Isimba Dam project steering commitee chairperson Badru Kigundu (right) and other Energy ministry officials enter into Unit 4 of the dam to assess the extent of damage in August 2022. PHOTO/TOBBIAS JOLLY OWINY 


How Isimba plunged Uganda into darkness

What you need to know:

  • Whereas officials say a defective radial outflow gate, a source at the dam says recurrent human errors and system inadequacies are responsible for the latest episode that has led to the shutdown of the plant.

At exactly 1.34pm on Friday, Energy minister Ruth Nankabirwa—in a tweet—indicated that four units at the 183.2MW Isimba Hydropower plant had been restored.

“We have good news coming in from Isimba. Unit 2 of Isimba dam is officially back on the grid. Next will be Unit 4 possibly in the next [three] days[,] which will be shortly followed by Unit 1 and lastly Unit 3,” she revealed.

On August 8, Isimba was taken off the grid following what was described as “massive flooding” in the dam’s powerhouse. It forced the operations and maintenance (O&M) crew of the dam to temporarily shut down the plant.

One of the O&M engineers, who was undertaking routine maintenance, is reported to have opened the wrong gates, leading to a gush of water submerging machines. The powerhouse that houses generators and turbines and other electro-mechanical and hydro-mechanical equipment for electricity generation laid in the riverbed—including all the four turbine units of the plant—were severely affected.

The recovery of Unit 2 of the dam, if substantial, serves a bit of relief to the Uganda Electricity Generation Company Limited (UEGCL), who can now discharge to the national grid at least 45MW since each of the units were built to discharge an average of 45.5MW.

On Wednesday, Parliament questioned the Energy ministry over the fate of the dam. It also tasked the ministry to justify why the government wants to import electricity—60MW—from Kenya.
A day later, on Thursday, Parliament ordered investigations into the dam’s shutdown upon listening to Ms Nankabirwa’s submission that was deemed unconvincing.

Deputy Speaker Thomas Tayebwa ordered the Committee on Natural Resources to investigate the shutdown and report back to the House in three weeks. Ironically, this is the same duration the power plant is expected to take before generation resumes.

Cabinet on Monday Okayed a proposal to import the electricity to meet the shortfall after Isimba dam was flooded last week allegedly due to a defective radial outflow gate.

New findings
On Friday, a member of the dam’s O&M crew—who spoke to Sunday Monitor on condition of anonymity—said recurrent human errors and system inadequacies are responsible for the latest episode that has led to the shutdown of the plant.

The source said while the O&M engineers running the dam are a fresh and young lot, they operate in isolation with usually limited backing of the experienced engineers. Our source also revealed that system operations were being violated at the same time.

“Whereas these O&M engineers trained in China, US, etc., we would imagine such a big team to be taken to Eskom or Bujagali Dam and spend some good time there as apprentices for three or six months, and then deploy them to man such assets, which did not happen,” our source said.

The source added: “The issues at the dam (Isimba) are administrative. Whereas UEGCL had ample time to prepare a team to run the power plant, they took them for training abroad, but the systems protocols are being flouted while the ‘young’ engineers seem to be working in isolation.”

Our source described as “just luck” the fact that “there were no people in there since it occurred in the morning.” Our source added that “many of the crew were yet to arrive at the plant” when the wrong spill gates were opened.
“It would have been a disaster with serious fatalities. You can imagine if it was a whole crew down there, they would all die,” the source said.

Lightning strikes twice
Sunday Monitor
has established that this is the second disaster hitting the plant due to human errors in less than three years. Although the matter was quickly swept under the carpet, in 2019, up to three technical officials perished at the dam when one of the “absent-minded engineers” opened the gates. Tragically, water is said to have sucked the officials to the grill and killed them.

Another official at the Energy ministry, who spoke to this newspaper on condition of anonymity, said one of the units of the dam has since commissioning remained dysfunctional due to so-called glitches.

“They have been running three units. The dam has never produced up to 180MW since commissioning because it cannot do that when one unit is down, and it has since been down,” the source at the ministry revealed.

According to the source, at the time of its commissioning, the Isimba plant had more than 384 defects—both structural and mechanical snags.

“The question is: Why do we have recurrent issues of flooding in the powerhouse? In 2019, the same dam flooded even when the contractor had not yet handed over to UEGCL, and today when our own engineers are there, one’s running the plant, it is flooding,” the source said, adding, “Should we say it is negligence by the UEGCL engineers or the contractor earlier in 2019, who are actually the experts in construction and plant management? One would be interested in knowing whether these snags were clinically addressed before the defects liability period ended, which has not happened.”

The source also said the government was conspicuously silent over the safety of the dam, which is not supposed to be flooded.

“Water is supposed to be in the turbines; not in the system because it weakens the facility and reduces the lifespan of the dam and the system,” the source reasoned.

