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Bioretention Longevity Project

Purpose

Very little information is available on the long-term performance of bioretention for treatment of stormwater runoff. Additionally, it is unknown what depth of bioretention is necessary to provide long-term treatment. This project is designed to assess chemical and biological performance of up to 5 depths of bioretention over 10 years.

Scope

Bioretention in experimental columns will be used to treat highway stormwater runoff over 2 years of compressed treatment representing 10 water years. Five depths will be tested during the first two water years (6”, 9”, 12”, 15”, 18”) after which two depths will be eliminated. Three replicates of each depth will be tested, plus an additional 3 replicates of the 18” depth that will receive clean water only. A full suite of chemicals will be measured in influent and effluent waters for the storm representing the end of a water year (approximately every 7th storm). Toxicology tests of acute impacts from influent and effluent water will be assessed for the storm ending each water year. These will include zebrafish embryo screens (every water year) and juvenile coho salmon exposure (first storm, end of water year 5 and 10).

Project Summary

Bioretention is a popular and effective method for treating stormwater runoff. This project addresses the need for long-term data on performance in terms of removing toxic chemicals and preventing acute toxic impacts. This study will be the first assessment of long-term performance of toxicity prevention.

Timeframe/timeline

Experimental treatment: 2 years (Oct 2019-Oct 2021)

Parameters measured

Fecal coliform

Total suspended solids

Dissolved organic carbon

Calcium, magnesium, sodium

Total and dissolved metals (As, Cd, Cu, Ni, Pb, Zn)

Polycyclic aromatic hydrocarbons (PAHs)

Alkalinity

pH

Nutrients (ortho-P, nitrate+nitrite)

Partners

USFWS Environmental Contaminants Division

Funders

SAM (Stormwater Action Monitoring)

Project Reports

Read the full report

Fungi Project

Purpose

Evaluate amendments to the default bioretention mixture (60% sand : 40% compost) for reduction of nutrients, bacteria, chemical toxicants, and toxicity to aquatic organisms.

Scope

Replicate installations (n = 3 per treatment) of bioretention amended with plants and/or fungi were constructed at the WSDOT ‘Ultra-urban stormwater testing facility’ in Seattle, WA where they treated stormwater from I-5 and the surrounding watershed over 2 years. Hydrology, chemistry, and toxicology was monitored for one storm per quarter.

Timeframe/timeline

Field Test: Feb 2017-Feb 2019

Parameters measured

Hydrology

Saturated hydraulic conductivity (Ksat)

Soil temperature & moisture

Chemistry

E. coli

Fecal coliform

Total suspended solids

Dissolved organic carbon

Total organic carbon

Total and dissolved metals (As, Cd, Cu, Cr, Ni, Pb, Zn)

Polycyclic aromatic hydrocarbons (PAHs)

Alkalinity

pH

Biological & chemical oxygen demand

Nutrients (ortho-P, total P, nitrate+nitrite, ammonia, total Kjeldahl N)

Toxicology

Zebrafish (Danio rerio) embryo survival and sublethal morphometrics (length, eye area, pericardial area)

Partners

USFWS Environmental Contaminants Division

Funders

SAM (Stormwater Action Monitoring)

Project Reports

View the full report

PAH Bacteria Project

Purpose

The purpose of this project is to evaluate the effectiveness of bioretention cells (filters made of soils, gravels, and plants) to reduce loads of organic contaminants and bacterial pathogens in stormwater.  Typical bioretention systems (e.g., raingardens) have demonstrated variable removal of such pollutants. Recent studies suggest that amendment with fungi and /or biochar may improve removal and breakdown of these contaminants. This study will evaluate these amendments as potential BMP recommendations for organic contaminant and bacterial pathogen removal from stormwater.

Scope

For one year (fall of 2019-2020), stormwater will be collected during targeted storm events and applied to a series of experimental bioretention cells. The stormwater flowing into and out of the cells will be collected and analyzed for organic contaminants and pathogenic bacteria. Soil samples will be taken from the cells periodically to evaluate the fate and transport of organic contaminants in bioretention cells.

Project Summary

Organic contaminants and bacterial pathogens are common stormwater pollutants which contribute to degradation of aquatic ecosystems, recreational water use, and fisheries production. These pollutants are not currently regulated in the stormwater permitting process because more information is needed on how to efficiently remove these pollutants from stormwater. In this study we will evaluate the capacity of typical bioretention soils, and potentially beneficial amendments (biochar and fungi), to remove these targets pollutants from stormwater.

Timeframe/timeline

2 years starting in fall 2018

Parameters measured

• Organic contaminants in water and soil

• Bacterial pathogens in water

• Soil moisture and temperature in bioretention cells

• Conventional water quality parameters (pH, DOC, TSS)

Elements Included in this Project

Three bioretention designs will be evaluated:

• Typical bioretention soil media (BSM: compost+ sand+ plants+ gravel drainage)

• BSM + fungi

• BSM + biochar

• BSM + fungi +biochar