Margaret S. Petersen
That's like the big dams. We used to talk about providing
A:
sediment storage
capacity for the project life, 100 years. Some of the dams are now getting to be
years
old, and some of the reservoirs are filling in, mostly the smaller dams. They are not Corps
dams. I don't know of any moderate to high Corps dam, although there may be some, where
they have gone in and excavated out sediment deposits to restore reservoir storage capacity.
There are a number of small structures constructed by irrigation districts or utility companies
where the reservoirs were small and have filled in and they have removed the sediment.
Sediment deposition in reservoirs is a serious problem in China, worse than ours.
[Pacific Gas Electric] in California has had this problem. The most critical part of the
problem is what to do with the sediment that has been removed because it can't just be
dumped downstream. That's not acceptable, environmentally.
Doesn't the sediment have a lot of heavy minerals in it?
Not necessarily. It depends on industrial activities in the upstream basin. Mountain streams
generally carry only naturally occurring minerals, except in California where there's often
mercury from gold mining in the
There's a lot of debris in the Sacramento District.
There was a lot of debris from the mining. The Lower American River is good sized
A:
cobbles, from the gold mining. Most of that material in the channels has moved down the
rivers and is now deposited in Suisun Bay. The overbanks are still cobbles.
But it's been, basically, washed down.
A:
Yes, that's over a hundred years.
It takes a while. What was the basic problem with the sedimentation in the Arkansas?
Basically, that you didn't want to fill the navigation channel?
A:
Well, the basic problem was how to pass the sediment through the system and down to the
Mississippi.
Right. So a matter of keeping it moving then?
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