State of technology for renewal of sewer force mains

This paper presents the results of a review of the state of technology for renewal of force mains. Force mains are critical components of many sewer collection systems with significant environmental and cost consequences for failure. The review identified several needs, including the need for rational and common design approaches for rehabilitation systems, quality assurance/quality control procedures, and better practices for operation and maintenance. The difficulty in assessing the condition of sewer force mains, leaving many owners with questions about the integrity of their systems, and the limited amount of technologies available for renewing a deteriorated main, has limited the amount of renewal work in the past. Most of the renewal activity has involved complete replacement of the force main. As the nation's force mains age further, greater emphasis must be placed on finding cost-effective ways to renew these critical assets. Fortunately, new products and technologies are now emerging for condition assessment, as well as rehabilitation. Some newer methods developed for gravity sewers and water distribution systems are being adapted for use in force main rehabilitation but design and performance data gaps remain to be filled.     

Predictive modeling of installation loads for directional drilled fusible PVC pipe

Today, trenchless technologies such as horizontal directional drilling (HDD) have increased significantly as an alternative installation method in the municipal sector. Installation of potable water, force mains, reclaimed water, and gravity sewer pipelines employing directional drilling have increased as demand for installations in difficult areas including under rivers or major highways and highly urbanized and congested utility corridors has increased. The nature of the HDD process necessitates the use of continuously joined pipe products capable of being pulled in, as opposed to being pushed, or “jacked” in as with segmental installations. Fusible polyvinylchloride pipe (FPVCP) is one such material for installation of water and wastewater, pressure and non-pressure infrastructure using HDD. This paper describes a model for predicting pull loads during HDD installations using FPVCP. Pull load data was captured using an in-line measuring device attached between the backreamer of the drill string and the product pipe to gauge exact loading transferred to the pipe. Detailed results from four field projects demonstrate excellent correlation between predicted and field data.     

A survey of sewer rehabilitation in Malaysia: application of trenchless technologies

This work presents a review of applicable sewer rehabilitation options using trenchless technology in Malaysia. The typical problems faced in wastewater collection systems are analysed and factors that determine the selection method are outlined. This study also highlights the necessary steps to be taken prior to the rehabilitation work. The trenchless technology reviewed here comprises repair, renovation and replacement options. The cost-effectiveness of different rehabilitation methods was identified to assess the economic viability of various options in the Malaysian context. This study reveals that not all the trenchless technologies available in the market are suitable for use in Malaysia, mainly due to incompatibility of the rehabilitation materials used. Furthermore, as trenchless rehabilitation generally involves higher capital outlay than open-cut methods, the choice of rehabilitation method has to be made on a case-to-case basis.     

A retrospective evaluation of the performance of liner systems used to rehabilitate municipal gravity sewers

This paper provides new results gathered as part of a 6-year project funded by the U.S. Environmental Protection Agency (USEPA) to document the in-service performance of trenchless pipe rehabilitation techniques. The results from a pilot study focusing on cured-in-place pipe (CIPP) rehabilitation technologies were previously reported and the research program was extended to allow collection of additional CIPP samples and also to extend the study to other rehabilitation technologies (specifically included in this Phase 2 research were fold-and-form, deform–reform, and sliplining technologies). The establishment of a database to house performance evaluation data for rehabilitation technologies used in the water and wastewater sectors is also described. The additional retrospective data for CIPP and other rehabilitation technologies are reported and an overall assessment of CIPP life cycle performance is provided. The examination of CIPP liners with up to 34 years in service and other rehabilitation technologies with up to 19 years of service has shown that all of the rehabilitation technologies are showing little evidence of deterioration in service. The test results for 18 CIPP samples from nine cities across North America indicate that properly designed and installed CIPP liners should meet and likely exceed the typical 50-year expected design life. For the fold-and-form, deform–reform, and sliplining technologies, there are only two to three samples per rehabilitation technology and hence less can be said about overall performance. Nevertheless, all of the samples tested still met the material property requirements at installations after 14–19 years of service. In summary, the results provide an excellent prognosis for the rehabilitation technologies evaluated.     

