51st Ave – 112nd Pl NE Intersection Improvements
This project was implemented by Snohomish County to improve traffic flow, sight distance, and stream conveyance through the intersection of 51st Avenue and 122nd PL NE. This involved widening of the roadway to allow installation of a new turn lane, traffic signal, and illumination system. As part of the widening efforts, two substantial culvert replacements were performed. An extensive dewatering and diversion system was used along with a major shoring system to allow for installation of an 18’ diameter x 52’ long steel arch culvert and a 24’ W x 12’ H x 65’ L precast concrete box culvert. During the stream bypass operations, wetland mitigation and stream restoration work was completed. Due to the poor soil conditions, geofoam was used as backfill around the box culvert to reduce loading. Once the culverts were complete, all the utilities were upgraded to include new water line, storm drainage, and sanitary sewer. Porous sidewalks were installed and asphalt was placed to complete this project on time in the fall of 2008.