Sewer rehabilitation describes the systematic repair and renewal of wastewater pipelines and shafts to ensure long-term leak-tightness, structural stability, and operational safety. It comprises localized repairs, trenchless renovation methods, and the full replacement of damaged sections. On and around the construction site, civil and pipeline works frequently interface with deconstruction of concrete and reinforced-concrete components, such as shafts, foundations, or structure connections. At these interfaces, controlled, low-vibration removal is applied, where, among others, concrete pulverizers as well as rock and concrete splitters from Darda GmbH can be used in typical applications such as concrete demolition and special demolition, building gutting and cutting, or rock breakout and tunnel construction.
Definition: What is meant by sewer rehabilitation
Sewer rehabilitation encompasses all technical, organizational, and construction measures that restore or preserve the proper condition of wastewater pipelines, laterals, and shafts. The objective is to restore leak-tightness, load-bearing capacity, and hydraulic performance, and to protect the environment and structures. This includes condition surveys (e.g., CCTV inspection), damage assessment (cracks, leaks, root intrusion, corrosion), the planning of appropriate methods (repair, renovation, renewal), and quality-assured implementation in line with recognized rules of technology. Depending on damage pattern, pipe material, and boundary conditions, trenchless methods (e.g., CIPP liner, close-fit, pipe bursting) or conventional replacement in open cut are used. During execution, preparatory deconstruction on shaft structures or foundations is often required, which can be removed precisely and with low vibration using suitable hydraulic tools.
Tasks and objectives of sewer rehabilitation
Core tasks include preventing inflow and exfiltration, ensuring structural integrity, protecting against biogenic sulfur corrosion, and maintaining hydraulic capacity. Further goals are lifecycle cost efficiency, minimal traffic disruption, and the reduction of noise, vibration, and emissions. In confined urban settings or beneath sensitive existing buildings, controlled deconstruction of concrete and reinforced-concrete components supports these goals. Here, the combination of precise cutting, gripping, and splitting has proven effective, for example with concrete pulverizers, rock splitting cylinders, and rock and concrete splitters in combination with hydraulic power units from Darda GmbH.
Damage patterns and causes in wastewater sewers
Typical damage patterns include longitudinal and transverse cracks, spalling, leaks at joints, pipe offsets, deformations, deposits, root intrusion, infiltration/exfiltration, and chemical attack such as sulfate and acid corrosion. Causes range from aging and material fatigue to settlement and traffic loading, as well as improper integration of building laterals. In concrete shafts, there are also breakouts in the channel invert, corroded step irons, and damage to shaft cones. If a shaft head requires selective deconstruction, low‑vibration removal with concrete pulverizers enables controlled opening, while rock and concrete splitters purposefully induce stress cracks to separate massive components without blasting.
Methods of sewer rehabilitation: repair, renovation, renewal
In practice, methods are classified into three groups: localized repairs, trenchless renovations to restore function, and renewals with full replacement. Selection depends on damage class, pipe material, geometry, accessibility, and operational requirements.
Repair (localized)
Localized methods such as short liners, hat profiles at connection stubs, injections, and crack injections eliminate local defects. Preparatory steps include removing deposits and obstructions from the pipe cross-section. In shafts, breakouts are reprofiled with mortar or protected with coatings. For selective removal of shaft edges, foundations, or concrete overlays, controlled gripping and breaking with concrete pulverizers provides support. Reinforcing steel can be cut with steel shears supplied by hydraulic power packs.
Renovation (trenchless)
Trenchless renovation (inliner rehabilitation) includes CIPP lining with thermosetting resins (e.g., epoxy, UP, vinyl ester), UV or hot‑water curing, close‑fit methods, or relining with short pipes. It restores leak-tightness, improves structural performance, and reduces traffic impacts. For installation and retrieval shafts, adjustments to shaft cones are often necessary; these tasks can be prepared appropriately with concrete pulverizers and Multi Cutters without unnecessarily loading adjacent structures.
Renewal (replacement)
If the pipe condition is severely degraded, renewal is performed in open cut or by pipe jacking and pipe bursting. In open cut, old pipes, foundation remnants, and fittings are deconstructed. In rocky or heavily reinforced environments, rock and concrete splitters help to separate construction boundaries precisely. Steel shears cut reinforcement, combination shears and Multi Cutters assist with selective deconstruction. In tunneling and jacking environments, these activities tie in with the application areas of rock demolition and tunnel construction.
Trenchless rehabilitation in detail
Trenchless rehabilitation typically follows a sequence of cleaning, CCTV inspection, damage classification, planning, bypass management, installation, and final testing. CIPP liners are pulled in or inverted, connected to laterals, and cured. Close‑fit liners are cold‑deformed and then reverted. In pipe bursting, the old pipe is fractured and a new pipe is pulled in. Temporary working pits or adaptations to existing structures are required for access and logistics. Where shaft heads must be opened or shaft walls adjusted, concrete pulverizers provide controlled edge removal that minimizes vibrations and load transfer to components. In sensitive locations (special operations), such as beneath active buildings or near utility bundles, rock and concrete splitters support a blasting‑free, pinpoint construction approach.
