Andre Unger

University of Waterloo | UWaterloo · Department of Earth and Environmental Sciences

This paper presents a decision support system for the integrated management of water distribution and wastewater collection networks. The proposed methodology utilizes system dynamics to integrate water mains and sewers with finance and sociopolitical sectors. It enables user rate‐setting and planning of integrated water and wastewater infrastructu...

We present a quasi-steady state mechanistic derivation of the Monod bioreaction equation based upon a conceptual model involving aqueous phase diffusive transport of substrate towards a spherical microbe; transport of the substrate across its surface membrane; and reaction depleting the substrate within the microbe. The resulting Monod coefficients...

This study develops a framework for asset management strategy of wastewater collection networks comprised of three interconnected decision-making layers: (1) Visions & Values, (2) Function, and (3) Performance, which are set according to the established concepts of strategic targets, policy levers, sustainability and life cycle. The asset managemen...

This study develops an implementation framework for asset management strategic planning of water distribution networks to meet sustainable infrastructure, socio-political, and financial targets over the life cycle of the infrastructure. The proposed framework is comprised of three decision-making layers: (1) Visions and Values, (2) Function, and (3...

Sabkha Matti is a potential discharge point for regional groundwater systems in the Rub’ al Khali topographic basin of Saudi Arabia. The hydrogeochemical evolution of this sabkha (salt flat) and the underlying aquifers were assessed by using a combination of geological, hydraulic, hydrochemical, and isotopic approaches. A compilation of the geologi...

An isotope and solute evaluation was applied to identify the origin and mechanisms of groundwater salinization in three major Tertiary aquifers in the Rub’ al Khali topographic basin. We demonstrate that the groundwater chemistry evolved from a low- (1,800 ppm) to high- (>120,000 ppm) salinity Na-Cl water type, regardless of the aquifer. The simila...

Sabkha Matti is the largest inland sabkha (2950 km2) in the Arabian Peninsula. The drainage area supporting this sabkha is >250,000 km2 and is the discharge point for part of the ten thousand meter thick regional groundwater systems ranging in age from Precambrian through Miocene in the Rub’ al Khali structural basin. A hydrologic budget was constr...

The goal of this case study is to demonstrate the application and utility of a developed System Dynamics (SD) model to assess the sustainability of strategic decisions for managing the wastewater collection (WWC) pipe network system for a medium-size municipality in Southern Ontario. Two asset management scenarios, suggested by the research-partner...

This work applies an advective-dispersive framework to simulate utility-wide residential water consumption, the analogy of a continuum transport process. In this context, the advective-dispersive process describes how changes in real water price and seasonal weather variability influence water consumption distribution, which ultimately governs mean...

This paper presents the development of a novel system dynamics (SD) model for better understanding the interrelation and feedback mechanism between the wastewater collection (WWC) and wastewater treatment plant (WWTP) systems. Causal loop diagrams (CLDs) are developed and discussed to depict and understand feedback and inter-connections between phy...

This paper examines a numerical modeling approach for two-phase flow and considers the contribution of a simple network of fracture intersections to the whole discrete fracture-matrix (DFM) flow system; it develops a benchmark problem for a non-wetting, dense, nonaqueous phase liquid (DNAPL) invading a water-saturated, discretely fractured, porous...

An unusually high concentration of nitrate (NO 3 ) ranging between 291 and 6790 mg/L (as N) was observed during a review of solute data for brine samples from the inland Sabkha Matti. A multi-tracer approach considering water chemistry, stable nitrate isotopes (δ ¹⁵ N and δ ¹⁸ O), and the radioactive isotope of hydrogen (tritium, ³ H) was utilized...

In most Canadian municipalities, wastewater collection (WWC) and wastewater treatment plants (WWTPs) are owned and managed by separate municipal governments. Linear sewer pipe networks are owned and managed by utilities at the lower tier of municipal government, and vertical treatment plant assets are owned and managed by regional governments at th...

Over the past decade, many performance indicators have been developed for water utilities to track their system performance. This study proposes a set of normalized and time-integrated benchmarking performance indicators for sustainable long-term management of water distribution and wastewater collection networks. The benchmarking performance indic...

Traditionally, highly deteriorated wastewater pipes are given priority in capital work activities. To this end, when capital budgets are limited, money is first allocated to replacing sewers in WRC Internal Condition Grade 5 (ICG 5), the worst condition based on WRc coding system, and the remaining budget is then used for the next condition groups...

Algebraic elimination of nodes at discrete fracture intersections via the star-delta technique has proven to be a valuable tool for making multiphase numerical simulations more tractable and efficient. This study examines the assumptions of the star-delta technique and exposes its effects in a 3D, multiphase context for advective and dispersive/dif...

