Optimizing between green and grey stormwater infrastructure using hydrologic modeling, life cycle costs, and a benefit analysis.

Abstract:

Millions of dollars are spent annually by municipalities implementing green and grey stormwater control measures (SCMs) to meet objectives such as flood control or water quality permit compliance. More recently, municipalities are also considering additional benefits to the environment and local communities that could be generated by SCMs. With so much capital at stake, accurate estimation of the performance and life cycle costs (LCC) of the potential SCM alternatives is important. This work gives an overview on an integrated decision support tool (i-DST) which evaluates the benefits and tradeoffs of green, grey, and hybrid SCMs. The i-DST watershed scale tool utilizes the EPA’s System for Urban Stormwater Treatment and Analysis Integration (SUSTAIN) to optimize the types and numbers of SCMs in order to minimize cost and maximize a user selected evaluation target. Prior work has shown that 1) the optimal stormwater management plan is unique for each watershed, 2) greyer SCMs offer benefits that should be considered, and 3) LCC and benefits may shift which SCM solutions are optimal based on stakeholder and community preferences. Initial testing of the i-DST planning tool is being undertaken on two watersheds in the United States (Los Angeles, CA; Denver, CO). The fully developed i-DST tool includes a BMP pollutant decay rate calibration tool, improved list of evaluation targets, greyer underground detention/infiltration SCMs, a LCC estimation, and a community benefit quantification. Modeling results demonstrate how the tool takes into account the unique physical/hydrologic characteristics and the municipal needs of the watershed in order to assist stakeholders in making holistic decisions for the optimal stormwater management plan.