A fruit company built two 40-foot high dams for irrigation and frost control in the Yakima Valley. Another built four dams on a branch of nearby Washout Creek. Still a third built a dam off a rivulet of the local irrigation district.

Nobody bothered to get construction permits, and state officials never saw the projects.

But a recent inspection showed that if all seven of those illegal dams failed simultaneously during an extreme weather event, millions of gallons of water could pour into one of the region’s agricultural hubs.

“If they all went at once, they’d wipe out Sunnyside,” said Doug Johnson, supervisor of dam safety for the state Department of Ecology in Olympia.
State officials began investigating illegal dams after discovering several while reviewing aerial photos of their own projects last spring.

In recent years, five dams built without permits and inspections have failed in Washington, causing flooding and property damage.

A comprehensive review of the Yakima Valley showed a number of orchard owners had built ponds for irrigation and frost control without obtaining the necessary permits. The review then expanded to other Eastern Washington agricultural areas, then to the rest of the state.

“We ended up with nearly 600 potential dams from looking at the aerial photos,” Johnson said. “We didn’t know for sure they were dams, but we suspected they were.”

Of those 600 sites, 96 were identified as “high hazard,” with three or more homes downstream. State officials have inspected 95 of the 96 — winter snows hit before the last one could be completed last week — and confirmed 68 dams. Thirty posed a major risk to residents downstream.

West of the Cascades, one dam already had holes in it when state inspectors converged on the site 16 miles west of Shelton in Mason County. Seven to 10 homes sit downstream from the dam, which is owned by Manke Lumber Co.

“It’s basically been taken care of, but if they ever want to rebuild it, they’ll have to go through quite a process. That was lucky that we caught it when we did,” Johnson said.

A man who answered the phone at Manke Lumber’s office in Shelton said no one else had made it to work that day because of the heavy snowfall and that he couldn’t comment on the dam.

Fifteen miles east of Spokane, state officials found a 30-foot high dam built on Deep Creek by the religious Hutterite community. The dam already had seepage problems when they inspected it, Johnson said.

A person authorized to speak for the religious community could not be immediately reached by telephone Tuesday.

By far, though, the biggest problems have been in central Washington, where one-third of the 30 high-hazard illegal dams lie in the Yakima Valley.

The community of Sunnyside is surrounded by dairies, orchards, hop fields and vineyards. But dams built to support some of those orchards could have endangered the community if they failed, Johnson said.

Avalon Fruit owns orchards in a 7-square-mile watershed upstream from the city. But the four illegal dams the company built have inadequate spillways with just 12-inch pipes to pass flows, Johnson said.

Two unpermitted 40-foot dams built by Evans Fruit Co. in the 1980s each hold 120 acre-feet of water, while a third dam built on Cowiche Creek near Tieton, west of Yakima, has 20 homes immediately downstream.

An acre-foot is the amount required to cover one acre to a depth of one foot deep.

Officials with the two fruit companies did not return telephone messages seeking comment.

If all seven dams near Sunnyside had failed at the same time during an extreme weather event, such as a sudden snowmelt or massive thunderstorm, more than 110 million gallons of water could have rushed toward the city — enough water to fill 166 Olympic-sized swimming pools.

Such an extreme event could cause “a mell of a hess,” Roza Irrigation District Assistant Manager Tim Collett said. But he also said the major weather event needed to trigger flooding of that magnitude would wreak havoc on everyone.

“We have more water stored in our canal system than those ponds do,” he said. “If something that big happens, we all better get out of the way.”

Ecology officials are working with landowners to improve the dams’ structures or offer permits for some that already meet requirements. They also are working with the state Horticultural Association and the state Water Resources Association, which supports local irrigation districts, to better educate members about regulations governing private dams.