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Engineers flagged flooding risk if dam is removed

Extreme tides would push water higher
By Derrick DePledge

The Daily Astorian

Published on February 15, 2017 9:13AM

Last changed on February 15, 2017 9:32AM

The Eighth Street Dam is the subject of a fight between Warrenton and the Skipanon Water Control District.

Joshua Bessex/The Daily Astorian

The Eighth Street Dam is the subject of a fight between Warrenton and the Skipanon Water Control District.

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Denise Lofman

Denise Lofman


WARRENTON — The engineering firm working with the Skipanon Water Control District on the removal of the Eighth Street Dam found that extreme tides would increase water elevation during low-flow conditions on the Skipanon River.

Extreme tides would likely keep the elevated water within the river’s banks or on property that already gets inundated when water levels are high.

The findings, issued in November 2015, did not change the water district’s conclusion that the dam is an obsolete hazard that should be removed. But the information was never formally shared with Warrenton, which backed away from a project to remove the dam last year amid questions about flooding risk.

Warrenton has declared an emergency over the dam and wants to restore the 54-year-old structure for flood control. The city is waiting for guidance from the U.S. Army Corps of Engineers about whether the dam is a component of the city’s levee system and should be under city, not water district, control.


Inflame tensions


The engineering firm’s findings will likely inflame tensions over the dam. Some on the City Commission, as well as the Nygaard logging family, have accused the water district and the Columbia River Estuary Study Taskforce — the water district’s former partner — of downplaying the flooding risk if the dam is removed.

Denise Lofman, CREST’s director, said the conditions where there is a possibility for extreme tides and higher water elevations only happen once every 60 years or more, longer than the 50-year design life of the dam. She said the dam was built to protect upstream property from a modest two-year flood during normal tide conditions.

Lofman said that during most of the scenarios that were modeled, removing the dam improved flood conditions by allowing water to leave more quickly out of the river. The water district has repeatedly said that removing the dam will not significantly increase flooding risk.

Lofman said that one of the main concerns during the project was to not make flood conditions worse by inundating new areas. The project, she said, would not have changed the flood pattern for property along the river that already gets inundated.

Potential flooding risk has been a sensitive topic throughout the debate between the city and the water district, so the disclosure of the engineering firm’s findings about extreme tides is certain to aggravate.

Mayor Mark Kujala believes any information about the potential flooding risk from removing the dam should have been publicly disclosed. “That’s my feeling,” the mayor said. “This should have been upfront when these questions were asked several years ago. When information came to light that this might impact, and we might not be able to achieve the things that we promised, that should have been said instead of saying there is no problem and we’re moving forward.”


Dam records


The Daily Astorian asked the water district and CREST last year for any documents on the dam that might address the city’s concerns about flooding. The newspaper renewed the request this month. CREST shared the engineering firm’s findings with the newspaper on Tuesday.

Lofman said the findings were not discussed with the city because the project was not moving forward. A $1.2 million agreement between the city, the water district and CREST to remove the dam and provide a single-lane bridge over the river for the city expired at the end of 2015. The City Commission voted 2-2 in May against renewing the agreement, and CREST later withdrew from the partnership with the water district.

The Nygaard family — and some at the city — have sought to draw CREST back into the controversy, claiming the task force misled the city and the community.

Lofman said the engineering firm’s findings would have been disclosed had the project moved forward. The Planning Commission would have assessed the engineering plan by the water district during hearings on the city permit needed to remove the dam. The Planning Commission would also have examined a city consultant’s technical review of the engineering plan. If the permit decision was appealed — a likely prospect given the debate at the time — the City Commission would also have reviewed the engineering reports.


City technical review


Some on the City Commission blamed former City Manager Kurt Fritsch for not disclosing the city consultant’s review of the engineering plan. But Fritsch said it would have been premature for commissioners to view the material before it reached the Planning Commission, since the City Commission might have had to hear the dam removal project on appeal. Fritsch, who warned the City Commission about tainting the permitting process, resigned last June under criticism over his handling of the dam.

Records viewed by The Daily Astorian suggest that the city’s decision to hire a consultant to weigh the engineering firm’s work was one of the factors that unraveled the project.

The consultant’s initial assessment, in spring 2015, contributed to CREST and the water district pulling their city permit application. The consultant, after exchanging information with the engineering firm over the next several months, concluded that the engineering plan did not accurately model the flood plain. The consultant also cautioned about the potential impact of even small increases in water elevation on the city’s levees. CREST was billed by the city for the consultant’s work.

The water district approved the engineering plan for removing the dam last year, noting the city consultant’s concerns, but ultimately finding that the plan was sound.

Had the dam removal project gone forward, it is likely that the city, or private property owners, would have asked for some type of flood mitigation unless the water district was able to satisfy all doubts about increased flooding risk.



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