Mark Knight

Application of system dynamics for developing financially self-sustaining management policies for water and wastewater systems

Recently enacted regulations in Canada and elsewhere require water utilities to be financially self-sustaining over the long-term. This implies full cost recovery for providing water and wastewater services to users. This study proposes a new approach to help water utilities plan to meet the requirements of the new regulations. A causal loop diagram is developed for a financially self-sustaining water utility which frames water and wastewater network management as a complex system with multiple interconnections and feedback loops. The novel System Dynamics approach is used to develop a demonstration model for water and wastewater network management. This is the first known application of System Dynamics to water and wastewater network management. The network simulated is that of a typical Canadian water utility that has under invested in maintenance. Model results show that with no proactive rehabilitation strategy the utility will need to substantially increase its user fees to achieve financial sustainability. This increase is further exacerbated when price elasticity of water demand is considered. When the utility pursues proactive rehabilitation, financial sustainability is achieved with lower user fees. Having demonstrated the significance of feedback loops for financial management of water and wastewater networks, the paper makes the case for a more complete utility model that considers the complexity of the system by incorporating all feedback loops.

Development of a system dynamics model for financially sustainable management of municipal watermain networks.

This paper develops causal loop diagrams and a system dynamics model for financially sustainable management of urban water distribution networks. The developed causal loop diagrams are a novel contribution in that it illustrates the unique characteristics and feedback loops for financially self-sustaining water distribution networks. The system dynamics model is a mathematical realization of the developed interactions among system variables over time and is comprised of three sectors namely watermains network, consumer, and finance. This is the first known development of a water distribution network system dynamics model. The watermains network sector accounts for the unique characteristics of watermain pipes such as service life, deterioration progression, pipe breaks, and water leakage. The finance sector allows for cash reserving by the utility in addition to the pay-as-you-go and borrowing strategies. The consumer sector includes controls to model water fee growth as a function of service performance and a households financial burden due to water fees. A series of policy levers are provided that allow the impact of various financing strategies to be evaluated in terms of financial sustainability and household affordability. The model also allows for examination of the impact of different management strategies on the water fee in terms of consistency and stability over time. The paper concludes with a discussion on how the developed system dynamics water model can be used by water utilities to achieve a variety of utility short and long-term objectives and to establish realistic and defensible water utility policies. It also discusses how the model can be used by regulatory bodies, government agencies, the financial industry, and researchers.

Investigation of Hot-Mix Asphalt Dynamic Modulus by Means of Field-Measured Pavement Response

The current Mechanistic–Empirical Pavement Design Guide (MEPDG) proposes the use of the laboratory dynamic modulus test to determine time–temperature-dependent properties of hot-mix asphalt (HMA) materials. To date, limited measurements have been performed to compare the HMA behavior of laboratory dynamic modulus test with the field measured pavement response. The objectives of this study were to compare and validate laboratory-determined HMA dynamic modulus with field-measured asphalt longitudinal strains. Under constant loading frequency, the laboratory-determined dynamic modulus for Hot Laid 3 (HL3) was found to decrease exponentially when the temperature of the asphalt mix increased. Controlled wheel load experiments, performed at a constant truck speed, found that HL3 asphalt longitudinal strain increased exponentially with an increase in asphalt middepth temperature. The comparison of both exponential relationships showed that the laboratory-determined dynamic modulus was inversely proportional to the field-measured asphalt longitudinal strain.

Field evaluation and analysis of flexible pavement structural responses under dynamic loads

This study investigates the structural responses of flexible pavements at the Center for Pavement and Transportation Technology (CPATT) test track located at Waterloo, Ontario, Canada. A comprehensive field testing program was performed to examine flexible pavement responses to a variety of loading conditions. Tests were completed using six tire types: 11R22.5, 275/80R22.5, 295/75R22.5, and 285/70R22.5 dual tires, and 455/55R22.5 and 445/50R22.5 wide-base tires, and tire inflation pressures that ranged between 482 to 827 kPa. A two-dimensional finite element model was developed using MichPave software to predict pavement responses. A simplified method was proposed to characterize HMA properties using the laboratory dynamic modulus test. The developed model simulations approximated the field measured responses to all loading configurations.

