Swansea Dam update - Have your say at TasWater

Swansea Dam update
September 2016
The plan to fix the Swansea Dam
This project has many steps and will involve multiple
agencies and contractors, TasWater expects these steps may
create further delays. Our plan accounts for this by taking a
flexible approach.
TasWater must empty the Swansea Dam for repairs. This
means we need to find a temporary alternative water supply
for Swansea. Our work to date has determined the two best
available options are:
• Temporary storage for drinking water,
while repairs are done
• A permanent connection to the new Melrose Dam
built by Tasmanian Irrigation.
TasWater is pleased to inform the Swansea
community that we intend to fully repair the
seepage from the Swansea Dam by Spring 2018,
but the exact timeline depends on many things,
including having normal rainfall patterns on the
east coast during the next two years.
Fixing a dam is difficult and there are no quick solutions,
but the community of Swansea has been very patient with
TasWater and we acknowledge it has taken too long to find
a solution.
Although there have been delays, TasWater has been working
methodically on this project, with a focus on the community’s
safety and the security of Swansea’s water supply.
TasWater’s approach means:
• The dam is not a threat to the town’s safety
• Swansea’s water quality continues to meet
Australian Drinking Water Guidelines
• TasWater can now present our plans to the
community with confidence.
www.taswater.com.au | Phone: 13 6992
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TasWater has reached an agreement with Tasmanian
Irrigation to connect to the Melrose Dam, currently under
construction. Their irrigators will then allow us to temporarily
draw water from the Swan Valley Irrigation Scheme to
Swansea’s water treatment plant.
While both options will give TasWater the time we need to
repair the Swansea Dam, there are good reasons for working
with Tasmanian Irrigation:
• A permanent connection to the Melrose Dam provides
an emergency back-up for Swansea if it is ever needed
• A permanent connection is the best option for avoiding
water restrictions during repairs of the Swansea Dam
• Building temporary storage is expensive and working
with Tasmanian Irrigation provides a significant saving.
As progress on the Swan Valley Irrigation Scheme continues,
TasWater will work with Tasmanian Irrigation to assess the
scheme’s readiness. If the scheme is not ready when needed,
TasWater will instead build its own temporary storage. This
option would be more likely to lead to water restrictions, in
the event of another period of dry weather.
Either way, TasWater’s goal is to have an alternative water
supply for Swansea available by late 2017 and to have the
Swansea Dam fixed by Spring 2018, at the earliest.
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Swansea Dam
Dam repair timeline
Dam safety and repair
All dates are provisional and many factors, including weather,
will ultimately determine the timeline for repairs.
The Swansea Dam was designed as a raw water source that
would be the envy of many towns. Once it is repaired it will be.
Late 2016
Project to construct a permanent
‘toe drain’ at Swansea Dam base
to capture some of the current
seepage and return it to the
reservoir. Scoping of possible
temporary storage
Seepage was detected shortly after the Swansea Dam was
completed in 2009. While every dam seeps to some extent,
the extent of seepage was deemed a problem. After an initial
investigation, a decision was made to lower the water level in
the dam. This reduces the pressure on the structure. TasWater
has continuously monitored the seepage problem to ensure
the dam remains safe to operate.
March–April 2017
TasWater and Tasmanian Irrigation
to determine readiness of Swan
Valley Irrigation Scheme.
We believe most of the seepage comes from an area in the
reservoir where deep excavation was used to access materials
for dam construction, but leaking may also be occurring from
other areas.
May–September 2017
Design and tender process for
temporary storage (if needed).
June–August 2017
Filling of Melrose Dam.
December 2017
Swan Valley Irrigation Scheme
supplies water to Swansea water
treatment plant.
If temporary storage is needed,
Oct 2017–January 2018 water restrictions are likely to
begin.
January–June 2018
Swansea Dam is emptied and
repaired.
Spring 2018
Swansea Dam refilled.
www.taswater.com.au | Phone: 13 6992
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Once drained, TasWater will be able to complete its
investigations of the extent of the problem and the repairs
needed. The concept is to construct a clay liner within the
dam, made from layers of compacted clay. This process is
partly reliant on the dam drying out and it is not yet clear
how long this may take.
Though we believe the main dam embankment is sound,
TasWater will also conduct a geotechnical investigation of the
embankment to see if any work is required.
Why has it taken so long for TasWater
to repair the Swansea Dam?
TasWater acknowledges we have taken too long to address
this problem.
We face a huge challenge in Tasmania. According to a
benchmarking survey against similar water utilities in
Australia and New Zealand, while Tasmania has just three
per cent of the population, we have 31 per cent of the water
and sewerage assets. That is the number of water treatment
plants, sewage treatment plants and dams we have to manage
for this small island. And TasWater is incredibly busy. In
2015–16, we started 466 capital projects, completed 270 of
those and we have another 305 projects continuing.
