On a recent project, Galliford, Costain and Atkins, which form the GCA Consortium working with United Utilities under the United Utilities Integrated Alliance (UUIA), undertook a major refurbishment of and extension to the Liverpool Waste Water Treatment Works (LWWTW). The new £200 million extension, which will keep the Mersey clean, is now half-way through its construction. When complete, the new plant at Wellington Dock will serve around 600,000 of Liverpool’s population, taking away sewage and treating it to the highest standards, before returning it to the river.
The extension is part of some £3.6 billion being invested by United Utilities across the North West to improve water quality and the environment by 2015. By upgrading the existing works and constructing a sequential batch reactor (SBR), the treated water leaving the new plant will be cleaner and greener, helping the continuing rejuvenation of the River Mersey and ensuring it meets strict European standards for water quality.
The construction site, one of the biggest on Merseyside at the present time, is a hive of activity. At its peak around 350 people will be working on the project. The completed plant will be able to cope with 11,000 liters of wastewater per second.
Prior to the expansion project, within the plant the untreated wastewater entered via gravity flow at 17 m deep where eight, 800-mm diameter direct-fed pumps transferred the flow into the treatment works near ground level.
The pumps were fed by an open channel that split into eight sections of 800-mm diameter pipe to directly feed the existing pumps. Part of the overall project involved refurbishing the pumps and this also brought to light the feed pipework and a need to renovate this to extend the overall life of the plant and assist with the overall upgrade.
Basically, the existing cast in pipes were no longer in a sound condition, having been installed in the 1980s. Due to salinity levels and debris in the incoming sewer they were reaching the end of their life and starting to rupture.
The project team, by working together, achieved an excellent delivery performance in environmental and safety management on a complex scheme.
The existing pipes protruded from the face of a concrete wall by approximately 800 mm. It was believed these pipes were no longer structurally sound. So, the first task to be undertaken was to cut back the existing pipe to the face of the concrete wall structure. It was then the intention to install a wall coupler that would bolt to the face of the wall. The wall coupler was to be encased in concrete. A new spool piece and valve would also be installed to marry up to the existing pump.
The program was potentially to have iLine Technologies, come in as the specialist lining contractor to install a CIPP liner after the new coupler had been established.
While it was believed that the existing pipe internal diameter was circa 800 mm, it was not possible to exactly determine the diameter because the pipe, being a live sewer, meant that iLine could not get to the inside of the pipe. This also meant the precise internal condition of the pipe was unknown.
The eight pipes in question were at the bottom of the channel, which was 17 m below road level and there was no vehicle access to the bottom of the well. A further limitation was that access to the valve side of the pipe was only moderate, with only enough space for two people and small tools to be utilized.
Access to the other side of the pipe was ‘technically’ possible. However it was not great as this was the inlet channel from the main sewer and therefore came with a significant high risk factor, a requirement for confined space access and working etc.
The deep channel was constantly full feeding the 8- x 800-mm diameter pumps. Early involvement started between iLine Technologies and GCA in early June 2013, some five months before actual construction work took place.
This early involvement meant that protection system and rehabilitation systems could be planned and established to meet the following potential obstacles during the works which included:
• Flexibility to allow for possible changes in diameter during the construction phase
• A quick to install system given the tight time scale requirements during the construction works
• A structurally sound system that could withstand negative pressure that would occur during pump shut down or during back washing
• A ‘one piece’ system that would cover the complete length of the renovated pipeline
• An end sealant to prevent any tracking of water between the host pipe and renovation system
The benefits of early inclusion of all parties and stakeholders during the planning phase had many benefits to the project when it ultimately took place. These benefits included early establishment of a regular program of management meetings that ensured all parties were fully ‘up to speed;’ short communication lines, which meant that decisions were made swiftly; a ‘one team’ mentality that allowed for shared ideas and a high regard for safety was instilled in all those working at the site.
