Serious questions remain about the Klamath River Renewal Corporation’s (KRRC) schedule and overall plan for removal of Iron Gate Dam.
Reprinted from KWUA’s newsletter
By Moss Driscoll
Director of Water Policy
Klamath Water Users Association
On April 22, KRRC submitted to the Federal Energy Regulatory Commission (FERC) its “optimal excavation schedule” and supporting information for removal of Iron Gate Dam. KRRC had recently sought and been granted an extension of the deadline to produce this plan. The plan and supporting materials are not available to the public, as KRRC has filed these documents as “controlled unclassified information” pertaining to “critical energy infrastructure.”
In a public statement, KRRC stated that it is seeking authorization from FERC to begin removal of Iron Gate Dam by May 13, 2024. On April 26, FERC responded to KRRC’s request, authorizing the company to begin removing portions of the embankment to the dam, but deferring final agency action on the actual removal plan.
Iron Gate Dam is 173-foot tall, earthen fill embankment dam. Excavation of the embankment is required to proceed at a rate that preserves a section of the dam that still can withstand a one percent probable flood for that time of year. In total, removal of Iron Gate Dam involves the excavation and transport of 690,000 cubic yards of material. For comparison, a dump truck generally hauls between 10 to 14 cubic yards in a single trip.
The need for caution when it comes to removing Iron Gate Dam has been closely scrutinized over the last year. Last April, an independent consulting engineer, Paul Schweiger, in reviewing KRRC’s overall plans, identified the need to evaluate and mitigate the risk associated with the potential for Iron Gate Dam to be overtopped during its removal. The concern stemmed from KRRC’s plan to still be removing the dam’s earthen embankment in September and October, when the chances of a large rain event increase.
KRRC’s engineers had previously identified overtopping and breaching of Iron Gate Dam due to a late season flood event as the “most significant Probable Failure Mode.” “All parties agree that the risk of Iron Gate overtopping due to a late season event would be unbearable and recovery could cost billions of dollars,” KRRC’s lead engineer, Mort McMillen, wrote in a technical memorandum last September.
KRRC is relying on an early start to removal of Iron Gate Dam as the primary measure to reduce the risk of dam failure and has assured FERC that Reclamation will assist with flow management from Upper Klamath Lake to allow construction to begin on time.
With water levels in Upper Klamath Lake still rising, a healthy snowpack remaining in the Cascades, and more precipitation in the forecast, Reclamation has nonetheless committed to KRRC that releases from Keno Dam will not exceed approximately 1,000 cubic feet per second.
Concern over potential flow restrictions with the outlet tunnel at Iron Gate Dam are heightened due to the failure of a 45-foot section of a ventilation pipe in the tunnel in January. The ventilation pipe was installed last year by KRRC to help ensure the free flow of water through the tunnel, but anchor bolts holding it failed shortly after the outlet was opened in January to start draining the reservoir. The loss of the ventilation pipe is causing cavitation within the tunnel at certain flows.
KWUA suspects that the cavitation occurring within the outlet tunnel at Iron Gate Dam likely explains in part the loss of 830,000 Chinook salmon fry that the California Department of Fish and Game (CDFW) released upstream of the dam in February. According to CDFW, the large mortality event was due to “gas bubble disease that likely occurred as the fry migrated through the Iron Gate Dam tunnel.”
In a public letter recently submitted to FERC, the Siskiyou County Board of Supervisors noted that the broken ventilation pipe remained in the river, downstream of the dam, for at least five days before being removed, posing a threat to public safety. The County’s letter alleges that KRRC failed to follow the notification process required under its Emergency Action Plan for this incident. The county’s letter further asks FERC to provide its assurance that failure of the outlet tunnel at Iron Gate Dam poses no current or future risk to the public.
KRRC had previously dismissed providing an alternative venting system to the pipe that failed in January as a risk mitigation measure.
In an April 9th letter to KRRC, FERC asked the company to address what would be done in the event the outlet tunnel at Iron Gate Dam becomes blocked by debris after the embankment has been excavated to a level below the level of the emergency spillway. FERC’s letter stated that it could not approve removal of Iron Gate Dam until this and other concerns had been resolved.
KRRC had indicated in previous filings that it would potentially attempt to breach the dam early as a contingency in the event the outlet tunnel becomes obstructed. KRRC’s April 22 filing apparently responded to this issue, although the information is not available to the public.
On April 17, FERC also responded in writing to U.S. Representative Doug LaMalfa, indicating that the agency was engaged in a “fact-gathering” inquiry, to determine KRRC’s compliance with FERC’s previously identified environmental and related requirements.
Reprinted from KWUA’s newsletter
