Water Resources: Hydraulics and Hydrology
A:
Yes. They were built before I got there.
Q ..
Yes, they were pretty old; they go back to the 19th Century.
That's right. The
thing I remember is that they were constructed of rock and
considerable erosion occurred during major storms. They are maintained by continually
repairing eroded areas with more rock.
Most Difficult Hydraulic Engineering Problem: Mica Dam
What was the most difficult hydraulic engineering problem you ever faced? We talked
about your Tujunga Wash flood channel problem.
A:
That wasn't hard at all. I think one of the most difficult hydraulic engineering problems
was on Mica Creek Dam, which is on the Columbia River in British Columbia, Canada.
I served on the consulting board for that project.
Mica Dam was designed by BC Hydro. It's a large earth dam about 450 feet high. It
required a large concrete chute spillway on a good rock abutment on the left side of the
dam. A large tunnel, which led to a powerhouse, was located on the right side of the dam.
A large
diameter diversion tunnel was located at streambed level near the center
of the dam. Lastly, outlets were required to release flood flows with high reservoir levels.
One solution which was considered was installation of gates in the diversion tunnel. By
constructing two gate piers at the tunnel, three large gates could be installed to control
outlet releases, except for one problem. Whatever type of gate that would be installed
could not operate under the 400 or more feet of maximum head. The next consideration
was to install two levels of smaller slide gates; one level at the tunnel entrance and the
other halfway up the dam. The upper level of gates would be a second entrance and a
separate small outlet conduit discharging into the large diversion tunnel. This plan had
several hydraulic problems and would be costly.
Finally, the plan that was adopted consisted of constructing two concrete plugs in the large
diversion tunnel; one at the entrance and the other about 400 feet downstream of the
entrance. Two 7 x lo-foot slide gates were installed in each tunnel plug. The part of the
diversion tunnel between the two tunnel plugs served as an expansion chamber.
The two sets of gates can be operated under equal heads for any reservoir level. For
example, for the maximum reservoir head of 450 feet with both sets of gates fully open,
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