Future technologies of trenchless renovation of the pipelines which have earlier been no-dig renovated

Every year, more and more projects are executed, for which different trenchless technologies are used. One of the biggest successful projects was renovation of sewerage in Szczecin. This investment was executed gradually in 2005 and 2006 year. It concerned the renovation of 48 km of sewerage for which many different trenchless technologies were used and it cost 288mln Euros. Many untypical problems had to be solved during realization of the project, e.g. project concerned the renovation using 1m long hat - sleeve. The other example for instance is the biggest in Poland microtunneling, realized in 2005, for pipes of 2400mm in diameter with the longest single distance of 473m. One of the most interesting successful renovations, which ended in 2002, was the project concerned renovation of over 100 – year old 900 to 1200 mm sewers with liners impregnated with polyester resins made by Per Aarsleff Poland. The company has been given the Polish trenchless statue “Expert 2006” in this year. This project was recognized by ISTT as the best renovation project in the world and was awarded a prize NO – DIG Award 2002.

Trenchless renovation of pipelines which has earlier been no-dig renovated is rather rare nowadays in Poland. But there are some cases when trenchless renovation ends with a failure. Sometimes even the renovating coating is being destroyed. The typical reasons are as listed below:

• Design mistakes which can result in choice of the coating of too little range or not resistant to failure,
• Application of improper technology, including choice of an improper material of the coating,
• Executing mistakes or renovation performance inconsistent with the project.

So even now, in case of the renovations which has ended with failure, the afresh renovation is required. The issue of trenchless renovation of the pipelines already renovated will surely become very important in several dozen years, when aging processes start to lead renovation coatings to damage.

Analysis of the costs of execution of trenchless renovation according to the expected exploitation time of renovated pipeline
The very important factors which determine the frequency of the future trenchless renovations of the pipelines are: durability of the applied material of the pipeline and durability of the material used for its trenchless renovation.

The costs of building, exploitation and renovation of the sewer in the function of time and depending on quality of materials used for pipeline and for the subsequent renovations are shown in fig.1. Even very small amount of extra money dedicated to enlarging sewer structure durability (e.g. applying better protection again corrosion or bottom abrasion of the sewer) is very profitable concerning time of its exploitation.

The costs of sewer construction, its exploitation and renovation (fig.1.) were defined for three variants. Fig. 1a) shows the cost for the case when low quality materials are used for sewer construction, fig.1 b) presents the case when better material is applied and fig. 1.c) shows the case when the best materials are used for sewer construction (concerning the sewer construction as well as the renovation coating). The costs of construction, exploitation, and renovation were gathered for a term of hundred years.

In these examples the prices are constant in time, adjusted to the level from 1990. The calculation is made in Danish currency and refers to the investments built before 1990. (Kuliczkowski A. 2005, pp. 193-200).

The analysis of the costs indicates that application of the best quality materials for sewer construction can bring huge profits.

Considering the diagrams in the fig.1 one should raise the basic questions: should the shortest of the proposed terms (term of 50 years), which occur between the two subsequent renovations, be a priori rejected and not taken into consideration? And on the other hand, could the longest term (term of 100 years), which divide two adjacent renovations, be accepted as absolutely satisfied? Yet more than 100 years durable sewer materials are known. So wouldn’t it be advisable to apply material – structure solutions for pipeline and renovation coatings, for which the predicted time of its exploitation would be much longer.

In many countries there are known examples of long-time exploited sewers. In Poland there are a lot of brick sewers, built in XIX century, but still in very good technical condition.

In fig. 2a the inside of brick sewer from XIX century is shown and fig. 2b presents reinforced concrete sewer laid over the subway line in Warsow, very close to it. Fig.2a shows very good condition of XIX century brick sewer, which has no any cracks, in opposite to reinforced concrete sewer (fig 2b), which has cracked up on short length as a result of ground settlement after the subway was built very shallow under the sewer.

Application of high quality materials for building and renovations of pipelines is surely reasonable because of great expenses which would have to be incured in case of potential damages. Every single damage costs really a lot. For instance the repair of the damage of oil pipeline in Texas, USA of 28’’ in diameter in March 2000 cost over $18mln, the other in Kentucky in January 2000 (steel petroleum pipeline of 24’’ in diameter) $7,1mln (Reports). Especially high costs are borne in case of sewerage renovation. According to analyses made in Germany, the scientists estimate that the cost of municipal sewerage renovation in Germany till 2015 will reach the value of about 50 billions € and private sewerage even 110 billions €. (Kuliczkowski A. 2005, pp. 193-200)

It’s very important to properly plan the potential renovation. If the technical condition of the pipeline indicates for need of its renovation in a relatively short time, it’s necessary to conduct this renovation, because, as the analyses show (Insituform), the direct cost of clearing out the effects of sewerage catastrophe can be from 3 to 4 times bigger than the cost of scheduled pipeline renovation. In addition so called social costs of sewerage catastrophe are really high. The ratio of social costs to direct costs can amount to from 1:1 to 4:1, depending on the size and the range of damage. (Insituform)

The factors which influence to the elongation of the time of failure - free operation of pipelines
The factors of basic importance for elongation of the first and the most important term – fig.1.- (between pipeline building and its first renovation) are listed below:

• The quality of materials used for pipe construction and (in case of some kinds of pipes) in additionally applied protective covers,
• The quality of pipeline laying,
• The way of pipeline exploitation.

