Herschel Henderly Describing Dorena Dam

Herschel Henderly was interviewed by Katy Barber in Eugene, Oregon on 23 October 1999.

Dorena was originally designed to have what we call cress gates. Those are the rotating gates that are kind of semi-circular and they rotate upward on long arms so that the water level could actually go quite a bit above the top of the concrete spillway and still be controlled. These gates could rise up and allow the water to spill over the top the spillway or come down and shut it off. My understanding is that because of cost economies they were trying to apply during World War II, this was under construction when the war started, it was decided to eliminate the cress gates. And then it was put in mothballs until the war was over. They just stopped construction and decided to come back later. When construction resumed, for whatever reason, the crest gates were not put back into the plan. So that’s why when we’re talking about design the Dorena design is not as capable as the Cottage Grove dam at handling some of the discharges, some of the flows we’re getting during storm events.

When we look back at ’96 and February of ’87, one of those Februarys where we had a pretty good storm event and a few small flood events beyond that, Dorena’s the one we really have to worry about. When we have heavy rains and very high inflows Dorena basin is bigger, it tends to be steeper, some of the hills are higher so they catch more snow which then melts pretty quickly if you get a warm rain on top of it so Dorena’s the one where we’ve come close to going over the spillway when we didn’t want to several times. Cottage Grove has never been much of a problem.

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