Total Maximum Daily Load (TMDL) for Dissolved Oxygen in the Waters of Lake Lucille in Wasilla, Alaska; Final rept

摘要

Lake Lucille is located in the city of Wasilla, Matanuska-Susitna Borough, about 72 kilometers (45 miles) north of Anchorage in Southcentral Alaska. The lake is part of a 586 hectare (1448 acre) watershed and is headwaters for Lucille Creek. The Alaska Department of Environmental Conservation (ADEC) 1998 Section 303(d) list of impaired waters identified Lake Lucille as water quality-limited because of low dissolved oxygen caused by nutrients (ADEC, 1998). Phosphorus loading is believed to have contributed to excessive growth of aquatic weeds in the lake, which in turn contributes to decreased dissolved oxygen concentrations (oxygen is consumed when the weeds die). Hydrologic modification of the lake is also believed to have contributed to the excessive aquatic weed growth because winter freezing no longer kills as many weeds as it used to. (Historically, larger areas of the lake were exposed to freezing conditions throughout the water column, which limited the extent of weed growth.) In addition to reducing dissolved oxygen concentrations, the weeds impair recreational use of the lake by snagging boat propellers and making the lake less appealing for swimming. The goal of this TMDL will be to eliminate any exceedances of the water quality criteria for dissolved oxygen. This will be accomplished by reducing the total phosphorus concentration and increasing the dissolved oxygen concentration to natural background levels through activities listed in the 'possible future actions' section of this report.