Prime
Isimba dam might burst due to defects, say experts
A team of engineers tour the turbines at Isimba dam last week following emergency shutdown of the plant about two weeks ago. PHOTOS/stephen otage
What you need to know:
Two weeks after the restoration of Isimba dam power to the national grid following a reported flooding incident on August 8, a blame game erupted between government agencies—UEGCL and Ministry of Energy—and the contractor, China International Water and Electric Corporation, after it emerged that the Shs2.2 trillion project is limping with defects categorised as “high risk” that require immediate repair to avert a disaster, write Frederic Musisi & Stephen Otage
On August 11, engineers, supervisors, IT specialists, welders, and cleaners—worked frantically to restore power in one of the turbines at Isimba dam.
The previous three days had been a nightmare after one of the workers opened a wrong gate during routine maintenance works on Unit three—one of the four Kaplan axial flow turbines—and then the automated gate jammed, causing a flood that submerged four floors, including the powerhouse.
Each of the turbine units has a generation capacity of 45.5Megawatts (MW) but only three have been active since the dam was commissioned on March 22, 2019.
It is on that day that Ministry of Energy officials led by the minister, Ms Ruth Nankabirwa, and the Permanent Secretary, Ms Irene Batebe, pitched camp at the site.
The construction of the dam cost $568m (Shs2.2 trillion), 80 percent a loan from China’s EXIM Bank. Hydropower dams are designed to last for 50 years.
The Ministry of Energy supervises the Uganda Electricity Generation Company Ltd (UEGCL), the statutory body charged with electricity generation, and operates Isimba.
Ms Nankabirwa and her team were ushered into the control room. Across the choppy waters, was a group of Australian dam engineers armed with monitors that fed footage to the CCTV room.
The images gleaned by the divers were startling. Concrete under the water at the spillway gates continued to wash away and crumbling, among other things.
The dam has four spillway gates. A spillway gate is raised and adjustable to allow the controlled release of water downstream whenever water levels in the reservoir—the large lake behind the dam—increase[s], including the probable maximum flood.
The water flows with a distinct force, so the concrete foundation must be rock solid but this wasn’t the case for Isimba. Some engineers are questioning the structural integrity of the embankment—the large concrete wall barricading the reservoir—on which the spillway gates sit, and which forms part of the 10-storeyed dam house that includes the powerhouse and offices.
The defective concrete spill/waterways, according to one UEGCL report, are among the 10 major catastrophic flaws categorised as “high risk.”
There is an imminent threat as the embarkment at the dam could burst leading to flooding as raised water could barrel across homesteads, leaving a trail of destruction.
The Isimba dam powerhouse which reportedly got flooded on August 8.
How we got here
As the construction falters from one crisis to another, these problems are not isolated to Isimba but stretch to Karuma dam.
The construction of both dams aimed at forestalling acute power outages that were crippling industries and domestic consumption. However, the tendering process was tainted with graft.
When China International Water and Electric Corporation (CIWE), one of the six bidders lost the Karuma dam to Sinohydro Corp, it was handed Isimba to appease officials.
No sooner had the construction of both projects at a combined $2b kicked off, than a war between UEGCL and its parent ministry broke out over the role of supervision.
READ:
UEGCL was handed the supervision of the Isimba project in December 2016 when construction was at 75 percent.
Initially, the dam was supervised by the Energy ministry. On the contrary, the ministry said UEGCL is attempting to find a scapegoat.
The contractor, CIWE, who had remained reluctant to address the lingering defects until the recent flooding, blames both the Energy ministry and UEGCL for the mess.
During a stormy meeting convened last Wednesday by the Prime Minister, Ms Robinah Nabbanja, CIWE, according to insiders, agreed to fix the remaining defects.
About seven years ago, a rift between the then Ministry of Energy leadership and UEGCL over the supervision and management of the two multi-billion-dollar projects, sucked in President Museveni.
Investigations by an ad hoc committee led by Prof John Stanley Senfuma was commissioned by the Energy ministry to look into shoddy works and claims of negligence by contractors.
Government officials painted a grim picture. Many years later, the quandary lingers.
“The contractor is using mild steel rod/ties instead of coupling which are being cut at the concrete surface. These exposed mild steel rods and ties will lead to corrosion in the future. The contractor has used concrete of inferior class in areas where it is likely to cause cavitation (voids) and scouring (wash-off or erosion of abutments),” the ad hoc committee report read in part.
After taking on the project from the Energy ministry, UEGCL claims it identified 776 defects of which 98 percent (762) and 72 percent(495) out of 690 notified defects have been closed so far.
“However, many critical snags [defects] are yet to be addressed and closed out by the Engineering, Procurement and Construction (EPC) contractor,” one UEGCL report indicates.
Most critical of the defects, all categorised as “high risk”, are cable rectification—requiring extensive replacement, project documentation—requiring improvement of the quality of and submission of operation.
