Dam Incidents in Finland 2014-2018

2018

21 dam safety incidents was reported to dam safety authority in 2018.

2017

There was 17 dam incidents in 2017. Huge storm caused 4 of these events.DESCRIPTION OF THE DAM

 

CAUSE FOR THE INCIDENT

DESCRIPTION OF THE INCIDENT

REPAIR WORK

Hydropower dam,

class 2

Internal erosion

Sinkhole

Grouting

Hydropower dam,

class 2

Internal erosion

Sinkhole

Grouting

Hydropower dam,

class 2

Power failure

Because of power incident at switchyard hydropower generators shutdown. Spare generators did not start automatically and the water level rose.

Spare generators were started manually.  

Hydropower dam,

class 3

Power failure

Storm cut trees over power lines. It was not possible to control the gates.  

 

Hydropower dam,

class 2

Power failure

Storm cut trees over power lines and the under voltage caused generator emergency shutdown.

 

Hydropower dam,

class 2

Power failure

Storm cut trees over power lines and the under voltage caused generator emergency shutdown.

 

Hydropower dam,

class 2

Water level rising above the HW limit

After power failure water level rose and went over the spillway crest.

Gates were lifted manually.

Hydropower dam,

class 2

Internal erosion

Signs of an erosion was noticed during the winter.

Tomography and pipes confirmed the signs. Grouting.

Hydropower dam,

class 2

Water level rising above the HW limit

The emergency HW was exceeded.

 

Hydropower dam,

class 1

Vandalism

There was a temporary pumping over an embankment dam near pumping station. Somebosy displaced the discharge pipe after which it deteriorated the dry slope.

Pumping was stopped. deterioration was repaired and Discharge pipe was secured.

Tailings dam,

class 2

Internal erosion

Beach area was too short.

Beach are was broadened. Seepage was repaired with filter and stabilizing berm.

Hydropower dam,

class 2

Internal erosion

Sinkhole

Grouting

Hydropower dam,

class 2

Internal erosion

Sinkhole

Grouting

Tailings dam,

class 2

Internal erosion

Leakage was found as a new pond was taken into operation.  

Leakage was repaired.

Tailings dam,

class 1

Water level rising above the HW limit

Overflow caused by inner pool overflow. This had not been noticed because of landscapes.  

Emergency repair works. Comprehensive repair and raising was done next summer..

Hydropower dam,

class 2

Freezing

Gates were frozen and the water overflow.

Gates were thawed.

 

2016

Twelve dam safety incidents was reported to dam safety authority in 2016. Internal erosion was the reason in four cases.

DESCRIPTION OF THE DAM

CAUSE FOR THE INCIDENT

DESCRIPTION OF THE INCIDENT

REPAIR WORK

Hydropower dam,
class 2

Internal erosion

During the night a sinkhole had emerged at the dam crest. Internal erosion had been found already before the event. Repair work was already underway.

Grouting as a preliminary repair work.

Tailings dam,
class 1

Headwater level rose exceptionally high.

The raising of the dam height had not been yet taken into operation and therefore water rose above cut off material and onwards to the next pond.

Discharge was immediately stopped. New pipeline was built into the other edge of the pond where the raise was already ready and in use.  

Tailings dam,
class 2

Headwater level rose exceptionally high.

The measurement of the surface water level had failed. The water in the pond had risen. The rising water had moved the charging pipe so that the pipe had come loose from the sealing film. After this the water had poured into the drain.

Pumping was stopped. The pond was emptied and repaired.

Tailings dam,
class 2

Internal erosion

Water that had been pumped from the safety pond had eroded a hole into the dam. Water got back to the safety pond through this hole.

 

Dam was repaired and the pumping was replaced on a safer spot.

Hydropower dam,
class 1

Other reason

Wrong gate was opened during a water release. Formwork and part of the reinforcements for the rehabilitation work were damaged.

The damaged parts of the rehabilitation work were redone.

Hydropower dam,
class 2

Internal erosion

During the night a hole had emerged at the dam crest. Internal erosion was discovered during the studies.

Grouting as a preliminary repair work.

