The purpose of this Earth Cache is to teach you about necessary geological features to plan a hydroelectric generating plant.
Hours: November 1-January 31 Sunrise to Sunset
February 1-October 31 Sunrise to 10pm
In order to log this geocache, please send me the answers to the following questions:
1. What types of rock comprise the Knox Group Undifferentiated?
2. Name two factors are needed for choosing a location for a hydroelectric dam.
3. Do you think this area was well chosen? Why or why not?
4. Pour a bit of water on one of the large white/gray limestone boulders you see at the listed coordinates. Would you say it is relatively permeable or impermeable? Why is this important in choosing a location for a hydroelectric dam?
Logan Martin was the second dam built as a part of an Alabama Power Company construction program that further developed the Coosa River in the late 1950s and the 1960s. The project included the construction of Weiss, Henry and Bouldin dams and the redevelopment of Lay Dam.
Source: AlabamaPower.com
Geology of The Area:
The area of Lake Logan Martin is geologically a part of the Knox Group Undifferentiated, which arose from the Ordovician-Cambrian Geologic Age around 45 million years ago. Rocks from this age are composed primarily of dolomite, limestone, and chert. These are sedimentary rock types. This is important in the choosing of the general area for the construction of the dam. Phyllite, siltstone, quartzite, conglomerate, and phyllite rock types are also in this area. These types are relatively impermeable and are more than 3,000 feet thick.
Factors needed for choosing a location for a hydroelectric dam:
1. Good topography along the river path with a wide flat valley that narrows at the dam site and has a height differential.
2. Favorable geological structure with a strong and stable rock structure to hold the weight of the dam and the water stored in it.
Sources: https://www.gsa.state.al.us/Home/DownloadPubDocument/?path=Circulars&fileName=C199D.pdf
Factors that Affect the Locations of Hydroelectric Power Plant Dams by Haresh Khemani
https://water.usgs.gov/edu/wuhy.html