This technical memorandum presents sampling protocol recommendations for using automated samplers to measure 6PPDQ in stormwater. The recommendations are based on a review of literature on the topic and on the 2023–2024 Field Protocol Sampling Study (field protocol study), which was designed to assess the potential loss of 6PPDQ to various sampling materials used during automated sampling programs. The project was funded by the Washington State Department of Ecology (Ecology).

This report presents the results of an exploratory study conducted in water years (WY) 2023 and 2024 to characterize 6PPD-quinone (6PPDQ) in stormwater runoff from highways in the Pacific Northwest. The study also evaluated 6PPDQ removal by stormwater treatment technologies, how field sampling protocols and equipment may impact 6PPDQ recovery in stormwater samples, and differences in 6PPDQ quantification between two analytical laboratories. This project was funded by the Washington State Department of Ecology (Ecology).

This memorandum provides design guidance to King County Wastewater Treatment Division (KCWTD) and Seattle Public Utilities (SPU) for presettling upstream of bioretention facilities that prioritizes effectiveness and the consolidation of presettling practices installed and related maintenance activities. Guidance is based on analyses of existing bioretention and proprietary and non proprietary presettling BMP effectiveness; a science review of basin particle production and settling; and KCWTD and SPU’s policies, procedures, and standards for capital projects.

The Redmond Paired Watershed Study (RPWS) aims to determine the effectiveness of watershed rehabilitation efforts at improving receiving water conditions at the watershed scale to provide widely applicable information for improving stormwater management in the region. This report summarizes the results of analyses that performed on the compiled data from monitoring efforts taking place from 2016-2019 to detect potential improving trends in receiving water conditions related to the implementation of rehabilitation efforts.

From 2016-2019, Herrera worked with the City of Redmond to collect water quality grab samples and perform analyses from three stream sites in the Monticello basin in Redmond, Washington. This analysis aims to determine if trends in receiving water quality can be attributed to increased street sweeping frequency in the basin. In total, 44 storm samples and 16 base flow samples were collected from each of the three sites and analyzed for total suspended solids (TSS), total phosphorus (TP), particulate copper, and particulate zinc.

The Bobby Morris Playfield Environmental Monitoring Project was designed by Herrera to evaluate environmental benefits and impacts of a new policy to use cork infill as an alternative to crumb rubber infill at synthetic turf playfields for the Seattle Department of Parks and Recreation. Herrera monitored and compared environmental conditions at three synthetic fields: Bobby Morris Playfield with new cork and sand infill material, Miller Playfield with old crumb rubber infill, and Woodland Park with new crumb rubber infill. The study results clearly showed that drainage

Seattle Public Utilities (SPU) and Herrera conducted a study to examine the pollutant removal effectiveness of regenerative air street sweeping compared to catch basin cleaning and structural stormwater BMPs. Herrera provided support for the experimental design, monitoring implementation, and reporting. The project entailed analyzing 33 catch basin, street dirt, and sweeper waste samples from 9 locations over one water year and determined that Street Sweeping is pound for pound one of the most cost effective BMPs available for sediment removal.

From 2014-2016, Herrera conducted water quality monitoring for Seattle Public Utilities (SPU) to evaluate the effectiveness of street sweeping on urban stormwater runoff. Herrera provided support for the experimental design, monitoring implementation, data analysis, and report review . Results were used to quantify the effect of street sweeping on stormwater quality by directly measuring runoff concentrations from roadways under swept and unswept conditions using a controlled paired-basin approach.

High Performance Bioretention Media (HPBM) consists of an 18-inch primary layer containing 60% sand, 20% coconut coir, and 10% high-carbon wood ash (biochar). While this improved bioretention soil media (BSM) offers a higher performance than typical bioretention media containing compost, sustainably sourcing coconut coir, iron filings, and activated alumina remains a challenge. An alternative to HPBM could be to keep the compost in the media and add fungi to attempt to mitigate the export of nutrients and obviate the need for less environmentally sustainable BSM compon