According to the source, the set of engineers currently manning the plant are yet to acclimatise themselves with the critical maintenance strategies such as reactive maintenance (run to failure), preventive maintenance (based on machine run schedule), and condition-based maintenance (measurable optimal performance parameters).

“There is an O&M team that is always developing system reports ranging from turbine and generator, governing, lubrication, cooling water, domestic water, HVAC, Scada, protection, hydraulic steel gates, etc. but these reports are either not adhered to or are not up-to-date to their technicality,” the source said.

Pending snags
Since its commissioning, the dam has experienced four major incidents, which almost caused the shutdown of the plant.

The government awarded a Chinese firm the contract for the $567.7m (about Shs2.1 trillion) Isimba project, which started in April 2015. The project was then commissioned in March 2019, and is expected to generate an annual 1,039GWh (gigawatt hours) of electricity a year, once it achieved a substantial completion mark on March 31, 2019.

A March 31, 2019 takeover certificate was issued to the EPC contractor on April 12, 2019 alongside a list of 775 documented snags and outstanding scope of works.

The parties (the government and contractor) agreed that the fixing of the defects be completed by September 30, 2019.

A review of the UEGCL’s June 2021 Status Report revealed that the Isimba Dam Defects Liability Period (DLP) has continuously been extended due to the various snags and defects that were detected after the dam was commissioned in March 2019. The DLP was extended for one year from April 1, 2021 to March 31, 2022.
The key defects included power house concrete cracks and roof drainage, embankment dams, installation of floating boom, leakages in power house roof, power firefighting system automation, tail water systems, and cabling in power house and switchyard.

Others included absence of platforms to access spiral casing, Unit 3 oil leakage, standby generators, elevators and lifts to lower redial gates with defective hydraulic hoists causing leakages of oil into the river.

Boom lines, for example, are designed to deflect or retain the floating waterweed and vegetation to prevent debris from blocking power plant intakes, in order to achieve/maintain generation efficiency, and to improve dam safety by preventing plugging of spillways or spill gates.

A review of fourth quarter reports (2020) for Karuma, Isimba and Nalubaale hydropower plants (HPPs), however, revealed the absence of boom lines at Kira and Nalubale, and Isimba. The one at Karuma was damaged . This, the Auditor General said, could be attributed to failure by the concession operator—Isimba and Karuma EPC contractors—to recognise the relevance of a boom line.

Without robust boom lines, the dams will be affected by the water hyacinth and floating islands, including damages to the hydraulic structures of the hydropower plant that get exposed, resulting in revenue loss due to the occasioned blackouts.

Although Sunday Monitor could not independently verify the claims, the Auditor General’s 2021 report on the Financial Statements of UEGCL stated that the ministry wrote to Exim Bank of China to extend the loan disbursement period of the DLP to cover for additional costs during the extension.

Last September, the government ordered China International Water and Electric Corporation (CWE)—which constructed the Isimba hydropower station—to rectify up to 584 defects detected at the plant before handing it over to the government.

Govt response 

While appearing on VPN—a KFM talk show—on Saturday morning, Ms Irene Bateebe—the Energy ministry’s Permanent Secretary—admitted human error resulted in the flooding of the powerhouse that resulted in the emergency shutdown on August 8.

“This incident had nothing to do with rising water due to the hydrology of the river. This was an issue of operation that resulted in water flowing into the powerhouse due to an entry not having been handled the way it should have been. So, the water forced its way into the powerhouse,” Ms Bateebe said.

She added: “You have certain manholes that open into the river where the water is coming from to flow into the dam. So at that level, you do have fog gates to ensure at any one time you are undertaking any routine maintenance, you do have access to the powerhouse. It is that entry that, unfortunately, during this maintenance, somehow remained open and water flowed in.”

Other panelists on the show, including former ombudsman Augustine Ruzindana, termed this as carelessness.

So, who will be held accountable? According to Ms Bateebe, it will take a thorough investigation before heads roll.

“Accidents cannot completely be avoided. You are dealing with human beings and once in a while, there will be a lapse…We will take some remedial action like additional competence and training, or stepping up safety measures,” she said.

Similar to Ms Nankabirwa’s submission to Parliament on Thursday, the PS said the repair costs will be absorbed by the operations budget of the UEGCL.

“We have been able to restore one of the units and that is alleviating the current load shedding problem. We expect the other two units will follow in the next weeks,” she said.

Mr Dickens Kamugisha from the Africa Institute for Energy Governance said the suspicion stems from the opaque processes that preceded the construction and commissioning of the dam.

“Government should get independent auditors to audit these dams; and not just Isimba, but other dams because this can happen in other dams,” he said.

Additional reporting by Elizabeth Kamurungi.


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