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 2...

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 m...

It is estimated that at least $1 trillion dollars will be required over the next 25 years to maintain the current level of water service in the United States. A “pay-as-you-go” approach is expected to allow water utilities to pay for these expenses using water price increases. These price increases incentivize water conservation, decreasing overall...

It is estimated that at least $1 trillion dollars will be required over the next 25 years to maintain the current level of water service in the United States. A “pay-as-you-go” approach is expected to allow water utilities to pay for these expenses using water price increases. These price increases incentivize water conservation, decreasing overall...

There is a need in engineering education toimprove the connection between design and engineeringscience. Students should be provided more opportunitiesto practice applying both science and design to a singleproblem in order to be better prepared for challengesthey will face when they enter the workforce. For thisreason, an instructor of a first yea...

Viewing water and wastewater infrastructure systems from a network or functional viewpoint down to an individual component goes hand in hand with life-cycle management. Therefore, three concepts are incorporated: (1) Strategic Planning; (2) Tactical Planning; and (3) Operational Planning. The data relevant to each of these areas are generated and m...

This study demonstrates how to implement a novel system dynamics (SD) tool for strategic water utility management and financial planning. With the use of data from several local water utilities in Ontario, Canada, the tool was run to simulate 20 years to investigate: (1) long-term fee hike rates requited for system financial sustainability; (2) ser...

The focus of this paper is to price the guarantee period of a brownfields redevelopment project, which is the present value of the sum of the cost of failure plus the cost of data collection. The cost of failure is essentially a contingency fee that the developers must reserve from the sale of each residential house to cover the risk of repurchasin...

It is estimated that at least $1 trillion dollars will be required over the next 25 years to maintain the current level of water service in the United States. A “pay-as-you-go” approach is expected to allow water utilities to pay for these expenses using water price increases. These price increases incentivize water conservation, decreasing overall...

The focus of this paper is to present a methodology to assimilate soil core permeability and trichloroethylene (TCE) soil gas concentration data, and then to assess their worth in reducing prediction uncertainty with a numerical model. The specific problem involves a residential development impacted by indoor air exposure of TCE contamination origi...

In part one, the authors considered 5 options currently in use for funding municipal water infrastructure, namely Option 1: Do nothing. Ignore it, and the problem will go away., Option 2: Government grant programs, Option 3: Pay-as-you-go, capital reserving, and borrowing, Option 4: Private public partnerships (PPP) and Option 5: Privatisation. Her...

Many water utilities are faced with the problem of rising operation costs, aging and deteriorating infrastructure, and the need for more funds required to fix and replace the leaky, broken, pipes, valve, plants etc. In part one of this paper, the authors consider five existing funding options and in part two, they present an innovative proposal for...

Causal loop diagrams are developed for wastewater collection networks to identify complex interactions and feedback loops among physical, financial, and social sectors. Causal loop diagrams are then incorporated into a novel system dynamics based decision support tool that can be used for financially sustainable management of wastewater collection...

This study develops and demonstrates a wastewater system dynamics model as a decision support tool that can assist utility managers to ensure financial sustainability while maintaining customer expectations for service performance. To achieve implementation of the model, a demonstration case study is developed using data from a medium-sized city in...

Volatile organic compounds are the primary chemicals of concern at many contaminated sites and soil vapor sampling and analysis is a valuable tool for assessing the nature and extent of contamination. Soil gas samples are typically collected by applying vacuum to a probe in order to collect a whole-gas sample, or by drawing gas through a tube fille...

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 dyn...

A system dynamics model first developed using the software STELLA, which explores the complex behaviour of the financially sustainable management of wastewater distribution infrastructure, was converted here into a system of coupled non-linear differential algebraic equations (DAEs). Each differential equation involved a time derivative on a primar...

This paper is an extension of the work by Yu et al. (2009) to examine exposure pathways of volatile organic compounds (VOCs) originating from a NAPL source zone located below the water table, and their potential impact on multiple residential dwellings down-gradient of the source zone. The three-dimensional problem geometry is based on the Rivett (...

Highlights ► Hydrology in the SJV has undergone drastic changes for a century or longer. ► The system is responding to past and present stresses. ► Availability for historic pre-development data is limited for input and calibration. ► The importance of using an integrated model is demonstrated. ► The pre-development hydrology should serve as an ini...

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 diagra...