The current tender system in Poland in most cases prefers the cheapest pipes, so usually rather not durable. For example as a result of the tender, the 50 – years -durable pipe can be chosen (fig.1a) and the 100-years-durable pipe can be rejected. The second one, more resistant for corrosion and abrasion, can be only 20% more expensive than the first one, but application 100-years durable pipe could elongate the time of the subsequent renovation from the period of 50 years after installation to the period of 100 years after installation (fig.1c). In a longer perspective, that would surely bring a lot of economic profit. The best quality pipes, usually the most expensive ones and with the elongated durability are not commonly used in Poland nowadays, mostly because of the lack of legislation which would allow to choose them during the tender.

The very important factor for elongation of pipeline exploitation is its proper laying and installing. The results of the examination of new-built pipelines prove, that many of them should be classified for renovation or replacement, in the moment when they are turned over for exploitation. For example the results of the PVC sewer examination (Kuliczkowska E. 2005), built within a few past years show, that its improper installation, inappropriate storage and transport resulted in the fact that many of these pipelines (49%) could not be classified to final reception. These examinations were led by employees of Technical University in Kielce. Technical University in Kielce is the only university in Poland, which has conducted sewerage inspection, in the territory of the whole country, using CCTV since 1991 till now. The University also carries out the expertise of the pipelines, which are or were renovated.

The examples of the trenchless renovations of the pipelines which has ended with the failure
There are many examples of trenchless renovations in Poland as well as in other countries, which ended with a failure. In Poland, most of these unsuccessful renovations are caused by:

• Application of the renovation coatings with too small load capacity, which are not resistant for loss of its stability or their improper placing in the renovated pipeline. The example of such renovation is presented in fig. 3. Here, for renovation of 1200mm reinforced concrete sewer pipe, structural PE-HD pipes 1000mm in diameter were used. The PE-HD pipe chosen for renovation was designed properly but the space between pipes wasn’t filled with cement mortar. This filling was one of the assumptions of static – strength calculation, which allowed to choose the given pipe for renovation with a specified circular stiffness. Very soon after renovation – a year after- PE-HD pipe failed (the bottom of pipe rose up to the top) as a result of ground water pressure, because the water filled the free space between pipe and old sewer immediately after renovation. In fig. 3a PE-HD pipe after failure is shown with the sewage flowing on the both sides of the risen bottom. In fig. 3b the same pipe is taken out onto the surface. The cross section, visible in fig.3b, has partly gained its original shape – less deformed than in fig. 3a.

• Appearances of leaky joints in short pipe modulus used for renovations. In fig. 4 the example of such a leaky joint in structural PE-HD pipes used for renovation is shown. Accretion after infiltration is visible on pipes joints.

• Application for renovation of pipes made of improper material, e.g. with to small thermal, chemical or abrasion resistance,

• Application of close–fit lining renovation with the incorrectly chosen diameters, for instance applying too large diameter of coating in close fit U-liner technology. In this case the coating can’t get back into circular shape and that causes its deformation and leads to cracking. The example of damaged close-fit PE-HD lining is shown in fig.5a. In fig.5b the example of improperly chosen materials for liners impregnated with resins is presented - foil doesn’t adhere to polyester liner impregnated with resin. The following two figures describe: fig. 5c inappropriate process of resin liner toughening and fig. 5d insertion of resin liner into the wrong place.

• Lack of eventual investor supervision during the renovation work, what can lead to abnormality during installation or even application by constructor of other substitutes, e.g. cheaper solutions, which differ from the project

There are many reasons of renovations which ended with failure. Repeatedly, the renovation ends with failure because of a few different factors, for instance mistakes in project calculation and improper installation. Every single case of unsuccessful renovation should be individually and independently analyzed.

Every unsuccessful renovation causes great financial loss and needs afresh renovation. But sometimes the afresh trenchless renovation can be impossible to execute. For instance in case when the U-liner stays unopened (fig. 5a) its afresh renovation might be unworkable because of hydraulic parameters. Every next coating, placed inside of the pipeline, would reduce the cross section of pipelines. The results of the CCTV inspection of new-built pipelines led by Technical University in Kielce (Kuliczkowska E. 2005) indicate that some of the pipelines should be classified for renovation or replacement just before they start to be exploited. The results of the new-built PVC sewer inspections mentioned before can serve as the examples.

