new-build reservoir wins a tight battle against time
pump being used to pour the wall sections of reservoir 3 -
Courtesy of Stonbury.
original Outwoods Reservoir (No.1) was constructed in 1882 in
Burton on Trent. An additional Reservoir (No.2) was added in
1962 in response to increased demand on supply. In 2017, South
Staffs Water awarded Stonbury the contract to replace Reservoir
No.1 which has proven increasingly expensive to update and
maintain and was taken out of service in 2016. Water is taken by
South Staffs Water from the Blithfield Reservoir (near Lichfield)
and pumped to the nearby Seedy Mill Treatment Works. Once
cleaned and treated it is then pumped into the network which
includes the storage reservoirs at Outwoods. The water is then
released from the storage reservoirs into the local supply as
needed. The Outwoods supply zone, fed from a number of storage
reservoirs at Outwoods in Burton Upon Trent, includes
approximately 26,000 properties in Burton upon Trent, Rolleston
on Dove, Barton under Needwood, Alrewas, Fradley, and Streethay,
with a combined total average daily demand of 23 million litres.
The project was challenging with a tight programme and proximity
of protected species but achieving the deadline meant ensuring
the supply network can continue to operate to provide a safe and
reliable water supply for current and future generations.
South Staffs had
originally been awarded planning permission for a new reservoir
on the footprint of Reservoir No. 1 in 2014. The project was
delayed due to unexpected work on other schemes within the South
Staffs Water supply network. Whilst the site was still able to
function it was important that both storage capacity and
resilience of the site were increased.
The decision was made to
locate the new reservoir on a greenfield area of the site rather
than in the footprint of Reservoir 1 to reduce the overall
construction programme and meet supply demand. This would not
only enable South Staffs to operate two reservoirs at all times,
but also opened up the opportunity to build an additional
reservoir in the future on the footprint of Reservoir No1. This
investment will help to guarantee the quality and reliability of
the local water supply for the next 100 years, and play a key
part in meeting growing demand from new housing being built in
1 on site after the Ecologist had completed their work -
Courtesy of Stonbury
Excavation and blinding of the base of reservoir 3 and 4
- Courtesy of Stonbury
Stonbury has worked
closely with South Staffs Water for many years and currently
holds a five-year Framework with them for Reservoir
Refurbishment. Nationally, the company typically refurbishes and
repairs around 450 service reservoirs each year; this, however,
is the first time that Stonbury has been made responsible for a
The tender process
involved a high level of optioneering of all possible solutions,
including temporary tanks, steel tanks and GRP tanks. The option
selected was a hybrid solution for a reinforced concrete
structure, which included precast concrete columns and roof
structure. This was deemed to be the most cost-effective
solution in respect of both whole life costs and design life, as
well as one capable of being delivered to the very challenging
completed the detailed design stage, which developed the outline
design, submitted at tender stage. It was decided to split the
reservoir into 2 (No.) 5Ml tanks to speed construction and
enable delivery of one of those tanks into service at the
earliest opportunity and further increasing long term storage
From the date that
Stonbury gained access to the site on the 9 March 2017, there
was a 16-week timeline specified by South Staffs before
commissioning the first reservoir by 1 July 2017.
Reinforcement being installed for base slab of reservoir
3 - Courtesy of Stonbury
Shortly before work was
due to begin, an ecology evaluation highlighted the presence of
Great Crested Newts on a housing development adjacent to the
site. As a European protected species, these animals, their
eggs, breeding sites and resting places are safeguarded by law.
Following a full
ecological survey an environmental specialist and licensed
ecologists were brought to site to work alongside Stonbury to
prepare the site for construction in the shortest possible
Whilst no GCN or nests
were physically found on site the erection of reptile barrier
fencing and hibernaculum ensured the protection of GCN during
and beyond construction.
Formwork being erected for a concrete pour on the walls
of reservoir 3 - Courtesy of Stonbury
Coping with the delay
The steps taken to
protect the Great Crested Newts did, however, have a severe
knock-on effect on the work schedule. A full eight days were
lost on the commencement of excavation work.
An additional element was
also added to the original specification: the construction of a
concrete valve chamber to house all the pipework coming into and
out of the reservoir. This was to be a 12.8m long by 6.8m wide
by 4.85m high structure.
