The Dam Facts: Part II in a Series

July 17, 2014

What Are the Dam Facts?

 

While working on the Dam Project significant knowledge about the Newlin Grist Mill dam was gained. The unexpected Dam Disaster provided a unique opportunity to study the dam and learn about its construction and history. The staff took the opportunity to examine, photograph, sketch, and record as much information as possible.

 

Dam Facts - #2:  Where are the Dam Foundations?

 

During the Dam Restoration Project, Newlin Grist Mill staff and contractors were surprised by what they did not find. As the rubble was removed, lines of stones revealed the location of both the front and back faces of the early dam. The final course of stone remaining was set directly on stream bed with no foundations. The bottom course of the new section of dam was consistently undermined along its front edge.

 

Speculation is that the constant turbulence from water pouring over the dam had eroded the stream bed below the dam causing the structure to be undermined and eventually collapsing during the storm in April. This theory was strengthened during analysis of the stone rubble being removed. The bottom stones were found at the bottom of the pile while the top and middle stones were mixed in the upper portion of the rubble. If the water had pushed the dam over, the stones would have been strewn in a horizontal pattern away from the dam. All of the stones were piled up directly in front of the dam so that was not the case. If the dam had gradually been washed away during the storm, the top stones would be on the bottom and the bottom stones would have ended up on top of the pile. It appears that the lower courses of the dam might have collapsed after being undermined and then the upper courses of the dam collapsed on top of them.

 

After analyzing the evidence of both construction and destruction, it was determined that a splash apron should be installed to keep from undermining the dam again. Large boulders were placed all along the front face of the dam to protect it.

 

The photo on the left shows the river gravel found beneath the lowest course of dam stones.

 

The photo on the right shows the iron stains result at the bottom of water ways and mark the stream bed where the dam builders started laying stones.

 

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