Sewer construction works

Sewer construction covers planning, new construction, rehabilitation and deconstruction of wastewater and stormwater pipelines including shafts, syphons and special structures. It combines geotechnical engineering, civil engineering (underground works), pipeline installation and demolition works. In dense urban environments, low-vibration methods, emission-reduced work practices and precise equipment are crucial – particularly for works on existing sewers, shaft structures and foundations. Where concrete and reinforced-concrete components must be opened or deconstructed in a controlled manner, sewer construction frequently uses concrete pulverizers as well as hydraulic rock and concrete splitters, often in combination with compact hydraulic power units. In addition to constructability, contemporary practice emphasizes lifecycle durability, low carbon footprints, noise and dust control, as well as accurate surveying and monitoring for neighboring assets.

Definition: What is meant by sewer construction?

Sewer construction denotes the entirety of measures for the creation, upkeep and renewal of municipal and industrial drainage systems: sanitary, stormwater and combined sewers, connections, shafts, special structures (e.g., stormwater retention or storage tunnels), pressure pipelines as well as associated excavation pits, shoring systems and soil stabilization. This also includes trenchless methods such as pipe jacking and rehabilitation techniques (relining, liner, short liner) as well as the controlled demolition of damaged or obsolete sections. Sewer construction follows hydraulic, structural and operational requirements: watertightness, load-bearing capacity, self-cleaning capability, durable bedding and safe integration into the subsoil. Interfaces to wastewater treatment plants and outlets, odor and corrosion control (e.g., H2S), as well as inflow and infiltration management are considered to ensure reliable operations.

Construction methods in sewer construction: open-cut, trenchless and rehabilitation

The choice of method depends on subsoil, groundwater, traffic conditions, route conflicts and protected assets (buildings, utilities, water bodies). In practice, methods are combined to minimize impacts and ensure quality. Permit conditions, construction logistics, carbon and cost benchmarks, as well as the potential for material reuse further inform the method statement and sequencing.

Open-cut method

Construction in an open trench is common where space is available and impacts are acceptable. Typical are engineered excavation pits with shoring, groundwater lowering, layered bedding and backfilling. When deconstructing old pipelines, foundations or shafts in the trench, pinpoint interventions are required: selective concrete crushers enable biting off and fragmenting reinforced components, while hydraulic splitters separate components and rock with minimal vibration – without impact or blasting. This protects neighboring buildings and existing utilities. Utility locating and safeguarding, controlled saw cuts, dust suppression and optimized spoil logistics are integral to maintaining safety and productivity in confined corridors.

Trenchless pipeline construction

Pipe jacking, microtunneling, horizontal drilling and pipe bursting reduce surface impacts. Entry and reception shafts are still required. In rock or highly cohesive soils, local openings are created, obstacles are resolved and components are adapted during driving or shaft construction. Here, hydraulic wedge splitters and hydraulic shear are useful to remove obstacles in a controlled manner and to create cutouts in steel or concrete components. Trenchless drives benefit from precise guidance, annulus grouting and ground conditioning; steering corrections and obstacle clearance must be planned to limit settlement and preserve existing serviceability at the surface.

Rehabilitation and renewal of existing assets

Rehabilitation follows the principle “as little intervention as possible.” Methods such as liners, short liners, inliners, pipe-in-pipe or partial renewal are combined with sewer shaft rehabilitation. For preparation, openings must be created, defective concrete areas removed or connections adjusted. concrete pulverizers assist in the gentle removal of damaged shaft walls, while hydraulic splitters selectively widen cracks to remove loose zones with reduced stress. For cured-in-place and GRP solutions, adhesion, curing parameters, end seals and reconnection quality are verified to ensure long-term tightness and structural capacity.

Materials and components in sewer construction

Material selection follows hydraulic, structural and chemical requirements as well as the installation situation.

• Pipe materials: concrete/reinforced concrete, vitrified clay, plastics (PE, PP, PVC-U), GFRP; pressure pipelines partly of ductile iron pipes or PE-HD. Jointing systems (e.g., spigot-socket with elastomer gaskets, welded joints for thermoplastics) and internal linings or coatings are selected to resist abrasion and corrosion.
• Shaft components: concrete and reinforced-concrete shafts, GFRP shafts, frames and cones, channel inverts, rungs and inspection openings. Depending on the medium, surfaces can receive protective mortars, coatings or liners to mitigate biogenic corrosion.
• Sealing systems: sockets, sleeves, injections, shaft sealing; corrosion-protection linings in biogenically corrosive environments. Flexible couplings and end seals accommodate movement and maintain watertight transitions to laterals and structures.
• Bedding and backfilling: frost-resistant, compactable, low-settlement; matched to pipe stiffness and traffic loads. Where required, geotextile separation layers or controlled low-strength material are used to stabilize subgrade and speed reinstatement.

Excavation pits, shoring and groundwater

Excavation pits and shafts secure access to the route. Shoring systems (e.g., soldier pile walls, sheet pile wall, shoring box) stabilize the excavation boundary. With high groundwater, lowering or sealing measures are required. Local adaptations to shoring elements, temporary foundations or shaft components are often carried out with hydraulic cutting and splitting tools to limit vibration and noise. Monitoring of deformation, groundwater levels and settlement, as well as controlled discharge and potential recharge, ensures stability and environmental compliance.