These delays, as well as
heavy rain severely affecting progress on several days,
presented Stonbury with the main challenge of the project. South
Staffs Water agreed to adjust the budget to allow for 12-hour
day and weekend working by the team, with some personnel then on
duty every weekend. The team of people assigned included up to
25 operatives at any one point.
Whilst the team were able
to work the additional hours to bring the project in on time,
accelerating the schedule meant that problems arose with the
timely delivery of key materials.
Concrete pump in position to pour concrete to wall slab
of reservoir 3 - Courtesy of Stonbury
The original date set for
commissioning the reservoir on 1 July 2017 was met, and the
first stage was to fill it for its seven-day testing.
The final inspection was
conducted by the client and the project deemed completed and
handed over. The reservoir was then dropped, re-cleaned, filled
and sampled for return to service the week commencing 10 July,
just 17 weeks from breaking ground.
Ahead of work beginning
on site, Stonbury and South Staffs embarked on a community
engagement programme with local residents. The reservoir is
close to housing, and concerns had been expressed during the
planning process that lorries entering and leaving the site
would have a negative impact on local roads which serve a
primary school and children’s nursery, and which regularly
experience congestion at peak times.
South Staffs Water
pro-actively engaged with the local residents and the nearby
primary school leading up to construction to ensure everyone was
informed and given the opportunity to raise concerns. The
project delivery team also set up a community portal system,
enabling members of the public to follow progress of the scheme
and to communicate directly with the delivery team, express
concerns and ask questions.
Keeping local communities
informed through a community portal has proved beneficial;
especially larger schemes close to housing. As well as providing
a level of transparency that can defuse potentially contentious
situations, it gave Stonbury the chance to keep local people
informed of changes to schedules, and to take on board
constructive suggestions informed by local knowledge that will
help us do a better job.
Feedback on the portal
led directly to changes being made during the works programme.
Early in the project, for instance, concerns were expressed
about the number of lorries making deliveries to the site at
peak times. As a direct consequence, the timings were changed to
spread lorry journeys through the day.
Stonbury were also able
to reassure locals that the final appearance of the reservoir
would enhance rather than detract from the appearance of the
site. Half of the reservoir is buried, so no views have been
detrimentally affected and Stonbury committed to creating a
natural looking, grass-covered mound using all of the top soil
Reservoir: Key facts
10Ml storage requirement.
Chamber size: 27.5m x 34m
x 6.1m high internal measurements x 2 cells.
Overall programme of 28
weeks, including all site works.
Over 300 tonnes of
reinforcement steel used in construction.
Scotchkoted 500mm pipework inside the reservoir -
Courtesy of Stonbury
Community engagement in
As well as providing
information, the community portal allowed a free flow of
questions and answers between the project team and local
residents as this exchange shows:
Gemma (local resident) -
20 March 2017:
Can you explain how the
trial holes are done please?
Barry Chapman (Project
Manager) - 20 March 2017:
Hi Gemma - Thanks for
showing an interest and that is a very good question.
The location of the mains
are known but we don’t know the depth. We have to get an
accurate depth of the main to ensure there is no conflict with
the new pipework that will be connecting into the new reservoir.
It also helps the designer to detail the pipe fittings required
to connect the pipework at different levels.
We estimate the depth of
the main to be 4m. There will be three trial holes excavated at
different locations on the site. A 14-tonne excavator will be
used to dig the holes. As the holes are so deep, a metal box
(called a trench box) will be lowered into the ground as
excavation proceeds. Once the main has been located, an engineer
will plot its location and depth. The hole will then be filled
with the excavated material and compacted. The trench box will
be removed as filling proceeds. Once this is complete, the
second trial hole will be excavated in the same manner. Let me
know if you have any other questions.
support columns and roof planks installed in reservoir 4
- Courtesy of Stonbury
Projects like this always
present challenges but the combination of unavoidable delays and
tight deadlines always create extra problems. Many of the UK’s
service reservoirs are now coming up to their ‘sell-by’ date,
and while refurbishment will always be the preferred option
where technically feasible, replacement will often offer an
economical, long-term solution for clients looking to protect
their assets and ensure continuity of supply into the future.
and publishers would like to thank Stonbury for providing
the above article for publication.