and the client saved $1 million for every day that the plant would have been shut down beyond the scheduled repair. The client also saved more than 127,000 gallons of water and 17,000 kWh by repairing their risers instead of replacing them. 3 tons of CO2 emissions were prevented from polluting the atmosphere and 2.5 tons of steel and concrete waste was prevented from going to landfills.  If you have steel risers that need repair and would like to learn more about HJ3’s CarbonSealTM reinforcement systems, contact HJ3 at info@hj3.com.