Approximately 2.5 acres of tributary drainage currently collects at three isolated catch basins located near a roadway sag on 108th Avenue NE. The existing storm drainage system is not connected to any downstream conveyance system, causing the upstream system to surcharge during significant storm events. As a result, stormwater surcharges from the lowest catch basin and flows onto the adjacent private properties.
The 108th Avenue Northeast Pipe Installation project will address this longstanding drainage deficiency by connecting the isolated storm drainage system to the downstream conveyance system, thereby reducing flood risk to the affected properties and improving the reliability of the City's stormwater infrastructure.
The 108th Avenue NE Pipe Installation project includes the installation of approximately 845 linear feet of 12-inch storm drainage pipe to connect the existing isolated upstream storm drainage system, to the downstream storm drainage system on 106th Avenue NE. The project also includes the installation of three catch basins along 106th Avenue NE and near the intersection of NE 120th Street and 108th Avenue NE to improve stormwater collection and roadway drainage. Additionally, a total of seven catch basins will be installed parallel to NE 120th Street to establish an optimal slope for the 12-inch storm drainage conveyance.
Due to the depth of the proposed storm drainage improvements and the extent of trenching required, the project will also include roadway restoration consisting of a grind and overlay along the majority of NE 120th Street and smaller portions of both 108th Avenue NE and 106th Avenue NE. In addition to restoring the pavement disturbed during construction, this resurfacing will provide the added benefit of addressing existing pavement fatigue and deterioration within the project limits.
The 108th Avenue NE Pipe Installation project supports the City Council’s Dependable Infrastructure goal.