Max water levels at Detroit Lake lowered; public meeting planned | Local

The maximum water level at the Detroit Reservoir will be lowered this year to reduce the potential impact of future earthquakes. The lowering of the water level could affect access to the boat ramp in dry years and is only part of the ongoing seismic preparedness work there.

The reservoir straddles Counties Linn and Marion on the North Santiam River near the city of Detroit and is an important source of drinking water for communities in both counties, including Salem. A 2020 seismic study found that the current maximum water level could “overload the overflow gates during a major earthquake,” according to a US Army Corps of Engineers press release.

To avoid this, the maximum height of the reservoir is reduced by five feet from 1,563.5 feet to 1,558.5 feet. While that doesn’t seem like much, authorities say it would greatly reduce the load on the locks during an earthquake.

However, the move could affect boat ramp access in a few years’ time as the waterline falls below the ramp lines, especially during the driest part of summer in August and September. The reduction is not expected to affect other recreational activities such as non-motorized boating, fishing, swimming, and camping.

“Structural analysis has shown that the overflow gates can buckle under the force of a full reservoir during a large earthquake,” the press release said. While officials say the risk of a complete breakthrough of the dam is small, they say this reduction is necessary to prevent damage to the overflow grilles.

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