Posted on Friday, June 29, 2018
Flows in the lower Snake and Columbia rivers during May were well above average and so was spill and levels of total dissolved gas in the tailwaters of dams, as well as in dams’ forebays, according to a second report on court-ordered spill.
The report was compiled by the U.S. Army Corps of Engineers’ Northwest Division Office and delivered, as required to the U.S. District Court in Oregon June 15. The Corps will provide one more spring spill report to cover the period through June 20, when court-ordered spring spill to TDG limits ended.
Spring spill to aid juvenile salmon and steelhead passage that began in the Snake River April 3 and on the Columbia River April 10 was ordered by Judge Michael H. Simon in an April 2017 decision.
The report describes spill operations by the Corps at four lower Snake River and four lower Columbia River dams during May.
A previous report covered the month of April. (see CBB, June 8, 2018, “NOAA Fisheries Delivers First Court-Ordered Spring Spill For Fish Report; Shows Complex Operations”).
Additional spring spill up to the maximum total dissolved gas levels allowed by state water quality rules, called gas caps, was ordered by the court one year ago. However, its implementation was delayed a year by the court to allow time for federal agencies to develop a spill plan.
The Bonneville Power Administration last week reported the power cost for the additional spring spill to be $10.2 million for fiscal year 2018. Those costs are largely the value of lost revenue if it was able to use the additional spill to generate electricity. BPA released its final costs June 21, 2018.
Total dissolved gas limits are intended to protect young fish from gas bubble trauma in the dams’ tailraces during spill.
“The month of May was characterized by well above average flows for the lower Snake and lower Columbia rivers along with above average air temperatures and widely varying precipitation across the Columbia Basin,” the June 15 report says.
It goes on to say that May precipitation was 96 percent of average on the Snake River above Ice Harbor and 78 percent of average on the Columbia River above The Dalles Dam.
However, runoff in the two rivers was far above normal, with the Northwest River Forecast Center runoff summary for May showing higher than average runoff. The Snake River at Lower Granite Dam was 149 percent of the 30-year average (1981-2010) with a volume of 10.3 million acre feet, while May runoff for the Columbia River at The Dalles Dam was 176 percent of the 30-year average, with a volume of 44.6 MAF.
Simon’s court order calls for the Corps to strive for spill at gas cap levels of 120 percent TDG at all eight dam tailwaters and at 115 percent in the forebays of each of the dams, which are limits set by the states of Oregon and Washington. However, during May gas caps were exceeded much of the time, particularly in dams’ forebays, when high flows caused spill higher than spill targets developed by the Corps.
The Corps said the spill cap operation this year is a more complex operation than in previous years.
“In its implementation of the 2018 Spring FOP (fish operations plan) in May, the Corps evaluated conditions every day to establish spill caps at a level that was estimated to meet, but not exceed, the gas cap in the tailrace and the next downstream forebay,” the Corps’ second report says. “This evaluation considered: environmental conditions (e.g., river flow, wind, water temperature, barometric pressure, incoming TDG from upstream, and water travel time) and project operations (e.g., spill level, spill pattern, tailwater elevation, proportion of flow through the turbines, and project configuration). For the month of May 2018, conditions constraining the spill cap at Bonneville and The Dalles dams did not occur.”
A disagreement on how “spill to the gas cap” should be interpreted occurred at the June 13 meeting of the interagency Technical Management Team. At that meeting, Julie Ammann of the Corps said that “We need to meet, not exceed, state water quality standards.” However, fisheries managers thought the Corps should be more aggressive by shooting for an average cap of 120 percent in the tailwater and 115 percent in the downstream forebay.
At Lower Granite Dam spill exceeded the Corps’ target spill (about 36,000 to 38,000 cubic feet per second) on all but about seven days in May, with flows at one point exceeding 180 kcfs and actual spill hitting 80 kcfs. Tailwater TDG percentage at Granite rose to the mid- to low-120s at the end of the month.
