When water rises behind the dam, it pressures the groundwater and causes it to flow.
That can lead to erosion, creating voids, which over time could become larger and lead to dam failure, Rinehart says. “That’s why we have to address this problem now,” Rinehart says. The contractor, Environmental Barrier Company LLC/Geo-Con of Monroeville, Pa., will drill through the dam into the foundation and inject grout into the fractured bedrock and sand and gravel glacial deposits to reduce seepage through the foundation.
“The grouting won’t stop the seepage completely, but any water that does flow will move so slowly it won’t damage the foundation,” Rinehart says.
The project is part of a dam safety initiative which began in 1999 to address vulnerabilities — like underseepage — that weren’t understood back in the early 20th century when the flood protection system was designed.
Underseepage already has been addressed — with relief wells and drainage systems — at Germantown, Taylorsville and Huffman dams.
Work is under way at Englewood Dam and should finish in 2012. The Lockington grouting project will begin in December and is expected to take six months.
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