Quantifying costs and lengths of urban drainage systems with a simple static sewer infrastructure model

A generic model is introduced that is capable of quantitatively representing the combined sewer infrastructure of a settlement. It consists of a catchment area module, which calculates the length and size distribution of the needed sewer pipes on the basis of rain, housing densities and area size. These results are fed into the sewer construction costs module in order to estimate the combined sewer costs of the entire catchment area.

The model could be successfully fitted to existing Swiss sewer systems, indicating that it can emulate their principal characteristics. It could also identify fundamental differences in sewer designs in cities with historic roots. The results confirm that there are economies of scale for combined sewer systems in Switzerland. The modelling approach proved to be an effective tool for understanding the factors underlying the cost structure for water network infrastructures.     

Changing Water and Sewer Finance: Distributional Impacts and Effects on the Viability of Affordable Housing

Usage-based charges finance an increasing share of water and sewer costs in the U.S. The shift has been especially sharp in New York City, where residential users traditionally did not pay usage-based charges. In this article, we examine the impact that a transition to universal metered billing would have on multifamily housing. We find that universal metering would result in large increases in water and sewer bills for many multifamily buildings in low-income neighborhoods. Comparing the predicted increases with the net operating income of landlords in low-income neighborhoods indicates that universal metering might pose a threat to the viability of much affordable housing.     

保障性住区的公共服务设施供给——以广州市为例

以广州市为例,从城市和居住区两个空间层面,实证性地解析了保障性住区公共服务设施的供给特征:城市层面,市级社会性公共设施之于保障性住区空间不可达;居住区层面,公共设施在配建和移交、供应环节均存在显著的供应易质、供应时滞、供应不足的问题。建议城市政府在保障性住区建设中要特别关注公共服务设施的配置,应该以降低中低收入群体的生活成本为原则,体现公益性。     

The geographic distribution of social housing in Ontario,Canada: Comparing public housing and locally sponsored,third sector housing

This paper provides a perspective on the contemporary debate over the production of social housing. Its main focus is on the issue that geographic patterns of service levels may be related to the type of supply program in place. The paper describes the social housing programs in Ontario, Canada over the post‐war period. Two main approaches have been taken: public housing, an essentially centralized program; and locally sponsored, third sector housing provided through non‐profit corporations and co‐operatives. The programs operated in different time periods and the analysis suggests they do have distinctive geographic distributions. The distribution of public housing shows strong correlations with need as defined by the incidence of poor housing conditions and mother‐led families. Provision under the localized program is also strongly correlated with the incidence of mother‐led families; however, the most consistent associations are with measures of socio‐economic status. These results may be partly understood in terms of the changing concept of housing need over the temporal span of the study. Program influences may be that the centralized nature of the public housing program enabled the direction of allocations to high need areas; whereas under the localized program the distribution is more closely related to the social differentiation of leadership roles in service provision under a third sector delivery model. As this approach becomes more prevalent it may be important to examine its potential impacts on service provision.     

Contingent Valuation of First-Time Sewerage Provision in South-East England

Section 101A of the Water Industry Act 1991 requires that sewerage undertakers provide a public sewer to replace private wastewater systems if certain conditions are met. These include identification of pollution and amenity problems attributable to the private systems and economic justification of public sewer provision. Economic justification necessitates that the costs and the benefits of public sewer provision are compared. An environmental valuation study, using the contingent valuation method, has been carried out in three locations in south-east England to provide the average monetary value of the benefits accruing to households with unsatisfactory private systems. A statistical analysis of the survey-response data has yielded a monetary value which can be used in the assessment of the benefits of first-time public sewerage schemes.     

