The objective of this project is to demonstrate that the highly distributed real-time control (DRTC) technologies for green infrastructure being developed by the research team can play a critical role in transforming our nation’s urban infrastructure.
These technologies include advanced rainwater harvesting systems, dynamically controlled green roofs, actively controlled detention systems, and controlled underdrained bioretention systems. The scope of work for this project includes: (1) modeling high-performance green infrastructure; (2) conducting field pilot investigations; and (3) cost analysis of implementation of DRTC technologies.Despite significant federal investment in combined sewer overflow (CSO) control over the past few decades, CSOs remain a significant point source of pollution to receiving water bodies in the United States. The research team hypothesized that dynamically controlled green infrastructure can significantly reduce wet weather contributions to combined sewers. To investigate this, a linear optimization model of a dynamically controlled rainwater harvesting cistern was compared to a simulation model of a conventional passive cistern. These models were run under baseline historical precipitation data with varying cistern storage capacities, as well as under various precipitation time series created with a statistical weather generator.
The optimized dynamic system significantly mitigated CSO discharges when compared to the simulated passive system under all tank storage capacities, and proved much more robust under a wide range of plausible precipitation scenarios resulting from climate change. Investigations at several pilot sites were conducted to determine the validity of model results and to demonstrate the practical implementation and quantitative benefits of DRTC technologies. Pilot sites included: (a) Advanced rainwater harvesting systems in New Bern, NC; Austin, TX; St. Louis, MO; Denver, CO; and Lawrenceville, GA; (b) Smart detention in Seattle, WA and Saint Joseph, MO; (c) Controlled green roof in Newtown Square, PA; (d) Controlled porous pavement in Omaha, NE; and (e) Under-drained bioretention system in Lawrenceville, GA. The obtained pilot site results support the hypotheses that DRTC technologies can greatly reduce contributions to CSOs, reduce stormwater runoff, and retain stormwater for future onsite use and that these systems are practicable.
The project has yielded useful technical results as well as examples of benefit/cost analysis for the types of systems evaluated in the pilots. The project has demonstrated that through both targeted field pilots and planning level analysis, the integration of these innovative systems provides a new suite of tools for utility operators to optimize investments in green infrastructure and potentially solve problems that are intractable, unachievable, or not cost effective using conventional passive solutions. Cities facing a high cost of expanding stormwater infrastructure with gray or green strategies can achieve the same benefit with a lower cost by retrofitting existing systems with real-time monitoring and controls.