Soil Borings at the Geddes Dam (1917)

Geddes Dam is located on the Huron River just east of US-23.

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Image Courtesy of Google

The current dam (shown below) was constructed after the previous dam failed in the great flood of June 1968.

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Geddes Dam from Dixboro Road

The previous Geddes dam was constructed in 1918 as part of a plan by the Detroit Edison Company to harness the Huron River for electrical power for all of Metro Detroit. The Argo, Barton and Superior Dams (among others) were constructed for this purpose as well.

I am very interested why the Geddes Dam failed in 1968 and in attempting to research the failure was led to the papers of Gardner S. Williams at the Bentley Historical Library. Williams designed the old Geddes Dam and oversaw its construction on behalf of Detroit Edison in 1918.

Before his design and construction efforts began however, he commissioned a site exploration to determine the soil conditions beneath the proposed dam site. Below are images of the first two pages from that study. The first page describes the methods used to complete the soil borings and the second describes some of the results.

 

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Page 1 – Courtesy of the Bentley Historical Library 

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Page 2 – Courtesy of the Bentley Historical Library

On Page 1 we find that Detroit Edison used a four-man crew to drive a 1-1/4″ pipe into the ground. The driving block was a 6×8″ by 3 foot piece of Oak dropped onto the pipe and suspended from a tripod. To collect the soil samples, they probably had to pull the whole pipe back out and then drop it back in to collect the samples at each recorded interval. Old boiler tube was also used as an outer casing to keep the hole from caving in the soft river sediments. Very simple, elegant and much more labor intensive when compared to the drill rigs currently used for soil investigations.

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A Modern Drill-Rig (Courtesy of the Central Mine Equipment Company)

Although the methods were a bit different, the results found on Page 2 of Williams’ Geddes Dam investigatoin are largely similar to soil investigations of today. Complete descriptions of soil types, layer thicknesses, salient features and other defining characteristics are all detailed to give the engineer and designer as complete a picture as possible of the subsurface conditions.

To highlight this, below is an example page from a modern soil investigation (courtesy of the Washtenaw County Parks and Recreation Commission):

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The results are much more formalized in this modern example (from almost 100 years after the Geddes Dam borings) and much more data is provided but the general outline is the same. Concise information on soil conditions as compete as possible for the designer and engineer.

Although this was not the intent of my research, discovering the soil boring records for the old Geddes Dam was a very cool find as it provides a historical context for modern soil investigation practices and also a strong connection with those engineers whose shoulders we are standing on (and whose roads, bridges, dam, etc… are still used today).

 

 

 

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