by Jamie Boswell CEng MICE, Jeff Bowman CEng MICE & Michael
(published October 2018)
structure view from the River Wear - Courtesy of Mott
installation of new eel and fish friendly screens at
Northumbrian Water Group’s (NWG) Lumley Raw Water Pumping
Station (RWPS) was the culmination of collaborative working
between multiple stakeholders, to transform the screening
methodology in an environmentally sensitive location. The final
solution provides an option that presents immediate
environmental benefits to aquatic life, with low on-going power
consumption, and significantly reduced operator requirements for
years to come. The project is part of a batch of four schemes,
all installing purpose-built fish-exclusion, fish recovery and
return screens at existing pumping stations across the
Lumley Raw Water Pumping
Station (RWPS) is a river intake situated on the River Wear,
close to Chester-Le-Street. The RWPS is used to abstract up to
57 million litres of water from the river per day to transfer
flows to Lumley WTW where the water is treated.
The Eels (England and
Wales) Regulations 2009, came into force in 2015. They require,
‘owners of water undertakings and other abstractions to fit
suitable screens or equivalent eel exclusion measures’, with
suitability defined in the Environment Agency’s (EA) Eel Manual.
The existing screening methods were non-compliant and beset with
maintenance and operational issues.
NWGs notional solution
identified a traditional screen used elsewhere in the region,
constructed within the intake structure and requiring individual
chutes to separate and return to the watercourse, entrained
aquatic life and river debris. This chute for the fish and eels
would have required landscaping of the downstream river bank,
which is densely covered with invasive plant species.
render of the steelwork superstructure - Courtesy of MMB
NWG awarded an
investigate and define (I&D) contract to Mott MacDonald Bentley
(MMB). During the I&D phase, MMB gave recommendations for new
screening facilities at Lumley, Warkworth, Broken Scar and
Blackwell Pumping Stations, as well as recommendations for
upgrades at Pont and Wellhope Burn.
In September 2016, MMB
was awarded a design and construct (D&C) contract worth c.£6m to
carry out the improvements on six sites, with works programmed
to continue until March 2020. The first project as part of the
initial phase of works requires upgrades at Lumley RWPS.
The main project
stakeholders for the scheme were Northumbrian Water Group, who
own and operate the pumping station and the Environment Agency
(EA), who provide screening guidelines, environmental permitting
and ultimately, compliance certification. MMB consulted and
worked closely with all stakeholders from an early stage to
ensure that any options considered the wider benefits to all
The preferred solution
entailed installation of 4 (No.) environmental fish exclusion (EFE)
screens within the flushing flow of the river. To accommodate
this, a new steel support structure was installed on top of the
existing concrete intake, constructed in 1975.
The existing intake was
inspected to confirm its structural integrity and the
performance of the existing substructure and new steel
superstructure was modelled for 1:1000-year flood conditions.
installation - Courtesy of Mott MacDonald Bentley
The RWPS is situated in
the lower reaches of the River Wear, 5km upstream of the tidal
limit. The station experiences a wide range of flow conditions,
with significant floods occurring on an annual basis. The
importance of Lumley RWPS in NWG’s strategic network meant that
the station had to remain operational throughout construction.
To ensure compliance, the
screens needed to be 8m in height, and apertures in the
supporting structure needed to be sealed to less than 2mm, to
prevent flows from short-circuiting the screens. Both during
construction and operation, the structure would be subject to
forces changing in magnitude on a daily basis.
The requirement for the
screens to be positioned within the flushing flow during all
conditions meant that the centre of gravity was close to the
front of the structure as each of the proposed EFE screens
weighed 3 tonnes. Construction of a new foundation immediately
in front of the intake was ruled out early due to the health and
safety risks associated with use of a cofferdam and NWG’s need
to continually abstract water.
The steelwork designers
were challenged to develop a solution that could be cantilevered
from the existing structure, enabling all fixings to be
installed above the waterline. To accurately determine the
effect of hydrodynamic forces, the proposed superstructure was
modelled using Fastrak Building Designer and was subjected to
various load combinations.
A laser scanned point
cloud survey was used to create a model of the existing
structure in Revit, allowing the steelwork designers to produce
an accurate 3D model of the solution, well in advance of
construction. The model was an excellent communication tool for
D&C, securing planning permission, community liaison,
fabrication, and sequencing of the works.
The river bank
immediately upstream and downstream of the intake slopes steeply
into the river and is densely covered with invasive plants,
precluding access to construction plant. Access route
constraints meant that cranes were limited to a maximum possible
lift of 5 tonnes. This constraint was identified during design
and the steelwork was carefully designed to be lifted in place
in sections of acceptable weight, reducing the requirement for
works at height over water.
Courtesy of Mott MacDonald Bentley
The project’s key driver
was to improve eel stocks within the River Wear – however, the
complete change in screening approach will significantly improve
aquatic biodiversity within the river, particularly at higher
The previous screening
regime at the pumping station used small diameter strainers
creating flow velocities over 1.2m/s, entraining fish and eels
of all life stages seeking refuge from the river flow in the
pumps and strainers. The new exclusion system prevents fish and
eels from being entrained, with velocities through the screens
reduced to less than 0.25m/s even in worst-case conditions;
lowest river level, maximum abstraction.
