Since the mid-1900’s, invasive aquatic weeds have been a significant problem in many of the lakes of the Clatsop Plains on the northern Oregon Coast. Weeds interfere with beneficial uses, such as boating, fishing and swimming, and have dramatically altered the chemical and biological features of the lakes. In 1994, the Oregon Department of Environmental Quality (ODEQ) added three of the lakes, Cullaby, Smith and Sunset, to the 303 (d) list of water quality impaired waters, due to the presence of the invasive aquatic weeds. ODEQ contracted with the Center for Lakes and Reservoirs and the Geology Department at PSU to develop management plans for the weeds and to evaluate the source of nutrients to the lakes that may contribute to water quality problems. Current water quality conditions, groundwater, and the watershed were studied.