Kennewick water supply project causes erosion behind Zintel Canyon Dam

A project to improve Kennewick's water supply had the unintended consequence of damaging the area behind Zintel Canyon Dam.

A gully 50 feet wide and 24 feet deep in places opened up in the canyon and adjacent irrigation ditch while the city was testing for a $4 million project to store water in an existing aquifer in the Southridge area, said Evelyn Lusignan, the city's customer service manager.

The unanticipated erosion ripped a divide in trails that link to a larger group of trails in the sagebrush behind the Washington State Patrol office, just off the interchange of Highway 395 and Interstate 82.

It left silt deposited behind the dam, which was built for flood protection in the 1990s.

"Frankly, trashing the land this way leaves me absolutely dumbfounded," said Al Potter, a Kennewick cyclist and hiker who has led efforts in the past to clean up the area.

Kennewick was running water through the Kennewick Irrigation District ditch into the ravine as part of testing for its project to use the aquifer to store water taken from the Columbia River in the winter, when it is plentiful, for use in the summer, Lusignan said. The city discharged between 35 million to 40 million gallons of water as part of the project.

"Obviously, the erosion is not a good thing," she said. "But, ultimately, the project is pretty amazing. Mother Nature has provided us a free storage system right out in the area we are growing."

The project still needs final approval from the state Department of Ecology.

Potter sent a letter in January to the city and to Benton County, asking them to consider buying the 322 acres to preserve the rare "sagebrush oasis" in the Tri-Cities. He sees the canyon trails, which cross privately owned and government property, as a link between a parking lot near the intersection of Ridgeline Drive and Bofer Canyon Road and the protected area.

Potter didn't hear back from either entity, and came across the erosion April 28 while water was still flowing through the ravine created in Zintel Canyon. The damage presents a serious safety hazard, with no warning signs posted for the still-unstable ground along the gully, he said.

Firefighters had to rescue a dog from the area May 17 after it fell into the washed-out area while on a hike with its owner.

"If you did this at Chamna, somebody would have been fired or put in jail," Potter said, referring to the natural preserve along the Yakima River in Richland. The city has hired Apollo Inc. of Kennewick to fix the steeper portions of the damage to the canyon and irrigation ditch. It will award another contract to remove sediment and repair the canyon walls. The city does not yet have an estimate of the costs of the repairs, Lusignan said.

To compound the situation, swallows have nested in the newly formed walls of the ravine. The migratory birds are protected by federal law during the breeding season, Potter said.

The city will work around the nests, Lusignan said.

"There are two nests in the area we will be working on, but we will not be disturbing them," she said.

The city was not wise to direct so much water through a canyon made of delicate windblown silt, Potter said. But he was pleased to see backhoes and other equipment working on the ravine.

The city was not wise to direct so much water through a canyon made of delicate windblown silt, Potter said. But he was pleased to see backhoes and other equipment working on the ravine.

"They are alleviating a hell of a safety hazard right now," he said.

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• Ecosystem Management
• Environment Evaluation