protections, irrigator access and hydro power generation are chief among the
concerns at the mid-Columbia River’s Wanapum Dam, where on Feb. 27 a 65-foot
long horizontal crack was discovered at one of the facility’s 12 spillways.
County Public Utility District, the dam’s owner, opted for a steep drawdown of
the reservoir behind the hydro project to reduce pressure on the damaged spill
structure. The utility reported last week that steep drawdown to, at minimum,
541 feet elevation has served to stabilize the cracked spillway pier monolith.
The Wanapum Dam forebay elevation had been maintaining at an average elevation
of 568 feet through February.
drawdown is the steepest ever since the dam when into operation in 1964. The
resulting reduced “head” has cut the dam’s hydro production capabilities in
half. Water pressure drives the turbines.
isn’t as much force, potential energy, above the dam,” said Grant spokesman
the current reservoir level, the gravity fed fish ladders are left high and
dry, and even if they weren’t salmon would now have a long drop once exiting
the top of the ladders.
biologists, engineers, and stakeholders are developing plans to modify the two
fish ladders at Wanapum Dam to allow migrating salmon and steelhead to safely
pass the dam when the adult spring chinook salmon run begins in mid-April. Over
the course of the spring, summer and fall, chinook, coho and sockeye salmon,
steelhead, bull trout, lamprey, shad and other fish species pass over the dam.
Wild spring chinook and steelhead stocks, as well as bull trout, are protected
under the Endangered Species Act.
ladder fixes could include the installation of a water pumping system to feed
the ladders and potentially some sort of slide to ease the fishes’ exit into
the Wanapum pool.
utility is also evaluating plans for capturing and transporting adult fish
around the reservoir.
at current reservoir levels, downstream juvenile fish passage will occur as it
has in the past.
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.
Rock Island, owned by Chelan PUD, is the next project upstream from Wanapum.
is collaborating with other PUD and federal dam operators to assure adequate
flows down through the system. The Hanford Reach below Grant’s Priest Rapids
Dam will not likely be greatly affected, though Wanapum reservoir’s limited
storage capabilities has been called on to make sure flows downstream were
adequate to keep fall chinook salmon eggs covered with water, and also protect
fry that emerge from those eggs.
Washington Department of Fish and Wildlife’s Bill Tweit called Wanapum pool “a
24-hour storage tool” that has been called on in the past to supplement
downstream flows. The most utilized tool is Grand Coulee Dam 200 miles upstream.
Its reservoir, Lake Roosevelt, has the most storage capacity in the
mid-Columbia. Grand Coulee is operating throughout the winter and early spring
to provide water to cover Hanford Reach, as well as chum eggs farther
of spring chinook returns that are imminent, “upstream passage is our first
priority,” Tweit told the Northwest Power and Conservation Council on
Wednesday. He filled the Council in on fish return projections for 2014.
and hauling fish, particularly late in the summer season, is likely not a top
option, Tweit said. Sockeye salmon spawners, which migrate in summer toward the
Okanogan and Wenatchee river basins, in particular are known often to be
negatively affected by overhandling.
evaluation of Wanapum Dam’s spillway pier monolith No. 4 is under way, with
Grant PUD and contractors conducting studies to determine the fracture’s
geometry, according to a Grant PUD press release.
evaluation is expected to continue through next week. Once complete, the utility,
along with an independent board of consultants and officials from the Federal
Energy Regulatory Commission, will use the data to determine the best way to
begin repairing the dam and raising the level of the reservoir.
PUD is working in conjunction with the Washington State Department of Ecology
to ensure that irrigators with land-use authorizations for surface-water
withdrawals from the Wanapum reservoir have information and technical
assistance they need to prepare for the upcoming irrigation season.
11 orchard irrigators affected by the reservoir drawdown have been contacted
individually by Grant PUD. Affected irrigators can access information from the
Department of Ecology on a web page devoted to the situation at
PUD continues working with the sheriff’s offices of Grant, Chelan, Douglas and
Kittitas counties to enforce the closure of the Wanapum reservoir shoreline to
the public. The Washington Department of Fish and Wildlife has also closed its
public-access sites on the shoreline and has increased patrol efforts. Sections
of the shoreline, including the riverbank and mud flats are extremely unstable
and have proven to be a serious safety hazard. The Wanapum Lower Boat Launch,
Wanapum Heritage Center and day-use park remain closed.
safe public recreation on the reservoir is one of Grant PUD’s goals as it moves
forward in its response to the situation at Wanapum Dam. The utility has
reopened public-access sites on the Priest Rapids reservoir, including the
Priest Rapids Recreation Area at Desert Aire and the Buckshot Recreation and
Wildlife Area. The Wanapum Dam Overlook is also open.
used during the analysis of the fracture include precise drilling into the
monolith, ground-penetrating radar and echo-imaging technology. Utilizing each
form of technology allows the utility to determine the location and geometry of
the fracture, according to Grant PUD.
from the utility, a board of independent consultants and officials from the
Federal Energy Regulatory Commission will use the data from the investigation
to determine how best to move forward to repair the structure and possibly
raise the elevation of the Wanapum reservoir to an intermediate level during
the restoration phase.
said that a boost of the reservoir level up to 560 feet would make the fish
additional damage to the dam was found during a thorough inspection, other than
some minor surface damage on spillways neighboring monolith No. 4.
repair spillway pier No. 4, Grant PUD is exploring the possibility of using
steel strand anchors that are drilled from the top of the dam through the
concrete structure into bedrock. The steel strand anchors would be set into
place with a specialized, high-strength grout, the utility says.
from the ongoing evaluation of the structure will help determine if this
process would be an effective way to repair the spillway pier. The independent
board of consultants and FERC will also evaluate the data and must approve any
action before it is implemented by Grant PUD.
utility is also working with Chelan PUD and other dam operators on the Columbia
River, along with federal, state and local agencies, as well as tribes and
other stakeholders impacted by the drawdown.
CBB, March 7, 2014, “Crack In Wanapum Dam: Reservoir Drawn Down 26 Feet,
Officials Assess Options, Fish Passage Strategies” http://www.cbbulletin.com/429942.aspx