Degassing and in situ development of a mobile gas phase takes place when an aqueous phase equilibrated with a gas at a pressure higher than the subsurface pressure is injected in water-saturated porous media. This process, which has been termed supersaturated water injection (SWI), is a novel and hitherto unexplored means of introducing a gas phase...

The Large-Scale Aquifer Pumping and Infiltration Test (LPIT) conducted at the Idaho National Engineering and Environmental Laboratory was modeled using TOUGH2 to simulate the highly transient water infiltration and perched-water conditions in the fractured basalt and sedimentary interbeds existing at the site. The fracture and matrix continua of th...

This work is the second installment in a two-part series, and focuses on object-oriented programming methods to implement an augmented-state variable approach to aggregate the PCS index and introduce the Bermudan-style call feature into the proposed CAT bond model. The PCS index is aggregated quarterly using a discrete Asian running-sum formulation...

This work is the first installment in a two-part series, and focuses on the development of a numerical PDE approach to price components of a Bermudan-style callable catastrophe (CAT) bond. The bond is based on two underlying stochastic variables; the PCS index which posts quarterly estimates of industry-wide hurricane losses as well as a single-fac...

This work provides an exploratory analysis on the relative importance of various factors controlling the fate and transport of volatile organic contaminants (in this case, TCE) from a DNAPL source zone located below the water table and into the indoor air. The analysis is conducted using the multi-phase compositional model CompFlow Bio, with the ba...

Gas saturation can develop in situ within initially water-saturated porous media by injecting a gas- supersaturated aqueous phase. Supersaturated water injection (SWI) is a novel technology with several potential applications to groundwater and soil remediation. These include supply of reactive gases for in situ bioremediation and recovery of immob...

Blending of ethanol into gasoline as a fuel oxygenate has created the scenario where inadvertent releases of E95 into soil previously contaminated by gasoline may remobilize these pre-existing NAPLs and lead to higher dissolved hydrocarbon (BTEX) concentrations in groundwater. We contribute to the development of a risk-based corrective action frame...

Landslides in Pleistocene sediments along the Thompson River, south of Ashcroft, British Columbia have been known since the area was first settled in the 1880s. Since the CP mainline was open to traffic in 1886, numerous landslides have occurred along both sides of the Thompson valley and have resulted in derailments and traffic disruption along th...

The physically-based surface–subsurface HydroGeoSphere model is used to examine the hydrologic budget of the 286.6 km2 Duffins Creek watershed, located 10 km northeast of metropolitan Toronto. The primary objective of this study is to demonstrate the utility of the model to simulate the three-dimensional hydrologic response of the surface and subsu...

Understanding the risk of indoor air exposure to residual contaminants in the subsurface following the redevelopment of contaminated land redevelopment project is a central issue at many brownfield sites. In this study, we examine various mechanisms controlling vapor phase intrusion into the indoor air of a typical residential dwelling from a NAPL...

A numerical model has been used to reproduce a series of laboratory experiments designed to examine the effects of ethanol on gasoline movement in the vadose zone, particularly in the capillary fringe. The multi-phase multi-component model, CompFlow Bio was modified to incorporate two significant effects of ethanol dissolved in the aqueous phase on...

The injection of carbon dioxide (CO2) into deep geologic CO2 storage sites entails risk that CO2 will leak away from the primary storage formation and migrate upwards to the unsaturated zone from which it can seep out of the ground. This chapter introduces a coupled modeling framework called T2CA for simulating CO2 leakage and seepage in the subsur...

Geologic CO 2 sequestration is being considered as a way to offset fossil fuel-related CO 2 emissions to reduce the rate of increase of atmospheric CO 2 concentrations. The accumulation of vast quantities of injected CO 2 in geologic sequestration sites may entail health and environmental risks from potential leakage and seepage of CO 2 into the ne...

Radon gas concentrations have been monitored as part of the operation of a tunnel (the Exploratory Studies Facility-ESF) at Yucca Mountain to ensure worker safety. The objective of this study was to examine the potential use of the radon data to estimate large-scale formation properties of fractured tuffs. This objective was examined by developing...

Geologic carbon sequestration is the direct injection of CO 2 into deep geologic formations for permanent disposal. Although numerous trapping mechanisms exist in the subsurface, it is possible that CO 2 will leak from the primary sequestration target and seep out of the ground. The unsaturated zone has the potential to attenuate leaking CO 2 and d...

The accumulation of vast quantities of injected carbon dioxide (CO 2) in geologic sequestration sites may entail health and environmental risks from potential seepage of CO 2 into the near-surface environment. We are developing and applying a coupled subsurface and atmospheric surface layer modeling capability based on the TOUGH2 framework to predi...

