River levels aren’t the only thing going up around here.
Since the snowmelt-charged Columbia River began rising in earnest about 10 days ago, the number of bridge lifts on the Interstate 5 Bridge have gone up as fast as a motorist’s blood pressure when the bridge’s gates go down.
Between May 15 and noon Tuesday, the Oregon Department of Transportation raised the I-5 Bridge’s lift spans 37 times — nine times on Saturday alone — due to reduced clearance for maritime traffic, said ODOT spokesman Don Hamilton.
The odds for the continued high frequency of bridge lifts are good for the foreseeable future, as the Columbia River remains high from snowmelt. The river was at 15.8 feet at 3 p.m. Tuesday and is forecast to rise above the 16-foot flood level around 3 a.m. Thursday and reach about 16.5 feet by the end of the week. Little flooding damage is expected.
When the Columbia is running low — in the 6.5- to 7-foot range — more vessels can pass under the bridge’s mid-river hump, which means bridge tenders get only two or three requests for a bridge lift from vessels a month.
But when the water rises and river flow increases, vessels have no choice but request a bridge lift. And bridge tenders have no choice but to comply.
“Under maritime law, we have to lift when a vessel requests it,” Hamilton said.
There is one exception. ODOT, which operates the bridge, has negotiated with the U.S. Coast Guard to ensure that bridge lifts not occur during peak weekday freeway travel — from 6:30 a.m. to 9 a.m. and 2:30 p.m. to 6 p.m. Monday through Friday.
There are an average of 425 bridge lifts every year, with about half of those being for bridge maintenance.
The duration of an average bridge lift is 8 minutes for a sailboat and 12 to 25 minutes for a tugboat with a barge, Hamilton said. Times can vary depending on the size and height of the vessel, the stream flow, and whether the vessel is going upstream or downstream.
Hamilton said the nine bridge lifts Saturday included a large number of pleasure craft. Those lifts kept the bridge out of commission for motorists for 106 minutes that day.
“But we have no restrictions,” Hamilton said. “If you radio it in, we have to do it.”
Mark Bowder: 360-735-4512 or firstname.lastname@example.org.