[brcs-announce] BB Dam removal Update from Steve Largent

[Norman R. Fred]

Wednesday (10-3-12) – At yesterday’s 
Construction Team meeting Molon reported hitting old sheet piling, rock 
and other debris while digging out the temporary dewatering structure 
which is why they believe they went through 5 different sheet pile 
drivers (breaking two) before being able to drive the sheets to the 
designed depth.  It is believed the current dewatering structure 
location is in the exact same location of the old diversion channel when the dam was built over 90 years ago.  This is supported by the fact 
that Molon also found gravel & cobble very similar to what is seen 
in the river.  The diversion channel served to pass river flow while the powerhouse was being built.  
 
Hitting this debris caused a slight delay in the expected completion date of the temporary dewatering structure.  It appears that Friday afternoon (10/5) or Saturday (10/6) at the latest is when Molon plans to begin passing water.  Yesterday Molon poured concrete around the stop log H-beams and apron.  Today they will begin to place large energy dissipating boulders on the downstream end of the apron to where it connects with the river below 
the dam.  12” x 12” X 7.5’ stop logs will be stacked in two identical 
columns each side of a center beam to retain the pond water.  Stop logs 
from each side will be removed periodically (approximately once a day) 
to gradually lower the pond.  S.
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