Multi-objective evolutionary optimization for greywater reuse in municipal sewer systems

Sustainable design and implementation of greywater reuse (GWR) has to achieve an optimum compromise between costs and potable water demand reduction. Studies show that GWR is an efficient tool for reducing potable water demand. This study presents a multi-objective optimization model for estimating the optimal distribution of different types of GWR homes in an existing municipal sewer system. Six types of GWR homes were examined. The model constrains the momentary wastewater (WW) velocity in the sewer pipes (which is responsible for solids movement). The objective functions in the optimization model are the total WW flow at the outlet of the neighborhoods sewer system and the cost of the on-site GWR treatment system. The optimization routing was achieved by an evolutionary multi-objective optimization coupled with hydrodynamic simulations of a representative sewer system of a neighborhood located at the coast of Israel. The two non-dominated best solutions selected were the ones having either the smallest WW flow discharged at the outlet of the neighborhood sewer system or the lowest daily cost. In both solutions most of the GWR types chosen were the types resulting with the smallest water usage. This lead to only a small difference between the two best solutions, regarding the diurnal patterns of the WW flows at the outlet of the neighborhood sewer system. However, in the upstream link a substantial difference was depicted between the diurnal patterns. This difference occurred since to the upstream links only few homes, implementing the same type of GWR, discharge their WW, and in each solution a different type of GWR was implemented in these upstream homes. To the best of our knowledge this is the first multi-objective optimization model aimed at quantitatively trading off the cost of local/onsite GW spatially distributed reuse treatments, and the total amount of WW flow discharged into the municipal sewer system under unsteady flow conditions.     

Valuing water service reliability and in-home water storage: A hedonic price model from Guatemala

Water service interruptions often impose considerable costs on water users, and lead more households to invest in in-home water storage infrastructure. Studying the value households assign to continuous water supply may help design more effective policies. Using a unique primary dataset from Guatemala City (n = 567), we estimate hedonic models of rental prices to derive marginal values of fewer water service interruptions and in-home water storage infrastructure. Results indicate that, on average, rental prices decrease by 0.7% with each day of water service interruptions and increase by 10% for housing units with storage infrastructure relative to those without it.     

Reliability-based layout design of sewage collection systems in flat areas

The sewer layout in flat areas significantly influences the final design which is desired to be optimized for the construction and operational costs. This study introduces a model for designing the layout of sewer networks considering their reliability. A reliability criterion is introduced and optimized using a simple simulated annealing scheme. The best layout with the maximum reliability represents an optimum sewer layout in which clogging in a sewer has the least effect on its upstream lines. A case study is solved using the proposed model. Then, for the obtained layout, the sewer specifications are designed using a dynamic programming model. The reliability somehow reflects the operational costs that can be taken into account in the system design by the proposed model. Furthermore, it is concluded that the network's reliability and construction cost are in conflict with each other such that more reliable layouts lead to more expensive designs.     

A gaming approach to networked infrastructure management

Operational decision-making processes for networked infrastructure management often occur as a multi-actor planning problem, implying these are based on negotiations between different stakeholders in addition to available system quality information. As such, does more accurate data about actual structural condition lead to other or better decision-making? A serious game is introduced, Maintenance in Motion, aiming at investigating the influence of information quality on rehabilitation decisions, for single- and multi-actor decision-making. Players manage drinking water, gas, sewer and street infrastructures. They are to balance their individual goal, cost-effectiveness, with their team utility, increasing overall infrastructure quality to minimise failure while minimising overall public costs. The game design, calibration and solution space are presented.     

A Bayesian network model to assess the public health risk associated with wet weather sewer overflows discharging into waterways

Overflows from sanitary sewers during wet weather, which occur when the hydraulic capacity of the sewer system is exceeded, are considered a potential threat to the ecological and public health of the waterways which receive these overflows. As a result, water retailers in Australia and internationally commit significant resources to manage and abate sewer overflows. However, whilst some studies have contributed to an increased understanding of the impacts and risks associated with these events, they are relatively few in number and there still is a general lack of knowledge in this area. A Bayesian network model to assess the public health risk associated with wet weather sewer overflows is presented in this paper. The Bayesian network approach is shown to provide significant benefits in the assessment of public health risks associated with wet weather sewer overflows. In particular, the ability for the model to account for the uncertainty inherent in sewer overflow events and subsequent impacts through the use of probabilities is a valuable function. In addition, the paper highlights the benefits of the probabilistic inference function of the Bayesian network in prioritising management options to minimise public health risks associated with sewer overflows.     

