YAKIMA - If built, the Black Rock Creek dam will be bigger than Grand Coulee dam.
It's a mammoth undertaking, but it is one of the options still being considered by the Bureau of Reclamation.
Grand Coulee is about 5,300 feet across and about 600 feet high, according to Dick LaFond, structural engineer from the Bureau of Reclamation's Denver office. The Space Needle in Seattle is only 600 feet tall.
The dam at Black Rock would be 6,700 feet long. The option that would create a larger lake would be 750 feet tall and the smaller lake dam would be 680 feet tall.
LaFond was one of several Bureau of Reclamation employees addressing findings as part of the Black Rock alternative project. The Black Rock Creek Reservoir project is one of several being considered to boost water storage in Washington state.
LaFond addressed the designs being considered for the site.
He said that if the project moves forward, a tunnel from the Columbia River at Priest Rapids dam will pipe water to Black Rock Creek. From the west end of the lake, a pipeline would pipe water to Roza Canal milepost 22.6.
"From there some water goes up and some down the canal," said LaFond.
The water going up the canal will catch those Roza Irrigation patrons farming west of where the pipeline ends.
LaFond said there are three different options being considered. The first option is a large reservoir, which would hold 1.3 million acre feet of water.
Option two is similar to option one, but adds a dam to create electricity. It is estimated the pump will have the capacity to treat 3,500 cubic feet of water per second.
The third option is a smaller reservoir, which would hold 800,000 acre feet of water.
LaFond said part of the project would include moving Highway 24 to the south rim of the reservoir.
Gerald Kelso, area manager for the Upper Columbia Basin office of the Bureau of Reclamation, who is in charge of the Columbia and Yakima river projects, said the Black Rock Creek plan is one of four that are being looked at as a storage solution for the Yakima Basin. He added that it is also the newest. The other projects have been investigated in the past, but have not moved forward.
Kelso said that Congress asked the Bureau to look at alternatives for additional storage in the Basin and asked them to consider fish, irrigation benefits and municipal supply benefits when coming up with a solution.
Since 2003, the Bureau of Reclamation's storage study of the Black Rock Creek Reservoir has been ongoing.
"With the money we have received from the state and federal governments, we've spent about $5 million so far, taking a look at the Black Rock project," said Kelso.
The total cost of the project is expected to be $3.5 to $4.5 billion, which is inclusive of all of the costs for the project.
"The proposed Black Rock project would have very significant material costs," said Kelso.
Kim McCartney, Yakima River Basin Storage Manager, said that as part of the study of the Black Rock project, water exchange was one of the issues looked at by the Bureau of Reclamation.
He said that a number of irrigation district leaders, including those from the Roza and Sunnyside divisions, have voiced interest in exchanging water, which would mean that the irrigation districts would run solely on water from the Columbia River.
"Every entity that participates will get 100 percent of their water from the Columbia River," he said.
McCartney said there are several criteria the irrigation districts have to meet, including having a proximity close enough to accept the water and the right class of water rights.
Also a concern is the potential of wasting Columbia River water, which McCartney said is something the Bureau of Reclamation doesn't want to happen.
The benefit of the water exchange will be that more water is left in the Yakima River for fishery use. Other entities not participating, or that don't qualify for the water exchange, will receive 100 percent of their water from the headwaters of the Yakima River.
Dick Link, geologist for the Bureau of Reclamation, has been investigating the actual possibility of whether or not a dam could be built at the site.
"Normally, we like to set our dams on bedrock," he said.
Link said in 2001 the Washington Infrastructure Services (WIS) was commissioned by Benton County to complete a preliminary analysis of the Black Rock reservoir.
He said that at the original site investigated by WIS there was concern because bedrock was found at 200 feet rather than the 20 foot level WIS assumed it would be at.
A site just to the west of the original study was believed to have been an old creek bed and bedrock was believed to be just under the surface.
"It turns out rock was considerably deeper than we thought. Bedrock was at 562 feet," said Link.
After further investigating the site, Link said his recommendation has been to abandon the second sight and move back to the original site.
Link said the Bureau of Reclamation also purchased a seismic survey done by the Shell Oil Company in the early 1980s, saving the project several million dollars.
With what is believed to be a fault line on the south side of the proposed reservoir, Link said there is evidence that the reservoir would be built on an active fault line. He added that there are seismic studies of the Hanford area that show earthquake activities in that area.
"Right now, we're assuming that it's active," said Link, adding that it is believed that it is linked to the Ahtanum and Union Gap faults.
He added that there is also evidence of three ancient slide areas in the area and he is unsure how a large quantity of water would affect the slides.
"More testing is ahead," said Link.
That was the same conclusion reached by hydrologist Kati Didricksen, who investigated if the ground will allow for a large quantity of water to be on it.
She said that they will continue to monitor ground water to watch for seepage between layers of the ground.
Didricksen said there are some layers that have severe leakage.
Summaries of the report completed by the Bureau of Reclamation are available at www.usbr.gov/pn/programs/storage_study.