Advances in material science and installation techniques are changing how water and wastewater pipelines can be built – especially in constrained environments – as Ovi Frunza, Tunnelling Director, Barhale, explains.
New high-strength Glass Reinforced Plastic (GRP) jacking pipes, engineered to act as direct carrier pipes at internal pressures up to 16bar even when conveying hot water or brine, are allowing design and construction teams to rethink the relationship between jacking, installation and long-term pipeline performance.
For organisations responsible for buried assets, these developments provide a more predictable and less disruptive way to install pipelines in locations where traditional methods are becoming harder to justify.
Perhaps the most significant change is the widening potential for trenchless installation. For many years, pipejacking has relied on steel, concrete or GRP pipes that act as structural sleeves. Once a drive is complete, the operational pipeline is inserted or welded through deep shafts and pulled along the tunnel. The method is proven, but each additional step introduces handling, extra jointing and more time on site. Welding at depth, managing long insertions and coordinating multiple seal systems can be difficult in urban areas or on live water networks.
Recent developments in GRP manufacturing are altering this approach. Refinements to glass fibre content, resin chemistry and curing processes increase pipe stiffness to improve resistance to buckling, provide reliable performance under jacking loads and resist internal pressure with high safety margins.
This enables a single GRP pipe to withstand the forces of a jacking drive and operate as the pressure-rated asset. The capability to carry high-temperature water or brine at sustained pressure places the latest systems within a range that previously required steel or ductile iron. GRP is also inherently corrosion-resistant and reduces pipe weight, which lowers handling demands and simplifies logistics on restricted sites.
The prefabricated GRP pipe can now be installed in a single continuous drive with no secondary carrier insertion, meeting both installation and operational requirements. This avoids hot works in confined spaces, reduces jointing and shortens the time required for construction. Each metre installed becomes part of the permanent asset, helping client and contractor teams maintain programme certainty when working within fixed access windows or outage periods.
Microtunnelling has always offered advantages for river, rail and highway crossings, where settlement control and interface management are essential. Now, with GRP acting as both jacking pipe and carrier pipe, these drives become more straightforward to plan because the shaft size can be reduced and the installation sequence is shorter. On environmentally sensitive sites or locations with limited working hours, this reduction in operational steps provides a practical way to control risk while keeping disruption to customers and communities to a minimum.
The economic context is also changing. The established orthodoxy was that pipejacking only became cost-effective at depths of six metres or more, with open cut generally preferred at shallower alignments.
This distinction is becoming less relevant. The excavation itself is only one element of an open cut programme which needs to consider costs such as temporary and haul roads, utility protection, traffic management, reinstatement and access arrangements. These wider costs now influence method selection as much as excavation depth, particularly in cities where surface space is limited and customer disruption must be carefully managed.
The move to GRP carrier-jacking pipes will accelerate this trend. The construction footprint is smaller, fewer surface activities are required, and drive lengths can increase.
As a result, pipejacking can be competitive at depths around three metres and viable even at shallower levels, especially if shoring is required, when the full programme impact is considered. For clients responsible for maintaining networks beneath busy transport corridors, the ability to reduce surface disruption is becoming a central factor in project planning.
Durability and long-term performance remain essential considerations. Earlier generations of GRP prompted caution from engineers more familiar with metallic and concrete pipework. Improvements in material properties and development of engineering guides on how to approach pipeline design for non-rigid materials are addressing these concerns.
Modern GRP resists corrosion and avoids tuberculation. It performs consistently in high-temperature environments. When paired with high-performance elastomeric gaskets capable of maintaining seal integrity at full pressure, the system provides a stable and predictable behaviour over its design life. The reduced number of joints compared with steel and the tolerance to minor angular deflection offer further reassurance in areas where ground movement may occur.
Also, GRP’s low absolute roughness coefficient ensures excellent hydraulic performance – resulting in less head loss and reducing the cost of operating the pipeline.
Environmental impact is another factor for contractors, water companies and regulators. GRP’s lower weight reduces transport demands and shaft sizes.
The single-stage installation method uses fewer materials and decreases the footprint of each site. The GRP pipe itself can also provide a lower carbon impact than other materials. Shorter programmes also help reduce carbon linked to plant use and temporary works. These elements support clients’ broader commitments to efficiency, sustainability and affordability.
Across the sector, the introduction of GRP carrier-jacking pipes is prompting a reassessment of how underground infrastructure is delivered.
By reducing interfaces, limiting surface disruption and supporting predictable programme delivery, the combination of GRP and microtunnelling is a practical alternative to open-cut installation in many settings.
As clients and contractors plan upgrades and new connections in complex urban environments, these systems are becoming a default option for delivering resilient water and wastewater assets with fewer constraints and reduced impact on the communities who rely on them.
