Water supply, wastewater, and stormwater systems are explored in this chapter, first individually... more Water supply, wastewater, and stormwater systems are explored in this chapter, first individually and then looking at them in an integrative manner. Key areas of potential integration of these three functions are in reuse of wastewater and stormwater to reduce the required net import of water for water supply. The
Selecting the Right Model to Analyze Collection System Flows and Hydraulics
Proceedings of the Water Environment Federation, 2005
... Shawn Dent, PE*, Len Wright, PhD, PE1, Jason Nikaido1 *Carollo Engineers PC, sdent@carollo.co... more ... Shawn Dent, PE*, Len Wright, PhD, PE1, Jason Nikaido1 *Carollo Engineers PC, sdent@carollo.com 1Carollo Engineers PC ... particular location, while in a distributed hydraulic model, routing of flow is calculated as a function of space and time throughout the system (Chow ...
Risk Management for Planning and Decision Making of Pipeline Projects
Pipelines 2007, 2007
The goal of risk management is to minimize expected costs over time where the costs are defined i... more The goal of risk management is to minimize expected costs over time where the costs are defined in some probabilistic fashion. Traditionally, total expected costs due to failure are summed for planning purposes over a meaningful spatial and temporal domain and assigned a weight based on the likelihood of occurrence. Expected costs are the product of the consequence of an event (e.g. failure) and the probability of the event occurring. This is the commonly applied definition of infrastructure risk; Risk = criticality x vulnerability. The total risk-based cost is then compared with expected life-cycle costs to take mitigation action to reduce risk. Actions may include insurance, inspection, monitoring, improved construction, or increased maintenance. Action is taken if the benefits in terms of avoided costs exceed the costs associated with risk reduction. Unfortunately the probability of occurrence of specific events is uncertain at best, and at worst the decision-maker is in total ignorance about the likelihood of an event occurring. In the face of uncertainty with respect to the probability of these events, guidance for prioritization of projects may be gained from ideas developed in portfolio investment theory, which is concerned with decision making under uncertainty. Common methods of benefit/cost-based decision criteria fail to account for uncertainty. An example risk-based calculation from the sanitary sewer field will be used to illustrate risk management at the planning level for pipeline rehabilitation projects using risk based decision criteria.
storm sewers (Zukovs et al. 1996). Conversely, separation has been an effective CSO abatement alt... more storm sewers (Zukovs et al. 1996). Conversely, separation has been an effective CSO abatement alternative in other urban areas (e.g., Minneapolis, MN). These cases indicate the site specificity of runoff, specifically with regard to land-use density and local rainfall characteristics. Clearly, a new look at some of these age old urban water management problems is in order. Skokie, IL offers one example of a "new look." Faced with a massive basement flooding problem caused by combined sewer surcharging, Skokie found traditional sewer separation to be technically feasible but unacceptably costly. Accordingly, controlled on and below street storage of stormwater was found to be a cost-effective (one-third the cost of separation) solution. Flow and storage control is achieved with a system of street berms and flow regulators. The premise of this retrofit system, which is almost completely implemented throughout the 8.6 square mile community, is that "out of control" stormwater is the root cause of combined sewer problems. As a side benefit, the Skokie system includes numerous pollutant-trapping sumps (Walesh and Carr 1998). Problems Commonly Associated with Present Day Collection Systems As described above, some collection systems in use today in the U.S. represent over 100 years of infrastructure investment. During that period the technical knowledge of the nature of wastewater has increased and the public expectation of the performance and purpose of collection systems has changed. What was considered state-of-the-art pollution control in 1898 is no longer acceptable. The societal goals which the engineer attempts to satisfy with a combination of technical feasibility and judgment have undergone drastic changes in the last 30 years (Harremoes 1997). Present day collection systems; many of which were designed and constructed in older periods when performance expectations and technical knowledge were less advanced than today, now must perform to today's elevated standards. At the same time, sprawling urban growth has strained infrastructure in many areas, exacerbated by poor cradle-tograve project management (Harremoes 1997). Designers of new collection systems must recognize and address the problems of past designs. The current status of collection system