The city of Wrangell is concerned about one of its dams. The city says the upper dam is seeping more water than usual.
At a city assembly meeting, public facilities director Amber Al-Haddad presented her findings. Her staff found some signs of concern on August 21.
“A week ago today, we noticed what appeared to be some new or addition seepage, at the toe of the dam on the east end,” she said.
State regulators gave a poor assessment of the dam in 2011, linked to seepage back then. Alaska Dam Safety engineers say the dam certainly has deficiencies, but cannot say the seepage poses any serious threats to the dam.
The dam is made of timber cribs, essentially logs stacked on top of each other. Later an embankment was put on top of that.
In 1993, the city assessed that the dam was stable, under normal conditions.
“ If we were to have a sizable earthquake that affected those dams we would likely see a failure in those dams,” Al-Haddad said.
The upper dam is classified as a high potential risk, the lower dam a low potential risk.
City staff is monitoring changes in the water flow. Though there is seepage, there are no signs of internal or external erosion.
The city has had concerns about the dam for a while. When deciding on building a new water treatment plant, city manager Lisa Von Bargen and some assembly members said the dam and reservoirs need an upgrade too.
The city wants to perform a dam stability assessment, though that wouldn’t be immediate.
The current Emergency Action Plan for the dams also needs to be updated. It was last revised in 2002. The city has already been working on this. A new plan is needed for federal funding the city is seeking.