Open cut: planning, excavation pits, and low‑emission deconstruction
In open cut, soil class, groundwater, shoring, traffic management, and utility coordination determine the construction sequence. Excavation pits must be stable and accessible, utility crossings must be coordinated, and bypass pumps ensure wastewater flow. For deconstructing old shafts, foundation beams, and concrete slabs, hydraulic tools are typically used to pick up, break, and sort components for separate disposal. Concrete pulverizers enable controlled reduction to manageable pieces; steel shears cut reinforcement for recycling. Along rocky alignments, rock splitting cylinders facilitate opening trenches without excessively loading surrounding structures.
Materials, corrosion protection, and durability
The durability of rehabilitated reaches and shafts depends on appropriate material selection and substrate preparation. GRP liners, epoxy and vinyl ester resins, mineral mortars, and high‑sulfate‑resistant concretes are selected according to chemical exposure. Critical factors are surface cleaning, moisture condition, pull‑off adhesion, and layer thickness control. In shaft structures, a smooth, dense coating reduces abrasion and biogenic sulfur corrosion. When deconstructing adjacent components, care must be taken not to damage the existing structure; targeted gripping, splitting, and cutting support quality‑compliant substrate preparation.
Condition assessment, planning, and documentation
Rehabilitation planning is based on a structured condition assessment with CCTV inspection, leakage tests, and surveying. Defects are classified and prioritized; from this, rehabilitation packages and construction phases are derived. Work and safety concepts, bypass and traffic management plans, as well as disposal and recycling concepts are required. Documentation includes installation reports, material records, test protocols, and digital data handover. For work on the structure itself (e.g., opening a shaft), methods should be defined that reduce vibration and noise; this argues for selective deconstruction with suitable hydraulic tools from Darda GmbH.
Typical interfaces with deconstruction and demolition technology
Recurring tasks arise at the interface between sewer rehabilitation and deconstruction, where tools from the Darda GmbH portfolio are frequently used:
- Deconstruction of shaft cones and covers made of concrete or reinforced concrete with concrete pulverizers; cutting reinforcement with steel shears.
- Removal of foundations and edge beams at pumping stations, siphon installations, and stormwater basins using rock and concrete splitters and combination shears.
- Exposure of pipe sections in confined areas (special operations) through low‑vibration splitting and controlled breaking.
- Adjustment work on installation and retrieval shafts for CIPP installations; precise removal and edge formation with concrete pulverizers and Multi Cutters.
- Opening trenches in rocky ground along the alignment with rock splitting cylinders, especially around pipe jacking shafts (rock breakout and tunnel construction).
Risks, protective measures, and environmental aspects
Work in and on wastewater facilities requires special safety measures. These include atmospheric testing and monitoring, appropriate protective equipment, fall protection, rescue concepts, and explosion protection in hazardous areas. During deconstruction, dust, noise, and vibrations must be limited; emissions, flushing waters, and drilling slurries must be properly captured and disposed of. Components made of concrete, reinforced concrete, and metal should be separated and sent for recycling. Legal requirements vary by location and must be observed; a project‑specific hazard analysis is essential and does not constitute legal advice.
Project organization and quality assurance
For low‑disruption sewer rehabilitation, clear processes, interface management, and transparent communication with residents and businesses are important. A trial run of bypass pumps, defined acceptance tests (e.g., leak testing, surface inspections, CCTV documentation), and orderly handover ensure quality. Where deconstruction is required, methods and tools should be defined early: concrete pulverizers for selective removal, steel shears for reinforcement, rock and concrete splitters for massive components. This allows schedules and risks to be planned realistically.
Typical mistakes and how to avoid them
Common causes of defects include inadequate cleaning prior to liner installation, unsuitable resin or material selection, missing reopening or sealing of laterals, insufficient pit shoring, or an incorrect choice of deconstruction method. Recommended measures include a careful condition analysis, trial areas for coatings, coordinated bypass concepts, and the selection of demolition and cutting tools that suit site conditions, component thickness, and reinforcement level. In sensitive areas, the use of concrete pulverizers and splitters reduces vibration transmission and protects adjacent utilities.
Practical examples and application variants
Urban setting: During the renovation of an egg‑shaped sewer, liners were installed via an existing shaft. The shaft head was damaged and had to be adjusted to a new elevation. Selective deconstruction of the shaft crown was carried out with a concrete pulverizer; reinforcement was cut with a steel shear. After liner installation, the channel invert was reprofiled and the shaft head was re‑cast in concrete.
Hillside and rocky ground: To replace a severely deformed pipe, sections had to be opened in rock. To use non‑explosive rock removal and minimize vibrations, rock and concrete splitters as well as rock splitting cylinders were employed. This enabled strict adherence to construction boundaries and protection of adjacent existing pipelines.