It was celebrations all round for a team from Glanville Environmental and South West Water recently.
This followed an announcement that an alternative (no dig) solution they had deployed to refurbish large manhole chambers on a major project, had been awarded a prestigious ‘Pure Award for Innovation’ by South West Water.
St Ives has a large gravity sewer catchment that ends at Porthgwidden, flows are then pumped up to nearby Carbis Bay via a rising main.
At the point where the flows reach the top of the hill, gravity takes over. Flows are then channelled through a large 750mm diameter concrete sewer pipe through Carbis Bay and onward to Hayle Sewage Treatment Works.
Over the past 30 years the 750mm diameter concrete pipe had become the victim of Hydrogen Sulphide (H2S) corrosion.
This is produced by the natural contact of sewage and saline (sea water) and had weakened the pipe and manhole chamber walls.
Due to risk of structural failure, a solution was designed to rehabilitate the system, returning the structural integrity and protecting the asset from future degradation.
The options for repair would mean excavating and replacing the chambers and bases with HPPE material that would be resilient to withstand heavy Hydrogen Sulphide attacks into the future.
This method was originally chosen, but Glanville and their client, South West Water, had reservations on its suitability.
The concerns were based on the time and road space it would take to excavate the ground and replace the chambers.
Mike Child, Project Engineer, at Glanville Environmental said, “Having considered the more traditional sewer rehabilitation methods, we consulted our client (South West Water), with a view to looking into a more innovative solution to address the problem.
The solution ideally needed to shorten the duration of the project, offer the best possible outcome for our client, road users and the communities of St Ives and Carbis Bay.”
Using their network of industry contacts, Glanville Environmental opened discussions with Hermes Technologie, a leader in providing innovative sewer rehabilitation solutions.
Following a site visit and information gathering on the condition of the chambers and H2S levels, a specialist cementitious grout was recommended as the best material to use.
This particular material was relatively new to the industry, having never been used on the South West Water sewer network, and to date, has only been used on a few hundred chambers across the UK.
In comparison, this product is used extensively in Europe on tens of thousands of chambers every year.
The method for applying the grout was also important.
Through consultation with South West Water, Hermes Technologie and a sub-contracted installer, it was decided that spraying the material onto the surface of the chambers was the way forward.
Victoria Hutchins, Project Manager at South West Water said, “We challenged Glanville to find a more efficient method for lining the manholes and they suggested a sprayed cementitious membrane.
This method, whilst widely used in Germany, is relatively new to the UK. Once we had reviewed the process and satisfied ourselves that it was suitable we were keen to undertake a pilot.
This work will now be monitored and, if they perform as anticipated, we will look to roll this method out more widely.”
The manhole rehabilitation took place as planned.
The spraying head sprays at right angles to the chamber wall and covers 360 degrees. This meant that the work was done via the manhole cover, from the surface, with no need for confined space entries.
The programme and footprint on site also benefitted from this work, as closing the road through Carbis Bay was causing large levels of disruption to road users, businesses and their customers.
It was estimated that by using this method, the time spent on the manhole chambers reduced by approximately 50%.
In real terms, this meant the whole project was completed earlier than planned, which was well received by local residents and businesses, road users and the client.
James Blake, Civils Delivery Manager, at Glanville Environmental, said “We are delighted to have won this award.”
“At Glanville Environmental we pride ourselves on keeping abreast of new technologies, evaluating the latest materials and trying out any new methods and techniques available to us.”
“It really is a testament to our company’s forward thinking and our total commitment to deliver the best possible service to our client and their customers.”
”The South West Water, Pure Awards, are much valued accolades within our industry and we are all very proud of this achievement.”
Pictured below are (left) James Blake and (right) Mike Child.