Articles & Case Studies


Posted: Monday 10th November 2008

As part of its ongoing responsibilities to provide and maintain sewer services, client Wessex Water has recently undertaken cleaning and maintenance works covering some 26 operational siphons known as the Bristol Siphon Cleaning and Maintenance project. Working under the guidance of Julian Britton, senior engineer with Wessex Water, the scheme was undertaken by main contractor May Gurney. The project was required to maintain flows through the siphons by removing fat deposits and debris in the siphons and inspect ancillary M&E structures supporting their operation.

Much of the work requires specialist cleaning equipment, techniques and experienced operators to achieve the high level of cleaning necessary to maintain the serviceability of the siphons, so May Gurney employed Glanville Cleansing Ltd as subcontractor for the actual confined space entry and rescue operation and to assist in the cleaning works. The value of the project was some £1.4 million.

Glanville owns and operates a significant fleet of specialist pipeline cleaning systems and specialist tankers which are utilised by confined space certificated and specially trained and highly skilled teams of operators to complete this type of work. The company also provides a range of specialist equipment in support of the man-entry teams including: High-Pressure Jetters, Specialist tankers and water bowsers which are also well-suited to support this type of operation enabling Glanville to achieve very high levels of cleaning with minimum man-entry intervention into the pipelines.

Where necessary all arrangements with regard to keeping residents in the areas of the works informed this was taken care of by the main contractor and Bristol City Council and disruption to the local community, businesses etc was kept to a minimum wherever possible.


In order to complete the cleaning works, a typical siphon cleaning operation comprises a BA- certified, confined space entry team, together with a trained rescue team, arriving on site, setting up of the necessary ‘Chapter Eight’ signing and guarding as required. Barriers are then set up as required around the manhole area.

Prior to making an entry into the siphon, a team briefing takes place between Site and BA supervisors, the BA team and the site Rescue team. A permit to work, method statements, risk assessments and entry permits is then completed and signed before any works are undertaken.

Before any personnel enter the pipeline the manhole cover is removed and a gas monitor is set up. The manhole is then gas tested and all information is recorded on the entry permits. The necessary tripod and winches and other support equipment are then set up at the manhole. The working BA team then enters the manhole and the rescue team is placed on standby in case they are required.

Working within the siphon, silt and debris are removed from the pipeline using a state-of-the-art high pressure jetting unit complete with deep lift vacuum/suction capabilities. When required, the cleaning crew dig out all silt which is shovelled it into the vacuum pipes and all fat is scrapped off the walls and removed in the same way.

Spoil loads from vacuum unit are transferred to 3,000 gallon capacity tankers which then transport the waste to a designated tipping site.

At the Bristol siphon sites, times to complete the works have varied within each individual siphon depending on the amount of silt and debris that needed to be removed. With cleaning operations completed, a CCTV survey of the siphon was carried out and a site supervisor confirmed that the siphon was cleaned to the required standard to complete the works.

The crew then evacuates the siphon, removing all subsurface and surface equipment and the manhole is closed. All relevant paper work is then completed with the site supervisor and the following days work arranged.


On completion of the works to date, Glanville’s teams and operations were praised by the main contractor, May Gurney, for the professional way in which the works were carried out, particularly given the significant confined space entry operations and the high standards of H&S on the various siphon sites, particularly given that some of the sites were accessed only by very deep shafts.

Commenting for Glanville Cleansing Ltd, Ian Davis, Contracts Manager (Cleansing) said: “We were very happy to have been given the opportunity to work on this prestigious contract for Wessex Water through the main contractor May Gurney. The contract was run very efficiently and the Health and Safety standards adopted were extremely high. Our confined spaces entry teams are trained to the very highest standards possible and this was evident by the way that we performed for our client.”

For the Critical Sewers Team of Wessex Engineering and Construction Services the contract management section within Wessex Water, Julian Britton said: “The siphon cleaning project was an excellent example of Wessex Engineering Construction working with its framework partners. The main contractor May Gurney planned and executed the works very efficiently in association with Glanville as a main subcontractor.”

Tel: 01822 852535
Fax: 01822 855875

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