Monitoring data from several studies conducted in western Washington have indicated that some pollutants are exported from bioretention systems using the default 60% sand – 40% compost bioretention soil media, most notably nitrogen, phosphorus, and copper. To address this concern, Herrera implemented a study in partnership with Kitsap County to improve BSM performance for the capture and retention of these pollutants. This study tested pollutant leachability and sorption for 26 media components and subsequently tested the best performers in column study.
Analysis of Bioretention Soil Media for Improved Nitrogen, Phosphorus, and Copper Retention. Final Report
Reference: Herrera. 2015. Analysis of Bioretention Soil Media for Improved Nitrogen, Phosphorus, and Copper Retention. Final Report. Prepared for Kitsap County Public Works, by Herrera Environmental Consultants, Inc., Seattle, Washington.