Earthen EarthCache EarthCache
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Earthen dams are one form of ‘embankment dams’. Earthen dams are really only compacted dirt and earth from sources nearby. The earth-filled dam is 44 ' tall, blocking the Long Tom River. The Army Corps of Engineers completed it in 1941.
You are standing on an earthen dam! An earthen dam is a man-made geologic feature that obstructs the flow of water. The lake behind the dam is called a reservoir; a man-made lake. As with most dams, this dam has a spillway (or weir) that water flows through intermittently (as needed as decided by Lane County & the Corp of Engineers). Look around this dam and note the steep sides down to the reservoir and to the road down below. The construction of this dam was multi-purposed. Mainly, it prevents unwanted flooding of the Eugene area. Before the dam was in place it was common for low levels to flood when there was too much rain. With the dam in place, the reservoir fills up until it becomes necessary to release specific amounts of water that can be controlled to lower the lake and to not overflow the river’s boundaries. Now the dam also creates dynamic habitats for multitudes of wildlife. It also serves the wildlife humans who boat, swim and generally party along the shores during the balmy summer months.
Dam thing leaks!
It was noted in early 2002 that earthen dam was not stable. Corps employees working at Fern Ridge Reservoir first noticed depressions and seepage on the downstream slope of the dam in July 2002. Two more depressions were discovered in February 2003. The depressions ranged in size from a few feet in diameter to 13 feet in diameter. At that time, the Corps suspected a failing drain system as the cause of the depressions.
Thus, in 2004 the lake was mostly drained as the dam was repaired. Grass seed was spread over the new dirt on the dam. Mother Nature had a sense of humor as the rain and cool temperatures prevented the grass from taking root. Thus, as soon as the dam was considered ‘completed’ it started having small slips and slides that the experts swore would not effect the safety of the dam.
This erosion layer that is sliding, according to the Army Corps of Engineers, does not affect the dam itself.
YOUR TASK IN ORDER TO LOG:
1) E-MAIL the owner your estimate of the height of the water level to the top of the dam where you are standing.
2) E-MAIL the owner one observation of ongoing maintenance of the earthen dam
3) POST to the page: watch for 5 minutes and list at least 2 animals that you observe in the area
4) POST to the page: estimate how much water (if any) was going through the spillway
5) POST to the page: an estimate of in the last week, how many days has it rained and if it rained, how hard did it rain?
6) Request- but not required: post a picture of yourself at the dam!
Additional Hints
(Decrypt)
Cnex naq jnyx hc gur ebnq gb gur gbc bs gur qnz. Vg vf n ynetr jnyxvat cngu!