YAKIMA -- The Yakama Nation and the biggest potential water customer for the proposed Black Rock reservoir say the project is too expensive and will not solve the future needs of the basin, further undermining support for the ambitious $6.7 billion proposal.

In a joint letter to federal and state officials, representatives of the Nation and the Roza Irrigation District said the study process should start over and that other less-costly alternatives should be reconsidered. Among them is expansion of Bumping Lake to a smaller capacity than has been discussed for decades.

The critical assessment by the Yakama Nation and the Roza district, two influential basin constituencies when it comes to water, could ultimately end any hope for construction of Black Rock.

The Nation's concerns, in particular, threaten prospects for Black Rock in light of its standing with Congress from which money for construction must come.

An underlying fear is that if billions of dollars are spent to build Black Rock, Congress will be less apt to support other projects to restore threatened fish.

The 72,000-acre Roza Irrigation District, which stretches from Terrace Heights to near Whitstran in Benton County, would have the most to gain from Black Rock. District farmers produce millions of dollars of valuable permanent crops. But while supporters of the Black Rock reservoir have sought to promote the project as a source of future water, Roza officials have not been swayed.

"I think there are a lot of people who know anything about this see that the handwriting is on the wall. The project is too grand and too expensive," said Ric Valicoff chairman of the Roza board of directors. "Let's not lose the momentum for something that truly could work."

The Nation and Roza Irrigation District say they believe expanding Bumping Lake should be considered for water storage. Bumping Lake has been a target for new storage for decades but was dropped early on in the storage study by the U.S. Bureau of Reclamation.

Among other measures that need more review, the five-page letter said, are fish ladders at basin dams, more conservation, a market-based approach to acquiring water and restoring habitat.

The letter, in response to the draft environmental study of Black Rock, partially blames Congress for narrowly drafting the legislation that authorized the storage study five years ago, a study that so far has cost some $16 million.

"... the congressional emphasis on Black Rock seems to have required the storage study to be conducted in reverse. An analysis of the problems, needs and issues, utilizing local expertise, should precede evaluating specific projects," the letter states. It is signed by Tribal Council Chairman Ralph Sampson Jr. and Valicoff.

Valicoff said in a telephone interview that the district believes more cost-effective solutions will meet the basin's needs. He said the Yakamas and the district believe a broad group of interested parties could devise a new package of measures to solve flow, passage and habitat issues in the basin and help agriculture.

Phil Rigdon, deputy director of the Nation's Department of Natural Resources, said the Nation's primary concerns have been the lack of review of broader solutions and Black Rock's potential to worsen radioactive groundwater pollution on the Hanford nuclear reservation east of the dam site, 30 miles east of Yakima on State Route 24.

"The concern that overlays this is what's not been looked at are other options that would be less costly," said Rigdon.

Black Rock supporters, including some of the Valley's most prominent farmers and business leaders, have lobbied extensively for the Roza and the Yakama Nation to endorse Black Rock. Having support from a major irrigation district and the Nation for the reservoir would have bolstered their pitch to Congress. But if supporters were disappointed by the groups' rejection of Black Rock, they weren't showing it.

Sid Morrison, former congressman and chairman of the Yakima Basin Storage Alliance, said he is not surprised by the letter. He said he is confused, however, about what is being requested.

"We all want the most comprehensive answer. As I read the study, Black Rock is the only one that answers all the questions and has enough benefits to spread the costs with no undue burden on anyone," he said.

The alliance, a grass-roots group that claims 40,000 supporters, suggests the benefits of Black Rock would outweigh its price tag. Those benefits include $2.6 billion in salmon recovery and about $3.5 billion in recreational benefits thanks to housing developments and a resort along the 10-mile lake.

The reservoir also would help junior irrigators by providing them at least a 70 percent supply of water each year along with providing water for municipal and industrial uses.

The alliance has harshly criticized the federal study and argued that it gave short shrift to Black Rock's benefits. The Bureau of Reclamation's study estimated the benefits at barely $1 billion, or a return of 16 cents on the dollar.

Black Rock is designed to draw water from the Priest Rapids pool on the Columbia River. The water would be pumped into a lake created by a 600-foot-high dam that would be larger than Grand Coulee Dam. The 1.6 million acre-foot reservoir would supply water to Lower Valley irrigators, allowing Yakima River water to better support fish life.

A nationwide conservation group hailed the stance taken by the district and the Yakamas, saying it mirrors its position. Michael Garrity of Seattle, associate director of Columbia Basin programs for the group American Rivers, said the organization made similar comments in its response to the environmental document on Black Rock.

The public comment period on the environmental issues ended Monday. A final impact statement and decision from the bureau about the future of storage is due later this year.

"I would say from a general standpoint that Black Rock is too expensive and too risky and doesn't address enough of the issues," he said. "It takes up so many resources that it is hard to see other needs in the basin being addressed."

Garrity said American Rivers believes the alternatives the state Ecology Department looked at in the environmental study -- and some other ideas -- will go a long way to meeting the basin's needs.

The state's portion of the study looked at aquifer storage, water marketing and enhanced conservation, said Derek Sandison of Yakima, regional director for Ecology.

"What they are saying is consistent with what we have said. They want to see a broad range of alternatives studied," Sandison said Wednesday in reference to the Yakama-Roza letter. "That doesn't depart much from our position."

* David Lester can be reached at 577-7674 or dlester@yakimaherald.com