CASE STUDY

Coppermills WTW

Construction of 12 Rapid Gravity Filters using an off-site ethos to maximum effect.

Coppermills WTW is located in North London

adjacent to the Walthamstow Wetlands and a 300-

acre reservoir system providing approximately one

third of London’s drinking water, supplying North

and East London primarily and to the wider London

water supply system.

EPS undertook the off-site construction of 12 filter

flumes in stainless steel which would traditionally

have been built on site in cast-in-situ concrete and

the main two filter feed pipework galleries which

would otherwise have been built on site. The site

labour reduction brought about was 92% in this area

with Zero accidents.

PROJECT COST

£46 Million

PROJECT START DATE

Oct 2014

CAPACITY

480 MLD

CONSTRUCTION PERIOD

8 Months

Project Background & Scope

CASE STUDY

Coppermills WTW

8 million litres per hour

300m additional surge capacity

12 new Rapid Gravity Filters with a volume of 95m2 each

10 men installed in 4 days 95 tonne of equipment

Original Civil programme 12 men, 24 weeks

Target programme 10 men, 3 weeks exceeded

95% reduction on deliveries

The treatment plant itself was built during the

1960s and completed in the early 1970s and now

processes 560 million litres of water each day.

Strategically and economically, this is arguably the

most important source of London’s water, serving

areas from the Financial district in the East to the

Government district in the Centre.

A potential challenge to capacity of the supply

from Coppermills was identified by Thames Water

in that effective capacity was potentially reduced

during periods of Algal bloom due to the increased

work load this placed on the 24 Rapid Gravity

Filters, which could restrict output to 380MLD

limiting headroom in the London Supply Demand

balance. As a solution, it was decided to build an

additional 12 Rapid Gravity Filters to augment the

existing infrastructural capacity on site.

New works required which were to provide an

additional 200MLD Rapid Gravity Filter process in

a fully automated process system which was to be

integrated so as to fully function in tandem with

or independently of, current site Rapid Gravity

Filters. Filters had to be capable of operating at

8 million litres per hour with one filter offline for

backwashing.

The final project scope agreed was to provide new

High Lift Pumping, provide 300m additional surge

capacity and build 12 new Rapid Gravity Filters

with a volume of 95m2 each on the North Western

part of the site.

Supply Chain Integration

After the initial engagement period and selection of

contractors, monthly collaboration meetings were

held led by the SMB design team with all of the

individual contractors present as required, the Thames

Water internal communication system was used for

communication for tracking and accuracy purposes.

At an early stage a discussion was had as to which

supplier was best for task on each part of the

construction. Based on an EPS suggestion, the

possibility of building tank internal H Flumes which

would have ordinarily made in cast in situ concrete

from steel was explored. This solution, after careful

consideration, was accepted and built.

The use of stainless steel for the H Flumes channels,

while technically challenging, provided significant

programme benefits, was cost effective, increased the

quality of the finished product and greatly reduced the

project’s carbon footprint.

Detailed collaboration between SMB, Leopold, MWH

and EPS allowed the detail design of these innovative

H flumes to be completed with a final design that was

both more cost effective and of higher quality than a

conventional concrete solution.

Digital Design & Off-site ConstructionThe Coppermills Water Treatment Works Rapid Gravity Filter plant extension employed digital design and Offsite construction widely and to great effect. Laser scanning of the tank and civil structures was carried out by SMB to confirm the exact dimensions of interfaces between civil and mechanical structures and to allow for accurate bespoke production minimising installation difficulties and predicting where customisation was required in advance.

A post production scan by MWHT of the fully assembled pipe rack allowed for increased surety during installation with the use of Airsquire software to compare ‘As Designed’ models with ‘As Built’ structures. This coupled with precise on-site location tools used by EPS reduced installation times significantly.

EPS began H Channel production simultaneously to site construction in our workshops in Mallow enabling delivery to site and installation a first of kind H channel in December 2018 directly on completing of the Concrete tank installation. Estimated installation times was subsequently halved by lessons learned during the first of kind installation. Full FAT testing was carried out on the H Channels in EPSs workshops in Mallow allowing for a factory finish on the site installation.

The North and South Pipework production took place between September 2018 and March 2019 in the EPS factory in Mallow. Initial designs which simplified installation and on-site assembly were altered in September to allow for electrical services to be fitted in Mallow. This required that rather than building a rack module and a separate access model as originally envisaged the rack was split lower down to allow all electrical services to be contained in the top section of each model.

Large bore (up to 1200mm) Stainless Steel and Skochkote pipework was fabricated and installed around client supplied equipment all of which was fitted, assembled and pressure tested in EPS Mallow in advance of being split down for delivery. Each Piperack was delivered in 6 sections, the 3 top sections including access and electrical services by low loader and the lower sections on flat beds trailers.

Added value through DfMA

CASE STUDY

SMB confirmed that each of the H flumes was

installed on average by 3 men in under a week,

using standard concrete construction methods, 12

men would have been required for 4 weeks. This

provides for a 94% reduction in site labour.

As each flume was delivered in a single load SMB

list a 95% reduction in deliveries compared to

building these on site in concrete.

Lifting operations, which statistically are the most

dangerous site activity, were reduced to 2 per cell.

Using traditional methods, a crane would have been

required for the full 4-week H flume install duration.

The flume design required Zero working at height.

Challenging traditional thinking in this project led to

benefits way beyond the specifics mentioned above.

The project met all of Thames Water’s benchmarks

as laid out in the statistics on the right.

Coppermills WTW

SAFE DAYS

890

PRECAST CONCRETE

3400 Tonnes

CARBON

40%

SAVINGS ON SITE PRELIMS

€6.5 Million

LABOUR USED ON SITE

92%

PROGRAMME

18 Month

WORKING AT HEIGHT

90%

installed in 18 weeks