Downstream, the Little Goose forebay saw TDG over 115 percent about half the month. Little Goose Dam tailwater TDG was over 120 percent 18 days.
Lower Monumental Dam forebay exceeded the 115 percent gas cap all but one day in May, reaching as high as 126 percent. The dam’s tailwater exceeded the gas cap 20 days in May.
The Ice Harbor Dam forebay exceeded the gas cap of 115 percent every day in the month. Flows at Ice Harbor approached 200 kcfs May 27, with spill at 140 kcfs (target spill was 80 kcfs). Ice Harbor tailwater exceeded the gas cap 22 of 31 days.
Spill on the Columbia River followed a similar pattern. McNary Dam flow hovered around the 500 kcfs mark for much of the middle and late parts of May. Spill hit 380 kcfs May 17, while the spill target was 150 kcfs. The McNary forebay exceeded the gas cap on all but three days in May. Tailwater TDG at McNary exceeded the gas cap all but five days in May.
John Day, The Dalles and Bonneville dams followed a similar pattern of flow and spill, but with fewer spikes in actual spill (the spill targets at John Day and The Dalles was about 95 kcfs, and about 125 kcfs at Bonneville).
The John Day forebay TDG exceeded the gas cap on all but four days in May (the first four days). The John Day tailwater exceeded the gas cap on all but the first four days of the month, reaching 134 percent TDG on two of the days.
The Dalles forebay exceeded the gas cap on all but the first four days of May and the tailwater exceeded the gas cap on all but four days, but the days were dispersed throughout the month.
The Bonneville Dam exceeded gas cap limits in the forebay and tailwater every day of the month (the sensor in the tailwater was out of commission the last half of the month).
There were some breaks in the spill protocol at Lower Granite, Little Goose and The Dalles dams. On May 2 at Lower Granite all generating units were out during the day while transmission repairs were underway. The Corps spilled as much water as possible during the outage, while controlling TDG as best as it could, and it stored water behind the dam in order to control the amount of water spilled.
Passage delays of adult chinook salmon caused TMT to ask for controlled spill of 30 kcfs during the day at Little Goose Dam May 30 to June 2. To do that, the Corps stored water and released it overnight.
On the afternoon of May 31 the Corps shut down all spill at The Dalles Dam for 25 minutes for an emergency rescue of a boat caught in the spillway.
The request for injunctive relief for more spill was enjoined with an earlier case argued in District Court. The initial case, heard by Simon, resulted in a May 2016 remand of the federal Columbia River power system biological opinion for salmon and steelhead listed under the Endangered Species Act.
The spill plea was initiated in January 2017 by plaintiffs in the original case, the National Wildlife Federation and the State of Oregon, among others, asking the court to begin ordering spill to maximum total dissolved gas levels as set by the states beginning April 3, 2017 and to continue for each year of the BiOp remand.
Simon agreed that more spring spill would benefit ESA-listed fish but delayed the action until 2018 while federal agencies completed a spill plan for the dams. The plan is for additional spill only during the spring of 2018 to TDG caps, as well as for earlier PIT-tag monitoring of juvenile salmon.
NOAA Fisheries, Northwest RiverPartners, the Kootenai Tribe of Idaho, the states of Idaho and Montana, and the Inland Ports and Navigation Group appealed Simon’s spill injunction in early June 2017 to the Ninth Circuit Court of Appeals. However a three-judge panel of the appeals court ruled April 2 in favor of Simon’s spill ruling.
Bonneville released the Administrator’s Decision, Implementation of the FY 2018 Spill Surcharge (FY 2018 Spill Surcharge Decision), memorializing the final decision to implement the Fiscal Year (FY) 2018 Spill Surcharge in an amount of $10.2 million for FY 2018, according to BPA. The regional utility will apply a rate of 0.71 mills per kilowatt-hour for June–September 2018; and an Annual rate of 0.23 mills per kilowatt-hour. The FY 2018 Spill Surcharge Decision also addresses comments received during the public comment period.