Events

This project showcases the literature review and research plan for evaluating the performance of a new field-scale bioswale design at the OSU OGSIR facility.

Introduction:

Stormwater management has become increasingly important in urban areas due to greater likelihood for sewer flooding and poor runoff water quality.  Conventional stormwater infrastructure utilizes overflow systems that direct excess untreated stormwater into other waterways.  However, this runoff may contain high concentrations of contaminants which vary by rainfall, hydrologic processes, and land use.  These issues spurred the creation of green stormwater infrastructures (GSIs).  GSIs are designed to control the hydrology and runoff water quality so it resembles that of less urbanized areas.  Bioswales are a popular type of GSI that use shallow depressions filled with engineered soil mixtures and landscaped with local vegetation.  This design has a strong track record in reducing peak hydrologic flows and removing particulate contaminants.  However, bioswales have a mixed track record in removing dissolved contaminants, with several studies demonstrating that the concentrations of dissolved contaminants in the effluent being higher than in the influent to the system.  Thus, there is a clear need to improve the bioswale design to enhance dissolved contaminant removal. 

Current OGSIR Design:

The OSU-Benton County Green Stormwater Infrastructure Research (OGSIR) Facility was built for conducting field-scale experiments on GSI technologies.  A unique aspect is the three “cells” that function as separate bioswales that are operated in unison for testing different technologies.  The system begins with intercepting runoff from pre-existing stormwater infrastructure and stores the water in an underground storage basin.  Then a sump pump transports the water to the sediment bay, where suspended particles settle out before the water overflows from weirs into the cells.  Each cell contains layers of a soil mixture (25/25/50 mix of municipal compost, mint compost and native soil), construction sand, gravel, and crushed rock.  The landscaping incorporates native Willamette Valley plants.  As the water enters the cells, it travels across the soil surface and percolates through the layers until it enters an underdrain that reconnects with the pre-existing infrastructure.

Research plan:

The upcoming field-scale experiments include a sediment tracer study, construction of a new bioswale design, and collection of water samples for evaluating the design performance.  The tracer study will utilize fluorescent and paramagnetic particles to provide a temporal and spatial understanding of sediment travel within the current design.  Then, one of the cells will be reconstructed with a new bioswale design to enhance dissolved contaminant removal.  Instead of engineered soil media throughout the cell, this bioswale will have three latitudinal sections.  The first section will be the current engineered soil media and native plants.  The next two sections will contain biochar (for PAH, PCB and dissolved metal removal) and RemBind® (for PFAS removal).  Other changes include making the cell gravity fed and adding an impermeable layer above the underdrain.  This will force the water through each sorbent section and will only exit the facility at the end of the cell.  Stilling wells will be installed to collect water samples for measuring water quality parameters throughout the bioswale.  Water samples will also be analyzed for heavy metals, nutrients, and potentially PFAS.  The results will be compared with data from the other cells to gauge performance improvement of the new bioswale design versus the original design.

This project presenter is available for live video chat on Sept. 1, 2020 from 1:00 - 2:45 p.m. PDT.