The other problems connected with the possibility of renovation leading
Considering the mentioned examinations (Kuliczkowska E. 2005) and the expertise (Kuliczkowski A. 2004, pp. 54) one can claim, that plastic is the material which, when improper installed, might cause a lot of problems during its potential renovation. Plastics pipelines have many advantages but their inappropriate application, transport, storage or mistakes in design may speed up their potential renovation or replacement. Their renovation might be difficult in execution or even unworkable. The examples of such abnormalities are shown in fig. 6 and 7. In fig. 6 the example of improper choice of pipe material (here PVC), not suitable for the conditions in which it should work, is presented. PVC pipe, 200mm in diameter, visible in fig.6 was installed on a steep and sunny hill, where the temperature differed from -300 in winter to +500C in summer. The result of such big temperature difference was the accelerated aging of pipe material, what in consequence led to its failure (after 20 years after installation). Trenchless renovation of such seriously damaged and deformed PVC pipe is currently impossible, among other, because of the necessity to guarantee the minimum diameter of sanitary sewer, which equals 200mm.

In fig. 7 structural PE-HD pipe, 1600mm in diameter is shown, installed in condition of existing ground water pressure. Because of the lack of a few pipes (imported from abroad) of stiffness required in the project and because of the necessity of hurry during instillation, pipes of the less than required ring stiffness were laid on a dozen meters. The pipes with lowered stiffness lost their stability in the bottom area after 3 years of exploitation (fig. 7). In this case pipeline trenchless renovation became unworkable and the pipes were replaced by new ones in traditional excavation way.

Considering the both examples discussed above one can state that in case of plastic special attention must paid to the following factors:

• Properly calculated project, including right choice of ring stiffness
• Appropriate choice of material, suitable for condition of pipeline exploitation; one should remember that high temperature, big difference between operational temperatures, or increased pressure will reduce the time of pipeline use and will accelerate the aging processes,
• Providing the proper conditions of storage, transport and pipe installation,
• Careful investor supervision during pipeline building, which prevents the contractor from the application of the other e.g. cheaper or not suitable solutions or application other parameters of installation.

The additional criteria, which should be considered during the design of the pipeline trenchless renovation
Analysis of the described above unsuccessful renovations indicates that during the design process one should take into consideration some additional criteria:

• Criterion of maximum elongation of material – structure durability solutions applied in pipeline renovations,
• Operational criterion, which allows to execute the next future renovation by using as many as possible available techniques,
• Criterion which allows in the future building up the connections or laterals in the renovated pipeline and which enables to find and precisely localize the possible leakage.

Conclusions
The 16 years of experience from CCTV inspections (Kuliczkowska E. 2005) and expertise of sewer construction (Kuliczkowski A. 2004, pp. 54) led by Technical University in Kielce, anxiously evidences of occurrence of the many pipeline damages, (especially in case of pipes made of plastic), even right after their installation or trenchless renovation.

So even nowadays, the problem of renovation of pipelines already no-dig renovated appears. Basing on economic analysis discussed in chapter 1 one can state that it’s profitable to apply materials of the longest durability for underground pipelines. One should also consider increasing the safety factor of renovating coatings to the value, which would guarantee durability of plastic pipes not for 50 years but for 100 years or even longer.

During the process of choosing trenchless technology of renovations one should take into consideration three criteria mentioned in chapter 5.

While designing the pipelines it seems to be worth to make some changes, described in details in the KA-2004 method (Kuliczkowski A. 2005, pp. 193-200, Kuliczkowski A. 2004, Rury kanalizacyjne). It regards for instance the defining of the minimum predicted time of pipeline exploitation, depending on the material used for pipe construction. The proposals described in the mentioned method are to help to minimize the costs of trenchless pipeline renovation and enable to choose the optimum time of their exploitation.

References
Kuliczkowska E. 2005, ‘Wyniki badan nowo wybudowanych przewodow kanalizacyjnych z rur PVC’, Gaz, Woda i Technika Sanitarna, no 10, pp. 16-20

Kuliczkowski A. 2005, ‘Bezwykopowa odnowa rurociagow i kanalow juz wczesniej bezwykopowo odnowionych’, Materialy konferencyjne, Politechnika Swietokrzyska, Kielce pp. 193-200

Kuliczkowski A. 2004, ‘Ekspertyzy konstrukcyjne przewodow wodociagowych podstawa doboru optymalnych technik ich bezwykopowej odnowy’, Inzynieria Bezwykopowa no 4, pp 54

Kuliczkowski A. 2004, : Rury kanalizacyjne, Projektowanie konstrukcji, Monografia no 42, vol.2 Politechnika Swietokrzyska, KielceMitteilungen Verband Zertifizierter Sanierungs- Berater für Entwässerungssysteme (E.V.) VSB 2003, Empfehlungen für kommunale Kanalnetzbetreiber zur Ausschreibung von Sanierungsleistungen, bi Umweltbau, no 3, pp. 73-74

Insituform Culvert Renewal Combating The Effects of Age on Our Roadway Systems, available:
www.ces.clemson.edu/t3s/workshop/2006/Melton.pdf
Reports of National Transportation Safety Board Washington, D.C. 20594, Pipeline Accident Brief