Omaha, Nebraska >> A civil engineer who formerly worked for the contractor doing the Oroville Dam spillway reconstruction has proposed a dual design spillway so the emergency spillway never has to be used again.

Henry Burke’s argument for a different design than what the state Department of Water Resources proposed, centers around the need for high-flow back ups.

Burke used to work for the contractor, the Kiewit Corporation, which is based in Omaha.

Erin Mellon, communications manager with the Natural Resources Agency, said his concept is being considered in the long term, though not by Nov. 1 this year.

“Absolutely the design of a second spillway is on the table,” Mellon said.

Something Burke emphasizes several times in his report is that the emergency spillway should never be used again. The existing redundancies are not close to sufficient, in his opinion.

That being said, there are two other water outlets at Oroville Dam other than the spillways, including the Hyatt Powerplant and the river outlet valves. Combined, their total capacity is less than 20,000 cubic-feet per second, or cfs.

He suggests building the second gated spillway to the right of the existing main spillway as a contingency for relieving high flows.

“The added redundancy and safety would be invaluable,” Burke said.

He said a second gated structure with anti-cavitation features is essential because things like malfunctioning radial gates, hoist motors or failing backup generators could render the existing spillway not usable, backing up water in the reservoir.

Burke also takes issue with DWR’s pronouncement the remodeled spillway will be able to handle 270,000 cfs flows down the main spillway. Mellon said that number was calculated based upon a reservoir level of 905 feet — above the emergency sillway lip — using physical modeling.

Regardless, by his calculations, the gates can only discharge 220,000 cfs, he wrote. With releases of that intensity, 354,000 cfs flows would be simultaneously gushing down the emergency spillway.

“It is just plain irresponsible to allow rushing water to flow over an unpaved slope,” he said. “The answer is a concrete spillway chute.”

He also notes the downstream levees only have the capacity of 160,000 cfs. With higher releases, major flooding occurs.

Burke has written articles about his ideas for the Engineering News-Record following the Oroville Dam crisis. See his published work in the Engineering News-Record at www.enr.com/authors/1050-henry-burke.

Burke is not the only one to pitch the dual design spillway concept. Kenneth Viney, a designer with a power industry consulting firm based in Napa, has filed his suggestions with the Federal Energy Regulatory Commission several times.

In April, he called for more than doubling the width of the proposed additional spillway and leaving the damaged canyon as it is because of safety concerns, as previously reported in this newspaper.

Reach reporter Risa Johnson at 896-7763.