Concerns about the potential economic consequences of earthquakes have increased in recent years as scientifically based probabilities of future earthquakes in many large urban areas have risen. These hazards disproportionately impact low-income communities as wealth disparities limit their capacity to prepare and recover from potentially disastrous events. In addition to major economic losses, the activities related to building recovery result in significant greenhouse gas emissions contributing to climate change. This article develops a framework that quantifies the complex relationships between pre-earthquake retrofit activities and their economic, environmental and equity implications to promote informed decision-making, using the city of San Francisco, California as a case study. This research consists of two sections. In the first section, a bi-objective optimization model is proposed to identify optimal earthquake risk mitigation policies to minimize total earthquake-related economic and environmental costs, simultaneously. Decisions entail the seismic retrofit, combined seismic and energy retrofit or complete reconstruction of building-type groups. The benefits of increased energy efficiency of the upgraded buildings are incorporated to evaluate decisions from a holistic perspective. In the second section, the model is extended to address the issue of inequitable budget allocation from a public-sector perspective. Vertical equity considerations are incorporated as an optimization constraint to distribute available resources aiming to limit the discrepancy of expected losses as a fraction of income between households across income groups. The tradeoff between equity and economic efficiency is explored. Results show that life-cycle environmental impacts constitute an informative performance metric to regional risk mitigation decision-makers, in addition to the more customarily used monetary losses. Although construction costs primarily dictate optimal decisions from an economic perspective, energy considerations largely impact optimal decisions from an environmental perspective.

Electricity consumption and greenhouse gas (GHG) emissions associated with wastewater flows from residential and commercial water use in three major cities of the United States are analyzed and compared for the period 2010–2018. Contributions of unit wastewater treatment processes and electricity sources to the overall emissions are considered. Tucson (Arizona), Denver (Colorado), and Washington, DC were chosen for their distinct locations, climatic conditions, raw water sources, wastewater treatment technologies, and electric power mixes. Denver experienced a 20% reduction in treated wastewater volumes per person despite a 16% increase in population. In Washington, DC, the reduction was 19%, corresponding to a 16% increase in population, and in Tucson 14% despite a population growth of 3%. The electricity intensity per volume of treated wastewater was higher in Tucson (1 kWh m−3) than in Washington, DC (0.7 kWh m−3) or Denver (0.5 kWh m−3). Tucson’s GHG emissions per person were about six times higher compared to Denver and four times higher compared to Washington, DC. Wastewater treatment facilities in Denver and Washington, DC generated a quarter to third of their electricity needs from onsite biogas and lowered their GHG emissions by offsetting purchases from the grid, including coal-generated electricity. The higher GHG emission intensity in Tucson is a reflection of coal majority in the electricity mix in the period, gradually replaced with natural gas, solar, and biogas. In 2018, the GHG reduction was 20% when the share of solar electricity increased to 14% from zero in 2016. In the analysis period, reduced wastewater volumes relative to the 2010 baseline saved Denver 44 000 MWh, Washington, DC 11 000 MWh and Tucson 7000 MWh of electricity. As a result, Washington, DC managed to forgo 21 000 metric tons of CO2-eq and Denver 34 000 metric tons, while Tucson’s cumulative emissions increased by 22 000 metric tons of CO2-eq. This study highlights the variability observed in water systems and the opportunities that exist with water savings to allow for wastewater generation reduction, recovering energy from onsite biogas, and using energy-efficient wastewater treatment technologies.

Regional seismic hazard analyses are necessary to assess the infrastructure performance within a region and ensure that mitigation funds are utilized effectively by probabilistically considering the suite of potential earthquake events. This research aims to efficiently represent the regional seismic hazard through a compact set of seismic inputs in the form of spectral acceleration (SA) maps by considering the spatial cross-correlation of SA at a wide period range. The SA maps can then be used to probabilistically estimate the performance of a portfolio of spatially distributed structures with different fundamental periods. Efficient representation reduces the number of required SA maps to decrease the computational demands of the infrastructure performance analysis in the subsequent steps. The added dimension of the between-period spatial SA correlation exacerbates the challenge of effectively simulating and selecting a set of SA maps to reproduce the hazard curves particularly at long return periods. Two approaches are proposed to generate an optimal set of SA maps: (a) a simulation-based methodology that uses state-of-the-art variance reduction methods and (b) a simplified methodology that aims to increase the ease of use and reduce the computational demands of the simulation. The two approaches are implemented and compared using the city of San Francisco as a case study to illustrate their feasibility. The simplified approach increases the scalability of the methodology to larger study areas at the expense of reduced accuracy in terms of seismic hazard curve and SA correlation errors.

