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Court-Ordered Spill Completed In June; Corps Sends Judge Last Of Three Reports Detailing Operations
Posted on Friday, July 27, 2018 (PST)

Flow and spill in the lower Snake and Columbia rivers during June dropped below the involuntary spill levels seen in May at four lower Snake River and four Columbia River dams, according to a third and last spill report on court-ordered spring spill that covers the month of June.


Spring spill operations required by a U.S. District Court decision to aid juvenile salmon passage through the eight dams began April 3 at Snake River dams and April 10 at the Columbia River dams, and ended June 20 in the Snake River and June 15 in the Columbia River. The court ordered the U.S. Army Corps of Engineers to provide additional spring spill at the dams to the maximum total dissolved gas levels allowed by state water quality rules, called gas caps. The target TDG level in each dam’s tailwater was120 percent TDG and 115 percent TDG in the forebays.


Total dissolved gas limits are intended to protect young fish from gas bubble trauma in the dams’ tailraces during spill.


The spill operation was ordered by U.S. District Court of Oregon Judge Michael H. Simon in an April 2017 decision. However, its implementation was delayed a year to allow time for federal agencies to develop a spill plan.


The report for June spill operations was compiled by the Corps’ Northwest Division Office and delivered, as required to the District Court, July 20. This is the final spring spill report which covers the period through June 20 for the court-ordered spill and through the end of June as spill transitions to summer spill operations, which is in accordance with the requirements of the Federal Columbia River Power System biological opinion for salmon and steelhead.


June was characterized by below average flow in both rivers, along with average to above average air temperatures and widely varying precipitation across the Columbia River Basin, the report says. Precipitation was 85 percent of normal in the Snake River upstream of Ice Harbor Dam, the most downstream of the four lower Snake River dams, and 82 percent of average at The Dalles Dam.


NOAA’s Northwest River Forecast Center said the June runoff for the Snake River at Lower Granite Dam, the most upstream of the lower Snake River dams, was 85 percent of the 30-year average (1981 – 2010), with a volume of 5.1 million acre feet. For the Columbia River at The Dalles Dam, runoff was 88 percent of the 30-year average with a volume of 23.1 MAF.


The report describes spill operations by the Corps at four lower Snake River and four lower Columbia River dams during June. Previous reports covered the months of April. (see CBB, June 8, 2018, “NOAA Fisheries Delivers First Court-Ordered Spring Spill For Fish Report; Shows Complex Operations,”, and May (see CBB, June 29, 2018, “Corps’ Second Spill Report To Court Details Impacts Of High Flows, Involuntary Spill In May,”


Unlike May when spill was mostly involuntary and often exceeded TDG limits, June spill rarely exceeded the limits and most of those exceedances were during the earliest few days of the month.


Spring spill at Lower Granite Dam transitioned June 21 to summer spill of 18,000 cubic feet per second 24 hours per day (see Fish Passage Plan at


Also transitioning to summer spill June 21 were Little Goose Dam (30 percent of total river flow 24 hours per day), Lower Monumental Dam (17 kcfs, 24 hours per day) and Ice Harbor Dam (alternating two-day treatments of 30 percent of total flow, 24 hours per day vs. 45 kcfs during the daytime and the spill cap during the nighttime. Nighttime spill hours are 2100–0800).


Columbia River dams transitioned to summer spill June 16. McNary Dam is spilling 50 percent of flow, 24 hours per day. John Day Dam uses an alternating two-day treatment of 30 percent vs. 40 percent of total flow, 24 hours per day. Spill level changes occur at 2100 hours. The Dalles Dam is spilling 40 percent of flow 24 hours per day. Bonneville Dam has alternating two-day treatments of 95 kcfs, 24 hours per day vs. 85 kcfs during the day and 121 kcfs during the nighttime. Nighttime hours are 2130-0430 through June 30.


In its report, the Corps said that the court-ordered spring spill operation was a more complex operation to implement than the past years’ operations. During the operation the Corps had to evaluate conditions each 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 evaluation had to take into account: environmental conditions, such as river flow, wind, water temperature, barometric pressure; incoming TDG from upstream; water travel time; as well as project operations such as spill level, spill pattern, tailwater elevation, proportion of flow through the turbines, and project configuration.


There were a couple of exceptions in June:


On the last day of spring spill operations at Lower Granite Dam, all six generating units were out of service due to a transmission line outage and the Corps had to spill 50 kcfs, run 5 kcfs through just one turbine and store water during the outage.


May 30 to June 2, spill at Little Goose Dam was reduced from involuntary spill to 30 percent of the river in order to help upstream passage of spring chinook salmon that had been stalled in the pool below the dam by the higher spill levels. To do this, according to the Corps, inflow above 128 kcfs (powerhouse capacity plus 30 percent spill) was stored in the Little Goose forebay as necessary above the minimum operating pool range of 633–634 feet. Each day, spill was increased so that total outflow was equal to inflow from 1200–1600 hours. Then spill was increased again, as necessary, to draft back to MOP between the hours of 1600 and 0400.


Over the four days of this operation, hourly average spill ranged from 38–80 kcfs (average 55 kcfs), the Corps said, which was above the spill cap of 26 kcfs , and the forebay elevation ranged from 633.1–634.8 feet (average 633.9 feet).


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.


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. See


Also see:


-- CBB, June 15, 2018, “Fish/River Managers Have Differing Interpretations On What ‘Spill To The Gas Cap’ Looks Like,”


--CBB, May 18, 2018, “Court-Ordered Spring Spill Now Moot As High Columbia/Snake Flows Forcing Involuntary Spill At Dams,”


--CBB, April 13, 2018, “Court Ordered Spring Spill For Fish Begins On Four Lower Columbia River Dams,”


-- CBB, April 6, 2018, “New Court-Ordered Spill Regime Based On Dissolved Gas Caps Begins This Week,”

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