Engineers discuss Kenmore flood-reduction projects

Top: The Simonds residence along 73rd Avenue Northeast flooded last December due to heavy rains. Above: Workers begin repairs to the banks of Swamp Creek last December.  - Submitted photo
Top: The Simonds residence along 73rd Avenue Northeast flooded last December due to heavy rains. Above: Workers begin repairs to the banks of Swamp Creek last December.
— image credit: Submitted photo

The city of Kenmore addressed residents’ concerns about flooding in the Swamp Creek area at a Sept. 2 public meeting.

Engineering consultants discussed past flood-reduction measures and plans for repairing damage from the record-storm event that occurred last December.

Swamp Creek has overflowed on numerous occasions since the 1970s because of urbanization, which causes increased runoff.

The city began implementing flood-reduction projects along the stream in 2003.

King County agreed to pay nearly $11 million for the improvements as mitigation for sanitary-sewer projects that took place in Kenmore.

The first wave of flood-reduction projects included:

• Replacing the 73rd Avenue bridge to eliminate the risk of debris clogs

• Raising the Kenmore Elementary access road to prevent flood waters from running onto nearby properties

• Lifting five homes that were at risk of flooding during 100-year events

• Realigning the creek to create gentler curves.

The city completed those improvements in 2005.

Next came a series of projects at Wallace Park in 2006, including modifications to a weir structure and construction of a fish bypass channel that allows safe dredging in the sediment pond.

The city also created new fish habitats along the stream and constructed flood-plain storage areas in select spots to prevent water from reaching residences during heavy rains.

A 100-year rain event last December tested all of the improvements.

Gushing waters tore away several banks and dislodged many of the fish-habitat elements, which included man-made log jams.

Four culverts also blew out upstream of Wallace Park, and both the bypass channel and sediment pond filled with silt.

In terms of flooding, the raised roads prevented water from spreading to residences south of the Kenmore Elementary access road.

Many of the properties east of 73rd Avenue Northeast, however, became inundated.

Engineers had proposed building a berm to prevent flooding in that area, but the majority of residents there opposed the idea, according to city officials.

Several properties north of the Kenmore Elementary access road also flooded, although those plots are located within the expected 100-year flood plain.

The city implemented emergency repairs in December, shoring up Swamp Creek’s eroded banks with rocks and plastic sheeting, and removing 2,500 cubic yards of sediment that had settled at Wallace Park.

Those projects cost $113,000, although Kenmore’s share was only $14,200.

Future repairs will include removing sediment from a backwater channel east of 73rd Avenue Northeast, replanting vegetation along the Swamp Creek stream banks, and anchoring all habitat logs into the ground.

The city of Kenmore is expected to pay $56,000 for the complete list of upcoming projects, which has an estimated price tag of $357,000.

Repairs are expected to be completed later this year.

The city has no current plans to reduce flooding east of 73rd Avenue Northeast.

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