Let’s Talk More Trash: The Results from Phase II of a Scalable Trash Capture Study
To address the issue of trash accumulation in waterways and storm drain systems, the California State Water Resources Control Board (SWRCB) adopted what are collectively referred to as “the Trash Amendments”. The City of San Diego has selected to pursue a Track 2 compliance option that involves installation, operation, and maintenance of full-capture devices, multi-benefit projects, and treatment and institutional controls. Before city-wide installation of full-capture devices, the City developed a two-phase pilot study to strategically test potential devices to determine suitability for implementation.
Our presentation at the 2019 CASQA conference highlighted the development of the pilot program, which included the development and results of a device and site selection methodology. The device selection methodology included an evaluation of SWRCB’s list of over 40 approved full-capture devices, which was narrowed down to ten pilot devices based on infrastructure configurations, operations, and needs. The pilot sites were chosen to be representative of the larger application area with standard sizing, configurations, and conditions that allow for uniform data collection and effective comparisons across the pilot study.
The presentation proposed for the 2020 CASQA conference will discuss the results of the monitoring program for the ten pilot devices and sites. The presentation will summarize feedback from City operations and maintenance (O&M) staff, and the recommendations for city-wide implementation based on these results. The presentation will also provide lessons learned from device installation and data collection completed during monitoring events.
The Pilot study follow-up presentation will focus on the monitoring program activities completed over the last year. To ensure effective city-wide roll-out of trash capture devices, data was collected on ten trash capture devices comprised of various types and configurations installed in diverse settings to evaluate the overall performance and maintenance level of effort (LOE) for each device. Data were collected during one dry weather and three wet weather events to observe the devices’ performance under various conditions and the associated maintenance for catch basin cleaning. Data metrics included maintenance duration, device condition, and performance metrics such as evidence of bypass and screen clogging, and presence of standing water as caused by the device. Evaluating device performance against these metrics ensures that selected devices meet the City’s key criteria, that the devices prevent trash from the storm drain system, do not require undue LOE to maintain, and do not create or exacerbate flood or vector hazards.
In addition to these data, O&M crew feedback was included in device evaluation to ensure that the selected devices were informed by maintenance-focused considerations. The O&M crew members were asked to identify which devices required excessive labor or equipment to maintain, which factors contributed to the increased LOE, and any potential device adjustments. With an extensive set of performance and maintenance data compiled, a suite of device types was selected for city-wide installation with accompanying site considerations and maintenance frequencies.
The results of the Pilot Study showed that inlet filters, custom combination inlet baskets and removable, L-shaped CPS devices had minimal evidence of bypass, screen clogging, cause of standing water and an overall low maintenance LOE. Additionally, observations of screen clogging, standing water, and rainfall depth helped inform the maintenance frequency for each device type showing that CPS devices, custom combination inlet baskets, and inlet filters require the most, moderate, and least frequent maintenance, respectively.
Overall, the study was grounded in meaningful data to ultimately determine device selection and contribute to a greater certainty of compliance and program success.