The Minneapolis Chain of Lakes, a series of five lakes covering some 445 ha (1,100 acres) within an urban residential setting, is an important recreational and aesthetic resource. The lakes support swimming, fishing, sailing, and canoeing and are almost entirely surrounded by public parkland. However, the lakes exhibit increasing cultural eutrophication. The city of Minneapolis obtained an EPA Clean Lakes grant for demonstrating vacuum street sweeping and first-flush runoff diversion as means for improving the lakes. The project was completed in 1981 following 2 years of monitoring and pilot implementation. In 1979 and 1980, the city regularly vacuum swept streets throughout the Lake Harriet watershed (46 curb-km in 340 ha). During these years, consultants monitored lake quality, weather, runoff flow, and quality in major storm drains to Lake Harriet, and quantity and quality of vacuum swept materials. Runoff data were used to analyze first-flush diversion. Data analysis resulted in estimated runoff coefficients ranging from 0.05 to 0.5 for individual drainage areas throughout the chain. Seasonal patterns of runoff quality were found. Total phosphorus export from the entire watershed of the chain was estimated to average 5.2 kg per hectare (1 pound per acre) in a climatologically normal year (with no allowance for sweeping or diversion). Detailed water and nutrient budgets, including ground water and inter-lake flows, were developed. Runoff and direct precipitation contributed nearly equally to the water budget, but runoff accounted for over 95 percent of phosphorus inputs. Water outflow was predominantly via seepage. Phosphorus retention in the lakes was high, totaling over 90 percent for the whole chain. Vacuum sweeping was found to remove 3 kg phosphorus/curb-km and 69.5 kg organic matter/curb-km (0.26 lb phosphorus/curb-mile and 74 lb organic matter/curb-mile) per sweeping. These are average values: seasonal variations were significant. Weekly sweeping was projected to remove 38 percent of Lake Harriet's phosphorus load. First-flush diversion was analyzed by taking into account the frequency distribution of storms with respect to total precipitation. Diversion was found to be cost effective in some areas and capable of reducing the phosphorus load to Lake of the Isles by 42 percent. A combination of sweeping and diversion throughout the Chain of Lakes watershed was found most cost-effective. This scheme could reduce the whole chain's phosphorus load by 27 percent, at an estimated 10-year cost of $4 million. Predicted transparency increases averaged .77 m (2 ft.) and ranged from .2 m to 1.9 m (one-half to five feet) for individual lakes.