Comprehensive Benefits Assessment with as a Step toward Economic Valuations of Ancillary Benefits of Green Storm Water Infrastructure and Non-Structural Storm Water Quality Strategies in San Diego, California

摘要

The City of San Diego, in developing water quality improvement plans for watersheds within the city, sought to assess the benefits to the citizens of San Diego of the anticipated investments in green storm water infrastructure and other activities they would undertake to reduce pollutant loads in urban runoff and storm water. The city and its stakeholders implemented initial stages of HDR's sustainable return on investment (SROI) approach to identify and communicate the value of additional benefits that could be realized from several dozen strategies and project types. The initial stage of this analysis involved identifying benefit categories in terms of the triple bottom line: financial, environmental, and social outcomes. Then, each benefit category, respectively, was further defined by key drivers of value. Next, the degree to which each strategy and project type could actually generate each type of benefit was assessed. This process ultimately led to an initial ranking of project options in terms of potential relative value. Some of the categories of benefits associated with green storm water infrastructure investments and other actions included habitat improvements, increased local water supply, greenhouse gas emission reductions, improved public health, and improved recreational opportunities. The connection between a stormwater management strategy and benefit category was characterized, depending largely on available information, in one of four ways. Monetizable: stormwater management strategies that are likely to generate the highest value would have monetizable benefits. The value of specific strategies would be derived from available peer reviewed studies. Measurable: strategies that generate measurable, but not monetizable, benefits are likely to generate comparatively lesser degree of value than monetizable ones. In this case, engineering design and studies may be able to quantify tangible impacts, but economic literature has not been sufficiently developed to assess value for that scale or type of project outcome. Potential: this scale of benefits characterizes project outcomes that are less clear and more speculative. These benefits have no peer reviewed studies showing that they were observed from implementation of the strategy in a quantifiable manner, but judgment and accepted theory suggested the benefits would be likely to occur. Not-applicable: benefits that no peer reviewed studies showed occurring from implementation of the strategy, and judgment and accepted theory suggested would be unlikely to occur. At this initial stage of analysis, the value of each stormwater management strategy was characterized in terms of the number of benefits that could be generated by the strategy and the degree to which they could generate monetizable value.