4 decades after Mount St. Helens blast, Kelso looks to replace water system affected by sediment

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4 decades after Mount St. Helens blast, Kelso looks to replace water system affected by sediment

The sediment retention dam in Toutle has become less and less effective as it fills, switching from catching about 80% of passing sediment to allowing 80% to pass, according to the U.S. Army Corps of Engineers.