On the basis of water quality problems associated with nutrients and sediments, Clopper Lake in the Seneca Creek watershed (02-14-02-08) was identified on Marylands 1998 list of WQLSs as being impaired. This document establishes Total Maximum Daily Loads (TMDLs) for the nutrient phosphorus and sediments entering Clopper Lake. Clopper Lake is an impoundment located within Seneca Creek State Park, near Gaithersburg in Montgomery County, Maryland. The impoundment lies on Long Draught Branch, a tributary of the Seneca Creek. The Seneca Creek lies in the Potomac River Drainage Basin. Clopper Lake was constructed for flood control and recreation. Clopper Lake has been previously impacted by a high sediment load. The lake also experiences occasional nuisance seasonal algae blooms, due to overenrichment by nutrients, which interfere with recreational uses. The death and decay of excessive algae can cause violations of the water quality standard for dissolved oxygen (DO), which can result in a disruption of the lakes ecosystem balance and cause fish kills. Analysis suggests that phosphorus is the limiting nutrient for the production of algae in Clopper Lake. Due to the propensity of phosphorus to bind to sediments, the overall strategy is to simultaneously address the water quality problems associated with phosphorus and sediments.