Using EFE screens ensures
no requirement to capture and release entrained fish and eels,
reducing trauma. The screens were chosen to meet current and
anticipated regulations for other fish species, ensuring ongoing
compliance in the ever-changing environmental landscape.
Cleaning of the existing
strainers required regular operator input, particularly during
storm conditions. The use of EFE screens ensures that the
process is completely automated and the screens only operate in
high silt conditions, with each screen anticipated to run for
less than 90 minutes per day. The screens are driven by highly
efficient motors, negating the requirement for booster pumps for
The environmental impact
of construction was considered throughout design. By modifying
the design to remove the need for a cofferdam within the river,
there were no significant works below the waterline and the EA
permitted the works to proceed without any formal silt control
Steelwork superstructure - Courtesy of Mott MacDonald
Approach to health and
sessions were held with NWG’s operations and maintenance team to
identify current procedures and develop the design with future
requirements in mind.
Working with Northumbrian
Water, MMB has developed a step change in its thinking in terms
of screen technology, moving away from maintenance-heavy
traditional chain driven systems to multi-sprocket driven
modular engineered polymer band screens. The screens feature
interchangeable plastic screening panels with no moving parts
below the water line. These should see reduced operational and
maintenance interaction, compared to traditional chain driven
systems, which are susceptible to chain failure and require
almost full disassembly in order to bring back into service.
maintenance undertaking was removal of debris from the intake
bays, requiring significant confined space work with single
point river isolations. The design confirmed at an early stage
that this requirement was unnecessary, and all maintenance could
be carried out from the deck level.
Close liaison between D&C
staff throughout design ensured that buildability was always
considered and the move to a cantilevered structure was agreed
at an early stage, as the use of a cofferdam had been identified
as by far the highest risk construction activity, both in terms
of safety and environmental impact.
There were no injuries of
any type or environmental incidents in over 11,000 hours worked,
despite the sensitivity and visibility of the site.
A strong safety culture
drove these results, evidenced by over 100 proactive H&S and
environmental reports during construction by operatives,
subcontractors, and visitors to site. To monitor, verify and
maintain these high standards, regular health, safety and
environmental audits, inspections and behavioural discussions
superstructure - Courtesy of Mott MacDonald Bentley
Programme and budget
The D&C contract
commenced in September 2016 with enabling works commencing in
June 2017. Construction works were completed in December 2017.
The site has been compliant since November 2017, significantly
beating the deadline of March 2018.
Planning meetings were
held between, designers, client, construction teams and key
suppliers early within the delivery phase. Potential ‘blockers’
were identified and confronted within design, reducing the
potential for standing time on site.
Key relationships were
formed between the steelwork and screen suppliers, ensuring all
four screens were comfortably installed ‘cartridge style’
without on-site modifications.
The D&C contract was
delivered for £1.15m, beating the target cost estimate of
£1.25m. The savings can be attributed to strong collaboration
between all parties, identifying key risks and constraints and
confronting them as a team.
Lumley Raw Water Ppumping
Table of designers, contractors and suppliers
Northumbrian Water Group
Mott MacDonald Bentley
Mott MacDonald Bentley
The Shadbolt Group
Fish exclusion screens
Intralox LLC Europe
The Deritend Group Ltd
Intelect (UK) Ltd
IDEC Technical Services
Northern Divers (Eng) Ltd
MMB and NWG worked
together to identify key local community stakeholders and
commenced engagement early to determine the final design of the
security features and screenings discharge arrangement.
The council, rowing, and
angling clubs were engaged ensuring that both construction
works, and the final solution would not impart any negative
effects to river users. Rendered 3D visualisations were utilised
to aid in communication and demonstrate the proposed sequence of
The new screens will
greatly reduce the amount of fish and Eel entrained at the
pumping station, and will remove a significant hazard to
migratory species, particularly sea trout, eels, and salmon,
with the benefits felt along the entire 100km length of the
river, from source to sea. Additionally, the screens will
improve resilience of the water supply to Lumley WTW.
structure as viewed from the bank - Courtesy of Mott
The other 5 (No.) sites
3 (No.) new fish recovery
and return (FRR) screens will be installed within the existing
wet wells at Blackwell RWPS between May and August 2018. The
installation and commissioning will build upon lessons learned
at Lumley RWPS.
Warkworth and Broken Scar
RWPS will then follow on in 2019 and 2020.
Each of the six Eel
Regulation schemes within the wider project require significant
engagement from stakeholders, particularly given the ecological
impact of the permanent and temporary works at each of the
sites. Strong collaboration between the Mott MacDonald Bentley
and Northumbrian Water Group core team has been central to
ensuring that the works have been able to continue without any
disruption to supply.
and publishers would like to thank Jamie Boswell, Design
Lead with Mott MacDonald Bentley, Jeff Bowman, Contracts
Manager with Mott MacDonald Bentley, and Michael Walsh,
Project Manager with Northumbrian Water Group, for providing
the above article for publication.