Multiobjective optimisation algorithm for sewer network rehabilitation

Understanding of deterioration mechanisms in sewers helps asset managers in developing prediction models for estimating whether or not sewer collapse is likely. Effective utilisation of deterioration prediction models along with the development and use of life cycle maintenance cost analysis contribute to reducing operation and maintenance costs in sewer systems. This article presents a model for life-cycle maintenance planning of deteriorating sewer network as a multi-objective optimisation problem that treats the sewer network condition and service life as well as life-cycle maintenance cost (LCMC) as separate objective functions. The developed model utilises Markov chain model for the prediction of the deterioration of the network. A multi-objective genetic algorithm is used to automatically locate an appropriate maintenance scenario that exhibits an optimised tradeoff among conflicting objectives. Monte Carlo simulation is used to account for LCMC uncertainties. The optimisation algorithm provides an improved opportunity for asset managers to actively select near-optimum maintenance scenario that balances life-cycle maintenance cost, condition and service life of deteriorating sewer network. A case study is used to demonstrate the practical features of developed methodology.     

Media discourse on ageing water infrastructure

Urban infrastructure in the United States is ageing, but media portrayal of this phenomena has been insufficient. Failures such as water main breaks are a daily occurrence in many cities. In addition, citizens are regularly reminded of the costs through increases in water and sewer rates. To explore media discourse on this issue, a content analysis of print media articles on water main breaks (Breaks), and water and sewer rate increases (Rates) for the period 1999–2012 was conducted. The analysis of approximately 500 randomly drawn articles on each topic found that media coverage of water infrastructure is an episodic affair with little attention to ongoing issues. Rates articles contained more details and a focus on governance, while Breaks articles addressed business concerns and were concentrated in older cities. The article concludes that media stories are not providing sufficient information to serve the needs of democratic governance of urban infrastructure issues.     

DOES INNER CITY PUBLIC HOUSING EXACERBATE THE EMPLOYMENT PROBLEMS OF ITS TENANTS?

ABSTRACT: This article analyzes whether inner city public housing exacerbates the employment problems of its tenants. Results from two evaluations of public housing demonstrations are used to test the potential impact of location, address discrimination, eligibility criteria, and rent schedules on tenant work behavior. To supplement this analysis, the effects of public housing on tenant employment, including self-employment, are estimated using a unique cross-sectional data set known as the Urban Poverty and Family Life Survey. The results do not support the claim that public housing, independent of tenant characteristics, contributes to employment patterns. While it is true that most public housing residents do not work, their counterparts in the private real estate market are no more likely to be employed or to have ever worked. Overall, these results indicate that the provision of public housing does not inhibit work behavior.     

Regional consortia and transaction costs for sanitation services in Brazil

Studies on public cooperation usually focus on its impact on the service costs experienced by service providers. However, engagement in public cooperation in service provision often seeks other outcomes, like service coverage (measured by the population served) rather than simply minimizing service expenditure. Moreover, public cooperation by local governments, as either ‘providers’ or owners, generates transaction costs arising from negotiation, monitoring, agency costs and the enforcement of cooperative agreements. However, to date, little empirical effort has been directed at determining the impact of transaction costs on service provision owners and service outcomes. This paper addresses this gap in the empirical literature by examining the relationship between cooperative agreements between Brazilian municipalities for water and wastewater provision and service coverage in the light of transaction costs. We find that transaction costs are higher for cooperative providers due primarily to low service coverage levels, especially in sewage services that demand high investment in assets with high specificity. However, lower expenditures may occur after initial up-front investment.     

On the Theory and Policy of Neighborhood Consolidation

Economic analysis suggests the desirability of an integrated land use and housing policy for declining cities; planned neighborhood consolidation would help to preserve both standard housing and neighborhood commercial and social amenities, and might reduce public service costs. Housing allowances could be used to compensate relocated tenants and to insure their capacity to pay standard rents in conservation areas. Property value gains in conservation areas could be expected to exceed losses in clearance areas, indicating a more efficient use of urban resources and enabling a local authority to compensate losers out of the proceeds of a tax on gainers.

