Sacramento District park ranger, Jacqui Zink (right), and Tahoe Divers Conservancy director, Phil Caterino, clean a weed barrier from Martis Creek Lake in Truckee, Calif., during a removal, cleaning and replacement project May 19, 2012. The gas-permeable barriers kill invasive plants by blocking sunlight, but don't disturb other plant and animal species. The U.S. Army Corps of Engineers and Tahoe Divers Conservancy have teamed up to sustainably eradicate invasive milfoil at the lake, managed by the Corps’ Sacramento District.