Aging infrastructure has become an increasingly crucial issue for both developed and developing countries. When this infrastructure is underground and needs to be replaced or rehabilitated, however, access can be a problem: in the intervening years since initial construction, roads, utilities, and other infrastructure has been built above, restricting our options.
Traditional open-cut construction may not be suitable for pipe replacement or rehabilitation for any number of factors:
- The underground space in the public right-of- way is congested with pipelines and utilities
- Traffic management in urban areas
- Street pavement damage and the cost of surface restoration may be prohibitive
- Under runways or taxiways which prohibits their closures
- Direct and indirect business losses
- Large amounts of spoil that could be contaminated
In these cases, trenchless technology is the solution.
Putting Our Experience to Work for You
WSP has a long track record of successful work with trenchless methods, and we have developed expertise and advanced the state of the art with various trenchless technologies. Using these techniques, we can assess, rehabilitate, or install underground infrastructure with little to no excavation, minimizing the disruption and environmental impact of the project, and reducing the impact on adjoining buildings, structures, utilities, and the public.
Some of our main areas of expertise include:
- Condition assessment of existing pipes and utilities
- Feasibility, conceptual, and preliminary studies
- Design, specifications, and contract administration for trenchless projects
- Design, specifications, and contract administration for pipeline rehabilitation projects
In the United Kingdom, we used HDD to construct the 132kV New Cross to Finsbury Market Cable Tunnel. The project was 6km long, between 20m and 30m below the surface, and bored through London’s basin geology.
Horizontal directional drilling (HDD) is a trenchless construction method for installing subsurface piping or conduits by using a surface mounted rig, first to drill a guided hole along a bore path consisting of a shallow arc and then to pull a string of pipe into the hole. In the United Kingdom, we were commissioned to provide geotechnical services for the undergrounding of 33kV overhead lines using HDD techniques under the M4, Junction 19 (with M32) Motorway.
Trenchless Rehabilitation of Pipelines
Trenchless technologies for water main and sewer rehabilitation typically includes the installation of a manufactured liner pipe within the host main and/or in-situ spray application of a liner material.
In selecting the preferred method for the rehabilitation, the following considerations need to be taken into account when selecting the rehabilitation methodology:
- Pipe material, internal corrosion and tuberculation, joint failure, and external corrosion
- Operation factors, including hydraulic conveyance limitations and water quality
- Condition of the pipeline foundation and depth of the pipeline and water table
- Hydraulic operating pressure and transient pressure requirements
- Number and type of fittings, including branch and service line connections, valves, fire hydrants, and repair sleeves
- Duration and level of service interruptions, and the provision of temporary service
- Site conditions and factors, including local utilities
- Traffic conditions
The rehabilitation is often done by cured-in-place-pipe (CIPP) lining, slip-lining, swage-lining, or carbon fibre reinforced polymer.