This study was implemented to assess the potential for groundwater contamination from infiltrating stormwater through a bioretention system constructed with a bioretention soil mix (BSM) composed on 60 percent sand and 40 percent compost (60/40 Mix). A new lined bioretention system installed at the southeast corner of 185th Avenue NE and NE Union Hill Road was studied from February 2012 through September 2013. Influent and effluent chemistry was assessed using automated samplers and continuous flow gauges. The study system was effective at treating

This study presents results from monitoring the performance of six full scale bioretention systems in Redmond, Washington from 2013 to 2015. The results from this study corroborate other recent studies in the region indicating that bioretention systems which utilize a BSM which meets the Ecology 60/40 specification will act as a pollutant generating source of nutrients and copper. These findings indicate that the previous assumptions regarding metals and nutrient reductions in bioretention, as summarized in two recent local literature reviews

Burnt Bridge Creek is a highly modified, urban stream that flows westward 12.6 miles from its agricultural origins, through the heart of Vancouver, Washington, to its terminus at Vancouver Lake. This study analyzed water quality data collected in 2011-2017 for parameters such as temperature, dissolved oxygen, fecal coliform, TSS and nutrients along 11 stations in Burnt Bridge Creek. Statistical analyses included Kendall’s tau correlation analysis to evaluate significant increasing or decreasing trends, Mann-Whitney test to detect significant differences between recent

The overall goal of this project was to develop new recommendations for a bioretention soil media (BSM) that protects beneficial uses of receiving waters and does not export nutrients and dissolved copper as is the case with the current BSM specification of 60 percent sand/ 40 percent compost (60/40). The project entailed selecting and testing media components, combining components in various ratios and placing the BSMs in columns for water quality testing, flushing and dosing the columns with stormwater to assess performance, conducting toxicological testing of

This report summarizes the data from five studies in the Puget Sound region that evaluated the hydraulic and water quality treatment performance of various bioretention soil mixes (BSMs). This study was conducted to help ascertain the duration and magnitude of metals and nutrient flushing from bioretention systems using the 60 percent sand, 40 percent compost (60/40) mix, to determine which media components contributed to pollutant export, and to establish whether other media compositions would perform better than the 60/40 Mix in bioretention systems. Of the 19 BSMs

From 2008 to 2011 Herrera assessed the hydrologic and water quality performance of a vegetated roof versus a metals roof and a pervious asphalt versus conventional asphalt basketball court in Redmond Washington’s Grass Lawn Park. The results from this monitoring indicated that the vegetated roof was effective at reducing peak flow rates and flow volumes; however, the vegetated roof was also a source of nutrients and copper relative to the adjacent metal roof. The results of the hydrologic monitoring of the basketball courts were confounded by the fact that

The primary goal of the Green Duwamish Water Quality Assessment (GDWQA) was to provide analytical tools to evaluate water quality issues in the Green-Duwamish River watershed from 2002 to 2003. Commercial/Industrial land use exhibited significant positive correlations with ammonia nitrogen, total zinc, and dissolved iron. High-density residential land use exhibited significant positive correlations with fecal coliform bacteria and dissolved zinc. Agriculture was most strongly correlated with orthophosphate, total phosphorus, and dissolved copper. Finally, effective

In 2001, King County initiated a comprehensive study of the Green-Duwamish watershed, called the Green-Duwamish Watershed Water Quality Assessment (GDWQA) Comprehensive Monitoring Program. The primary purpose of the program was to collect and analyze water quality data within the Green-Duwamish watershed. As part of the GDWQA, King County implemented the microbial source tracking (MST) study described herein to address bacterial contamination in the watershed and to better understand the relationship between land use and bacterial loadings. Human sources were most

Herrera Environmental Consultants, Inc. (Herrera) was requested by Skagit County Public Works to assist County personnel in evaluating the current landfill gas (LFG) management system and determine if the aging system should be repaired, modified, replaced, or abandoned based on the current and projected landfill gas generation while protecting human health and the environment