Maintenance manuals, power house roof need panel replacements and installation of guard lines, water weed and debris management system require supply and installation of a barrier system to trap weeds, and commissioning of a fire-fighting systems needs design review or recommissioning of designs systems.
Negligence, incompetence
Other defects are safe access, draft tubes and stairs to spill ways—requiring appropriate safe access facilities, a new unit cooling system—requiring to revert to the original design with heat exchanges in the power house, intake gates control modification—requiring rectification and installation to achieve independent gate philosophy.
The wearing of spillway waterway concrete requires total overhaul.
The UEGCL chief executive officer, Mr Harrison Mutikanga, in a June 30 correspondence to Ms Batebe specifically red-flagged the crumbling waterway concrete, saying it was of “great risk to the overall stability of the dam with possible catastrophic consequences.”
“UEGCL considers this risk to be of paramount importance as any delays to correct these failures only serves to increase the likelihood of these risks materialising and exposing government to great financial and reputational risk,” Mr Mutikanga wrote.
The State Minister for Energy, Mr Sidronius Okaasai, told Daily Monitor in an interview last Thursday that Isimba dam has a number of flaws.
One of the malfunctioned spillways at the dam. Experts want immediate repairs on the spillways.
“Obviously, there are managerial and technical issues that we need to address,” Mr Okaasai said.
The dam remains under the Defects Lability Period (DLP)— the time period specified in the contract during which a contractor is legally required to return to a construction site to repair any defects, which is due to expire later this year.
Officials are mulling its extension for another six months.
A senior ministry official told this newspaper separately on condition of anonymity that UEGCL also has its problems, including staffing the project with inexperienced engineers who could not adequately rein in the errant EPC contractor.
When the dam flooded, UEGCL summoned its experienced teams deployed at Nalubaale/Owen Falls and Kiira dams in Jinja District who restored power in the turbine.
Four years ago, a flooding incident nearly halted the commissioning ceremony.
The August 8 flooding incident, energy industry experts say, should serve as an eye opener for those in charge.
At the behest of the Works and Transport minister, Gen Katumba Wamala, a team of engineers from the Uganda Institution of Professional Engineers (UIPE) and Engineers Registration Board (ERB) visited the site, early last week.
During engagements, UECGL officials said since the handover in 2016, the contractor is yet to provide the operating manuals to them.
Officials also claimed that last month’s flooding was as a result of a malfunction of one of the cranes meant to open one of the sluice gates to enable engineers get access to the problematic unit three turbine during routine maintenance.
“The power house flooded when the contractor was remedying the defects. We also established that he was thin on the ground. The flooding was more to deal with the methodology of work, UIPE’s president,” Mr Andrew Muhwezi said.
It is difficult to understand how the contractor remains thin on the ground when we have such many problems,” he added.
The ERB chairman, Mr Isaac Mutenyo, red flagged the crumbling waterway concrete which continues to extend to the embankment.
“Cavitation (formation of vapour bubbles within a liquid at low-pressure regions that occur in places where the liquid has been accelerated to high velocities)—the high pressure of falling water from the spillways—is something destructive to engineering structures. You have water falling at a certain speed and because of differences in pressure the air bubbles formed cause pressure that is causing damage to the spill way gates,” he said.
“The concrete underneath is damaged and ordinarily the designs should have made provisions for this pressure, but it also looks like the designs were not done well,” Mr Mutenyo said.
“In the design[s], the designer who happens to be the contractor didn’t put much emphasis on the operations,” he added.
Mr Simon Otoi, an energy audit consultant, criticised the works.
“Quality control of [construction] materials was not done properly. The contractor was testing materials in his laboratory and the engineers who were supervising just signed on whatever he offered. There was no independent take from say Ministry of Works or otherwise to ensure that the contractor was doing the right [thing],” he said.
Years later, UEGCL, Ministry of Energy and CIWE are locked in frantic discussions to fix this crisis.
In February, Mr Otoi said they undertook an environmental audit that ought to have been considered during construction.
For the spillway, he said UEGCL and the contractor have to find money to immediately repair the damage.
“I’m not saying its poor quality; it has to be first tested in an independent laboratory. But never should something be done and concluded by one person,” Mr Otoi said.
Who is to blame?
UEGCL was handed the supervision of the Isimba project in December 2016 when construction was at 75 percent.
Initially, the dam was supervised by the Energy ministry. On the contrary, the ministry said UEGCL is attempting to find a scapegoat. The contractor, China International Water and Electric Corporation (CIWE), who had remained reluctant to address the lingering defects until the recent flooding, blames both the Energy ministry and UEGCL for the mess. During a stormy meeting last Wednesday convened by the Prime Minister, Ms Robinah Nabbanja, CIWE, according to insiders, agreed to fix the remaining defects.