Demolition and deconstruction of existing assets: controlled and low-vibration

Near existing utilities, gas and power routes as well as sensitive structures, low-impact methods are important. concrete pulverizers allow precise removal of shaft heads, foundation beams and upstands. hydraulic splitters work with high spreading forces and create crack corridors through which massive components are subdivided into transportable pieces – useful in narrow shafts and for special demolition. For reinforced structures, steel shears are additionally used to cut reinforcement in an orderly manner. For mixed materials and adjustment cuts in rehabilitation openings, cutting tools are suitable. Hydraulically driven tools are supplied by compact hydraulic power packs that can be positioned in shafts or at the edges of work areas. Sequenced removal, dust suppression and load control on working platforms reduce risks during dismantling.

Tools and hydraulic equipment in sewer construction

The choice of equipment depends on material, component thickness, installation position and environmental constraints (vibration, noise, emissions).

• hydraulic splitters: Crack formation in concrete and rock, ideal for pinpoint openings, shaft adaptations and controlled removal without impact energy. Effective where vibration limits apply and access is constrained.
• concrete pulverizers: Selective demolition of concrete shafts, foundations, inverts; combination with steel shears for cutting reinforcement. Suitable for pre-crushing to reduce handwork and speed up removal.
• hydraulic shears and cutting tools: Variable cutting tasks on metal, concrete edges and plastics during gutting and cutting. Interchangeable jaw geometries support different thickness ranges and materials.
• steel shears: Deconstruction of sheet pile walls, beam sections or reinforcement in the sewer environment. Clean cuts facilitate subsequent handling and recycling.
• cutting torch: special demolition when segmenting steel tanks in treatment plants or steel-pipe syphons where spark formation must be minimized. Hot work is coordinated with permits and fire watch.
• hydraulic power packs: Power supply for the tools mentioned; in sewer construction, compact, reliable operation in confined workspaces is essential. Low-emission drives and hose management enhance safety in shafts and pits.

Geotechnics, rock and pipe jacking

In rock or heterogeneous strata, the transition between trench excavation, shaft construction and driving is demanding. Local rock outcrops, boulders or concrete layers from earlier construction phases can be removed with rock wedge splitters and hydraulic splitters with reduced stress. This supports rock excavation and tunnel construction for entry shafts and short drives and reduces risks to surrounding buildings. Pre-splitting and controlled breaking lower vibration levels and help maintain face stability, while grouting or ground improvement mitigates inflow and voids.

Planning: hydraulics, gradient and operation

Hydraulic design covers design flows, gradients, degrees of filling, air management and self-cleaning. Route selection considers utility crossings, safety distances, accessibility for inspection and maintenance. Construction phasing and traffic concepts minimize closures. For interventions in existing sewers, diversion measures (bypasses) and provisional operating conditions must be ensured. Resilience to extreme rainfall, redundancy concepts and the integration of digital planning and GIS-based asset data improve operability and documentation.

Quality assurance, testing and documentation

Quality results from coordinated execution and robust evidence:

1. Preparatory checks: subsoil, utility records, locating, damage classification, conveyed media.
2. Execution control: bedding layers, compaction, component dimensions, correct integration of sealing systems.
3. Acceptance: leakage tests and pressure tests, CCTV inspection, evenness and gradient, settlement control, as-built documentation.

For rehabilitations, material certificates and installation logs are added; for deconstruction, a complete disposal documentation chain must be observed. Depending on method and material, additional checks include mandrel tests, laser profiling, smoke testing for infiltration pathways and weld or joint inspections for pressure-rated sections.

Safety and environmental protection

Occupational safety, emission control and water protection have high priority in sewer construction. This includes secured access, fall protection, controlled ventilation in shafts, ATEX zone requirements in hazardous areas, dust suppression and noise reduction measures, as well as soil and groundwater protection. Hydraulic splitting and cutting methods contribute to a safe, environmentally compatible workflow through low vibration levels and metered force transmission. Legal and normative requirements must be checked project-specifically and implemented appropriately. Confined space permits, continuous gas monitoring, rescue concepts with tripod and winch, spill prevention and hot-work permits are coordinated within a project-specific safety plan.

Special applications and special operations

In the environment of sewage treatment plants, stormwater tanks and syphon installations, tailored solutions are required. For the deconstruction of steel components, tanks or fittings, steel shear and cutting torch are suitable. In confined shafts with limited load capacity of the work platforms, compact, hydraulically powered tools offer advantages. For gutting works and cut of openings in existing sewers, concrete pulverizers and hydraulic splitters ensure controlled cuts and stress-relief strategies – important for safeguarding adjacent structures. Operational constraints such as shutdown windows, bypass pumping with N+1 redundancy and odor control are planned to maintain treatment performance and environmental protection.

Best practices in sewer construction

• Early coordination with other network owners to minimize conflicts.
• Align subsoil and groundwater strategy with construction method, shoring and bedding.
• Prioritize low-vibration methods for work on existing assets and in sensitive locations.
• Open components only as far as required for installation or rehabilitation; use controlled demolition instead of area-wide demolition.
• Size hydraulic tools to suit the task and operate them with suitable hydraulic power packs.
• Maintain a complete testing and documentation chain: from preparation through acceptance.
• Implement instrumentation and monitoring for settlement, vibration and groundwater to protect adjacent structures.
• Plan material flows and waste segregation early to maximize reuse and recycling and to reduce transport impacts.
• Use clear traffic and stakeholder communication plans to minimize disruption and maintain access.
• Prepare contingency strategies for weather, inflow peaks and unexpected obstructions to keep schedules resilient.