Using Graywater and Stormwater to Enhance Local Water Supplies An Assessment of Risks, Costs, and Benefits (2016) / Chapter Skim
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7 Costs and Benefits
7 Costs and Benefits
Pages 121-140
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From page 121... ...
These facts may make it challenging benefits may include providing a community with aesthetic to provide a viable and fair comparison of the key benefits of improvements due to increased green space or reducing trafa stormwater or graywater project to its costs: the costs are fic disruptions associated with periodic urban street flooding generally identified and monetized, but many key benefits during intense rain events. Public education and increased may not be readily amenable to monetization.1 This may cre- individual awareness of local water supply and related isate an unfortunate imbalance in how beneficial use projects sues may be considered as social benefits -- although ones are perceived and evaluated, unless considerable effort is ap- that can be particularly difficult to quantify and monetize.
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From page 122... ...
• Public health effects (e.g., reduced heat stress from urban greening, reduced disease from combined sewer overflows, increased disease from failures in graywater or stormwater treatment or exposure control) • Aspirational and public education value related to tapping local resources and promoting sustainability • Increased robustness, resiliency, and reliability of local water supply portfolios, by diversifying mix of source waters • Increase in "local control" of water resources and water supply (e.g., reducing reliance on regional or imported supplies)
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From page 123... ...
However, there is a dearth Summary of Cost Data of well-documented data on the full costs of such projects, particularly their life-cycle costs, because most are new with This section summarizes the limited available data on the minimal data about long-term maintenance costs and perfor- financial costs of graywater reuse and stormwater capture and mance effectiveness. use at the household and neighborhood scales.
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From page 124... ...
Some or lower than potable water rates in many cities,6 and they systems that are more complex than laundry-to-landscape are significantly lower if combined wastewater charges are kits can still be installed by homeowners with basic plumb- considered. However, the plumbing cost, which is omitted ing and electrical skills, reducing out-of-pocket installation but may be the most expensive component, especially for a costs but requiring investment of the homeowner's time.
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From page 125... ...
At a potable water charge of $10 per 1,000 gallons (including associated waste water charges) , potential water supply cost savings for a household might amount to approximately $23 to $53 per year for a laundry to-landscape system and $50 to $130 per year (on average)
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From page 126... ...
roof, includbeen conducted. Widespread potable water use reductions, if ing a first flush diverter and a pump.
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From page 127... ...
. Various social and environmental benefits may arise from household-level applica tions of graywater for toilet flushing, including water awareness benefits and the aspirational value associated with contributing to water conservation.
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From page 128... ...
. FIGURE 7-2 Comparative lifetime unit costs of alternative water supply options, based on typical costs for California water utilities.
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From page 129... ...
FINANCIAL BENEFITS Existing publicly available cost data for regional stormwater capture are limited to southern California, so the full Financial benefits include the monetary (i.e., cash flow) range of costs in other locations may not be represented.
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From page 130... ...
Nonmonetizable benefits include social health and safety and water quality benefits. Several costs are also associated with this increased local water supply.
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From page 131... ...
In all cases, financial benefits depend on the user actuavailability of a low- or no-cost water supply does not change ally reducing potable water demands. In addition, financial household water use -- an assumption that remains untested benefits may be decreased if potable water rate adjustments (see Box 3-2 for discussion of other assumptions and uncer- are needed because of reduced demand to cover fixed utility tainties of the analysis)
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From page 132... ...
An example of water supply cost savings arises in the A potentially significant cost savings may be realized when context of southern California, where developing local water stormwater capture and use enables a community to costresources (including graywater and stormwater) can offset effectively address combined sewer overflow (CSO)
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From page 133... ...
Potable water savings associated with a 2,200-gallon-capacity stormwater capture tank depend on the region (and associated seasonal precipitation levels and patterns) and intended water uses (irrigation alone, toilet flushing alone, or a combination of both if stored water volumes suffice)
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From page 134... ...
. Although Philadelphia de signed these strategies to address water quality concerns (rather than water supply shortages)
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From page 135... ...
Environ- major environmental benefits to surface waters, particularly mental benefits of graywater and stormwater could include in areas with combined sewer systems. Stormwater capture greenhouse gas reductions if on-site water use results in sig- or infiltration can reduce and delay peak surface water flows nificant energy savings.
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From page 136... ...
This study is unique in its attempt to quantify city-wide impacts on groundwater levels from implementation of distributed green infrastructure. FIGURE 7-8-1 Simulated water table mounding in response to infiltration from green infrastructure in the combined sewer region of Philadel phia, Pennsylvania.
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From page 137... ...
Furthermore, because energy pro- local water sources while avoiding the required material and duction requires water (e.g., for cooling in electric power energy inputs needed to supply potable water for irrigation plants) , energy savings can also result in water savings.
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From page 138... ...
For example, at the household level, a family that instorage and filtration, the primary energy demand is pump- vests in stormwater capture and beneficial use via large cising (beyond the embedded energy in system materials)
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From page 139... ...
Longer payback periods area (e.g., where stormwater capture and recharge reduces were estimated for rain barrels (5-26 years) and cisterns (14 regional demands for scarce and expensive imported wa- to more than 50 years, not accounting for labor)
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From page 140... ...
Where stormwater is diverted current literature contains little energy data for conventional into combined sewer systems, additional energy savings of and alternative systems. Conventional water systems in the between 0.3 and 1.2 kWh/m3 may be obtained.
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