A life-cycle assessment approach is used to analyze the energy demand and greenhouse gas emissions associated with potable water usage trends in three major cities of the United States in different regions and climates and relying on different types of raw water sources. Between 2011 and 2016, a decreasing trend in per-person water consumption is observed despite growing populations. The per-person water consumption decreased by 10% in Tucson (Arizona) and Washington, DC, and by 16% in Denver (Colorado). Leveraging certain distinctive water and electricity supply characteristics of the case study cities can provide insights into potential interventions and cross-comparison for generalizing trends. In Tucson, potable water production is the most energy intensive and electricity is produced mainly from coal. The greenhouse gas emissions of the per-person water consumption in Tucson are about five times higher compared to Denver and Washington, DC, thus water savings in Tucson should be particularly pursued. GHG emissions decreased in the period by even higher percentages than water use: 15%, 14% and 27% between 2011 and 2016 for Tucson, Washington, DC, and Denver, respectively. In 2015, just four years’ worth of forgone GHG emissions in Tucson were somewhat higher than the total GHG emissions associated with water consumption in all of Washington, DC, a city with the same population size as Tucson. Results show that cities should prioritize promotion of water savings to decrease the average per-person water consumption because it can be achieved and can compensate for increases in population. Lower greenhouse gas emissions can be attained in tandem with the local electric power industry.

<p>The urban water system is complex, comprised of water treatment and distribution, wastewater collection and treatment, and stormwater management (to avoid combined sewer overflow, flooding, and water quality permit violations). These components are often managed by separate agencies and companies, with their respective goals and budgets. In fact, they should all be working together towards the same overarching objective of urban water systems: to provide water to people and the economy for both indoor and outdoor uses at the lowest economic and energy costs and at the lowest achievable level of pollution.</p><p>We present an integrated model of urban water systems that accounts for changes in population, water consumption patterns, water saving technologies, raw water sources, water and wastewater treatment technologies, decentralization of wastewater treatment plants, water reuse demand, stormwater control measures, economic activities, electricity and other energy supply, landscape, weather, and climate. The methodological basis includes environmental life-cycle assessment (LCA) and life-cycle cost analysis (LCCA). The model is globally applicable. For effective decision making, we have created a decision making tool with an extensive, very detailed database to allow for specific, holistic analyses of the unique demographic, economic, and physical characteristics of urban areas.</p><p>The target audience for our model, tool, and results includes the government planners and regulators of the urban water system, water and wastewater agencies and companies, urban users of water (both individuals and companies), and real estate developers.</p><p>Through case studies of cities in different regions and climates over time, we show that water consumption does not have to follow population growth, in fact, it has dropped in many cities where the average per-person water consumption has been reduced due to water conservation measures. Water withdrawal and potable water production in some cities are more than four times more energy intensive than in others, and the energy intensity is expected to increase in many parts of the world due to droughts and overwhelmed water sources. Due to differing electricity mixes and corresponding greenhouse gas emissions, the average per-person water consumption in some cities is more than four times more impactful than in others, but reductions are feasible. Tailoring water quality to an application is a key to lowering energy and emissions. We show how we can diversify irrigation sources for agricultural production in and around cities, including the potential energy and emissions implications of wastewater recycling. Using the integrated decision support tool (i-DST), which allows for the comprehensive life-cycle cost and environmental assessment of gray, green, and hybrid stormwater control measures, we can estimate the needed investments in the gray and green infrastructure, and find that in areas with water scarcity, stromwater is a viable source of water.</p>