Environmental, Economic and Social Evaluation of Alternative Stormwater and Watershed Management Approaches

Lisa A. Peterson

doi:10.17918/00000086

Land development increases impervious surfaces, which requires the implementation of stormwater management solutions. Stormwater management solutions can be a significant cost of a development, as well as a significant contributor to the environmental impact on communities, either negative or positive, depending on the solution chosen and the environmental metric considered. Optimized stormwater solutions require participation from landowners, developers, engineers, community members, and government. When a development is installed on property with a stream and the various stakeholders seek optimized watershed outcomes, an opportunity also exists to improve downstream water quality. This dissertation uses environmental life cycle assessment (LCA) and life cycle cost (LCC) approaches, as well as a social ecological system (SES) framework to understand the environmental and economic implications and tradeoffs of achieving optimized stormwater and watershed management solutions in a community. The combination of these three approaches cover the three pillars of sustainability, namely environmental, economic and social. LCA and LCC methods are applied to compare four cradle-to-grave stormwater and watershed management solutions - stormwater pre-treatment wetland beds with floodplain restoration, underground stormwater infiltration basin (USIB) with stream bank restoration, permeable pavement with stream bank restoration, and surface basins with stream bank restoration, as well as several variants. The site used in the study is a nearly 40-hectare privately-owned new development in a rural area of Lancaster County, Pennsylvania, with a watershed feeding the Chesapeake Bay. All solutions are sized to manage 15,000 m3 of stormwater per the U.S. Environmental Protection Agency National Pollutant Discharge Elimination System (NPDES) requirements for the industrial site development as planned for a 100-year lifetime of the stormwater management solution implemented as well as improvement to the downstream water quality. The LCA method is further applied to bound the cradle-to-gate environmental impact of plastic box and arch USIB stormwater management solutions per cubic meter of stormwater to be managed. Sensitivity analysis is performed on major factors identified in the LCA and LCC. With stormwater and watersheds in the United States being managed in a command and control style, citizens can feel like victims of regulations instead of being partners when embracing solutions [1]. With the involvement of stakeholders who value environmental health, solutions can be sought to not only manage stormwater but to also improve downstream water quality. People make decisions based on a variety of factors including technical data, cost estimates, and personal preference; to reach optimal solutions, input is required from all interested parties. The SES method is applied to three community environmental groups in one county in Pennsylvania to identify the crucial elements of the SES framework to achieve sustainable citizen involvement in stormwater and watershed management whereby those citizens provide grassroots support to implement optimized solutions. In the case study investigated in this dissertation, floodplain restoration and surface basins produce less than 10% of the global warming of the USIB and permeable paving solutions over a 100-year lifetime. For floodplain restoration and surface basins, the global warming potential resulting from the maintenance phase is slightly higher than the installation phase. For the global warming potential of permeable paving and USIB, the installation phase dominates. From a cost perspective, assuming a 5% discount rate over a 100-year lifetime, the floodplain restoration is 80% more costly than surface basins, but 60% of the cost of the permeable paving and less than 20% of the cost of the USIB. Installation phase costs are dominant for all scenarios. With limited LCA research on USIB structures, this first look at installation phase global warming impacts of USIB structures indicates that plastic arch structures, ranging from 55 to 210 kg CO₂ eq. per m3 stormwater, generally result in lower potential global warming impact; but there is significant overlap with plastic box structures, ranging from 70 to 430 CO₂ eq. per m3 stormwater. Therefore, site specific design layout will be important to analyze for each site to choose the best solution within the plastic USIB family of solutions. Analysis of citizen watershed alliance organizations in the Lancaster County geographic region via Ostrom's SES framework identifies the key factors of citizen members in addition to local governmental leadership and local chapters of national advocacy associations to achieve optimized solutions. Citizen involvement increases commitment and passion since citizens are often directly affected by the environmental impact of the projects and solutions selected. They may also be indirectly impacted by taxation for stormwater and watershed costs covered by governing bodies. Similarly, citizens may benefit from avoided taxpayer costs when partnering with business and industry for solutions that address stormwater and water quality improvements on a regional basis rather than only on a site by site basis. Keywords: Chesapeake Bay; Life cycle assessment; Life cycle costing; Social ecological systems; Stormwater; Sustainability

Environmental, Economic and Social Evaluation of Alternative Stormwater and Watershed Management Approaches

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Environmental, Economic and Social Evaluation of Alternative Stormwater and Watershed Management Approaches

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