Because of the increased need for sustainable construction in an ever urbanizing culture, new sustainable drainage systems are being developed and implemented. Bioswales are becoming an increasingly popular form of sustainable urban drainage used for parking lots and subdivisions. But little is known regarding the effectiveness of bioswales in really cleaning storm run-off. If bioswales are not working to the level which they are theoretically designed for, then untreated water is being put back into natural waterways. This can cause potential problems for water body health as well as local aquatic and plant life. This thesis aims to investigate the effectiveness of a particular bioswale in effecting the storm water quality for one season. This is done by measuring the dissolved oxygen contents, temperature, pH, and nutrient content at several locations along the swale and comparing them with Oregon Department of Environmental Quality water quality standards. The investigation showed some improvement in the water quality as it progressed through the swale. Many water quality standards were not met. However, the data is inconclusive because it is only testing the swale during one season and no water was leaving the swale.