Drastically reduced hazardous waste disposal
Safe removal of PCB and lead-containing paint
The Kanmon Bridge is one of Japan’s most significant pieces of transport infrastructure, connecting Honshu Island and Kyushu Island across the Kanmon Strait. Commissioned in November 1973 and carrying approximately 30,000 vehicles per day, the bridge stretches a total length of 1,068 metres and represents a critical link in Japan’s national road network.
In 2011, a comprehensive refurbishment project was initiated to address the ageing coating systems across the full length of the bridge. The project was divided into 10 sections, each covering approximately 23,000m², with the full refurbishment program expected to span 10 years. The road owner, NEXCO West, engaged Yokogawa Construction as the prime contractor to oversee the works.
In 2013, Ocean Tec (OT), one of the first RPR customers in Japan, introduced the RPR heat induction paint removal method to NEXCO West and Yokogawa Construction as a superior alternative to conventional removal methods. Following multiple demonstrations and the presentation of test data, RPR was formally approved by NEXCO as a Value Engineering (VE) solution for the project. Ocean Tec was subsequently engaged as a subcontractor to carry out the coating removal works across sections 3 and 4 of the bridge, covering a combined surface area of 20,000m².`
The Kanmon Bridge presented a uniquely complex set of coating removal challenges. The existing paint system consisted of multiple layers including zinc spray coating, phenolic zinc chromate anticorrosive paint, phenolic micaceous iron oxide paint, and chlorinated rubber paint, with coating thicknesses ranging from 500 to 2,000 microns across the structure.
Critically, the paint materials on the Kanmon Bridge contained measurable levels of PCB (polychlorinated biphenyls) and lead, both of which are classified as hazardous substances requiring strict management during removal and disposal. This made waste minimisation and contamination control a primary concern for the asset owner throughout the project.
Traditional removal methods such as sand blasting and ultra-high pressure (UHP) water jetting had already been banned on the project due to the significant risk of airborne and waterway contamination. Chemical paint stripping was also considered but proved less effective under cold weather conditions, limiting its viability as a year-round solution. The project required a method that could safely handle hazardous coatings, operate in all weather conditions, minimise waste volumes, and deliver the removal rates needed to meet the contracted timeframes across a large and complex bridge structure.`
Ocean Tec deployed three RPR heat induction units across sections 3 and 4 of the Kanmon Bridge, operating teams of 3 to 4 persons per unit covering the roles of operating, scraping, and material handling. Work was carried out 7 hours per day, 6 days per week, using a 4:1 transformer configuration with a 20cm induction head suited to the varied surface profiles of the bridge structure.
The RPR induction process thermally debonds the coating from the steel substrate by generating localised heat directly within the paint layer, causing it to release cleanly without the need for abrasive media, harsh chemicals, or water. This made it ideally suited to the Kanmon project, where hazardous material management was paramount. Because the coating is lifted and scraped as solid flakes rather than being blasted into airborne particles or dissolved into liquid waste, the volume and cost of hazardous waste disposal was dramatically reduced compared to any alternative method.
The scope of work covered the ordinary surface areas of the bridge, with the zinc spray layer preserved as required. Splicing parts and fillet weld zones, which required specialist treatment, were addressed separately using a chemical remover. Subsequent surface preparation was carried out via sodium bicarbonate blasting prior to recoating.
Section 3 commenced as a trial phase from August 2014 through to March 2015, with section 4 following from April 2015 through to August 2015. The work achieved an average removal rate of 40 to 50m² per day per unit, and the full 20,000m² scope was completed within the contracted time limit. The outcome was recognised as excellent by the asset owner and was subsequently reported across multiple industry publications and media outlets in Japan.`