The early inclusion also meant that mock ups and samples of the proposed lining could be provided and trial installations could take place to ensure everyone was happy with what was proposed to be used by way of product.
The Work Site
The project was located in the industrial area and old port of Liverpool and the works were located within the current construction site at LWWTW. The site benefited from a very significant Community Program informing the population of Liverpool about progress and has Facebook and Twitter feeds so a constant information stream keeps interested locals aware of progress.
However, the actual renovation work focused on a major element of customer care, as the eight pumps lifted raw sewerage into the treatment works. So, any disruption to this pumping regime could have had a potentially detrimental effect on the majority of Liverpool’s population. United Utilities, GCA and iLine had to be very mindful of this potential for disruption.
The works required four of the pumps to be decommissioned at a time during the renovation leaving only four working. As such, the works had to be planned to coincide with expected low flow times with constant monitoring to pick up any potential increase in flows.
After several rounds of meetings with all the stakeholders involved, iLine Technologies ultimately proposed the use of an epoxy resin impregnated, ambient cured liner, which would be installed in one length of around 2.2 m long and 800 mm diameter. Such liners could be installed in all eight pump feeding pipes.
The material chosen met several requirements including:
• It met with extensive wear tests undertaken by independent accredited testing houses
• It offered a fully structural design, which was able to withstand negative pressure
• One complete length could be installed with no joints along the installation length
• Site specific installation equipment could be manufactured for this work site
• It offered compatible end sealing epoxy
The use of epoxy liners is well known but what made this project unique was the involvement of several external experts in pipeline renovation. This range of companies included:
• Trelleborg – the material supplier of resin and patches
• Trenchless Consultants – which assisted in the structural design work
• Sika Chemicals – which supplied the end sealant
• Exovia Testing – which provided final testing of the installed material
Prior to the final go ahead and work starting onsite, a sample installation was undertaken on an unused section of what was believed to be a similar pipe to that being renovated. After installation and inspection, final approval for the works was granted.
In November 2013, four of the eight pumps were isolated to allow the rehabilitation work to proceed. In order to isolate the pipework, the flow was diverted further upstream and warning systems put in place to constantly monitor flow levels. Once isolated, the pipes were accessed and cleaning was completed. Detailed measurements were then taken to confirm the pipes’ suitability of the proposed system. Liners were assembled above ground and lowered the 17 m using electric hoists.
The installation equipment had been specifically designed and manufactured in Germany some four weeks earlier to enable program dates to be met. Once in position, the liners were ambient cured for some eight hours each. To enable the program date to be met, round-the clock working was undertaken to ensure successful completion and the minimizing of flood risk.
Once cured, the liners were sealed and testing was undertaken by Exovia prior to the flows being returned. This testing was expedited to gain initial results in just 24 hours. As all liners were installed correctly, and the testing confirmed this, the flows were returned. iLine left site for a period of two weeks before returning to install the other four liners in a similar process.
Perhaps it should be highlighted that a number of firsts were achieved on the project which has allowed others to benefit from the technology. These firsts included:
• Experience of large diameter and long length part-liners has helped innovate the rehabilitation and extension of life for existing pipework
• The innovative design process has allowed liners not normally associated with negative pressure environments to be used
• Bespoke solutions to a specific contract will help develop the envelope for other trenchless opportunities
Overall, the project was complex and challenging but with all parties working together it demonstrated how innovative engineering solutions can overcome difficulties and deliver outstanding results.
According to iLine business development manager John Beech, “While to many casual onlookers this project it may appear to have been just a few short liner patches. In truth, this was something of a complex and challenging operation given the location, depth, size and length of the patches involved. The need to ensure the plant was kept operating whilst the renovation took place also added to the stress. Our team, working alongside and closely with the client teams and the various manufacturers and services involved, has achieved something with this project that few thought was actually possible. All those involved should all be very proud of such an accomplishment.”
This article was provided by iGroup, Northampton, United Kingdom.