What's Happening Now?
Starting Saturday, August 23rd, the contractor will use Ultra-High Pressure (UHP) water jetting uses water pressurized beyond 25,000 psi to remove rust and other contaminants from surfaces, leaving a clean, rust-free profile without chemicals or abrasives.
The contractor is using proprietary chemicals called Blastox®, which are used to stabilize heavy metal wastes for a wide range of industries.
Blastox® is a specially engineered abrasive additive that, when mixed with standard blasting media, chemically reacts with lead particles. This reaction forms an insoluble lead compound that prevents the lead from leaching into the environment.
Sound Amplification Reduction Systems
A noise variance permit has been approved by the Portland Permitting & Development Noise Program considering construction noise will reach higher than normal 85 dBA permitted sound levels. This Permit is available upon request.
The contractor has also installed noise reduction tarpaulins, or acoustic tarps, which are a multi-layered fabric designed to absorb and block sound, reducing noise pollution in loud environments like construction sites, bars, and factories.
Additionally the contractor as deployed Tier 4 diesel engines. Tier 4 diesel engines reduce construction site noise by improving engine efficiency and utilizing advanced exhaust aftertreatment systems, leading to quieter operation and significantly lower sound levels compared to older Tier standards.
Project Background
The Portland Bureau of Transportation completed the award-winning NW Thurman St. Bridge Rehabilitation Project in 2014. The historic handmade and antique bridge was lovingly restored with a new sidewalk, deck, and rail system. The riveted steel beams were replaced with modern replica versions. As a result, the weight restriction was lifted from the 110-year old bridge, the oldest intact span in Oregon.
This new project will refresh the paint on the bridge and do additional needed repairs to extend the bridge's lifespan.
The 110 year-old Balch Gulch Bridge was built during the 1905 Lewis and Clark Centennial Exposition and World’s Trade Fair as a gateway to Portland’s developing Willamette Heights neighborhood. As the oldest intact bridge in the region and one of only few remaining of its type in the entire nation, the pin-connected steel deck truss is a noteworthy historic and engineering treasure. In fact, Dr. Robert Hadlow, Oregon Department of Transportation Historian, espoused the bridge as “one of the most significant spans in Oregon.”
Project Scope
Considering the age of the bridge and its poor condition, it would have been so easy to replace it with a shiny new one. However the easy path was not chosen. Given its unique characteristics, its special place in Portland history, and its eligibility for the National Register of Historic Places, rehabilitation of the Balch Gulch Bridge was really the only viable option.
In order to adequately address the bridge deficiencies, replacement of components above the trusses is required.
Street lights will also be installed along the bridge to provide additional illumination for pedestrians and all vehicles traveling along NW Thurman Street.
Goals During Construction
The decision to preserve the historic bridge inspired the public and government agencies alike. It also inspired PBOT to set the following goals:
- Modernize and revitalize the aesthetic appeal of the bridge while still preserving the it's unique historic character
- Provide additional paint layered protection to ensure the lifespan of the bridge the original appearance of the 1905 historic bridge handrail, but strengthen it to meet modern safety standards
- Replace structural members that have deteriorated, while shoring the historic trusses in place
- Ensure that Lower Macleay Park remains open to the public during construction
- Keep the public constantly informed of progress by holding meetings, establishing a telephone hotline, creating a project website and publishing monthly newsletters
Provide continued pedestrian access along the bridge during construction