The Alaska Department of Transportation has good news for Lake Hood's aviators. Years of efforts to improve the water quality of Anchorage's highly-trafficked float plane base have paid off, and the water quality now significantly exceeds Alaska Department of Environmental Conservation standards.
Lake Hood, the world's largest and most heavily populated seaplane base, had a major pollution problem in 2004. Aircraft de-icing fluid, used to prepare airplanes for take-off in frigid winter temperatures, was flowing into the lake via drainage and snow melt, where it sucked oxygen from the water.
The fluid is made from propylene or ethylene-glycol solutions. Once in water, glycol converts into water and carbon dioxide, which absorbs dissolved oxygen. In both Lake Hood and Lake Spenard, the lack of oxygen prevented aquatic organisms from growing.
The airport and Alaska Department of Environmental Conservation worked jointly on a plan to reverse the harm caused by the fluid. With help from a variety of tactics beginning in 2005, including the diversion of runoff away from the lakes, they estimated an 89 percent reduction in fluid entering the lake.
They now report the tactics worked even better than expected. Water quality in both lakes has improved steadily. In 2009, lakes Hood and Spenard surpassed DEC standards for lakes without resident fish. In the last two years, they exceeded the DEC's "most stringent standard" for lakes with resident fish.
But they cautioned Alaska anglers: "Don't get your fishing poles out" because there are still no fish in the lakes.