This aerial photo shows the shoreline of Zephyr Cove in the southeast part of Lake Tahoe. A boat dock extends into the lake, and U.S. Route 50 goes north-south through the photo (north is to the top). A small wetland (outlined) extends from U.S. 50 Route to the east. Part of the wetland is a marsh (the dark-colored area near the road) and the rest is a swamp (the light-colored area), treed with alder and willow. Beneath the marsh and the swamp, uraniferous organic muck, clay, silt, and sand have accumulated to as much as 7 feet thick containing nearly 10,000 pounds of uranium. About 20 to 30 similar, small, uranium-rich wetlands, occur along stream valleys draining into Lake Tahoe for a few miles north and south of Zephyr Cove. Spring and stream waters in this area contain as much as 40 parts per billion uranium. Man's activities in this highly-developed recreational area may release uranium that has accumulated in these wetlands for several thousands of years, and thereby lower water quality.