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FeedsHome: Summer 2009 › Lead Story › Get into rehab
Get into rehab
04/06/2009 | Channel: Water, Maintenance
Rob Whale talks about the apparent neglect in maintaining our oldest, most critical assets and looks at the solutions available
Sewers and drains are a vital part of the nation’s infrastructure and play an essential role in protecting the environment as well as maintaining the nation’s health.
It has been said that the UK has the world’s oldest and most comprehensive waste water network, with over 300,000km in use today. Around five per cent, about 15,000 km of these, are one metre and over in diameter and of man-entry size, with a large proportion being the product of Victorian, or even earlier engineering, where former open water courses have been covered over using a variety of materials to form culverts.
The large diameter Victorian structures are predominantly of brick construction and they have served us well, but like any other engineered solution, they must be maintained.
A typical failure pattern of the brick sewer begins with signs of missing mortar. Usually a lime based material, mortar joint failure leads to a cycle of infiltration of ground water combined with the exfiltration of waste water from within the structure. This can then lead to the dangerous cycle of joints opening up further, with more of the surrounding soils becoming washed out by further infiltration and exfiltration, resulting in voids (essentially areas of empty space), above and around the sewer. This could in turn, lead to already leaking, adjacent water mains then failing catastrophically as their support diminishes through the ongoing voiding. Ultimately, the sewer collapses, leading not just to the failure of that asset, but also to other adjoining structures and utilities.
As well as the obvious costs of a now expensive, open cut repair, there may be claims for interruption from businesses, loss of revenue to public transport providers, traffic disruption, the mobilisation of the emergency services, damage to adjacent utilities plant and flooding claims, not to mention the bad publicity to the assets owner.
By maintaining our assets, we can affect repairs in a cost effective manner, often without resort to excavations, road closures and the otherwise more costly and disruptive operations.
It has been estimated that at the present rate of renewal / renovation, the current average anticipated service life for a UK sewer is around 900 years.
Structural rehabilitation options
Structural rehabilitation includes repair, renovation and renewal of sewer systems. Rehabilitation can be considered in the two broad categories of stabilisation and lining. Stabilisation can be achieved by sealing joints and openings, it is important to
note however, that it is only appropriate if the original structure is structurally sound. Systems in use include grouting and pressure pointing. Lining can be considered in terms of being either a Type I or Type II system.
Type I Linings
A type I lining is where the lining and the existing sewer combine to act as a rigid composite section. To do this, a bond is required between the lining and the existing sewer. The Sewerage Rehabilitation Manual recommends that type I techniques should only be used in man-entry sewers, where a high degree of confidence in the achievement of bond with the existing structure can be achieved. Examples of the materials used in type I lining are:
Techniques such as Insitu Ferrocement lining, a Ferro Monk solution, can offer a number of significant advantages.
Firstly, the system is designed around a precast invert, which is designed to be handled and grouted into position in order that it can normally accommodate dry weather flows. This can, in many cases, negate the need for expensive overpumping installations.
The rest of the installation is carried out in situ, with layers of mesh and sprayed Ferrocement being applied and finished to the required thickness. A flexible system, it can be used in many complex situations.
Type II linings
Type II linings differ in that the lining is designed into a structural pipe within its own right and does not require a bond with the existing sewer. Full-length linings are commonly installed using one of the cured-in-place methods.
Originally developed in the early 1970s, this no-dig, trenchless technology, became more widely available following the expiry of the original patents and the market began to open up.
There are now a number of systems on the market, the main types being based around a resin impregnated felt sock. The resins become cured either through exposure to increased temperature (using hot water or steam) or ultra violet light.
Installation can be through either inversion, which is by effectively unfolding the impregnated tube through the asset to be rehabilitated by the introduction of water or air, or by dragging the liner through the sewer and inflating it with compressed air or a calibration hose. CIPP lining spans a large diameter range, from the smaller domestic diameters, through to man-entry sizes.
On the smaller diameter assets, where repairs are needed over only short lengths of pipe, isolated patches may offer a more cost effective solution.
Environmentally friendly
An exciting new product introduced into the UK, which is being offered by Ferro Monk Systems, is Ultracoat. In keeping with current national environmental standards Ultracoat is a ‘green’ product – 100 per cent epoxy with no volatile organic compounds. It has a high safety value and can be applied in confined spaces with no risk of combustion to hazardous materials.
Originally developed in the USA over 15 years ago and with over 40,000 manholes rehabilitated to date, it is a tried and tested system, ideal for rehabilitating waste water systems.
The material is resistant to a range of chemicals, as well as to algae and bacterial growth, giving greater protection to structures that are under attack from these agents.
The solution was recently used on three projects for Anglian Water, where a number of concrete chambers at pumping stations were suffering severe hydrogen sulphide attack.
Choice
With a myriad of solutions on offer, finding the right one can be challenging. One way to ease the situation is to call upon the expertise of a company that can offer a range of products and so is better placed to be able to give appropriate advice on the most cost effective options available.
Rob Whale is chief quantity surveyor at Ferro Monk Systems, one of the UK’s leading waste water asset and pipeline rehabilitation specialists. Ferro Monk Systems remains one of the few UK sewer rehabilitation contractors to maintain a man-entry capability, alongside its remote techniques including cured-in-place and remote patch lining. Ferro Monk Systems has been carrying out sewer rehabilitation works for nearly 30 years and has the integrity, experience and skills to provide quality, cost effective solutions, including ones for large diameter structures.
