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Sahalee Way NE Drainage Improvement Project
Status update
July 9, 2025
Crews opened Sahalee Way NE to traffic between NE 50th Street and NE 37th Way at 8 p.m. on Thursday, July 3, 2025.
The road was closed 24/7 from Saturday, June 28, 2025, at 6 a.m. to Thursday, July 3, 2025, at 8 p.m., to replace and repair two failing drainage pipe culverts under the road.
During our excavation, crews encountered unexpected underground utilities, including eight-inch gas lines, which are twice the size originally anticipated. These discoveries have added complexity to the project and required additional time to complete safely.
Why did we close the road:
- Sahalee Way NE is too narrow to fit the large excavator and keep traffic moving. Crews also needed daylight to safely work around three underground gas lines.
- If the damaged pipes had collapsed, water could have rushed out and cause sinkholes - or completely washed out the road above.
- If that had happened, the road could have been closed for up to a year while crews fully rebuilt it.
Project overview
King County replaced one pipe and rehabilitated another under Sahalee Way NE between NE 50th Street and NE 37th Way near the City of Sammamish. The joints in the metal culvert under the 4600 and 4800 block of Sahalee Way NE were failing and water was seeping into the ground making the soil soft. If these pipes had not been replaced, the water entering the ground may have reduced the stability of the slope and caused the area to slide.
We understand that closing Sahalee Way NE was a significant impact to the community. We did everything we could to keep the closure as short as possible, this includes working over the weekend. If we hadn't done this work now, and a pipe collapsed, the emergency repair might have caused the road to be closed for up to a year.
This area has been subject to some large slides that closed the road for many days in the mid-1990s and earlier. Approximately 20,000 vehicles use this road every day.
Frequently asked questions
There are two large drainage pipes that run under Sahalee Way NE between NE 50th Street and NE 37th Way. When working, these pipes drain water away from the hillside reducing the risk of a slide. Both of the pipes were damaged and needed to be replaced:
- Thirty-inch metal pipe that was rusting and cracked was replaced by sliding a new heavy duty plastic pipe that is 18 to 24-inches wide into the current pipe and routing water to the new pipe.
- Twenty-four-inch metal pipe is old and rusting. It was filled with concrete and retired. A new heavy-duty 24-inch plastic pipe was installed nearby and replaced the current pipe.
Photos
Crews gather to review the remaining work after completion of this portion of the Sahalee Way NE Drainage Improvement Project. The asphalt is freshly paved and needed to cure before it is driven on.
A much sturdier pipe now runs under Sahalee Way NE. This pipe can handle water from a 100-year flood.
The joints in this 24-inch pipe underneath 4600 Sahalee Way NE were failing at the top. With enough pressure, it is possible the pipe could have caved in. If the pipe had caved in, water would have built up soaking the soil around the pipe and possibly causing the surrounding slope to slide. Additionally, as the cracks gets wider and soil is washed away, sink holes could develop and parts of the road could fall into this empty space. We filled this pipe and built a new culvert above it.
This was the culvert near the 4600 block of Sahalee Way NE. When the culvert sticks out like this, you can see that soil underneath has eroded and fallen away. Eventually, the pipe is no longer supported, and it fails completely.
This is a picture from 1996 in the same area. King County repaired a sunken and cracked Sahalee Way NE. The instability of the ground in this area is the reason we pay such close attention to these culverts. The culverts are an important way to manage water under the road.