Manhole Rehabilitation Companies
Manhole rehab specialists, cementitious, geopolymer, and epoxy linings to extend asset life and stop I&I.
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Concrete Repairs Ltd
United Kingdom
Concrete Repairs Limited (CRL) is a specialist asset maintenance contractor who is here to help you with the inspection, repair & refurbishment of your concrete water assets. CRL provide comprehensive repair and refurbishment services tailored to the needs of the water and wastewater sector throughout the UK. These include the inspection, repair, refurbishment and upgrading of service reservoirs, contact tanks, water towers & wastewater treatment plants. With over 65 years of experience, CRL understands the importance of maintaining water quality and supply to customers. Therefore, when planning repairs, we prioritise effective programming of the work and optimal utilization of the assets being repaired. Our choice of repair methodologies and materials always reflects this commitment. At CRL, we pride ourselves on being a reliable partner to the water companies. We collaborate closely with them to identify problems early, quantify the necessary repairs, and establish a timeline for refurbishment. Throughout this process, we focus on ensuring the longevity and optimal performance of the assets. CRL provide proven and successful cost-effective repair and refurbishment options which meet our clients’ objectives of upgrading and increasing the life of their structures. CRL is capable of undertaking individual projects of up to £20M, either under competitive tender, or through Partnering/Framework arrangements. Our broad experience across various sectors ensures we deliver efficient, robust, and technically advanced services.
Buyer's guide
The buyer's guide to manhole rehabilitation
Manhole Rehabilitation Methods: Structural Lining, Chemical Grouting, and Frame Replacement
Manhole rehabilitation addresses structural deterioration (cracking, spalling concrete, corroded brickwork), infiltration of groundwater through joints and walls, and exfiltration of sewage to groundwater. Deterioration mechanisms include: microbially induced corrosion (MIC) where H2S gas generated in anoxic sewers reacts with surface moisture and oxidises to sulphuric acid (pH below 2 at crown), dissolving calcium silicate hydrate in concrete at rates of 1 to 10 mm per year in aggressive systems; hydrostatic groundwater pressure causing joint opening and cracking; and freeze-thaw cycling in cold climates causing spalling. Manholes with concrete crowns at or below the sewer water table are at highest MIC risk.
Rehabilitation methods by deterioration type: structural repair by spray-applied cementitious liner (minimum 10 mm, alkalinity-resistant, epoxy-modified mortar achieving pH 13 to resist ongoing MIC) for MIC-damaged concrete; polyurea or polyurethane spray lining (1 to 5 mm, 100 percent solids) for watertight membrane against infiltration; chemical grouting (polyurethane grout, expanded in situ at cracks and joints) to stop active infiltration before structural lining; and full fibre-reinforced plastic (FRP) liner insertion for severely deteriorated manholes requiring structural replacement without excavation. Frame and cover replacement addresses surface level adjustment (raising by frame extension rings) and load-bearing capacity (upgrade to D400 or E600 class covers per EN 124).
Post-rehabilitation testing: vacuum test (EN 1610 acceptance test, apply -0.1 bar vacuum for 5 minutes, pressure rise below 0.025 bar indicates acceptable leak tightness) for new or rehabilitated manholes. CCTV inspection inside the manhole after rehabilitation verifies lining coverage, joint treatment, and absence of voids. Cost comparison: spray cementitious lining of 1.8 m diameter manhole 3 m deep: $800 to $2,000; polyurea lining: $1,200 to $3,000; full FRP liner: $3,000 to $8,000; open excavation and replacement: $10,000 to $30,000. Trenchless rehabilitation is preferred in trafficked roads where excavation cost and traffic management cost would multiply total project cost by 3 to 5 times.
Frequently asked questions
What causes manholes to deteriorate?
