Flood imminent unless pump station upgrades

Renton, King County leaders discuss budget for Black River flood management

There’s one thing standing between Renton valley and major flooding, and it’s almost 50 years old.

A pump station that reduces flood risk in the industrial districts of Renton, Kent and Tukwila is in need of a slew of repairs and updates. King County Flood Control District (FCD) said the critical upgrades will require $2 million of the flood control district’s budget.

Without the Black River Pump Station in good use, 370 Renton structures, 2,800 acres and $4.4 billion worth of property are in danger of flooding. Here’s a map of the areas protected by the pump station:

Black River Pump Station flood district map by Haley Ausbun on Scribd

City leadership took a recent tour of the facility that helps protect Renton valley from devastating floods. The King County Road Services Maintenance Division operates and maintains the station.

While the city doesn’t operate it, staff are advocating the station receive these upgrades. Renton Public Works Administrator Gregg Zimmerman said when touring the station you can see it’s old and needs to be brought to today’s standards. He said the updates are important to the city, and they want to make sure it gets done. Such a critical facility desires newer, more reliable, equipment.

The Black River Pump Station, sitting in Southwest Renton, prevents flooding that would come from Springbrook Creek by pumping the drainage from the creek’s basin. That water then goes into the old Black River channel, flowing into the Duwamish River near Fort Dent Park. In times of high flow the drainage from Springbrook used to back up and flood parts of the flat valley, before the pump station was built at the creek’s forebay. The station is mainly needed in heavy rain, Zimmerman said.

“Almost one half of the Springbrook Drainage Basin lies within Renton,” City Councilmember Armondo Pavone stated in a press release from King County Council. “This makes the Black River Pump Station upgrade essential for the protection of our community and commerce.”

Built in 1972, the station has only seen one major improvement— an upgrade of the diesel fuel system. While the main pump runs on a new electric motor, several lesser-used pumps still have a diesel engine. Even though fueled pumps are used less, they maintain the flow in high-tides, or if a power outage knocks out the main electric pump. This station also has provisions that help salmon get into headwaters.

The FCD Executive Committee, chaired by county councilmember Reagan Dunn, stated three of the seven engines in the high-use pumps must be replaced. If funding is approved those are scheduled to be added in August 2020.

The proposal will go to the FCD Board of Supervisors when they determine the 2020 budget on Oct. 30, after the Renton Reporter’s press deadline.

“It is absolutely critical for the welfare of Renton, Tukwila and Kent communities that the Black River Pump Station is in prime condition,” Dunn stated in the release. “This funding ensures that these communities are insulated from flooding risk.”

The pump station will need more than three engines: since January, work has also been done on a number of other station improvements, which will continue over the next eight years. This includes assessing seismic risk to the station in the event of an earthquake, upgrading the salmon passage systems and creating a capital project strategy for these, and future, projects.

In January 2015, King County completed a capital needs assessment of the entire pump station. All the mechanical, fish migration, electrical, control and structural changes recommended totaled $10.84 million in estimated engineering and construction costs.

In another 2015 document, the costs of replacing the three high-use pumps was estimated at $1.42 million.

Both documents are available below:

Black River Pump Station Needs by Haley Ausbun on Scribd

Black River Needs Assessment by Haley Ausbun on Scribd

The station prevents most flooding events. The only time the pumps wouldn’t stop Springbrook Creek from flooding, is if the Green River were to reach Stage Four flooding. In that situation regulations state the pump station would need to slow down, thus putting Springbrook Creek at risk of overflowing. In Zimmerman’s 30 years with the city he’s never seen it, and said if it were to happen the valley would have bigger problems.

“If the situation gets like that, we’d have problems all over the place. That’s a huge flood and storm event that would cause that,” Zimmerman said.

Another Renton priority being discussed by FCD is regulating levee heights along the Duwamish River. Zimmerman said it’s important that any levee changes to that river are also taken care of at the Black River Pump Station forebay. Whatever standard gets applied to the region, needs to also happen at the pump station to prevent flooding, he said.

More information is available here.