Implementing quality control in HDD projects—a North American prospective

The Horizontal Directional Drilling (HDD) industry in North America has experienced a tremendous rate of growth within the last decade. However, the development of acceptable operating standards and quality control (QC) and quality assurance (QA) procedures significantly lags behind the current utilization level of HDD. This gap is now considered to be one of the main obstacles for wider acceptance of HDD by the engineering community in North America. This paper describes various risks and quality-related problems in HDD practice. Recent efforts to promote and regulate quality project delivery in HDD projects are outlined. Thereafter, quality control and quality assurance are defined in the context of HDD. It is recommended that a universally recognized standard such as ISO 9000 be adopted as the basis for an industry-wide quality management system. Examples of how to customize selected ISO 9000 clauses to meet the directional drilling industry's QC/QA needs are given. Additionally, a new approach for QC during HDD installation is described and its merits discussed.     

Adaptive quality control and acceptance of pavement material density for intelligent road construction

During conventional road construction, quality control and acceptance (QC/QA) are based on limited spot tests of material density at random locations which may not be representative of the compacted area and may consist of potential bias. This research presented an innovative material-machine-information and human-decision integrated system for adaptive QC/QA using the intelligent compaction (IC) technology to overcome the above limitation of conventional testing. In this integrated system, compaction properties such as material stiffness are monitored in real time with 100% coverage of compacted areas by instrumented IC rollers. By monitoring compaction process and roller–ground interactions, this system can be used to determine compaction target values, which are in-turn fed back to the IC system to optimize compaction efforts and improve construction quality. This approach can also be used to determine compaction uniformity for the as-built in order to assess pavement performance. Recommended further development of the intelligent road construction technology is presented to fully leverage the IC technologies in the future.     

Simulation-based life cycle cost modeling and maintenance plan for water mains

Life cycle cost (LCC) is an essential approach to decide on alternative rehabilitation strategies for infrastructure systems, such as water mains. The research presented in this article identifies several rehabilitation methods for water mains, which are classified into three main categories: repair, renovation and replacement. A simulation-based LCC (SLCC) model is developed to compare different rehabilitation scenarios/alternatives for various types of water mains (i.e. cast iron, ductile iron, concrete, polyvinyl chloride and asbestos cement). Results show that ‘open trench’ and ‘slip lining’ are the most appropriate methods for the ‘repair’ and ‘renovation’ categories, respectively. However, the most suitable method for the ‘replacement’ category is ‘pipe bursting’ for pipe diameters less than 750 mm (<30″) and ‘open cut’ for pipe diameters greater than 750 mm (>30″). A rehabilitation plan is developed based on the SLCC results. This plan recommends repairing pipes using ‘open trench’ until the breakage rate reaches 0.5 breaks/km/year, then, replace the pipe beyond this threshold. Based on the designed SLCC model, web-based software is developed to determine the optimal rehabilitation scenarios. The developed model and software help academics and practitioners (e.g. municipal engineers) to predict the suitable new installation and/or rehabilitation programs as well as their corresponding costs.     

Data acquisition and analysis for water main rehabilitation techniques

The ability to regularly deliver safe drinking water is a constant challenge to municipalities worldwide. In Canada, the replacement/rehabilitation cost of water mains is estimated to be $28 billion (1997–2012). Therefore, selecting cost-effective repair and/or rehabilitation scenario(s) is essential to optimise the quality of existing water mains and minimise unnecessary rehabilitation costs. The research presented in this paper identifies several rehabilitation methods for water mains, which are classified into three main categories: (1) repair (i.e. open trench, sleeves); (2) renovation (i.e. slip lining, cement mortar lining, epoxy lining, cured in place pipe (CIPP)); and (3) replacement (i.e. pipe bursting, micro-tunnelling, horizontal directional drilling, auger boring, open cut). Due to complexity, scarcity, and enormity of data required to perform life cycle cost (LCC) and select the cost-effective scenario(s), the research presented focuses on LCC data acquisition and analysis. Data were collected from contractors and municipalities in Canada. Rehabilitation decision trees were developed as a preparation step for future LCC implementation. Breakage rate analysis was successfully developed to predict the intervals of various rehabilitation alternatives. The research presented is relevant to researchers and practitioners (municipal engineers, consultants, and contractors) to prioritise pipe inspection and rehabilitation planning for existing water mains.     

A risk management approach to safety assessment of trenchless technologies for culvert rehabilitation

Proper functioning of culverts is not only critical to protecting the transportation system from flooding but also critical to maintaining the expected service life of the overall transportation system. During the service life of culverts, they deteriorate due to many reasons such as corrosion caused by road salt, blockage by debris and sediment, poor construction techniques, etc. Trenchless technologies have been used by several State Departments of Transportation (DOTs) to rehabilitate deteriorated drainage structures without disrupting the traffic and within a relatively short span of time. These technologies provide many benefits in terms of cost, time, quality, and expected service life. However, the safety aspects of these techniques have not been discussed and documented in detail probably due to the complexity and the lack of safety standards and specifications directly associated with the techniques. This paper discusses the application of a risk assessment framework to assess potential safety issues of currently available trenchless technologies for culvert rehabilitation. The findings of the study will provide additional information to improve the decision making process in selecting and planning culvert rehabilitation projects.     