infrastructure in the U.S. represents a combination of combined, sanitary and separate storm sewers. These collection systems vary in age from over 100 years old to brand new. While general design practices in the U.S. today are not drastically different than 30 years ago, current innovative research in Europe and Japan suggest that broad societal goals such as "sustainability" are not being achieved by current design practices in the U.S. Old combined sewers discharge raw sewage to receiving waters. I/I is a costly and wasteful problem associated with sewers. Sanitary sewer overflows (SSOs) discharge raw sewage from failed or under-designed separate systems. NPS pollution associated with urban areas is discharged from separate storm sewers. Proper transport of solids in sewers is still a misunderstood phenomenon, causing significant operational problems such as clogging, overflows, and surcharging. 6-4 This section provides an overview of the problems commonly associated with collection system infrastructure currently in use in the U.S. Designers of new collection systems must recognize these problems and address them with modern tools. Unsustainable design practices must not be allowed to be perpetuated in the field of urban water management. The useful life of the infrastructure is too long to simply design big systems to compensate for uncertainty. Following this section are sections describing innovative technologies being investigated and ways they might be used in the 21st century. Combined Sewer Systems CSS now constitute one of the remaining large-scale urban pollution sources in many older parts of major cities (Moffa 1990). In large urban areas, raw sewage, combined with stormwater runoff, regularly discharges to receiving waters during wet-weather. Water quality problems arise from NPS pollution in the stormwater portion of the discharge mixing with the sanitary wastes associated with the combined sewer. Low dissolved oxygen, high nutrient loads, fecal matter, pathogens, objectionable floatable material, toxins, and solids all are found in abundance in combined sewage (Moffa 1990). This mixture has led to some of the more difficult control problems in urban water management. However, CSS problems of today are the result of technology dating back to 1900 and earlier.
Defining Collection System Performance Criteria to Meet Level of Service Goals
World Environmental and Water Resources Congress 2007, 2007
Defining collection system performance criteria is a critical step in the master planning process... more Defining collection system performance criteria is a critical step in the master planning process because it sets the metrics by which existing collection system infrastructure will be evaluated to meet level-of-service goals by which future facilities will be designed. It is important to recognize the difference between planning criteria and design criteria for judging the performance of collection system infrastructure. Planning criteria relate to those metrics that are used to analyze the adequacy of existing facilities and to project future infrastructure needs for financial planning purposes. These criteria are not intended to provide the same expected levels of safety and protection that design criteria provide. It is generally inappropriate to use standard design criteria as planning criteria, especially when significant wet weather flows impact an existing collection system (as is the case with an aged combined sewer system). For example, new sewers are designed to convey flow under non-surcharged conditions, while surcharging may be permissible during the analysis of existing sewers, especially during wet weather flows. Wet weather flow may dramatically affect the performance of collection systems. Master planning collection system infrastructure requires an assessment of the performance criteria used to size the systems during wet weather flows. Determining how to measure the performance of existing facilities and deciding on a design event or condition, or level of service, for wet weather planning may not be straightforward. This is especially true when basing the performance on an expected flow duration series. Literature and regulations offer little guidance on the design condition or design flow event frequency to use. Choosing a large event can incur significant capital costs, while too small of an event may lead to unacceptable overflow frequency and volume. This paper examines collection system performance criteria for both planning and design purposes that can be used for completing modeling analyses and identifying capital improvements. The planning and design criteria help define the type, location, and extent of the facility deficiencies that should be corrected to maintain service reliability. Criteria for dry weather flow as well as wet weather flow conditions caused by infiltration and inflow are included. Examples are included to illustrate how results can vary from one approach to another, and affect the extent of capital improvements as well as the level service of the collection system.
