A bioswale is a linear, vegetated stormwater control measure engineered to intercept, convey, and treat surface runoff. Typically constructed with a shallow, graded channel, bioswales incorporate engineered soil media, mulch layers, and regionally appropriate vegetation to enhance hydraulic residence time and promote infiltration, sediment deposition, and biogeochemical pollutant removal.
As stormwater enters the system, flow velocity is reduced, allowing suspended solids to settle while the soil matrix and root zone facilitate filtration and adsorption of contaminants such as hydrocarbons, nutrients, and heavy metals. Depending on design parameters, a bioswale may also include underdrains or check dams to increase treatment performance and support site-specific hydrologic goals.
Bioswales function as part of a broader green infrastructure strategy, reducing peak flows, mitigating erosion, and improving downstream water quality while providing ancillary ecological benefits through vegetative habitat and soil enhancement.
Our bioswale media blends are engineered to attenuate a broad spectrum of organic and inorganic contaminants commonly found in urban runoff, including suspended solids, pesticides, and dissolved heavy metals. Each mix incorporates a high-quality organic amendment that supplies a stable carbon source to enhance sorption processes, promote microbial activity, and support the development of a resilient soil–plant–microbe system.
Gail Materials’ 80/20 Bioswale Growing Media is formulated to conform to the performance criteria established in current Southern California Best Management Practices (BMP) and Low Impact Development (LID) guidelines.
This engineered media consists of 80% ASTM C33–compliant sand and 20% premium organic amendment (by volume). The blend delivers high hydraulic conductivity and optimal air-filled porosity while maintaining sufficient fines and organic matter to support pollutant sequestration. The resulting root zone provides robust structural support and biological functionality for a wide range of approved vegetative species, while facilitating the removal, adsorption, and/or transformation of contaminants prior to infiltration or conveyance to stormwater infrastructure.
STORMWATER FILTRATION
Our bioswale mixes are engineered to support a broad range of California native species as well as commonly specified ornamental plants used in stormwater bioretention systems. The media’s physical and chemical properties—such as hydraulic conductivity, air-filled porosity, cation exchange capacity, and organic matter content—are balanced to promote vigorous root establishment, sustained plant health, and long-term system performance under variable moisture conditions.
In addition, Gail Materials offers the ability to customize soil blends to address project-specific stormwater quality objectives. By adjusting parameters such as organic matter type and percentage, mineral composition, grain-size distribution, and the inclusion of targeted sportive amendments, we can tailor the media to enhance removal efficiencies for specific contaminants of concern, including nutrients, hydrocarbons, pesticides, or dissolved metals. This engineered flexibility allows project teams to optimize bioretention performance in alignment with regulatory requirements, watershed management goals, and site-specific pollutant load profiles.
LEED CERTIFICATION FRIENDLY
Contact our office for guidance on how bioswale installations and engineered bioretention media can contribute to LEED-certifiable stormwater management strategies. Our team can help identify applicable credit categories—such as Sustainable Sites, Water Efficiency, and Materials & Resources—and determine how your project’s bioswale design, performance criteria, and media specifications may support point acquisition under current LEED rating systems.