The amendment of biochar into roadside greenways represents a marvelous opportunity to improve local infiltration rates and treatment of urban stormwater runoff through the enhancement of existing roadside filter strips and swales without the high costs of purchasing additional highway right-of-way or constructing new stormwater treatment facilities. These principles could easily be allied to both the treatment of stormwater runoff in urbanized areas, where open pervious infiltration space is at a premium, and for the retrofit of existing BMP facilities to improve function, reduce stormwater runoff and increase groundwater recharge. In addition, biochar amendment helps to enrich the soil and provide an enhanced environment for the establishment and growth of plants and microbes necessary for a healthy ecosystem and to aid in the removal of nutrients and contaminants from stormwater runoff. This research project evaluated the effects of biochar amendment in roadside soils on the soils’ water retention and infiltration characteristics, as well as biochar’s ability to remove harmful nutrients and suspended solids from stormwater runoff. In this study, a 4% mix (by mass) of commercial wood biochar, pyrolyzed at a temperature of 550℃, was amended into existing roadside soils to create filter strips and a swale located along a major highway in Middletown, Delaware. Roadside filter strips amended with or without biochar were carefully instrumented to measure infiltrating water quality, soil moisture content, surface runoff characteristics and water quality entering and exiting the filter strips. Results for over 125 storm events, measured over a two-year period, showed that the addition of biochar to the roadside soils decreased the stormwater peak runoff rates from the impervious roadway surface by an average of 80% and the cumulative runoff volumes by an average of 85%. When compared to soil tillage alone, biochar reduced the peak runoff rate by 56% and the total runoff volume by 68%, respectively, over tillage alone. The effect of biochar amendment on reducing stormwater quantity and improving stormwater quality will be presented.