Three primary deterioration mechanisms affect manholes. First, microbially induced corrosion (MIC): anaerobic bacteria in sewers produce hydrogen sulphide (H2S) gas, which oxidises to sulphuric acid at the damp crown and walls above the waterline by Thiobacillus bacteria, attacking concrete (pH below 2 at the surface). Concrete loss rates of 1 to 10 mm per year occur in severe cases. Second, groundwater infiltration: hydraulic pressure forces water through cracked joints and walls, which erodes mortar joints (particularly in brick manholes) and washes fine particles into the sewer (I&I - infiltration and inflow). Third, traffic loading: heavy vehicle loading causes settlement of manhole frames, cracking of cone sections, and joint displacement, exacerbated by differential settlement in fill material around the manhole.
What is the difference between grouting and lining a manhole?
Grouting addresses active water infiltration: polyurethane or polyacrylate grout is injected under pressure through drilled holes into cracks, joints, and the surrounding soil annulus. The grout expands on contact with water, filling voids and forming a watertight plug. Grouting is a pre-treatment step to stop active water ingress before applying a structural liner; grouting a still-wet surface is practical, whereas lining requires a relatively dry surface. Lining applies a structural layer to the interior of the manhole to restore structural integrity, smooth the surface, and provide a corrosion-resistant barrier. Cementitious liners (spray-applied, 10 to 25 mm) resist ongoing H2S attack by high alkalinity. Polyurea liners (1 to 5 mm spray) are impermeable membranes used primarily for watertightness rather than structural repair. The two are often used together: grout first, then line.
How long does manhole rehabilitation last?
Service life of rehabilitated manholes depends on the method and ongoing exposure. Spray cementitious mortar lining in a moderately corrosive sewer (H2S below 200 ppm): 20 to 30 years. High-build epoxy lining (3 to 5 mm): 15 to 25 years in moderate corrosion. Polyurea spray lining (flexible, crack-bridging): 25 to 40 years if UV-protected (polyurea degrades under UV if not topcoated with polyurethane UV coat, relevant for manholes with open covers). Full FRP liner (factory-manufactured, installed as one-piece or assembled ring section): 50-plus years. Open-cut replacement with precast concrete manhole: 50 to 80 years. Longevity is heavily dependent on the ongoing corrosion environment; any rehabilitation in a high-H2S system (above 500 ppm H2S in sewer atmosphere) will fail more rapidly without ongoing gas control at source (ventilation, dosing of nitrate or iron salts to suppress H2S generation).
How are manholes inspected before rehabilitation?
Pre-rehabilitation condition assessment uses: (1) Visual inspection by entry (where safe) or CCTV camera mounted on a mast lowered into the manhole - identifies cracking, spalling, joint defects, active infiltration points, and MIC damage zone extent; (2) Hammer-sounding of concrete to identify delamination and hollow sections (hollow sound indicates debonded material at risk of fall); (3) Concrete carbonation test (phenolphthalein indicator spray - uncarbonated concrete pH above 10 stays pink, carbonated zone pH below 8 stays colourless); (4) H2S gas measurement (4-gas meter before entry for health and safety, and continuous monitoring during inspection; H2S above 10 ppm requires SCBA or forced ventilation); (5) Dimensional survey for frame level, cone geometry, and liner thickness estimation. Inspection results are used to specify the appropriate rehabilitation method and material quantities.
Illustrative scenario · Urban sewerage infrastructure
A composite drawn from typical projects in this category, not a single client engagement. Figures are indicative.
- Challenge
- A UK sewerage undertaker in the North West of England identified 240 manholes on a main interceptor sewer route as having severe microbially induced corrosion, with concrete loss rates of 5 to 8 mm per year at the crown. Seven manholes had collapsed crown sections, and the route passed under a major arterial road. Open excavation and replacement would have caused estimated 14 million GBP in traffic disruption costs over 3 years.
