16th Street Combined Sewer Overflow Separation Project

City of Astoria, Oregon

Gibbs & Olson provided surveying, design, and construction phase services for the City’s 16th Street combined sewer overflow (CSO) separation project. The CSO project is the latest in a series of projects intended to reduce the discharge of untreated combined storm and sanitary sewer system overflows into the Columbia River. The project physically separates the stormwater from the sanitary sewer system. Improvements included design and construction of 12,400 feet of storm, 720 feet of sanitary sewer, and 1,900 feet of water pipelines. The 16th Street project is located along the south edge of the City of Astoria’s commercial district and extends into the City’s residential neighborhoods. Gibbs & Olson utilized a subconsultant to perform geotechnical investigations to properly address subsurface issues. Historical and cultural resource evaluation was also an important since part of the project area is within the footprint of historic Fort Astoria and its associated cemetery. There are also historic trolley tracks within a one block area of the project. 16th Street remained open during construction while the Irving Street bridge repairs (a separate project) were completed. Gibbs & Olson worked closely with the City to carefully plan for 16th Street traffic control, construction sequencing and staging within the narrow and steep right of way.