The results of a series of ponded infiltration tests in variably saturated fractured basalt at Box Canyon, Idaho, were used to build confidence in conceptual and numerical modeling approaches used to simulate infiltration in fractured rock. Specifically, we constructed a dual-permeability model using TOUGH2 to represent both the matrix and fracture...

To address regulatory issues regarding worker safety, radon gas concentrations have been monitored as part of the operation of a deep tunnel excavated from a highly fractured tuff formation. The objective of this study was to examine the potential use of the radon data to estimate large-scale formation properties of fractured rock. An iTOUGH2 model...

Geologic carbon sequestration is the direct injection of CO2 into deep geologic formations for permanent disposal. Although numerous trapping mechanisms exist in the subsurface, it is possible that CO2 will leak from the primary sequestration target and seep out of the ground. The unsaturated zone has the potential to attenuate leaking CO2 and decr...

The purpose of this report is to present analogue studies and literature reviews designed to provide qualitative and quantitative information to test and provide added confidence in process models abstracted for performance assessment (PA) and model predictions pertinent to PA. This report provides updates to studies presented in the Yucca Mountain...

Fully implicit, fully coupled techniques are developed for simulating multiphase flow with nonequilibrium mass transfer between phases, with application to groundwater contaminant flow and transport. Numerical issues which are addressed include: use of MUSCL or Van Leer flux limiters to reduce numerical dispersion, use of full or approximate Jacobi...

The numerical model CompFlowC++ is used to examine the relative importance of different formulations of a forward dissolution rate model, within the range of parameters measured from laboratory and field studies, for predicting the mean and uncertainty in dense nonaqueous phase liquids (DNAPL) dissolution times in heterogeneous sandy aquifers. We a...

Variable spatial and temporal weighting of the advective contaminant mole fraction term is explored as a means of reducing numerical dispersion of contaminant plumes in a multi-phase compositional simulator. The spatial schemes considered are upstream, central and a non-linear flux limiter, while fully-implicit and Crank-Nicolson time weighting are...

Many industries produce and store hazardous chemicals, which, when released into the subsurface, form a dense non-aqueous phase (DNAPL) which sinks below the water table. Since DNAPLs are slightly soluble in water, it may take hundreds of years to dissolved the non-aqueous phase source of contamination. During this time, an enormous plume of contam...

The numerical model CompFlow is used to study the mechanisms controlling vacuum extraction, coupled with air sparging, as a means for remediation of heterogeneous formations contaminated with dense nonaqueous phase liquids (DNAPLs). Two dominant mechanisms are demonstrated to control this remediation technology. First, at early times, the gas phase...

Abandoned and improperly sealed boreholes, monitoring wells, and water supply wells are common features at many contaminated sites. These features can act as conduits that transmit contaminants between aquifers separated by otherwise continuous aquitards. In this work the leaky boreholes are represented as highly conductive one-dimensional line ele...

A noniterative algorithm for handling prescribed well bore boundary conditions while pumping or injecting fluid in a three-dimensional heterogeneous aquifer is described. The algorithm is formulated by superimposing conductive one-dimensional line elements representing the well screen onto the three-dimensional matrix elements representing the aqui...

A numerical model is used to study the efficiency of air sparging, coupled with vacuum extraction, as a means of remediating heterogenous formations contaminated by dense non-aqueous phase liquids. Two dominant mechanisms were previously demonstrated to control this remediation technology. First, at early times, the gas phase directly contacts the...

Once the aperture distribution at an applied stress level is determined, a hydraulic gradient is applied across the fracture and fluid flow is determined. Nodal pressures created by flow deform the aperture distribution coupling hydraulic to mechanical behavior. Stress versus relative closure results indicate that stress increases nonlinearly with...

This work involved using ITOUGH2 to simulate the Large-Scale Ponded Infiltration Test (LPIT) at Idaho National Engineering and Environmental Laboratory (INEEL) in order to calibrate parameters controlling the infiltration of water in fractured basalt using a dual-permeability modeling approach. This supports the higher objective of building confide...

The purpose of this Analysis/Model Report (AMR) is to document natural and anthropogenic (human-induced) analog sites and processes that are applicable to flow and transport processes expected to occur at the potential Yucca Mountain repository in order to build increased confidence in modeling processes of Unsaturated Zone (UZ) flow and transport....

Geologic carbon sequestration is one strategy for reducing the rate of increase of global atmospheric carbon dioxide (COâ ) concentrations (IEA, 1997; Reichle, 2000). As used here, the term geologic carbon sequestration refers to the direct injection of supercritical COâ deep into subsurface target formations. These target formations will typically...