- Location: NW Rock Creek Road between NW Skyline Blvd. and NW Elliott Road
- Schedule: Emergency repair completed March 2020. Landscaping work October 2020.
- Estimated Cost: Preliminary estimate $500,000 - $700,000
- Video: A time-lapse video of the culvert replacement.
October 2020 Landscaping
Planting of trees and other plans on the slopes above the new culvert under NW Rock Creek Road was completed on October 7, 2020. No additional lane or road closures will be needed. Learn more.
NW Rock Creek Road was closed between Skyline and Elliot due to a failed culvert. This project replaced the old culvert with a new one that is larger and more durable.
The map at right shows the location of the culvert failure. The old culvert was 30 feet below the road surface, two feet in diameter and made of corrugated steel. It carried a tributary of Rock Creek. The new culvert is four feet in diameter and made of a non-rusting material called high density polyethylene.
The bottom of the old culvert rusted out, allowing it to clog with dirt and rocks. After a heavy rain, the blocked culvert backed up stormwater on the uphill side of the road, creating a lake that put pressure on the road embankment and threatened adjacent property.
Our maintenance crew installed a pump to direct water over the top of the road. The pumping equipment remained in place and blocked the road to traffic.
Our engineering staff investigated the culvert failure and designed a permanent repair. The culvert is at such a great depth under the road that replacing it required removal of hundreds of dump truck loads of material. A general contractor began repairs in February and completed work in March. The road reopened to traffic on March 30.
Property owners and visitors had access to properties from each side of the closure. Through traffic had to detour around the closure using NW Elliot Road and NW Skyline Blvd. NW Rock Creek Road has relatively little traffic in this rural area. The short stretch of road above the culvert is one lane wide, with safety barricades, due to the steep slopes on either side of the road. The barricades will be replaced with permanent guard rails at a later date.
For Your Safety
The collapsed culvert threatened to undermine and flood the road. The public was kept away from the work zone during the closure for safety.
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