The Menagwins sewerage catchment was experiencing chronic issues with winter ground water infiltration, causing prolonged spills from a CSO.
Discharges from the CSO had the potential of serious impact to the local ecology, which in turn could lead to the risk of EA enforcement should that impact be realised. Action was required to address this issue.
A number of areas in the catchment were identified as requiring rehabilitation to remove infiltration and these were all successfully addressed.
One particular area, however, was not without its challenges. This scheme required an innovative solution, one that challenged convention and defied gravity!
The Sawles Road sewer pipe was experiencing severe infiltration problems.
But because of the location and the confined spaces involved, access to the manhole where the liner was to be inserted into the mains system (in the conventional manner), to the next manhole over 100 metres away, was not possible.
The project team looked at the options and the decision was made to run the liner upstream.
Although this method has been used within the industry, this was a company first for Glanville’s.
Over pumping was set up to control the flow of waste water but the real challenge was how to control the infiltration entering along the length of the sewer being lined.
This barrier was overcome by erecting a scaffold tower and draping the liner from the top (pictured).
The liner was then carefully placed into the mouth of the manhole and water pumped into the trunk to create a ‘head of pressure.’
This exercise also involved working out how high the scaffold needed to be to ensure the pressure was sufficient enough to push the infiltration flow back towards the pumps as the liner slowly progressed upstream.
In effect creating a moving dam.
It was critical to maintain the correct head of pressure throughout the lining process until it was completed.
Once the ‘tail end’ of the liner reached the upstream manhole the curing process was started.
The liner was successfully cured within a six-hour period.
The Glanville Environmental Site Agent, Adam Kelly, said, “This was a challenging project that took place in a difficult and restrictive location.
However the team’s expertise and efforts have paid off, as the project was a complete success, significantly reducing the infiltration flow into the mains by approximately 25%, mitigating the chances any future spills and possible pollution issues.”