The Dam Speaker on April 19, 2019
by Jackie Deal
Blair Nash head of the Sutherlin Water Control District spoke at our Friday 3 pm get-together about Cooper Creek and Plat I reservoir and the Cooper Creek Dam. Over 60 park residents listened and eagerly asked questions about “our” dam and its condition and the potential dangers.
Blair assured us that only a total collapse of the dam (brought on by an attack from aliens maybe) would endanger us. The dam could probably withstand a 4.0-5.0 “sub-Cascadian impact” (earthquake), which might be a 9.0 on the coast. The dam is an earthen dam; it was excavated down to a solid rock foundation, about 10-15 feet, and then filled with “compacted earth”.
A little History lesson: the Water Control District was formed in the 1950-1960s to address the frequent flooding in Sutherlin. The District is 100% debt free and has a one million dollar bank account. However “refurbishing” the dam when needed will cost approximately 6 million. The Federal government will chip in about 2/3 of that amount.
Before the dam and reservoir the Fire Department stocked 80-100 sand bags to fight the floods at their facility. Now they have no sand bags. In 50 years the dam has settled only 2 inches and there has been no horizontal movement. Sample cores, taken recently show that the soils are more “plastic” now than formerly and that is considered a good thing. They have been doing core sample studies for several years and will probably continue for another year.
The biggest problem for the reservoirs is heavy rain. If 2-3 inches of rain is predicted, Blair drains the reservoir down 3 inches. Cooper reservoir is flushed yearly and Plat I is drained down to minimum every October 15 and it fills every February 1. The Cooper reservoir could probably withstand a “hundred year flood.”
Someone questioned the logging going on around the reservoir. Blair said that the Water District removing old trees that might be a fire hazard. The timber will be sold for funds for the dam maintenance.
In conclusion, Blair assured us, “I would have no problems sleeping at the base of the dam.” No one volunteered to join him!