The COE has scheduled time for repairs to be made to the siphon at Norfork this week. The repair that was made back in June was a temporary repair that was meant to last until a replacement for the broken part was received by the manufacturer. The repair scheduled for this week is to beef up the temporary repair until this winter (January-February), when the permanent repair will be made.
The COE anticipates that the siphon will be shut down about noon tomorrow (Tuesday 7/29). They will allow it to drain the rest of the day in preparation for work on Wednesday. They plan to then refill the siphon and restart minimum flow through siphon by COB on Thursday (8/1).
Starting tomorrow morning, SWPA will start the “speed-no-load” operation at the dam, which will overlap with siphon-use the entire morning. From noon on, only speed-no-load will be used to meet minimum flow requirements (when SWPA is not generating for hydroelectric purposes). If all goes as planned, water levels should be at or near what you would see at minimum flow- it simply will not be coming out of the siphon for a couple of days. They will not be spilling water to meet the minimum flow requirements as they did back in May-June- temperatures on the lake-side of the dam are way too warm for that to be a viable option this time of year. As this is the time of year when low D.O. is starting to become an issue, the COE and AGFC will be closely monitoring D.O. levels in the tailwater all week to ensure they do not become a major issue when speed-no-load is operating. The COE does not anticipate that it will become a problem and thinks that all downstream parameters will be within the guidelines of the low D.O. plan of operation for the fishery.
Please let me know if you have any questions. I will send out an update once they notify AGFC that repairs are completed.
Trout Biologist Supervisor