Risk-Based Design of a Sanitary Sewer Overflow Control Plan
World Water & Environmental Resources Congress 2003, 2003
Detailed flow and rainfall measurements, accompanied by long-term simulation, were used to identi... more Detailed flow and rainfall measurements, accompanied by long-term simulation, were used to identify the inflow and infiltration response characteristics of the sanitary sewer collection system in Vallejo CA. This response has produced sanitary sewer overflows on numerous occasions throughout various locations in the collection system. A mix of collection system rehabilitation, capacity upgrades, storage and increased treatment capacity may be used to control future wet-weather flows to a regulatory standard. A major limitation to optimizing the design of these wet-weather controls is a relatively high uncertainty regarding the effectiveness of collection system rehabilitation to control wet-weather flows. The ability of collection system rehabilitation activities to control wet-weather flows will in turn affect the performance of all downstream controls, including conveyance, storage and treatment. If rehabilitation effectiveness is over-estimated, overall control performance will not meet design standards, and if underestimated, significant overexpenditure of resources is possible. A risk-based approach was used to identify the importance of rehabilitation effectiveness on the overall design. Probability density functions of wet-weather pollutant control for storage, treatment and rehabilitation were derived from direct observations and used to estimate the overall reliability of various mixes of design alternatives. Based on this analysis, a concentrated smallscale rehabilitation project was used to reduce the uncertainty associated with estimating the performance of rehabilitation for sanitary sewer overflow (SSO) control. The results of the rehabilitation test were used to refine the risk-based design of the SSO control plan. Actual rehabilitation costs were used to estimate a costeffectiveness relationship for this specific collection system. A process model was used to link the performance and costs of storage, treatment, conveyance and rehabilitation. This design model was formulated as a nonlinear optimization problem, and a generalized reduced gradient search algorithm was used to find the best mix of alternatives to meet various regulatory goals in a cost-effective manner. Various levels of cost and risk were then generated with this model for meeting performance expectations, aiding the design team by concentrating their efforts on an array of non-dominated solutions.
Proceedings of the Water Environment Federation, 2004
(1) Carollo Engineers -Denver, CO (2) Carollo Engineers -Walnut Creek, CA (3) Vallejo Sanitation ... more (1) Carollo Engineers -Denver, CO (2) Carollo Engineers -Walnut Creek, CA (3) Vallejo Sanitation and Flood Control District -Vallejo, CA The quantity and quality of information that owners of collection systems in the U.S. are currently collecting come in the wake of a long history of less-than-complete record keeping for pipeline maintenance, condition assessment and rehabilitation efforts. Business models of collection system planning and operation such as asset management techniques are proving the value of high-quality information when used in a decision-making environment. However, complete knowledge of the condition of a collection system is difficult and expensive. The data gap created by the uninspected portion of the collection system represents a large source of uncertainty for decision makers, who apply decision-support models for long-term capital and O&M spending. The purpose of this paper is to describe a discrete classification technique used to estimate uninspected pipeline conditions and present results from an application of this method to a sewer collection system in Vallejo, California. Linear regression techniques using Ordinary Least Squares (OLS) have been applied in many instances for predicting the state of the uninspected portion of a pipe network. These models tend to have a limited ability to predict the condition of uninspected pipes. One problem is that these models are usually based on pipe age. Intuitively pipe age should be highly correlated with condition. However, unrecorded historical rehabilitation efforts cloud the relationship between time and condition, along with other environmental and spatially based factors that affect condition in a non-homogeneous fashion. For example, a pipe may be recorded as being 50 years old, but there may be no record that the same pipe was rehabilitated several times over this period, and my be in excellent condition. Likewise, a different 75 year-old pipe may be in good condition, while a relatively new pipe (e.g. 15 years old) may be in very poor condition because it was installed in corrosive soils and underneath a highly traveled roadway. Discrete statistical models may be more appropriate for this problem. Alternative regression techniques such as logistic regression and discriminant analysis techniques that include spatial relationships as well as the consequences of error (i.e. classifying a pipe's condition as good when it should be poor), can be an improvement over linear regression models based on age. The model developed for Vallejo uses an inspected pipeline condition dataset and descriptive characteristics of the inspected pipes (e.g. type, dia meter, groundwater stage, etc.), to correlate the condition of the uninspected pipes based on their descriptive characteristics using the alternative regression techniques. Once the conditions of the pipes in the uninspected dataset are estimated, this dataset can be coupled with the inspected pipe condition database to provide comprehensive information on the condition of the entire pipeline network. The condition of each pipe (whether inspected or uninspected) can then be coupled with rehabilitation and replacement costs to develop a rehabilitation prioritization plan. The model developed for Vallejo has the advantage of increasing the reliability of the uninspected condition estimates and has successfully been applied to a collection system with over 8,500 pipes.
