South African utility Eskom was forced to implement rolling blackouts for the second time this year after a coal silo supplying a 4.1-GW coal-fired power plant collapsed on Nov. 1.

A crack was observed in one of the three 1994-built coal storage silos serving the 13-year-old Majuba Power Station in Mpumalanga Province at about 12:30 p.m., Eskom reports.All personnel working in the area were immediately evacuated and station output was reduced from 3.6 GW to 1.8 GW. The 10,000-ton silo collapsed at about 1:12 p.m. on the plant’s conveyer belt. No injuries were reported.

Eskom says it then involved its emergency command center to ensure that the power grid was protected from total collapse. Mobile coal feeders were also transported to the Majuba site to enable a manual feed of coal to five of the six units, so that the power plant could operate at a minimum half-load. However, the utility was forced to implement load shedding on Nov. 2.

A visual inspection was last conducted at Majuba, which is the youngest coal plant of Eskom’s fleet, in September 2013, and the concrete structure of the silo was found to be in good condition. “An investigation is already underway into the cause of the incident, but it appears that this is an isolated incident specific to the coal infrastructure at Majuba,” Eskom said.

On Wednesday, the utility said that the risk of rolling blackouts, which it had previously warned could affect major cities around the nation throughout the week, had diminished, even though dam levels at hydropower peaking plants were lower than usual. An additional 1.4 GW of capacity at Majuba has been restored so far, and Eskom expects to synchronize more to the grid later today despite weather hurdles.

“The wet weather does pose a challenge especially at Majuba given that some of the coal handling is taking place out in the open. We have implemented a wet coal management strategy to ensure that the wet coal risk is reduced in our other power stations. It is however not possible to neutralise this risk completely, especially over periods of prolonged, high rainfall,” Eskom said.

Although the cash-strapped utility that generates almost all of South Africa’s power has embarked on an ambitious plan to increase power capacity, it operates on near-zero reserves margins. Eskom is building two 4.8-GW coal-fired power plants, but both have been beset by delays.

Earlier this year, it was forced to shed load for the first time since 2008, requiring large industrial users to reduce demand to avoid a total collapse of the grid.

Industry observers have called on the government to implement structural changes to the power market and give private players more opportunities to develop new generation capacity. Meanwhile, South Africa has sought to raise $1.8 billion by selling stakes in other state-owned companies and real estate to financially rescue Eskom, which suffers wide revenue gaps.

Eskom last year asked the National Energy Regulator of South Africa (NERSA) for approval to increase tariffs by 16% to offset a revenue shortfall it expects of up to R225 billion ($21 billion) over the next four years, but NERSA allowed the utility only to raise prices by 12.69% next year.

Sonal Patel, associate editor (@POWERmagazine, @sonalcpatel)