Service mains through the basements

The practical nature of much research work in some countries is illustrated by this report from the Civil Engineering Institute of the Bauakademie of the German Democratic Republic. It describes how the crucial installation of mains supplies in urban rehabilitation - for district heating, water supply, electricity, telephones - is achieved by forming a continuous 'tunnel' through the basements or cellars of old terraced buildings, and running the new supply networks in specially constructed service ducts, thus avoiding costly and complex road works.     

Service mains through the basements

The practical nature of much research work in some countries is illustrated by this report from the Civil Engineering Institute of the Bauakademie of the German Democratic Republic. It describes how the crucial installation of mains supplies in urban rehabilitation ‐ for district heating, water supply, electricity, telephones ‐ is achieved by forming a continuous ‘tunnel’ through the basements or cellars of old terraced buildings, and running the new supply networks in specially constructed service ducts, thus avoiding costly and complex road works.     

Automated detection of surface defects in water and sewer pipes

Automation is gaining momentum in industry, particularly in rehabilitation and inspection works of underground infrastructure facilities. This paper describes a model for automating inspection and identification of surface defects in underground water and sewer pipes. The paper describes the current efforts in identification of surface defects in underground water and sewer mains, and presents an automated system designed to assist infrastructure engineers in diagnosing defects in this class of pipe networks. It describes the general architecture of the system and its basic components, and focuses primarily on four modules designed for automating image acquisition, image processing, features extraction and classification of defects.     

Renovation of brick interceptor sewers

Brick interceptor sewers began to be built in Europe (London, Paris, Hamburg) in the 18th century. The sewers were built from solid ceramic brick (so called sewer brick) or clinker brick. This paper presents a study of damage to brick interceptor sewers built in the 19th century and at beginning of the 20th century in Poland. Damage to the sewer structure and to the surrounding ground and its causes are identified. On the basis of results of in situ investigations, laboratory tests and structural and strength analyses, the condition of sewer structures in Poland was assessed as a pre-failure one. Underground infrastructure pipes of urban areas can be repaired in trenches or using trenchless techniques. Although trenchless technologies have been known in Poland for more than 25 years, there is still the lack of knowledge and imagination on the part of designers – so different problems in renovating process of brick interceptor sewers are described.     

In-lab and on-site measurements of hot mix asphalt density: Convergence and divergence hypotheses

The life cycle of hot mix asphalt (HMA) depends on the material density. Bulk specific gravity and air void content are crucial factors for quality control and quality assurance (QC/QA) procedures used to evaluate contract specifications. Densities measured in the laboratory are reliable and accurate but are obtained very slowly. On-site measurements are made using non-nuclear portable devices and are often considered biased and unreliable. The object of this work was to evaluate a proposed theoretical framework for interpreting in-lab and on-site measurements and to propose strategies for using non-nuclear portable devices in QC/QA. A decrease in porosity yielded in-lab specific gravities that converged. In contrast, due to the high dielectric constant of water the divergence of in-site measures was observed. A conceptual framework and two practical equations are provided.     

Comprehensive review of structural deterioration of water mains: physically based models

This paper provides a comprehensive (although not exhaustive) overview of the physical/mechanical models that have been developed to improve the understanding of the structural performance of water mains. Several components have to be considered in modelling this structural behaviour. The residual structural capacity of water mains is affected by material deterioration due to environmental and operational conditions as well as quality of manufacturing and installation. This residual structural capacity is subjected to external and internal loads exerted by the soil pressure, traffic loading, frost loads, operational pressure and third party interference. Some models address only one or a few of the numerous components of the physical process that lead to breakage, while others attempt to take a more comprehensive approach. Initial efforts were aimed mainly towards development of deterministic models, while more recent models use a probabilistic approach to deal with uncertainties in defining the deterioration and failure processes. The physical/mechanical models were classified into two classes: deterministic and probabilistic models. The effect of temperature on pipe breakage is discussed from three angles; the first deals with temperature effects on pipe-soil interaction, the second deals with frost load effects and the third provides a brief review of various attempts to statistically quantify influence of temperature on water main failure.This paper complements the companion paper “Comprehensive review of structural deterioration of water mains: statistical models”, which reviews statistical methods that explain, quantify and predict pipe breakage or structural failures of water mains.     