- Approach
- Classified manholes into three condition bands by CCTV inspection and hammer-sounding. Band A (18 manholes, collapsed crown): emergency polyurea spray lining plus GRP structural ring insert. Band B (82 manholes, severe MIC but structurally sound): spray-applied sulphate-resistant cementitious mortar (15 mm, pH 13) with polyurethane grout at active infiltration joints. Band C (140 manholes, moderate MIC): spray-applied cementitious mortar (10 mm) only. All works completed using confined space teams without road closure, using CCTV verification of lining coverage post-completion.
- Outcome
- All 240 manholes rehabilitated within 18 months at a programme cost of 3.8 million GBP versus 18 million GBP estimated for open excavation and replacement. Post-rehabilitation CCTV showed lining coverage above 98 percent on all Band A and B manholes. Vacuum testing of all rehabilitated manholes confirmed EN 1610 acceptance criteria. Post-rehabilitation Legionella sampling of the groundwater monitoring boreholes adjacent to the sewer route showed no groundwater contamination from sewer exfiltration.
Questions to ask shortlisted providers
5
- 01
What pre-rehabilitation inspection scope do you propose, and will each manhole receive individual condition grading before you specify the rehabilitation method?
Batch-specifying the same rehabilitation method for all manholes in a programme without individual condition grading results in under-treating severely deteriorated manholes (liner fails early) and over-treating lightly damaged manholes (wasted spend). A condition-graded programme with at least three bands (emergency structural, standard structural, and cosmetic) delivers better value. Inspect before specifying: any contractor proposing a rehabilitation method before completing inspection is not following good practice.
- 02
What is the design life of the rehabilitation method for our specific sewer corrosion environment, and what is your evidence for this from installed references?
Service life claims for spray cementitious liners (20 to 30 years) in moderate H2S environments may reduce to 8 to 12 years in severe environments (above 500 ppm H2S). Ask for references of installations in similar H2S concentrations and evidence of performance after 10-plus years. A contractor who cannot provide references from comparable environments is relying on material data sheet claims that may not reflect real-world performance.
- 03
What is the H2S concentration in our manholes during working hours, and what confined space safety plan do you have for your operatives?
Under the Confined Spaces Regulations 1997 and HSE guidance, H2S above 1 ppm requires enhanced monitoring; above 10 ppm requires SCBA or forced ventilation; above 20 ppm requires immediate evacuation. Manhole rehabilitation in a high-H2S sewer atmosphere without an appropriate confined space safety plan is a serious HSE offence. Ask for the gas monitoring protocol, PPE specification, and emergency rescue plan for your specific sewer before accepting the contractor's proposal.
- 04
What post-rehabilitation testing regime is included in the scope, and will vacuum testing be performed on every manhole?
Post-rehabilitation vacuum testing to EN 1610 (pressure decay rate below 0.025 bar per 5 minutes) is the standard acceptance test for rehabilitated manholes where watertightness is the objective. Without post-rehabilitation testing, there is no evidence that active infiltration has been sealed. Some contractors offer visual inspection as a substitute for vacuum testing; this is not adequate for manholes in high groundwater areas where infiltration is a primary driver of the programme.
- 05
How will sludge, debris, and lining material displaced during rehabilitation be captured and disposed of, and what is the waste classification for the spent material?
Manhole rehabilitation generates waste including removed concrete spall, cleaning debris, and spray material overspray. In manholes on sewers carrying industrial effluent or from combined sewers, this material may contain elevated metals, hydrocarbons, or biological contamination requiring waste characterisation before disposal. A contractor who disposes of manhole rehabilitation waste to standard skip without characterisation may be committing an illegal disposal offence under the Environmental Protection Act 1990.
What drives cost in this category
4
- Manhole diameter, depth, and condition band
- Spray cementitious lining of a standard 1.2 m diameter manhole 3 m deep (moderate MIC, Band B): 1,200 to 2,500 GBP per manhole. A 1.8 m diameter deep (6 m) manhole with severe MIC requiring polyurea plus structural GRP ring: 5,000 to 12,000 GBP per manhole. Full open excavation and replacement: 15,000 to 40,000 GBP per manhole depending on depth and road condition. For a 100-manhole programme, the rehabilitation versus replacement cost difference is typically 800,000 to 3,000,000 GBP, justifying significant investment in inspection and rehabilitation planning.