Hydropower dam,
class 2

Other reason

During the water release a huge driftwood stuck into the gate. Main part of the wood was lifted with the crane. But a fork of the tree got stuck into the other gate. Elements of the lifting gear were damaged (twisted) as the gate was lowered.

Elements were repaired.

 

Hydropower dam,
class 2

Vandalism

Somebody made a burglary into the hydropower station and adjusted the controlling system. Generators cut out and one of them was broken.

Police caught the guilty person red-handed.

Generators were restarted and one of them was repaired.

Hydropower dam,
class 1

Internal erosion

A sinkhole appeared at the slope of the embankment. Retaining wall had been leaking.

The dam was repaired.

Hydropower dam,
class 2

Deterioration of the dam structure

Alarm system reported gate malfunction. A cog had fallen off and therefore automatics had not limit switch. The gate pushed the lifting machinery off the concrete structure.

 

The lifting machinery was fixed as well as all the other damaged structures. System was improved safer.

 

Waste dam,
class 3

Frost

The surface of the frozen dam embankment had melted during a fast thaw. Silted water had run along the dam embankment inside and outside the pond.

Filter was built to hold the dam embankment material.

Hydropower dam,
class 2

Gate malfunction

Upper part of the binary gate rose higher than it was planned for. It came off its groove. Inhibitor beam had not been replaced after the maintenance work.   

Gate was repaired and beam was replaced.

 

2015

Twenty dam safety incidents was reported to dam safety authority in 2015. Eight of these incidents related to tailings dams.

DESCRIPTION OF THE DAM

CAUSE FOR THE INCIDENT

DESCRIPTION OF THE INCIDENT

REPAIR WORK

Flood embankment,
class 1

Weak condition of the dam structure

During the flood situations a spring through the embankment.

Emergency repair work was done as the renovation was planned.

 

Tailings dam,

class 2

Facing cave in

Above the damaged part the embankment structure seemed to have high concentration of water.

There was no signs of internal erosion. The explanation was intensive autumn rain where by the water level was high in seepage drain. Seepage wells were redesigned to solve the problem.

 

Earth dam,

class 1

Damage in dam structure

Dam was in such a bad condition that the iron bar sank in. Wet moraine was detected during the dam studies. Downstream from the wet spot moraine was dry and tight. 

Assumption was that there might be an old water pipe. Dam will be opened next summer (2016).

Earth dam,

class 2

Damage to the dam structure

Significant changes were noticed in ground water levels. There was an assumption of the internal erosion.

Further investigations will be made and the investigations and repair works will be started.

Flood embankment,

class 1

Damage to the dam structure

Damage in dam structure was noticed in the monitoring results. Sonar proved the erosion. Calculations showed that the collapsing could be possible.

Dam was repaired.

Tailings dam,

class 2

Seepage

Water was seeping through the rock facing.

Inverse filter was built. It had drainage pipes for monitoring.

Tailings dam,

class 2

Leakage

Sealing membrane was broken and water was therefore leaking under the dam.

Pond was compacted with moraine and afterwards filled with tailings.

Tailings dam,

class 2

Leakage

Flow near the inlet pipe eroded the facing. Water inside the dam caused an internal erosion.

Quarry material was digged of the leakage spot. The spot was compacted with strainer, clay and rock material.

Hydropower dam, class 2

Gate malfunction

Spillway gate was stuck during a test drive.

Flow was cut down at the upper dam. Spillway was cleaned and hoisting machinery was retooled.

Earth dam,

non-classified

Deterioration of the dam structure

Wooden stop logs of the spillway had given away. The pond had emptied.  

 

Earth dam,

class 1

Change in the amount of seepage

Bore hole was planned to drill through a filter behind the dam. This did not succeed. As the drilling pipe was lifted up, a lot of water rose up as well.

Seepage in the bedrock is strong. Filter resists the seepage and boreholes opened the way to the seepage water. 

The amount of material was increased behind the dam.

Tailings dam,

class 3

Water level rising exceptionally high

Measurement equipment for the water level was broken. Water overflowed.

Pumping to the pond was stopped. 

