Eightmile repairs described

October 28, 2018

Icicle Peshastin Irrigation District has described the repairs it made this year to the Eightmile Lake dam. 

These were done to shore up the 90 year old dam after a forest fire in the lake's headwaters last year brought concerns about debris flows and heavy spring runoff.

As reported on KPQ News Radio, the dam was damaged in the 1990's from an earlier flood. Moreover, per the irrigation district, the outlet pipe was partially plugged and could only pass about 5 cubic feet per second (CFS). It was designed to handle more than 25 CFS. Both problems made the dam more vulnerable to high water.

After declaring an emergency, the irrigation district flew an excavator to Eightmile Lake in early May and started repairs. It removed about 50 feet of the earthen portion of the dam and hardened the area with rip-rap, increasing the spillway from about 13 feet to 63 feet wide. It also removed part of the old rock and cement wall that was no longer supported. With water flowing around both sides of it, workers worried that debris would collect, cause the wall to break off, and release a surge of water down the creek.

According to KPQ News Radio, it was early August before the lake level fell enough for the district to check the outlet pipe. It found that the old made-in-place log stave pipe was not plugged but had collapsed in several places. It replaced the pipe and lowered the lake further. By late September the lake level was 16 feet below the new spillway. The district claims this amounts to about 1,200 acre feet of flood control storage space, or the volume of water in a storm that drops 4 inches of rain in an hour.

With new measuring equipment installed by the Department of Ecology at and below the dam, the irrigation district claims it can now monitor and warn of any problems. Based on this, it announced on October 9 an end to the emergency it had declared on March 13. The district says the dam is much safer than it was at the beginning of this year, but it still is not up to today's dam safety standards.

It does not appear that these repairs enlarge the irrigation district's ability to take more water from Eightmile Lake. Its right to do that is highly disputed. Numerous conservationists observed in their July 30 comments on proposed Icicle water projects that the dilapidated condition of the Eightmile dam before this year's emergency showed how little interest the irrigation district has had in exercising all the water rights allocated to it nearly a century ago. Based on this, they assert that it has forfeited or relinquished its right to take more water.