Water is one of the essential commodity for the survival of a human being. This research paper de... more Water is one of the essential commodity for the survival of a human being. This research paper deals with the Sustainability of Water and the methods of saving water. Rain water harvesting and the Recycling of Water are the two methods for saving and using the water. This paper deals with the challenges of urban water sector, history of urban water management and the reforms to be taken. Water is a commodity which is in scarcity, both in rural areas and urban areas. In urban areas, people and Urban Local Bodies (ULB's) waste water. Water is also an economic, political and social commodity.
This study has been prepared within the UNU-WIDER project on Development under Climate Change, di... more This study has been prepared within the UNU-WIDER project on Development under Climate Change, directed by Channing Arndt. UNU-WIDER gratefully acknowledges the financial contributions to the project by the Finnish Ministry for Foreign Affairs and the Swedish International Development Cooperation Agency-Sida, and the financial contributions to the research programme by the governments of Denmark (Royal Ministry of Foreign Affairs), and the United Kingdom (Department for International Development-DFID).
Mitigation and Adaptation Strategies for Global Change, 2012
We assessed the potential impacts of increased river flooding from climate change on bridges in t... more We assessed the potential impacts of increased river flooding from climate change on bridges in the continental United States. Daily precipitation statistics from four climate models and three greenhouse gas (GHG) emissions scenarios (A2, A1B, and B1) were used to capture a range of potential changes in climate. Using changes in maximum daily precipitation, we estimated changes to the peak flow rates for the 100-year return period for 2,097 watersheds. These estimates were then combined with information from the National Bridge Inventory database to estimate changes to bridge scour vulnerability. The results indicate that there may be significant potential risks to bridges in the United States from increased precipitation intensities. Approximately 129,000 bridges were found to be currently deficient. Tens of thousands to more than 100,000 bridges could be vulnerable to
Conversion of a natural watershed into its equivalent kinematic wave rectangular plane has long b... more Conversion of a natural watershed into its equivalent kinematic wave rectangular plane has long been a concern in the practice of stormwater numerical simulations. Based on the principles of mass and energy, the actual watershed and its virtual kinematic wave plane can be related by the watershed shape factor that involves the waterway length and slope, and watershed area. In this study, two dimensionless watershed shape functions are derived to use parabolic function and trigonometric Sine curve for watershed conversion. These two watershed shape functions produce good agreements with the maximum overland flow length method for hypothetical square watersheds. Also, these two watershed shape functions are able to reproduce similar kinematic wave plane widths as reported in a calibrated model. Furthermore, in this study, these two watershed shape functions are tested by nine observed rainfall events and three levels of modeling details. These 54 case studies reveal that the parabolic shape function consistently produces better agreements with the observed runoff hydrographs. Also, a model with more drainage details results in more concentrated flows or higher peak flows. On the contrary, a model with a low resolution tends to decrease the peak flow because of the significant surface detention volume spread in the overland flow.
Costs of Best Management Practices and Associated Land for Urban Stormwater Control
Journal of Water Resources Planning and Management, 2003
... in terms of January 1999 dollars based on the Engineering News Record Construction Cost Index... more ... in terms of January 1999 dollars based on the Engineering News Record Construction Cost Index (ENR ... As part of the literature review, several case studies on urban stormwater design were evaluated. ... A key component of the capital cost of control options is the value of land. ...
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