American River at Numbus
Free Parking Coordinates 38 38.006, -121 13.432
TO LOG this cache stand as near as possible to 38 38.119, -121 13.469 to observe acceptible answers to the following questions about the area. Some research may be required. FIRST send us the answers offline with your reply email address. THEN, go ahead and post your found log. PLEASE send to our email address rather than using the MESSAGE CENTER link. (I will NOT reply nor communicate through the Message Center)
- QUESTIONS:
- Read Plaque and tell us what is unique about this bridge or research to discover what makes this bridge distinctive?
- Judge the river width at this point.
- Describe the Geologic differences between the North and South banks of the river.
- What is the use of the derrick like structure a few yards to the West?
- How many operable sections in the major structure ¼ mile to the East?
- Post the requested proof of find photo taken anywhere near the site of yourselves, or your GPS, on YOUR FOUND LOG having fun and obviously taken somewhere near the site or around the Fish Hatchery area - OR - submit some other acceptible proof of find
The American River Division of the Central Valley Project provides water for irrigation, municipal and industrial use, hydroelectric power, and recreation. Flood control is provided through a system of dams, canals, and power plants. The Folsom Unit consists of Folsom Dam, Lake, and Power plant; Nimbus Dam and Power plant; and Lake Natoma, all on the American River.
Nimbus Dam is on the American River in Sacramento County, California, 7 miles downstream from Folsom Dam. It re-regulates the releases for power made through the Folsom Power plant. Nimbus Dam is a concrete gravity dam 1,093 feet long and 87 feet high. Eighteen radial gates, each 40-feet by 24-feet, control the flows. The total volume of material used in the dam is 121,100 cubic yards. Reclamation operates the dam. Nimbus Dam and Power plant was completed and accepted by the Government in July 1955. Nimbus Dam forms Lake Natoma, with a capacity of 8,760 acre-feet and a surface area of 540 acres.
The Nimbus Power Plant, constructed and operated by Reclamation, is located on the right abutment of Nimbus Dam, on the north side of the river. Its two generators has a combined output of 3,500 kilowatts. It started operating in 1955.
Nimbus Fish Hatchery. Construction of Folsom and Nimbus Dams blocked access to natural spawning grounds of salmon and steelhead trout. To compensate for the loss of these spawning areas, Reclamation constructed a fish hatchery about a quarter of a mile downstream from Nimbus Dam. The hatchery is on the left bank of the river, about 0.3 mile below the dam. It is operated by the State of California with Reclamation funds. Work began on April 20, 1955 and was finished and accepted on October 17, 1955.
Whether you arrive on two or four legs, two or four wheels, or follow the American River Bike Trail, a visit to the Nimbus Fish Hatchery should not be missed. Watching the spawning fish and learning about their adventures makes learning fun. While there are no formal guided tours, there's plenty to make a self-guided tour worth your while. Around the first week of November the salmon make their way up a "fish ladder" to lay eggs in the ponds at the top. The Hatchery has a capacity of 30,000,000 eggs. That's a lot of salmon!
GEOLOGY: American River Bluffs. The Sacramento Valley is a structural trough occupying approximately the northern third of the Great Valley Geomorphic Province. This area is near the edge of a structural trough associated with the bedrock formation of the Sierra Nevada province. The trough is filled with marine, lacustrine and alluvial deposits. The American River at Nimbus is composed of variable topography. Along the north side, the higher elevations consist of the resistant material (bedrock) that composes the bluffs and slopes along the American River, while on the south side the lower relief is the result of a combination of low topographic, erodible material located within the floodplain of the American River, and of areas of man-made embankment fills above natural grade. The site is generally underlain by thin veneer of colluvium derived from the poorly to semi-consolidated sediments of the Turlock Lake Formation, over semi-consolidated sediments of the Laguna Formation. Quaternary and Tertiary-age alluvial deposits are composed of medium dense to dense silts, sands and gravels.
The Laguna and Turlock Formations unconformably overlay the Mehrten Formation, and which is exposed in rock cut on the north side of the American River channel. The Mehrten Formation is composed of moderately indurate andesitic conglomerates, sandstone and breccia.