For further information visit www.ferromonk.co.uk
It has been said that the UK has the world’s oldest and most comprehensive waste water network, with over 300,000km in use today. Around five per cent, about 15,000 km of these, are one metre and over in diameter and of man-entry size, with a large proportion being the product of Victorian, or even earlier engineering, where former open water courses have been covered over using a variety of materials to form culverts.
The large diameter Victorian structures are predominantly of brick construction and they have served us well, but like any other engineered solution, they must be maintained.
A typical failure pattern of the brick sewer begins with signs of missing mortar. Usually a lime based material, mortar joint failure leads to a cycle of infiltration of ground water combined with the exfiltration of waste water from within the structure. This can then lead to the dangerous cycle of joints opening up further, with more of the surrounding soils becoming washed out by further infiltration and exfiltration, resulting in voids (essentially areas of empty space), above and around the sewer. This could in turn, lead to already leaking, adjacent water mains then failing catastrophically as their support diminishes through the ongoing voiding. Ultimately, the sewer collapses, leading not just to the failure of that asset, but also to other adjoining structures and utilities.
As well as the obvious costs of a now expensive, open cut repair, there may be claims for interruption from businesses, loss of revenue to public transport providers, traffic disruption, the mobilisation of the emergency services, damage to adjacent utilities plant and flooding claims, not to mention the bad publicity to the assets owner.
By maintaining our assets, we can affect repairs in a cost effective manner, often without resort to excavations, road closures and the otherwise more costly and disruptive operations.
It has been estimated that at the present rate of renewal / renovation, the current average anticipated service life for a UK sewer is around 900 years.
Structural rehabilitation options
Structural rehabilitation includes repair, renovation and renewal of sewer systems. Rehabilitation can be considered in the two broad categories of stabilisation and lining. Stabilisation can be achieved by sealing joints and openings, it is important to
note however, that it is only appropriate if the original structure is structurally sound. Systems in use include grouting and pressure pointing. Lining can be considered in terms of being either a Type I or Type II system.
Type I Linings
A type I lining is where the lining and the existing sewer combine to act as a rigid composite section. To do this, a bond is required between the lining and the existing sewer. The Sewerage Rehabilitation Manual recommends that type I techniques should only be used in man-entry sewers, where a high degree of confidence in the achievement of bond with the existing structure can be achieved. Examples of the materials used in type I lining are:
- Ferrocement
- Gunite
- Glass reinforced plastic
- Glass reinforced cement
Techniques such as Insitu Ferrocement lining, a Ferro Monk solution, can offer a number of significant advantages.
Firstly, the system is designed around a precast invert, which is designed to be handled and grouted into position in order that it can normally accommodate dry weather flows. This can, in many cases, negate the need for expensive overpumping installations.
The rest of the installation is carried out in situ, with layers of mesh and sprayed Ferrocement being applied and finished to the required thickness. A flexible system, it can be used in many complex situations.
Type II linings
Type II linings differ in that the lining is designed into a structural pipe within its own right and does not require a bond with the existing sewer. Full-length linings are commonly installed using one of the cured-in-place methods.
Originally developed in the early 1970s, this no-dig, trenchless technology, became more widely available following the expiry of the original patents and the market began to open up.
There are now a number of systems on the market, the main types being based around a resin impregnated felt sock. The resins become cured either through exposure to increased temperature (using hot water or steam) or ultra violet light.
Installation can be through either inversion, which is by effectively unfolding the impregnated tube through the asset to be rehabilitated by the introduction of water or air, or by dragging the liner through the sewer and inflating it with compressed air or a calibration hose. CIPP lining spans a large diameter range, from the smaller domestic diameters, through to man-entry sizes.
On the smaller diameter assets, where repairs are needed over only short lengths of pipe, isolated patches may offer a more cost effective solution.
Environmentally friendly
An exciting new product introduced into the UK, which is being offered by Ferro Monk Systems, is Ultracoat. In keeping with current national environmental standards Ultracoat is a ‘green’ product – 100 per cent epoxy with no volatile organic compounds. It has a high safety value and can be applied in confined spaces with no risk of combustion to hazardous materials.
Originally developed in the USA over 15 years ago and with over 40,000 manholes rehabilitated to date, it is a tried and tested system, ideal for rehabilitating waste water systems.
The material is resistant to a range of chemicals, as well as to algae and bacterial growth, giving greater protection to structures that are under attack from these agents.
The solution was recently used on three projects for Anglian Water, where a number of concrete chambers at pumping stations were suffering severe hydrogen sulphide attack.
Choice
With a myriad of solutions on offer, finding the right one can be challenging. One way to ease the situation is to call upon the expertise of a company that can offer a range of products and so is better placed to be able to give appropriate advice on the most cost effective options available.
Rob Whale is chief quantity surveyor at Ferro Monk Systems, one of the UK’s leading waste water asset and pipeline rehabilitation specialists. Ferro Monk Systems remains one of the few UK sewer rehabilitation contractors to maintain a man-entry capability, alongside its remote techniques including cured-in-place and remote patch lining. Ferro Monk Systems has been carrying out sewer rehabilitation works for nearly 30 years and has the integrity, experience and skills to provide quality, cost effective solutions, including ones for large diameter structures.
For further information visit www.ferromonk.co.uk