Hydropower dam, class 2

Gate malfunction

Hoisting wire rope for the spillway gate was broken. 

New hoisting wire rope was delivered.

Hydropower dam, class 2

Power failure

There was various power failure at the power station. Last one was not possible to set off by the remote control room.

The machines were restarted. Lowering the water level was slow because water level down was also at the highest permissible level

Earth dam,

class 1

Change in the amount of seepage

Wet spot was found at the dam slope. Inspection hole revealed a spring.

A reverse filter was built.  

Tailings dam,

class 2

Water level rising exceptionally high

Decant well had clogged. Water discharged through the overflow pipes.

Outside help was needed for washing the well.

Tailings dam,

class 2

Water level rising exceptionally high

Decant well was broken because of the ice. Water flow into another pond in which water was also very high.

Spare decant wells were taken in use. Outlet pipes were equipped with valves as safety precaution.

Tailings dam,

class 1

Water level rising exceptionally high

Inlet pipe had piled up material so that flow was directed out of the pool. Snow made it difficult to observe the problem.  

Pumping was stopped. The place of the overflow was raised with moraine.

Hydropower dam, class 2

Fire

There was a fire in the powerhouse generator.

Fire brigade put out the fire. Power plant was out of service for investigations.

Waste dam,

class 3

Probable leakage

The drain of the safety pond indicated a leakage.

Excavation was made to reveal the reasons. The sewage water pipe was broken during the investigations. Plant was put to a halt.

 

2014

Thirteen dam safety incidents were reported to the dam safety authority in 2014. Four of these incidents were caused by a power cut. And three of these four were caused by the same storm. Here are short descriptions of these thirteen incidents.

DESCRIPCION OF THE DAM

CAUSE FOR THE INCIDENT

DESCRIPTION OF THE INCIDENT

REPAIRWORK

Coffer dam, class 1

Underdimensioning of the supporting beam

A coffer dam collapsed when they were lowering the water level behind the dam during the commissioning.

Redesign of the coffer dam and building process

Coffer dam, class 1

Underdimensioning of the supporting beam

A beam twisted as the coffer dam was in use.

Installing supporting structure

Hydropower dam, class 2

Power cut

A tree tore down power line during a storm. It was not possible to use the dam gates.

Backup system was brought into use for the time of the repair work.

Hydropower dam, class 2

Power cut

A tree tore down power line during a storm. It was not possible to use the dam gates.

Backup system was brought into use for the time of the repair work.

Regulating dam, class 3

Power cut

A tree tore down power line during a storm. It was not possible to use the dam gates. The upper water level dropped under the normal level.

Gates were closed manually.

Regulating dam, class 2

 

Breakage of the gate mechanism

Thunderstorm damaged the lifting mechanism of the flood gate.

The mechanism was repaired.

Hydropower dam, class 2

A settlement in the earth fill dam

Empty space had been accidentally left under the old wooden structures.  the wooden structures had softened and they yielded.

The pit was filled.

Hydropower dam, class 1

A settlement in the earth fill dam

An outlet pipe of a pump house goes through the dam. The pipe had broken and it was leaking

The pipe was repaired.

Tailings dam,
class 2

Piping

Sludgy water was noticed in the drainage collector.  

The discharge pipe was relocated further from the dam structure. Afterwards the dam was opened for the assessment of repairing need. 

Levee, class 1

Damage to the dam structure

Pipeline for a new house had been installed through the dam (without a permission).  

The pipeline was relocated and damage was repaired.

Hydropower dam, class 2

Machinery breakage

Hydropower machinery (oil distribution casing) was broken during the spring flood.

Flood gates were used instead of the turbines. T machinery was repaired. 

Hydropower dam, class 2

Water level rising above the HW limit  

Machinery was tested during the maintenance. The incident was caused by human error.

Water level was lowered as soon as the fault was discovered.  

Waste dam, class 3

Water level rose close to emergency HW

Warm weather and warm water caused a huge need for cooling water.   

Dam was heightened and the monitoring was intensified and some water was released to another bond.

 

Published 2015-11-17 at 7:04, updated 2019-09-09 at 9:10

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