Real Time Controls of Stormwater Facilities in Oregon: Lessons Learned from 10 years of Operation

Existing stormwater management facilities (e.g., detention basins, water quality basins) represent substantial historical infrastructure investments. However, these systems have often been designed using methods (e.g., peak event matching) that do not address the effects of hydromodification, and may need to be expanded in order to address current watershed management challenges and enhanced control objectives brought about by increasing urbanization, changing climate and regulatory pressure. Expansion of existing facilities can pose a major financial burden to MS4 agencies and may be limited by requirements to also maintain the original design basis of the facility. However, technology advances over that last decade in continuous monitoring and adaptive control (CMAC) of distributed infrastructure allow existing infrastructure to be used more effectively rather than increasing the size of existing facilities and/or building new facilities. Similar to SCADA systems for water and wastewater, this modern approach for stormwater involves aggregating information from on-site sensors (e.g., water level, flow rates), weather forecasts (e.g., probability of precipitation, quantitative precipitation forecast), and other potential information (e.g., streamflow data, precipitation data) in order to make automated decisions about when and how to store or release water. These improvements in function can often be achieved with minimal changes to the current physical infrastructure, avoiding the need for substantial land acquisition and/or earthwork. [b]Original Pilot Implementations[/b] Clean Water Services (District) has evaluated the use of real time controls as part of its District-wide stormwater management approach, specifically with Opti's CMAC technology. The initial two pilot projects using CMAC technology were implemented in 2016 (Figure 1). By preparing for forecasted storm events in advance and calculating the minimum release rate from the pond on a minute-by-minute basis during storm events, both applications were intended to enhance hydromodification control performance in more frequent 'channel forming' events while maintaining the original flood control purpose of the facilities in major events. These systems were also expected to achieve improvements in water quality performance compared to passive systems. Finally, the real time control solution provides the ability to adapt system operations in response to feedback from monitoring data and/or changes in watershed characteristics. Based on the initial successes of these pilots (Figure 2), the District explored additional opportunities for retrofit projects, and evaluated the cost and benefits of this approach (i.e., the 'business case'). This evaluation included:

Identification and prioritization of opportunities for additional real time control retrofits, including a District-wide GIS-based screening (Figure 3).
Modeling case studies of the benefits of real time controls at the scale of individual facilities, and for multiple facilities networked within a subwatershed (Figure 4).
Whole lifecycle cost comparison of real time control approaches to passive alternatives. The District also developed a long term strategy or 'roadmap' for broader implementation of real time controls, including integration with existing monitoring and information technology systems, installation methods, system operations and adaptations to maintain and improve performance, facility operations and maintenance, integration with flooding emergency response, and project phasing. District IT staff, maintenance personnel, capital improvement engineers, and system operators have contributed to this effort. Based on these efforts two more projects have been implemented in the watershed, with more planned for future implementation.

Reflecting on a Decade of Smart Stormwater Management:
A decade later, the team is reflecting on the pilot process, operations, and performance of these systems, specifically:

What were the challenges to implementing the pilot projects?
Are the sites performing as expected compared to the initial modeling?
What have been the benefits and challenges of operating CMAC systems over the past 10 years?
How is the District progressing with the long term strategy of broader implementation?
What are the opportunities and barriers to broader implementation?

This presentation will include:
(1) lessons learned from pilot project implementations,
(2) challenges and opportunities from the operation of CMAC over the last 10 years (Figure 5),
(3) measured performance evaluation compared to the initial modeled performance (Figure 6), and
(4) progress and challenges in broader implementation of CMAC across the watershed. The findings from this effort are expected to be transferrable to other MS4 permittees and stormwater designers who are considering innovative strategies to address challenging stream protection, pollutant load reduction requirements, and associated BMP retrofit obligations.