This dam showed significant seepage after the 2007 and 2008 flooding events. In the first photo below a large slump is shown on the downstream right hand abutment. This occurred as a result of water flowing through the fractured sandstone an out letting below the dam. After the June of 2008 flood state and federal engineers planned a breach cut in the dam. This breach was done to limit the amount of water and the head pressure that this dam could hold back in order to prevent a massive failure.
A plan was set in place to place a grout curtain on the right had abutment and then restore the dam to its original shape and place large rock relief drains on both the left and right downstream sides. The grouting was completed in 2012, 22,000 cubic feet (over 81 redi-mix concrete trucks) of grout was placed.
Following the grout repair the excavation and earthwork repairs were completed in 2013. A borrow site was found on top of the hillside to the west of the dam 6,500 cubic yards of clay were hauled down and compacted in place. Also just under 3,000 tons of rip-rap and drainfill rock were placed to create the downstream relief drains. The total cost of the entire repair was just over $1.4 million.
The photo above shows the slumps on the downstream right hand abutment from water flowing through the fractured sandstone bedrock. This was an immediate concern for the dam’s failure.
The photos below illustrate the earthwork portion of the job which totaled $188,673.78
Original Breach cut excavated after the 2008 flood event.
Excavating rock from original breach cut – wet condition
Filling and compacting breach cut with borrow material
Excavating Right Drain
Final Excavation of Right Drain to Lodi Silt Stone
Placing Drainfill on Right Drain
Placing Drainfill in Right Drain with aggregate conveyor.
Right Drain with Drainfill and base of riprap
Bucketing up Drainfill for left drain – completed right drain in background
Excavated and prepped Left Drain for Drainfill
Nearly done placing left drainfill
Backfilling left drain
Borrow area hauling fill down to Dam
Borrow Area – Hauling fill down to Dam