WET News

14 WET NEWS DECEMBER 2014 Manhole rehabilitation's seal of • When groundwater infiltrated the sewers through manholes, Anglian Water had to allay the EA's concern over the effect on the downstream network. THE CONCEPT • The whole rehabilitation process follows the simple routine of high pressure cleaning, grit blasting, joint sealing, grout injection and finally spray lining • The Hermes Technologie spray lining system and Ergelit mortars • It offers a comprehensive method including joint sealing to prevent water ingress from leaking joints using rapid set mortars • The spray lining is applied using centrifugal spray heads or by wet spraying methods NEED TO KNOW 1 Keeping the vehicle footprint as small as possible was also of great concern due to the impact of residents and road space used 2 On completion the system is then purged and cleaned using water 3 The use of different mortars means PH values from 1 to 13 can be withstood 4 A key business driver for Anglian Water is a reduction in the embodied carbon associated with its capital works I n what is believed to be one of the largest single projects of its type to be awarded to date in the UK, Anglian Water's @One Alliance recently appointed PBF Drainage Services as contractor for a major manhole rehabilita- tion project, the Langham and Boxted Manhole Sealing scheme in Colchester. The main driver for the project was to reduce groundwater infil- tration to the sewerage network through the manholes, which had deteriorated over time. Incoming flows had reached a level that adversely affected the downstream network and Water Recycling Centre. This led to the Environment Agency (EA) consulting with Anglian Water to provide a solu- tion to the infiltration. The man- hole sealing and rehabilitation process used will stop all water infiltration caused by high ground water levels in the area. Anglian Water has a pro- gramme of proactive investiga- tion and rehabilitation of its sew- erage infrastructure to maintain serviceability for its customers. A key business driver for Anglian Water is a reduction in the embodied carbon associated with its capital works. Trenchless and no-dig solutions such as manhole spray lining and sewer lining play a significant part in achieving this target. The project plan was devel- oped based on surveys carried out two to three years ago to establish accessibility, condition, construction material, size and depth of each manhole. The aver- age manhole depth is 3.2m, with a ring diameter of 1.2m. The deep- est manhole is 5m and PROJECT SPECS • Reduce groundwater infiltration to the sewerage network • Rehabilitate 100-plus manholes • Small footprint equipment had to be used • Carry out a full site walkthrough THE VERDICT "This is the largest single project of its type to be awarded to date in the UK that we are aware of" James Stern, managing director, PBF Drainage Services ONSITE TRENCHLESS TECHNOLOGY the shallowest is 1.2m. Prior to commencing the project PBF Drainage undertook a full site walkthrough and this along with good planning prevented the operations crew from encounter- ing any hidden surprises. According to James Stern, managing director of PBF Drain- age: "We are hoping to finish ahead of schedule depending on the weather. Although the weather does not affect the appli- cation of the rehabilitation mate- rials it simply makes for harder working environments, and will cause access issues for manholes that are off-road." Vehicle footprint Access to some of the manholes was always deemed to be one of the major problems that would be encountered during the project duration as certain manholes were located within gardens and fields. To overcome, this selected manholes were rehabilitated using the specially-engineered equipment within the vehicle that is all fully demountable and can therefore be used to apply the spray coatings within difficult access areas. Options for hand application were considered but to allow for greater consistency within the lining program a great deal of thought went into design- ing the equipment. The Hermes Technologie M-Coating system, using Ergelit cement based mortars, utilises a rapid set mortar called 10SD, a grout injection mortar called KBI and an Ergelit spray lining mortar called KS1. To apply the various mortars different techniques are used. An air or battery-operated Manual works were used in some manholes to seal leaking joints and stop infiltration points prior to final spray lining or where access was difficult to completely rehabilitate the manhole A deteriorated manhole showing significant groundwater infiltration Manhole rehabilitation's seal of

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