The Wugu-Yangmei overpass, which was opened just four months ago, has developed cracks and an impartial third party will be invited to investigate and determine their cause, the Ministry of Transportation and Communications (MOTC) said yesterday.
Three different cracks were found on Thursday morning at the 45km marker in the overpass’ northbound lane — the longest crack being 30m in length.
The National Expressway Engineering Bureau, which constructed the overpass, said its preliminary investigations showed that heavy rainfall brought by Tropical Storm Trami may have caused the groundwater level to rise, which subsequently led to the cracks forming on the road’s surface.
The bureau closed traffic lanes in the section and began repairing the damaged road surface at 10pm on Thursday. Both lanes were open for traffic by 12pm yesterday.
The 40km overpass was constructed along the Sun Yat-Sen Freeway (National Freeway No. 1) to divert the traffic between Wugu (五股) in New Taipei City (新北市) and Yangmei (楊梅) in Taoyuan County during peak hours. The section between Jhongli (中壢) and Yangmei was first opened for traffic in December. The launch of the section between Wugu and Jhongli was postponed four times due to delays caused by a shortage of workers.
The overpass became fully operational on April 22. The construction costs topped NT$88.2 billion.
Civil engineering experts said that the cracks were the result of shoddy work by the contractor. They disagreed with the bureau’s explanation that the cracks may have been caused by an upwelling of groundwater, saying that the bureau should always factor in the influence of groundwater in the design of national freeways.
The Bureau’s First District Engineering Office head Chen Fu-chiang (陳福將) said the cracks were found on the section of the overpass that is on solid ground, not on the overpass itself.
“We did not find cracks on other parts of the overpass, so the overpass is safe,” he said.
Chen said the overpass’ retaining walls have drainage holes through which excess groundwater can be discharged and the holes have been functioning normally.
“The heavy rainfall caused the groundwater to rise very quickly and the refill dirt on the embankment was quite solid. This prevented the water from draining as fast as it should, which forced some of the water to flow in the direction of the road surface rather than through the drainage walls,” he said.
Chen said the bureau had decided to set up several observation points between the overpass’ 44.9km and 45.3km markers over the weekend to determine remedies for the situation.
According to Chen, the bureau will drill wells in the embankment and bore holes in the retaining walls to help drain the overflowing groundwater.
MOTC Deputy Minister Jonathan Chen (陳純敬) said the ministry has asked the bureau to conduct thorough inspections of the overpass to see if the same problems exist in other sections. He said that the bureau also needs to identify the cause of the cracks
“One can only prescribe the right medicine if one knows what the illness is,” he said. “Some have alleged that the cracks appeared because the construction contractor did shoddy work and scrimped on materials, while others have attributed it to improper design. All these allegations are mere speculations at this point.”