of a blowout has been reduced, but Grant County Public Utility District
officials are still puzzling over what to do about a worrisome 2-inch, 65-foot
long horizontal crack discovered late last month along one of the 12 spillways
at central Washington’s Wanapum Dam on the Columbia River.
damage was first discovered on Feb. 24 by a dam worker who noticed a section of
the spillway deck had shifted slightly. Utility engineers then examined the
area and found that one of the spillway pier monoliths had moved 2 inches out
inspecting the spillway on Feb. 27 saw a horizontal fracture about 2 inches
wide at the base of the monolith.
take pressure off the damaged spillway pier, the utility began to draw down the
reservoir behind the dam by about 26 feet. The reservoir above the dam is now
at its lowest level since the hydro project began operating 1964.
drawdown is intended to take pressure off the damaged structure, and allow
better assessments of the damage and judge what might be done to correct the
problem. Overall the structure, with its 10 turbines and generators, is 8,637
feet long and 180 feet tall. Its construction began July 1959 and was completed
in October 1963.
something that we’re taking very seriously,” said Grant PUD spokesman Chuck
Allen. “It’s going to be this low until we come up with a long-term plan.”
Tuesday, Grant PUD lowered its Emergency Action Plan classification for the
Wanapum Dam spillway incident to a “non-failure emergency.” The utility had
been operating under the condition of a “developing failure” since Feb. 28.
announced Wednesday that its Emergency Action Plan (EAP) includes the
notification procedures in the event of a “non-failure emergency” at Wanapum
Dam, including situations that would necessitate the utility maintaining low
water levels behind the dam to prevent a more serious emergency. The EAP
describes the initial roles and responsibilities of Grant PUD personnel and
other agencies based on the capabilities of each agency to respond in the event
of an emergency situation at Wanapum Dam.
news of a downgrade comes as a result of engineering surveys conducted March 3
and 4 that show continued stabilization of the fractured area found on the spillway.
As of 6 p.m. Tuesday, survey results show that the impacted area is stable,
according to a Grant press release. The fracture has closed and the damaged
section of the spillway monolith has moved back upstream by nearly 1.75-inches
as a result of the utility’s actions to lower water above Wanapum Dam and
reduce pressure on the damaged spillway.
PUD continues to work in conjunction with the Federal Energy Regulatory
Commission as well as upstream dam operators and stakeholders to monitor and
evaluate this incident. Public safety and the safe operation of the dam is the
utility’s top priority.
PUD in collaboration with other entities is also actively studying options to
assure safe passage of adult and juvenile salmon and steelhead past Wanapum Dam
if the current drawdown of the Wanapum reservoir continues into the migration
upstream passage begins in April and continues into mid-November. Juvenile
salmon and steelhead begin to swim downstream around the third week of April.
In the event that water remains low into the migration season, options to
provide upstream passage include modifications to existing Wanapum Dam fish
ladders as well as the potential to trap and haul fish via trucks around the
reservoir, according to a Grant PUD press release.
current water levels, the Wanapum Fish Bypass would be operational, allowing
juvenile salmon and steelhead to safely pass over the dam. The utility will
continue to coordinate with partner agencies, tribes and Chelan PUD to
determine the best options moving forward.
Dam, 415 river miles from the mouth of the river at the Pacific Ocean, is the
sixth dam that, as an example, migrating salmon and steelhead must negotiate on
their way up the Columbia to spawn. Those fish include wild spring chinook
salmon and steelhead stocks that are listed under the Endangered Species Act.
Listed bull trout also travel up and down the system.
is located downstream of Vantage, Wash., and 18 miles upstream of Priest Rapids
Dam, which is also owned by Grant PUD.
Rapids Dam is located on the Columbia River, 24 miles south of Vantage and 200
miles downstream from Grand Coulee Dam.
next hydro project, nearly 40 miles upstream, is Chelan County PUD’s Rock
Island Dam at Wenatchee.
County PUD announced Tuesday that it has stopped generating power at Rock
Island Dam in response to drawdown by Grant County PUD at Wanapum Dam. With the
lowered river level below Rock Island Dam, Chelan PUD is taking steps to
protect its generating equipment and to safely operate its generators within design
criteria during the Wanapum drawdown.
the time being, the river flow will be managed by spilling water through the
spillways at Rock Island. Rock Island Dam has a generating capacity of 629
the Wanapum pool is drawn down for any length of time, it could cause problems
for spawning salmon and steelhead that need access to Rock Island fish ladders.
Those spring chinook and steelhead are headed for such rivers as the Wenatchee,
Entiat, Methow and Okanogan. Such fish runs typically start showing up in
number in mid- to late April. Runs of summer chinook and sockeye salmon come
two PUDs, and others, are “having multiple daily conversations” to plot
strategy to assure that fish can proceed up and downstream unimpeded, according
to Keith Truscott, Chelan PUD’s Natural Resources director.
don’t want to have that happen,” he said of the possibility that fish can’t
access fish ladder entrances or safely exit such systems.
going to look at the entire system,” Truscott said of juvenile and adult
passage routes at Chelan’s Rock Island and Rocky Reach dams. The Wanapum
reservoir situation should not impact juvenile fish migrations.
the impacted portion of Wanapum now stable, Grant PUD staff, consultants and
regulators are developing a plan to determine the root cause of the spillway
monolith fracture, which was discovered on Feb. 27, and how best to repair the
utility has reopened public-access sites below Wanapum Dam, including the
Priest Rapids Recreation Area at Desert Aire and the Buckshot Recreation and
Wildlife Area. Those sites had been closed shortly after the crack discovery
and Wanapum drawdown.
Wanapum Lower Boat Launch, the Wanapum Heritage Center and day-use park remain
closed. However, the Wanapum Dam Overlook is open.
under the authority of its federal license, the utility has temporarily closed
the Wanapum reservoir shoreline. Article 18 of the utility’s operating license
with the Federal Energy Regulatory Commission states that Grant PUD “… may
reserve from public access such portions of the project waters, adjacent lands,
and project facilities as may be necessary for the protection of life, health
authorized personnel are allowed access to the Wanapum reservoir shoreline.
Sections of the shoreline, including the riverbank and mud flats are extremely
unstable and have proven to be a serious safety hazard.
utility continues to post signs informing the public of the shoreline closure
and is actively working to patrol the area. State and local law enforcement
agencies will be notified whenever anyone is observed trespassing in areas
closed to the public. All boat launches on the Wanapum reservoir are closed to
PUD remains able to meet customer electricity needs with its current power
supply portfolio. Wanapum Dam continues to generate electricity, yet at a
reduced rate. Under normal river conditions, and considering that three of the
dam’s 10 turbines are offline because of maintenance and turbine replacement,
the dam has the capacity to generate roughly 700 megawatts. Given the drawdown
in the water levels behind Wanapum Dam, capacity has been reduced to
approximately 360 megawatts.
spillway is the portion of the dam that allows water to “spill” past the dam as
opposed to running through the turbines. The spillway consists of multiple,
independent structural sections that support the spillway gates.
drawing down the level of water behind Wanpum Dam, if two of the dam’s 12
spillway sections failed now, the amount of water that would flow through the
spillway sections is 100,000 cubic feet of water per second.
amount of water is significantly less than under normal operations and would be
within the range of average river flow, approximately 120,000 cubic feet per
second,” according to a Grant PUD press release.
up-to-date information on this issue, please visit www.grantpud.org