Political obstacles to neighborhood consolidation are formidable. However, such a policy would be more humane than the alternative of letting neighborhood depopulation run its course while wasting rehabilitation funds in a fruitless gesture of even-handed distribution.     

Editorial

This article deals with the questions of how different organizational models of housing management affect employee and residential influence over management decisions and how they affect housing costs. The answers are drawn from my own and other empirical studies of Municipal Housing Companies and housing cooperatives concerning their organization, costs, and residents. Another source has been a special study of management employees holding positions in their local trade unions. With growing size of housing management organizations, there has been more functionalization and specialization, as well as more centralized decision‐making. This study shows that residents often see this as diminishing their influence and lowering the service level. Caretaking employees have experienced a division of personnel with varying degrees of direct individual influence for different groups. The employees’ formal collective influence appears on the other hand to be greater in large than in small organisations. A decentralized management organization gives more room for both residential and employee influence and a wider professional role for the employees. The study has not confirmed any large‐scale effects, such as lower costs, that could be expected from larger management organizations.     

Local Housing Agencies in Rural Wales

This paper explores patterns of local housing agency collaboration in rural Wales between 1988 and 1994. It considers how the financial and land-transfer contribution of public sector partners has changed over this period and examines the implications of these changes. The paper attempts to outline possible future patterns of joint activity and looks at how changes may im pact upon the nature and scale of housing service delivery. It concludes that amidst many uncertainties (relating in particular to the demarcation of roles), one final outcome of current processes, typified by local government reorganisation, may be a centralisation of housing provision which will threaten locally based control and undermine accountability.     

Quantifizierungen von Grundwassereintritten in städtische Abwassersysteme mittels stabiler Isotope

Infiltration of groundwater into sewer systems increases the costs for wastewater treatment plant operators. This study explores groundwater infiltration to urban sewer systems in the city of Nuremberg (Germany). Measurements of stable isotopes at the water works, storage tanks, groundwater, and the sewage network were carried out to define input end members for mass balance calculations. Only minor differences in oxygen stable isotopes (δ¹⁸O_H2O) were found between most sewer and drinking water samples which ranged around (??9.5?±?0.1) ‰. One exception was water from a water works at Genderkingen that is situated about 80 km south of Nuremberg. Here, drinking water from bank filtrate of the Lech River had more negative δ¹⁸O_H2O values of ??11.4?‰. This difference of 1.5?‰ revealed maximum possible groundwater contributions of 41?% by mass balance calculations. To obtain more accurate results, we suggest testing the use of deuterium-enriched water (D₂O) added to the sewer system.     

An economic loss model for failure of sewer pipelines

Estimating the costs of failure for sewer pipelines is usually accompanied with uncertainties because of the difficulty in capturing the relationship between the physical and economical characteristics of failed pipelines. To reduce such uncertainties economic loss models are usually used to evaluate the consequences of failure. This paper presents a methodology to estimate economic loss as a result of sewer pipelines’ failure using cost benefit analysis approach. Costs of sewer pipelines’ failure in addition to costs resulting from avoiding such failures are identified and analysed. To validate the proposed methodology, actual costs from a real failure incident were compared with the proposed model outputs. The model could estimate the direct and indirect costs with a deviation ranging between 10–12% and 22–30%, respectively. By implementing the proposed methodology on two case studies, it was found that the indirect costs as a result of sewer pipelines’ failure represent a significant portion ranging between 89 and 94% of the total costs of failure. Also, it was found that costs related to environment, delays to work and traffic disruptions contribute by 12–35% to the indirect costs.     

长春市南湖中街公租房项目探析

近年来,长春市积极响应国家保障性住房政策,推出万套公共租赁房政策,为“夹心层”这部分社会群体提供了新的住房契机与住房选择,也很大程度上完善了保障性住房体系的建设。本文选取南湖中街公租房项目,对其规划设计、建筑立面、建筑户型、节能取暖设施设计、小区配套及商业服务、环境、景观绿化、交通方面等内容的阐述。试图探索出一条更适应我国国情发展方向的公共租赁房之路。以推动我国保障性住房体系高效合理的发展。