Flooding last week prompted a brief from city of Renton at the Feb. 10 council meeting, alerting councilmembers and the public where the main damage was done.
The Cedar River reached 9,000 cubic feet per second (cfs), a significant peak flow, and the Green River reached 12,300 cfs.
“In my 30 years here at city of Renton it’s only the second time I’ve ever seen the Green River go above 12,000 cfs,” Renton Utilities Systems Director Ron Straka said.
On Thursday, Feb. 6, rainfall and snow melt in the mountains started the high river flows in both Green and Cedar River, which were categorized at phase four flooding, which is a severe level. On Monday, Feb. 10, the rivers were both at phase three.
City staff said it was an ongoing issue, but they expected it to recede by Thursday, Feb. 13.
The city did not have a financial estimate on the damage done by the flood yet, but Renton Emergency Management Director Deborah Needham told councilmembers during the last major flooding event in 2009, the city experienced $4 million worth of damage. Much of the costs can be reimbursed through FEMA, Needham said, but first they require a Presidential Disaster Declaration from the President of the U.S. The county needs to meet $7.5 million worth of damages to receive a declaration, and the state in total must have $10.5 million in damages.
If the city gets FEMA funding, that will recoup 75 percent, the state then may kick in 12.5 percent. That would leave Renton will only the remaining 12.5 percent of costs.
State Route 169 experienced closures due to flooding, mudslides and debris over the weekend and early into this week. Nile Avenue and May Valley Road also experienced road closures. Overall, public works staff said Renton’s storm system and flood protection facilities performed well and prevented significant problems or damage.
Significant flooding impacted facilities all along the Cedar River. The most damage was along the Cedar River Trail, Community Services Administrator Kelly Beymer said. The undermining of the river’s bank brought the edge only a couple feet away from the paved trail. City staff have barricaded 75 yards on either side. They will need to bring engineers in to decide what to do about the damage, Beymer said.
Like some residences near the river, the Riviera Apartments experienced river flowing into its parking lot, but city staff reported it did not reach the apartment complex.
At the Renton Maplewood Golf Course, 14 holes were still open but significant flooding closed four of the newly-built holes. Those were closed over the weekend. The Elliot Fish Spawning channel was also overtopped and trees were down along the trail area.
The lower walkway along the Cedar River and the grass behind the Renton Senior Activity Center experienced high flooding as well.
The Renton Municipal Airport is located next to the mouth of the river flowing into Lake Washington. As a result, debris including large logs and other things swept away during the flood have clogged the waterside of the airport. In a Feb. 10 committee meeting, city staff said it was “crazy” the amount of debris that went out into the lake.
In preparation for the flooding, the South Boeing Bridge next to the Cedar River Trail Park was hydraulically raised into the air. It protected the bridge from damage and prevented river backup. The bridge was upgraded by Boeing in 1998 to raise this way, staff said.
Carco Theatre is the only interior city infrastructure to receive flooding, at several inches in the basement level. City staff said while flooding did not go over the sandbags the city put to protect it, the sump pumps failed to keep up with rising flow and brought in groundwater. The staff then brought in additional sump pumps and staffed the basement 24-7 to keep the basement over. Once the basement dries out they will assess the damage.
The city staff said they will be checking other city infrastructure for any additional damage, including trails and walkways that were impacted by the flooding, once the river flow goes down.
During the flood event, city staff monitored river gauges and reported out any road closures and expected weather conditions. Staff cleared landslide debris from Maple Valley Highway, sandbagged city facilities, cleaned up Carco Theatre and prepared for emergency notifications. Councilmember Randy Corman thanked city staff for the preparation that was done before the flooding, that made it a less significant disaster than what could have been.