Decision support model for selection of rehabilitation methods of water mains

The deteriorating condition of water mains in Canada and US calls for rehabilitation strategies that accounts mainly for budget and level of service constraints. These water mains have received ‘D’ grade in the two countries. Decision support models can assist decision makers regarding when to rehabilitate and whether to repair, renovate or replace section(s) of water mains. The literature indicates that decision models should account for life cycle cost, uncertainty, long-term planning, targeted levels of service and budget constraints. The objectives of this paper are to: identify and group rehabilitation methods, present decision support model to rank and select most suitable rehabilitation method(s), and study the impact of rehabilitation methods on the functional and structural performance of water mains. The developed decision support model accounts for life cycle cost of each competing scenario along with the associated uncertainty. The model, unlike available models, can effectively account for vagueness, qualitative assessments and human judgment associated with input data. A case study of a water main network was analysed in order to demonstrate the use of the developed model and to illustrate its essential features. The results obtained indicate that the model can support the generation of well-informed decisions in a timely manner.     

Sewer asset management – state of the art and research needs

ABSTRACT

Sewer asset management gained momentum and importance in recent years due to economic considerations, since infrastructure maintenance and rehabilitation directly represent major investments. Because physical urban water infrastructure has life expectancies of up to 100 years or more, contemporary urban drainage systems are strongly influenced by historical decisions and implementations. The current decisions taken in sewer asset management will, therefore, have a long-lasting impact on the functionality and quality of future services provided by these networks. These decisions can be supported by different approaches ranging from various inspection techniques, deterioration models to assess the probability of failure or the technical service life, to sophisticated decision support systems crossing boundaries to other urban infrastructure. This paper presents the state of the art in sewer asset management in its manifold facets spanning a wide field of research and highlights existing research gaps while giving an outlook on future developments and research areas.     

Accounting for Polycyclic Aromatic Hydrocarbons in Public Water Supplies

Asset management plans were prepared in 1989 and 1994 by water companies in England and Wales for submission to the Office of Water Services. These plans constituted the financial programming required by water companies to meet specified standards of service, particularly with respect to water quality. Detailed studies have previously established that problems associated with iron from unlined ferrous mains, particularly in soft water areas, is often the main cost 'driver'for water distribution investment. However, many of the so-called unlined iron mains were treated with a coal-tar pitch lining for corrosion protection before installation, and residues of this painted lining can give rise to unsatisfactory levels of polycyclic aromatic hydrocarbons in drinking water.
The paper describes how desk-study research, followed by the development and application of a modified 'focused downstream series sampling'water-quality modelling technique allowed polycyclic aromatic hydrocarbons to be accounted for in two water company asset management plan submissions. The paper also raises a number of fundamental implications with respect to the occurrence of these carcinogenic compounds in drinking water.     

A qualitative analysis of early defects present in PVC-U sewers but not observed in rigid pipes

The objective of the study was to analyze early defects in PVC-U sewer pipes that are not observed in rigid pipes. Field investigations were conducted on newly laid PVC-U sewer pipes in more than a dozen cities in Poland using CCTV equipment and a special device for measuring deflections. The analysis focused on qualitative data concerning defects observed in PVC-U sewers. Three types of defects, i.e. dents, deflections and buckling, were thoroughly analyzed to determine whether trenchless rehabilitation of such pipes is possible and to improve the existing sewer deterioration models. The major conclusions concern the types, sizes and frequencies of defects in PVC-U pipes, their causes, and the possibility of future rehabilitation as well as the improvement in the deterioration models.     

Trenchless construction: An emerging technology in United Arab Emirates

The development of trenchless methods has gained impetus in the construction industry in United Arab Emirates due to increasing amounts of investment in underground infrastructures that are new, deteriorating, or under capacity. This paper presents the results of a questionnaire survey of trenchless construction methods used by municipalities and contractors in United Arab Emirates. The survey provides an indication of current and expected future trends in the application of trenchless construction technologies including types of technologies employed and percentage of projects that employed trenchless technologies. The survey results indicate that trenchless technology is gaining increasing popularity among contractors and municipalities across United Arab Emirates. The survey results also indicate that trenchless technology is gaining increasing popularity among municipal engineers across UAE. The survey revealed current, and by extrapolation likely future growth, in utilizing trenchless construction methods and the average expenditures of municipalities in UAE for new construction and for rehabilitation.