Bioretention Soil Media Study

Location: Spokane, WA

Aimee Navickis-Brasch, Phd, PE served as the Principal Investigator and Project Manager for this research project which was conducted in collaboration with the City of Spokane, The Lands Council, the University of Idaho, and Gonzaga University. The goal of the study was to develop a specification for a bioretention soil media amended with biochar that meets Ecology treatment performance criteria for reducing regulated stormwater pollutants specifically total suspended solids (TSS) and dissolved metals (Copper and Zinc). Additional water quality parameters tested include ammonia (NH3), nitrate-nitrite (NO3-NO2), total nitrogen, total and dissolved phosphorus, and hardness. Two different biochars were evaluated which included biochar characterization (following IBI) of the physioichemical properties. The research project followed the Washington State Department of Ecology requirements for Quality Assurance Project Plans (QAPP). The scope of work included developing the quality assurance project plan, constructing the laboratory setup, conducting flow through column testing a stormwater composed of natural stormwater and chemical standards, analyzing the data, and summarizing the findings into a final technical evaluation report. Results from the study were used to develop a bioretention soil media specification which guided the construction of three bioretention cells in Spokane. The cells are now being monitored in the field by the City of Spokane as one of the eight Eastern Washington Studies being conducted in compliance with section S8 (Monitoring) of the Phase II NPDES MS4 permit.