As part of a corridor link and long term maintenance project, Norwich-based utility consultant Kier Eastern (part of the Kier Group) recently undertook a programme of sewer cleaning and lining work on behalf of University of East Anglia (UEA), under the direction of Tim French. The contract to complete the necessary work was awarded to Dyno-Rod of Mahoney Green, Rackheath, Norwich, with lead project engineers J Vaughan and S Plane.
The work was to be undertaken beneath the Sainsbury Centre for Visual Arts, part of UEA, a prestigious and well known building in Norwich and comprised the rehabilitation of existing cast iron pipe work, which was in a poor condition and in many locations, badly pitted and corroded. Dyno-Rod advised that the most sensible and practical solution would be to
Dyno-Line the existing drainage pipe. The works were undertaken as part of the overall improvement and refurbishment of the Sainsbury Centre. The work would result in a new pipe within the old damaged pipe, which would be resilient to ground movement, impervious to leaks or root penetration, and which offers minimal cross-sectional loss (and therefore carrying capacity) whilst increasing hydraulic efficiency. The lining is also guaranteed for 15 years.
In a project costing approximately £35,000, including materials, the cast iron drainage pipes to be rehabilitated included diameters of 100 mm, 150 mm, 225 mm and 300 mm. Dyno-Rod strongly recommended the use of epoxy resin liners as they have no odour, no shrinkage and are environmentally friendly when used. The CIPP felt liner is first impregnated with epoxy resin. The impregnated liner is then inverted through the pipeline using either a scaffold tower (for water inversion) or an air inversion drum.
In total some 18 sections of foul and surface water drainage were Dyno-Lined with epoxy resin-based products. Some of the sections were challenging due to their length and location underneath the main Crescent Wing, which houses major artefacts. For example, one section of 225 mm diameter foul drain measuring 57 m long was successfully lined, as well as a section of 300 mm diameter surface water drain measuring 28 m. In total approximately
300 m of drainage pipe were lined.
Prior to the lining operations, a CCTV camera survey of the drainage system was completed to ascertain exactly where specific problems were located. Due to the varying diameter of the pipelines, a combination of small, portable CCTV cameras were used, with remote control crawler-mounted units being utilised on the large diameter pipe work over 225 mm diameter.
Many of the materials for the epoxy resin impregnated felt liners were purchased by
Dyno-Rod and sourced through John Kelly of CJ Kelly Associates Ltd, the UK lining consultant for German-based MC Building Chemicals, amongst others. The epoxy resin chemicals are supplied to order and mixed on site. Once mixed the resins have a limited ‘pot life’ and cure at ambient temperature. Lining installation timing was vital with the lining having to be in place in the pipeline prior to hardening. The felt liner material is supplied on a roll and is ‘wetted out’ just prior to inversion. On inversion and curing the liner forms a bond with the host pipe to complete the lining.
The entire project took place over a period of 5 weeks, which also included any necessary high-pressure water jet cleaning of affected pipe work prior to lining. In addition, certain sections of pipeline required specialist cleaning using a flail and spinning jet arrangement. There were also sections of drainage system that were only accessible to Dyno-Rod once other on site sub-contractors had completed specific works.
Working space inside the building was always at a premium. On larger sections of pipeline it was necessary to ‘wet out’ some 40 to 60 m of felt liner at a time. This required approximately 3 kg of resin per metre of liner and approximately 80 to 120 m of calibration hose to expand the liner once inverted. On these larger sections it was necessary to employ a minimum of 4 to 5 people to complete the job as quickly and smoothly as possible. With a limited ‘pot life’ for the resin and with the job being undertaken during the summer months, it was important that installation was right first time.
Dyno-Lining offers important benefits in terms of avoiding disruption. The trenchless system also enables costs to be controlled and ensures a speedy return to full pipeline function. In the case at UEA, there was no need to take the affected pipelines off-line ensuring a true ‘win/win’ situation with no special arrangements required.
Over the five week period on site work was frenetic and highly energetic and enormous emphasis was placed on Health & Safety and working together. Dyno-Rod was delighted at the manner in which it was able to work with Kier Group and both parties were highly pleased with the end result. Dyno-Rod guided Kier Group on the benefits of epoxy resins over other available lining options and Kier Group supported the recommendations accordingly. Given the limited working space available close cooperation with suppliers meant that materials were delivered in a timely manner just as required and, when needed, ensuring deadlines were met and client expectations managed.