- Traffic management and access constraints
- Manhole rehabilitation without road closure (using CCTV inspection, compact spray equipment, and no major excavation) avoids the largest cost variable on trafficked routes. Lane rental charges under the Traffic Management Act 2004 Section 74 run 2,500 GBP per day beyond the permitted period on principal roads. Emergency access manholes in high-traffic areas may require night-shift working (30 to 50 percent uplift on labour rates) to meet highway authority permit conditions.
- Confined space and H2S management
- In high-H2S sewer environments (above 50 ppm), rehabilitation requires three-person confined space teams with SCBA (one operative working, one standby at surface, one emergency response). This reduces production to 3 to 5 manholes per day versus 6 to 10 manholes per day in low-H2S environments, increasing labour cost by 30 to 60 percent per manhole. H2S gas scrubbing of the manhole atmosphere before entry (using forced ventilation with activated carbon scrubbers) adds 200 to 500 GBP per manhole in equipment cost.
- Post-rehabilitation testing and verification
- Vacuum testing to EN 1610 costs 150 to 350 GBP per manhole. CCTV verification of lining coverage costs 100 to 250 GBP per manhole. For a 100-manhole programme, post-rehabilitation verification adds 25,000 to 60,000 GBP to programme cost. The consequence of omitting verification (liner failure, sewer exfiltration to groundwater, road subsidence) on a principal road can cost 100,000 to 500,000 GBP per event in emergency repair, traffic management, and liability claims.
Key regulations and standards
4
- Confined Spaces Regulations 1997: Entry into Manholes and Sewers
- Manholes and sewers are defined confined spaces under the Confined Spaces Regulations 1997. Entry requires: risk assessment identifying hazards (H2S, methane, oxygen deficiency, engulfment), written safe system of work, trained and competent confined space operatives, gas monitoring before and during entry (4-gas meter: O2, H2S, CH4, CO), standby man at surface, and rescue plan. H2S above 1 ppm triggers enhanced monitoring; above 10 ppm requires SCBA or forced fresh air ventilation. Non-compliance is a serious health and safety offence.
- EN 1610:2015: Construction and Testing of Drains and Sewers
- BS EN 1610:2015 is the European standard for construction and testing of drain and sewer systems including manholes. Section 14 specifies acceptance testing for manholes: air test at -0.1 bar gauge pressure, 5-minute hold, pressure rise must not exceed 0.025 bar (indicating leak). EN 1610 is referenced in UK sewerage undertaker asset adoption standards and in CDM 2015 project documentation as the test standard for post-rehabilitation acceptance of manhole watertightness.
- Environmental Protection Act 1990: Duty of Care for Manhole Rehabilitation Waste
- Waste produced during manhole rehabilitation (concrete spall, cleaning debris, spray material waste) is subject to the waste duty of care under Environmental Protection Act 1990 Section 34. Contractors must: classify waste correctly (non-hazardous or hazardous depending on sewer type and contamination), use licensed waste carriers for transport, and dispose of waste at licensed sites. Transfer notes must be retained for 2 years. Incorrect waste classification and disposal to an unlicensed site is an offence punishable by unlimited fines.
- Water Industry Act 1991: Sewerage Undertaker Duties and Asset Standards
- Water Industry Act 1991 Section 94 requires sewerage undertakers to maintain an effective system of public sewers and to have the sewers cleaned and emptied. Collapsed or severely deteriorated manholes that cause surcharging, customer flooding, or groundwater contamination represent a breach of the Section 94 duty. Ofwat's reporting requirements include sewer flooding incidents attributed to sewer and manhole condition, incentivising proactive rehabilitation programmes to avoid ODI penalties and Section 18 enforcement action.