TasWater must spread its available resources throughout
the entire state, spending money and effort where it is most
needed.
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Swansea Dam
How much water does Swansea need?
On average, Swansea uses around 200 megalitres of water
every year and up to one megalitre per day during the peak
tourist season. The Swansea Dam has a capacity of more than
400 megalitres, or enough to sustain Swansea for two years
from the reservoir alone. The current water level in the
Swansea Dam would only last four months.
Is there enough water in the Swan River
to supply both TasWater and the Swan
Valley Irrigation Scheme?
Yes.
TasWater is licensed by the State Government to draw water
from the Swan and Meredith rivers. The conditions placed on
our licence put a priority on the supply of drinking water from
the Swan River, above all other uses.
TasWater’s annual extraction from the Swan River is less than
one per cent of its annual flows. On average, this is around
200 megalitres per year. In comparison, during the drought
of January 2016 more than 30,000 megalitres of water passed
downstream from TasWater’s extraction point.
Will there be more water restrictions
for Swansea?
Possibly.
The water restrictions first introduced in January 2016 were
the result of drought. Swansea is supplied with drinking
water from the Swan River. The Swansea Dam is a back-up
to prevent the need for water restrictions but currently that
back-up is not big enough. If there is another drought before
the Swansea Dam is repaired, then restrictions may be
needed.
Secondly, if TasWater has to construct temporary storage it
will be much smaller than the existing dam, which makes
water restrictions more likely.
Based on a careful analysis of seasonal rainfall figures,
measurement of flows in the Swan River and the amounts of
water already allocated for irrigation, TasWater is confident
there should be more than enough water for Swansea, but
ultimately all options depend on rainfall and in the event of
another drought, water restrictions will be needed.
www.taswater.com.au | Phone: 13 6992
GEN 2016 - 146
TasWater also has a licence to extract water from the Meredith
River in winter and spring if flows are high enough, but there
has only been one instance of this in 2010.
Similiarly, Tasmanian Irrigation is licensed to pump water
from the Swan River into a new 2,000 megalitre dam near
Cranbrook on the Melrose property. The provision of any water
to TasWater falls within that allotment and is not extra water
taken from the Swan River.
If the Swan River slows or stops flowing, as it did in 2013 and
2015, this will not be due to TasWater or Tasmanian
Irrigation’s activities, but due to drought.
Will the people of Swansea pay more for
their water during these repairs?
No.
While TasWater’s fees and charges do change over time, the
cost of TasWater’s repairs to the Swansea Dam will not be
passed on to the people of Swansea.
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Swansea Dam
History of the Swansea Dam
The history of the Swansea Dam coincides with a nearly
constant period of reform in Tasmania’s water sector. This
dam’s construction was started by Hobart Water, then
managed by Southern Water and TasWater must now fix it.
While not an excuse for delays, this near-constant period of
change, and especially of staff turnover, has made it difficult
to maintain a consistent approach until recently.
2008
Hobart Water and Glamorgan Spring Bay Council
launch the Swansea Water Project, to end Swansea’s
permanent boil water alert by building a new dam
and water treatment plant.
DPIPWE grants water licences for the Swan and
Meredith rivers.
2009
Southern Water formed and takes control of project.
Construction begins at the former site of a small farm
dam, but heavy rain and flash flooding cause delays.
Shortly after filling, Southern Water workers detected
seepage downstream of the dam wall.
2010
Decision made to near-empty the dam.
Water treatment plant commissioned.
Boiled water alert lifted.
2011
2012
Following a comprehensive review, Southern Water
decides to continue operating dam at low level to reduce
safety concerns.
Geological review determines previously unknown
complex nature of underlying geology.
Concept designs for Swansea Dam repair work.
2013
Ongoing negotiations on design and sourcing of
materials slows project.
TasWater is formed.
Dam was reassessed against dam safety guidelines for
its lower operating level and was found to be safe.
2014
New drainage has been constructed around the dam
to prevent unwanted water from entering the dam,
maintaining the desired level.
2015
Ongoing strategic review of dam operations, including
reassessing safety measures, storage levels and
prevention of contamination.
2016
Swansea is placed on Stage 2 water restrictions for the
first time.
www.taswater.com.au | Phone: 13 6992
GEN 2016 - 146
Keeping you informed
TasWater will continue to provide updates to the Swansea
community as the project moves ahead, including another
newsletter before the end of the year. You will also be able
to follow the project via TasWater’s YourSay website, at
www.yoursay.taswater.com.au.
If you have questions about the project, you can contact
Community Engagement Officer Trent Swindells on 6237 8523
or via [email protected]
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