Numerical DAE Approach for Solving a System Dynamics Problem

AbstractA system dynamics model first developed using modeling and simulation software that explores the complex behavior of the financially sustainable management of water distribution infrastructure was converted into a system of coupled nonlinear algebraic differential equations (DAEs). Each differential equation involved a time derivative on a primary variable specifying the temporal evolution of the system. In addition, algebraic (secondary) equations and variables specified the nonlinearity inherent in the system as well as any controls on the primary variables constraining the physical evolution of the system relevant to the problem at hand. The objective of this exercise was to demonstrate that spurious oscillations in the modeling and simulation software solution are numerical aberrations. Furthermore, the numerical DAE solution is absent these same oscillations, exhibits point-wise stability, and converges to the physically correct solution. While the modeling and simulation software employed a ...

Horizontal Directional Drilling Pipeline Design and QA/QC Using the BoreAid Software Program

This paper describes a structured framework for the design and construction of horizontal directional drilling (HDD) projects. This framework is implemented in a new HDD software design program BoreAid . The framework consists of five interlinked modules: 1) bore planner; 2) load/deflection calculator; 3) drill planner; 4) bore pressure estimator; and 5) equipment/tooling selection. Each module is discussed in detail and a case study example is presented to demonstrate how this new framework methodology can be used as a HDD project quality assurance and quality control tool and to increase the probability that the project will be completed on time and within budget by ensuring industry good practices are followed.

Development of Unit Cost Indices and Database for Water and Wastewater Pipelines Capital Works

The objective of this work is to develop a unit cost database and index for water and wastewater pipelines capital works, and estimate inflation in their construction cost. This was accomplished by analyzing tender summaries and progress certificates from the cities of Niagara Falls and Waterloo, Ontario, Canada, that span the period from 1980 to 2008, as well as using data from RS Means construction cost database. This work describes the source data, data preparation procedure, and development of unit cost database and indices. The process first involved developing scaling relationships between the cost of standard components and their sizes by regression analysis using data from tender summaries and the RS Means database. Next, unit costs of reference watermain and sanitary sewer projects and standard components are computed. Finally, a relational database is developed to store the data and to perform the unit cost analysis.

Forecasting the Unit Price of Water and Wastewater Pipelines Capital Works and Estimating Contractors’ Markup

Municipalities and water utilities need to make realistic estimates for the replacement of their aged water and wastewater pipelines. The two main objectives of this article are to present a method to forecast the unit price of water and wastewater pipelines capital works by investigating inflation in their construction price, and to quantify the markup that contractors add to bid a project price. The Geometric Brownian Motion model with drift is used for investigation. Results show that the inflation in water and wastewater pipelines reference projects were 6.41% and 5.52% per annum, respectively. These values compare to the inflation in the Standard & Poor’s/Toronto Stock Exchange (S&P/TSX) Composite Index of 6.93% per annum. In contrast, inflation in Canada’s Consumer Price Index (CPI), and Engineering News-Record’s Construction Cost Index (ENR’s CCI) for Toronto are estimated to be 2.53% and 2.85% per annum, respectively. The spread in the inflation rate between the reference price indices and that of either ENR’s CCI or CPI is a measure of the market price of catchall financial premium (defined as markup) that contractors add to project cost to account for profit, risk, and market conditions. This spread is estimated to be 3.56% and 2.67% per annum for water and wastewater pipeline capital works, respectively.

PPI-BoreAid: A Preliminary Design Tool for Horizontal Directional Drilling using Polyethylene Pipeline

PPI-BoreAid is a free online tool that allows users to perform preliminary pipe design analysis for polyethylene (PE) pipes installed using a horizontal directional drill (HDD). It allows users to determine suitable PE pipe dimension ratios (DR) to satisfy installation and in-service loads required in ASTM F1962 and Chapter 12 of the Handbook of Plastics Pipe Institute (PPI) Polyethylene Pipe Design, 2nd edition. During PPI-Boreaid development, several conservative aspects of the current PE pipe design methodology and PE pipe properties were noted. This paper discusses the requirement for the development of PPI-BoreAid as a preliminary PE pipe design tool, and provides suggested changes to the aforementioned documents. Sample calculations are presented to demonstrate how the new application can be used to select a suitable PE pipe for a site specific HDD project.

Water Mains Degradation Analysis Using Log-Linear Models

The development of reliable lifecycle intervention plans for water distribution systems depends on better understanding of water main degradation behavior. Traditionally, water main failures have been studied as Weibull/Exponential processes. This paper investigates the application of log-linear model for assessing metallic water main structural degradation. A comparison of the proposed model with the existing Weibull/Exponential based model is presented. Water mains inventory, operational and performance data from a Canadian municipality are used in the analyses. Conclusions concerning the adequacy of existing models and the applicability of proposed models are made. Municipalities and water utilities can use the method provided herein as a tool for desktop condition assessment and risk based failure analysis.