missing, explaining their er- Double Loop 1/2"PCohduotd
n i
us R
String
Air Pipe
ratic response, i.e., not active
Extension
Cap
or inactive.
In the future the support
system will be modified to
1 1/4" Pipe
provide better mechanical
Air Lift
(with air supply
Air Probe
protection. The installation
to bottom)
with Valve
procedure was also modi-
fied to minimize the exces-
sive loading incurred on the
Outer Drilling
Shell
swivel connection during
installation.
Chain
The chains were found in
a sand layer that represent a
radial cross section along the
centerline of the pier (Fig.
28). Extrapolation of the point
Anchor
measurements of scour depth
at the chains showed that this
4-in. layer of sand returned
to the surface approximately
on the same radius as the
bubbles observed during in-
Figure 27. Equip-
stallations. Figure 29 shows
ment used to install
Inner Drilling
Shell
the contour lines of the scour
the scour chains.
1" x 8' Pipe
hole as defined by the sedi-
ment chains. The active fish (140.020 MHz) was
above the sand layer defined by the chain, con-
Figure 26. Equipment used to install the fish.
firming that scour did occur. In the process of
restoring the riverbed to the "natural" contour,
the sediment chains were reset. The instrument
started to rise and the ice sheet was still intact
fish will be reinstalled using a different mast ar-
around the pier. During this period, one fish
rangement for sheltering the fish.
(140.020 MHz) was active for 9 hours before re-
turning to the inactive state.
(Except for the top fish on
poles 1 and 2 in front of the
Pier
pier, all remaining fish
were stable in their signal
strength at the inactive
level.) Returning to the in-
active state coincides with
the ice sheet being broken
up and moving freely. Al-
though the ice continued to
Redeposited
move by the pier for the
Gravel
Sand
next 24 hours there was no
Layer
additional scour activity.
When the chains and the
Riverbed
instrumented fish were re-
covered in August to evalu-
Footing
ate their performance, the
top fish on poles 1 and 2 in
front of the pier (140.090
Figure 28. Cross section of the scoured and redeposited gravel wedge.
and 140.130 MHz) were
17
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